Consistent use of @Nullable in spring-test

This commit also removes nullability from two common spots: ResolvableType.getType() and TargetSource.getTarget(), both of which are never effectively null with any regular implementation. For such scenarios, a non-null empty type/target is the cleaner contract.

Issue: SPR-15540

spring-aop/src/main/java/org/springframework/aop/TargetSource.java

@@ -16,8 +16,6 @@
 
 package org.springframework.aop;
 
-import org.springframework.lang.Nullable;
-
 /**
  * A {@code TargetSource} is used to obtain the current "target" of
  * an AOP invocation, which will be invoked via reflection if no around
@@ -59,7 +57,6 @@ public interface TargetSource extends TargetClassAware {
 	 * @return the target object, which contains the joinpoint
 	 * @throws Exception if the target object can't be resolved
 	 */
-	@Nullable
 	Object getTarget() throws Exception;
 
 	/**

spring-aop/src/main/java/org/springframework/aop/framework/CglibAopProxy.java

@@ -326,8 +326,12 @@ class CglibAopProxy implements AopProxy, Serializable {
 			// TODO: small memory optimization here (can skip creation for methods with no advice)
 			for (int x = 0; x < methods.length; x++) {
 				List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(methods[x], rootClass);
-				fixedCallbacks[x] = new FixedChainStaticTargetInterceptor(
-						chain, this.advised.getTargetSource().getTarget(), this.advised.getTargetClass());
+				Object target = this.advised.getTargetSource().getTarget();
+				Class<?> targetClass = this.advised.getTargetClass();
+				if (targetClass == null) {
+					targetClass = target.getClass();
+				}
+				fixedCallbacks[x] = new FixedChainStaticTargetInterceptor(chain, target, targetClass);
 				this.fixedInterceptorMap.put(methods[x].toString(), x);
 			}
 
@@ -374,7 +378,7 @@ class CglibAopProxy implements AopProxy, Serializable {
 	 * {@code proxy} and also verifies that {@code null} is not returned as a primitive.
 	 */
 	@Nullable
-	private static Object processReturnType(Object proxy, @Nullable Object target, Method method, @Nullable Object retVal) {
+	private static Object processReturnType(Object proxy, Object target, Method method, @Nullable Object retVal) {
 		// Massage return value if necessary
 		if (retVal != null && retVal == target &&
 				!RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
@@ -409,7 +413,7 @@ class CglibAopProxy implements AopProxy, Serializable {
 
 		private final Object target;
 
-		public StaticUnadvisedInterceptor(@Nullable Object target) {
+		public StaticUnadvisedInterceptor(Object target) {
 			this.target = target;
 		}
 
@@ -430,7 +434,7 @@ class CglibAopProxy implements AopProxy, Serializable {
 
 		private final Object target;
 
-		public StaticUnadvisedExposedInterceptor(@Nullable Object target) {
+		public StaticUnadvisedExposedInterceptor(Object target) {
 			this.target = target;
 		}
 
@@ -472,9 +476,7 @@ class CglibAopProxy implements AopProxy, Serializable {
 				return processReturnType(proxy, target, method, retVal);
 			}
 			finally {
-				if (target != null) {
-					this.targetSource.releaseTarget(target);
-				}
+				this.targetSource.releaseTarget(target);
 			}
 		}
 	}
@@ -503,9 +505,7 @@ class CglibAopProxy implements AopProxy, Serializable {
 			}
 			finally {
 				AopContext.setCurrentProxy(oldProxy);
-				if (target != null) {
-					this.targetSource.releaseTarget(target);
-				}
+				this.targetSource.releaseTarget(target);
 			}
 		}
 	}
@@ -612,9 +612,7 @@ class CglibAopProxy implements AopProxy, Serializable {
 
 		private final Class<?> targetClass;
 
-		public FixedChainStaticTargetInterceptor(
-				List<Object> adviceChain, @Nullable Object target, @Nullable Class<?> targetClass) {
-
+		public FixedChainStaticTargetInterceptor(List<Object> adviceChain, Object target, Class<?> targetClass) {
 			this.adviceChain = adviceChain;
 			this.target = target;
 			this.targetClass = targetClass;
@@ -650,7 +648,6 @@ class CglibAopProxy implements AopProxy, Serializable {
 		public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
 			Object oldProxy = null;
 			boolean setProxyContext = false;
-			Class<?> targetClass = null;
 			Object target = null;
 			try {
 				if (this.advised.exposeProxy) {
@@ -658,12 +655,9 @@ class CglibAopProxy implements AopProxy, Serializable {
 					oldProxy = AopContext.setCurrentProxy(proxy);
 					setProxyContext = true;
 				}
-				// May be null. Get as late as possible to minimize the time we
-				// "own" the target, in case it comes from a pool...
+				// Get as late as possible to minimize the time we "own" the target, in case it comes from a pool...
 				target = getTarget();
-				if (target != null) {
-					targetClass = target.getClass();
-				}
+				Class<?> targetClass = target.getClass();
 				List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
 				Object retVal;
 				// Check whether we only have one InvokerInterceptor: that is,
@@ -709,7 +703,6 @@ class CglibAopProxy implements AopProxy, Serializable {
 			return this.advised.hashCode();
 		}
 
-		@Nullable
 		protected Object getTarget() throws Exception {
 			return this.advised.getTargetSource().getTarget();
 		}
@@ -729,9 +722,8 @@ class CglibAopProxy implements AopProxy, Serializable {
 
 		private final boolean publicMethod;
 
-		public CglibMethodInvocation(Object proxy, @Nullable Object target, Method method,
-				Object[] arguments, @Nullable Class<?> targetClass,
-				List<Object> interceptorsAndDynamicMethodMatchers, MethodProxy methodProxy) {
+		public CglibMethodInvocation(Object proxy, Object target, Method method, Object[] arguments,
+				Class<?> targetClass, List<Object> interceptorsAndDynamicMethodMatchers, MethodProxy methodProxy) {
 
 			super(proxy, target, method, arguments, targetClass, interceptorsAndDynamicMethodMatchers);
 			this.methodProxy = methodProxy;

spring-aop/src/main/java/org/springframework/aop/framework/JdkDynamicAopProxy.java

@@ -159,7 +159,6 @@ final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializa
 		boolean setProxyContext = false;
 
 		TargetSource targetSource = this.advised.targetSource;
-		Class<?> targetClass = null;
 		Object target = null;
 
 		try {
@@ -189,12 +188,10 @@ final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializa
 				setProxyContext = true;
 			}
 
-			// May be null. Get as late as possible to minimize the time we "own" the target,
+			// Get as late as possible to minimize the time we "own" the target,
 			// in case it comes from a pool.
 			target = targetSource.getTarget();
-			if (target != null) {
-				targetClass = target.getClass();
-			}
+			Class<?> targetClass = target.getClass();
 
 			// Get the interception chain for this method.
 			List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);

spring-aop/src/main/java/org/springframework/aop/framework/ReflectiveMethodInvocation.java

@@ -103,8 +103,8 @@ public class ReflectiveMethodInvocation implements ProxyMethodInvocation, Clonea
 	 * but would complicate the code. And it would work only for static pointcuts.
 	 */
 	protected ReflectiveMethodInvocation(
-			Object proxy, @Nullable Object target, Method method, Object[] arguments,
-			@Nullable Class<?> targetClass, List<Object> interceptorsAndDynamicMethodMatchers) {
+			Object proxy, Object target, Method method, Object[] arguments,
+			Class<?> targetClass, List<Object> interceptorsAndDynamicMethodMatchers) {
 
 		this.proxy = proxy;
 		this.target = target;

spring-aop/src/main/java/org/springframework/aop/support/AopUtils.java

@@ -329,7 +329,7 @@ public abstract class AopUtils {
 	 * @throws org.springframework.aop.AopInvocationException in case of a reflection error
 	 */
 	@Nullable
-	public static Object invokeJoinpointUsingReflection(@Nullable Object target, Method method, Object[] args)
+	public static Object invokeJoinpointUsingReflection(Object target, Method method, Object[] args)
 			throws Throwable {
 
 		// Use reflection to invoke the method.

spring-aop/src/main/java/org/springframework/aop/target/EmptyTargetSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,6 +32,13 @@ import org.springframework.util.ObjectUtils;
  */
 public class EmptyTargetSource implements TargetSource, Serializable {
 
+	/**
+	 * The canonical (Singleton) instance of this {@link EmptyTargetSource}.
+	 */
+	public static final EmptyTargetSource INSTANCE = new EmptyTargetSource(null, true);
+
+	private static final Object EMPTY_TARGET = new Object();
+
 	/** use serialVersionUID from Spring 1.2 for interoperability */
 	private static final long serialVersionUID = 3680494563553489691L;
 
@@ -40,12 +47,6 @@ public class EmptyTargetSource implements TargetSource, Serializable {
 	// Static factory methods
 	//---------------------------------------------------------------------
 
-	/**
-	 * The canonical (Singleton) instance of this {@link EmptyTargetSource}.
-	 */
-	public static final EmptyTargetSource INSTANCE = new EmptyTargetSource(null, true);
-
-
 	/**
 	 * Return an EmptyTargetSource for the given target Class.
 	 * @param targetClass the target Class (may be {@code null})
@@ -87,6 +88,7 @@ public class EmptyTargetSource implements TargetSource, Serializable {
 		this.isStatic = isStatic;
 	}
 
+
 	/**
 	 * Always returns the specified target Class, or {@code null} if none.
 	 */
@@ -104,11 +106,11 @@ public class EmptyTargetSource implements TargetSource, Serializable {
 	}
 
 	/**
-	 * Always returns {@code null}.
+	 * Always returns {@code DUMMY_TARGET}.
 	 */
 	@Override
 	public Object getTarget() {
-		return null;
+		return EMPTY_TARGET;
 	}
 
 	/**

spring-aspects/src/main/java/org/springframework/transaction/aspectj/AbstractTransactionAspect.aj

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -73,12 +73,9 @@ public abstract aspect AbstractTransactionAspect extends TransactionAspectSuppor
 				}
 			});
 		}
-		catch (RuntimeException ex) {
+		catch (RuntimeException | Error ex) {
 			throw ex;
 		}
-		catch (Error err) {
-			throw err;
-		}
 		catch (Throwable thr) {
 			Rethrower.rethrow(thr);
 			throw new IllegalStateException("Should never get here", thr);

spring-beans/src/main/java/org/springframework/beans/factory/wiring/BeanConfigurerSupport.java

@@ -141,13 +141,11 @@ public class BeanConfigurerSupport implements BeanFactoryAware, InitializingBean
 					!this.beanFactory.containsBean(bwi.getBeanName()))) {
 				// Perform autowiring (also applying standard factory / post-processor callbacks).
 				this.beanFactory.autowireBeanProperties(beanInstance, bwi.getAutowireMode(), bwi.getDependencyCheck());
-				Object result = this.beanFactory.initializeBean(beanInstance, bwi.getBeanName());
-				checkExposedObject(result, beanInstance);
+				this.beanFactory.initializeBean(beanInstance, bwi.getBeanName());
 			}
 			else {
 				// Perform explicit wiring based on the specified bean definition.
-				Object result = this.beanFactory.configureBean(beanInstance, bwi.getBeanName());
-				checkExposedObject(result, beanInstance);
+				this.beanFactory.configureBean(beanInstance, bwi.getBeanName());
 			}
 		}
 		catch (BeanCreationException ex) {
@@ -168,13 +166,4 @@ public class BeanConfigurerSupport implements BeanFactoryAware, InitializingBean
 		}
 	}
 
-	private void checkExposedObject(@Nullable Object exposedObject, Object originalBeanInstance) {
-		if (exposedObject != originalBeanInstance) {
-			throw new IllegalStateException("Post-processor tried to replace bean instance of type [" +
-					originalBeanInstance.getClass().getName() + "] with (proxy) object of type [" +
-					(exposedObject != null ? exposedObject.getClass().getName() : null) +
-					"] - not supported for aspect-configured classes!");
-		}
-	}
-
 }

spring-context/src/main/java/org/springframework/context/annotation/ComponentScanAnnotationParser.java

@@ -38,7 +38,6 @@ import org.springframework.core.type.filter.AspectJTypeFilter;
 import org.springframework.core.type.filter.AssignableTypeFilter;
 import org.springframework.core.type.filter.RegexPatternTypeFilter;
 import org.springframework.core.type.filter.TypeFilter;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
@@ -64,7 +63,7 @@ class ComponentScanAnnotationParser {
 	private final BeanDefinitionRegistry registry;
 
 
-	public ComponentScanAnnotationParser(@Nullable Environment environment, @Nullable ResourceLoader resourceLoader,
+	public ComponentScanAnnotationParser(Environment environment, ResourceLoader resourceLoader,
 			BeanNameGenerator beanNameGenerator, BeanDefinitionRegistry registry) {
 
 		this.environment = environment;
@@ -75,9 +74,6 @@ class ComponentScanAnnotationParser {
 
 
 	public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
-		Assert.state(this.environment != null, "Environment must not be null");
-		Assert.state(this.resourceLoader != null, "ResourceLoader must not be null");
-
 		ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
 				componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);
 

spring-context/src/test/java/org/springframework/jmx/IJmxTestBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,19 +22,19 @@ package org.springframework.jmx;
  */
 public interface IJmxTestBean {
 
-	public int add(int x, int y);
+	int add(int x, int y);
 
-	public long myOperation();
+	long myOperation();
 
-	public int getAge();
+	int getAge();
 
-	public void setAge(int age);
+	void setAge(int age);
 
-	public void setName(String name) throws Exception;
+	void setName(String name) throws Exception;
 
-	public String getName();
+	String getName();
 
 	// used to test invalid methods that exist in the proxy interface
-	public void dontExposeMe();
+	void dontExposeMe();
 
 }

spring-context/src/test/java/org/springframework/remoting/rmi/RmiSupportTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -449,24 +449,21 @@ public class RmiSupportTests {
 	}
 
 
-	public static interface IBusinessBean {
-
-		public void setName(String name);
+	public interface IBusinessBean {
 
+		void setName(String name);
 	}
 
 
-	public static interface IWrongBusinessBean {
-
-		public void setOtherName(String name);
+	public interface IWrongBusinessBean {
 
+		void setOtherName(String name);
 	}
 
 
-	public static interface IRemoteBean extends Remote {
-
-		public void setName(String name) throws RemoteException;
+	public interface IRemoteBean extends Remote {
 
+		void setName(String name) throws RemoteException;
 	}
 
 

spring-core/src/main/java/org/springframework/core/ResolvableType.java

@@ -86,7 +86,7 @@ public class ResolvableType implements Serializable {
 	 * {@code ResolvableType} returned when no value is available. {@code NONE} is used
 	 * in preference to {@code null} so that multiple method calls can be safely chained.
 	 */
-	public static final ResolvableType NONE = new ResolvableType(null, null, null, 0);
+	public static final ResolvableType NONE = new ResolvableType(EmptyType.INSTANCE, null, null, 0);
 
 	private static final ResolvableType[] EMPTY_TYPES_ARRAY = new ResolvableType[0];
 
@@ -95,7 +95,7 @@ public class ResolvableType implements Serializable {
 
 
 	/**
-	 * The underlying Java type being managed (only ever {@code null} for {@link #NONE}).
+	 * The underlying Java type being managed.
 	 */
 	private final Type type;
 
@@ -146,7 +146,7 @@ public class ResolvableType implements Serializable {
 	 * with upfront resolution and a pre-calculated hash.
 	 * @since 4.2
 	 */
-	private ResolvableType(@Nullable Type type, @Nullable TypeProvider typeProvider,
+	private ResolvableType(Type type, @Nullable TypeProvider typeProvider,
 			@Nullable VariableResolver variableResolver, Integer hash) {
 
 		this.type = type;
@@ -188,10 +188,8 @@ public class ResolvableType implements Serializable {
 
 
 	/**
-	 * Return the underling Java {@link Type} being managed. With the exception of
-	 * the {@link #NONE} constant, this method will never return {@code null}.
+	 * Return the underling Java {@link Type} being managed.
 	 */
-	@Nullable
 	public Type getType() {
 		return SerializableTypeWrapper.unwrap(this.type);
 	}
@@ -761,7 +759,10 @@ public class ResolvableType implements Serializable {
 	}
 
 	private Class<?> resolveClass() {
-		if (this.type instanceof Class || this.type == null) {
+		if (this.type == EmptyType.INSTANCE) {
+			return null;
+		}
+		if (this.type instanceof Class) {
 			return (Class<?>) this.type;
 		}
 		if (this.type instanceof GenericArrayType) {
@@ -903,7 +904,7 @@ public class ResolvableType implements Serializable {
 	 * Custom serialization support for {@link #NONE}.
 	 */
 	private Object readResolve() {
-		return (this.type == null ? NONE : this);
+		return (this.type == EmptyType.INSTANCE ? NONE : this);
 	}
 
 	/**
@@ -1567,7 +1568,6 @@ public class ResolvableType implements Serializable {
 				resolveToWildcard = resolveToWildcard.resolveType();
 			}
 			WildcardType wildcardType = (WildcardType) resolveToWildcard.type;
-			Assert.state(wildcardType != null, "Wildcard type not resolved");
 			Kind boundsType = (wildcardType.getLowerBounds().length > 0 ? Kind.LOWER : Kind.UPPER);
 			Type[] bounds = boundsType == Kind.UPPER ? wildcardType.getUpperBounds() : wildcardType.getLowerBounds();
 			ResolvableType[] resolvableBounds = new ResolvableType[bounds.length];
@@ -1583,4 +1583,15 @@ public class ResolvableType implements Serializable {
 		enum Kind {UPPER, LOWER}
 	}
 
+
+	@SuppressWarnings("serial")
+	static class EmptyType implements Type, Serializable {
+
+		static final Type INSTANCE = new EmptyType();
+
+		Object readResolve() {
+			return INSTANCE;
+		}
+	}
+
 }

spring-core/src/main/java/org/springframework/core/SerializableTypeWrapper.java

@@ -37,19 +37,19 @@ import org.springframework.util.ObjectUtils;
 import org.springframework.util.ReflectionUtils;
 
 /**
- * Internal utility class that can be used to obtain wrapped {@link Serializable} variants
- * of {@link java.lang.reflect.Type}s.
+ * Internal utility class that can be used to obtain wrapped {@link Serializable}
+ * variants of {@link java.lang.reflect.Type}s.
  *
  * <p>{@link #forField(Field) Fields} or {@link #forMethodParameter(MethodParameter)
- * MethodParameters} can be used as the root source for a serializable type. Alternatively
- * the {@link #forGenericSuperclass(Class) superclass},
+ * MethodParameters} can be used as the root source for a serializable type.
+ * Alternatively the {@link #forGenericSuperclass(Class) superclass},
  * {@link #forGenericInterfaces(Class) interfaces} or {@link #forTypeParameters(Class)
  * type parameters} or a regular {@link Class} can also be used as source.
  *
  * <p>The returned type will either be a {@link Class} or a serializable proxy of
  * {@link GenericArrayType}, {@link ParameterizedType}, {@link TypeVariable} or
- * {@link WildcardType}. With the exception of {@link Class} (which is final) calls to
- * methods that return further {@link Type}s (for example
+ * {@link WildcardType}. With the exception of {@link Class} (which is final) calls
+ * to methods that return further {@link Type}s (for example
  * {@link GenericArrayType#getGenericComponentType()}) will be automatically wrapped.
  *
  * @author Phillip Webb
@@ -123,13 +123,12 @@ abstract class SerializableTypeWrapper {
 	 * @return the original non-serializable type
 	 */
 	@SuppressWarnings("unchecked")
-	@Nullable
 	public static <T extends Type> T unwrap(T type) {
 		Type unwrapped = type;
 		while (unwrapped instanceof SerializableTypeProxy) {
 			unwrapped = ((SerializableTypeProxy) type).getTypeProvider().getType();
 		}
-		return (T) unwrapped;
+		return (unwrapped != null ? (T) unwrapped : type);
 	}
 
 	/**

spring-core/src/main/java/org/springframework/core/annotation/AnnotatedElementUtils.java

@@ -423,7 +423,7 @@ public class AnnotatedElementUtils {
 
 		// Exhaustive retrieval of merged annotation attributes...
 		AnnotationAttributes attributes = getMergedAnnotationAttributes(element, annotationType);
-		return AnnotationUtils.synthesizeAnnotation(attributes, annotationType, element);
+		return (attributes != null ? AnnotationUtils.synthesizeAnnotation(attributes, annotationType, element) : null);
 	}
 
 	/**
@@ -726,7 +726,7 @@ public class AnnotatedElementUtils {
 
 		// Exhaustive retrieval of merged annotation attributes...
 		AnnotationAttributes attributes = findMergedAnnotationAttributes(element, annotationType, false, false);
-		return AnnotationUtils.synthesizeAnnotation(attributes, annotationType, element);
+		return (attributes != null ? AnnotationUtils.synthesizeAnnotation(attributes, annotationType, element) : null);
 	}
 
 	/**

spring-core/src/main/java/org/springframework/core/annotation/AnnotationUtils.java

@@ -1482,8 +1482,7 @@ public abstract class AnnotationUtils {
 	 * @param annotationType the type of annotation to synthesize
 	 * @param annotatedElement the element that is annotated with the annotation
 	 * corresponding to the supplied attributes; may be {@code null} if unknown
-	 * @return the synthesized annotation, or {@code null} if the supplied attributes
-	 * map is {@code null}
+	 * @return the synthesized annotation
 	 * @throws IllegalArgumentException if a required attribute is missing or if an
 	 * attribute is not of the correct type
 	 * @throws AnnotationConfigurationException if invalid configuration of
@@ -1495,14 +1494,11 @@ public abstract class AnnotationUtils {
 	 * @see #getAnnotationAttributes(AnnotatedElement, Annotation, boolean, boolean)
 	 */
 	@SuppressWarnings("unchecked")
-	@Nullable
-	public static <A extends Annotation> A synthesizeAnnotation(@Nullable Map<String, Object> attributes,
+	public static <A extends Annotation> A synthesizeAnnotation(Map<String, Object> attributes,
 			Class<A> annotationType, @Nullable AnnotatedElement annotatedElement) {
 
+		Assert.notNull(attributes, "'attributes' must not be null");
 		Assert.notNull(annotationType, "'annotationType' must not be null");
-		if (attributes == null) {
-			return null;
-		}
 
 		MapAnnotationAttributeExtractor attributeExtractor =
 				new MapAnnotationAttributeExtractor(attributes, annotationType, annotatedElement);

spring-core/src/main/java/org/springframework/core/style/DefaultToStringStyler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.core.style;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
@@ -77,7 +78,7 @@ public class DefaultToStringStyler implements ToStringStyler {
 	}
 
 	@Override
-	public void styleField(StringBuilder buffer, String fieldName, Object value) {
+	public void styleField(StringBuilder buffer, String fieldName, @Nullable Object value) {
 		styleFieldStart(buffer, fieldName);
 		styleValue(buffer, value);
 		styleFieldEnd(buffer, fieldName);
@@ -91,7 +92,7 @@ public class DefaultToStringStyler implements ToStringStyler {
 	}
 
 	@Override
-	public void styleValue(StringBuilder buffer, Object value) {
+	public void styleValue(StringBuilder buffer, @Nullable Object value) {
 		buffer.append(this.valueStyler.style(value));
 	}
 

spring-core/src/main/java/org/springframework/core/style/ToStringCreator.java

@@ -152,7 +152,7 @@ public class ToStringCreator {
 	 * @param value the field value
 	 * @return this, to support call-chaining
 	 */
-	public ToStringCreator append(String fieldName, Object value) {
+	public ToStringCreator append(String fieldName, @Nullable Object value) {
 		printFieldSeparatorIfNecessary();
 		this.styler.styleField(this.buffer, fieldName, value);
 		return this;

spring-core/src/main/java/org/springframework/core/style/ToStringStyler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.core.style;
 
+import org.springframework.lang.Nullable;
+
 /**
  * A strategy interface for pretty-printing {@code toString()} methods.
  * Encapsulates the print algorithms; some other object such as a builder
@@ -46,7 +48,7 @@ public interface ToStringStyler {
 	 * @param fieldName the he name of the field
 	 * @param value the field value
 	 */
-	void styleField(StringBuilder buffer, String fieldName, Object value);
+	void styleField(StringBuilder buffer, String fieldName, @Nullable Object value);
 
 	/**
 	 * Style the given value.

spring-core/src/main/java/org/springframework/util/CollectionUtils.java

@@ -404,6 +404,12 @@ public abstract class CollectionUtils {
 			this.map = map;
 		}
 
+		@Override
+		public V getFirst(K key) {
+			List<V> values = this.map.get(key);
+			return (values != null ? values.get(0) : null);
+		}
+
 		@Override
 		public void add(K key, @Nullable V value) {
 			List<V> values = this.map.computeIfAbsent(key, k -> new LinkedList<>());
@@ -411,17 +417,11 @@ public abstract class CollectionUtils {
 		}
 
 		@Override
-		public void addAll(K key, List<V> values) {
+		public void addAll(K key, List<? extends V> values) {
 			List<V> currentValues = this.map.computeIfAbsent(key, k -> new LinkedList<>());
 			currentValues.addAll(values);
 		}
 
-		@Override
-		public V getFirst(K key) {
-			List<V> values = this.map.get(key);
-			return (values != null ? values.get(0) : null);
-		}
-
 		@Override
 		public void set(K key, V value) {
 			List<V> values = new LinkedList<>();

spring-core/src/main/java/org/springframework/util/LinkedMultiValueMap.java

@@ -75,6 +75,12 @@ public class LinkedMultiValueMap<K, V> implements MultiValueMap<K, V>, Serializa
 
 	// MultiValueMap implementation
 
+	@Override
+	public V getFirst(K key) {
+		List<V> values = this.targetMap.get(key);
+		return (values != null ? values.get(0) : null);
+	}
+
 	@Override
 	public void add(K key, @Nullable V value) {
 		List<V> values = this.targetMap.computeIfAbsent(key, k -> new LinkedList<>());
@@ -82,17 +88,11 @@ public class LinkedMultiValueMap<K, V> implements MultiValueMap<K, V>, Serializa
 	}
 
 	@Override
-	public void addAll(K key, List<V> values) {
+	public void addAll(K key, List<? extends V> values) {
 		List<V> currentValues = this.targetMap.computeIfAbsent(key, k -> new LinkedList<>());
 		currentValues.addAll(values);
 	}
 
-	@Override
-	public V getFirst(K key) {
-		List<V> values = this.targetMap.get(key);
-		return (values != null ? values.get(0) : null);
-	}
-
 	@Override
 	public void set(K key, V value) {
 		List<V> values = new LinkedList<>();

spring-core/src/main/java/org/springframework/util/MultiValueMap.java

@@ -32,7 +32,7 @@ public interface MultiValueMap<K, V> extends Map<K, List<V>> {
 	/**
 	 * Return the first value for the given key.
 	 * @param key the key
-	 * @return the first value for the specified key, or {@code null}
+	 * @return the first value for the specified key, or {@code null} if none
 	 */
 	@Nullable
 	V getFirst(K key);
@@ -50,7 +50,7 @@ public interface MultiValueMap<K, V> extends Map<K, List<V>> {
 	 * @param values the values to be added
 	 * @since 5.0
 	 */
-	void addAll(K key, List<V> values);
+	void addAll(K key, List<? extends V> values);
 
 	/**
 	 * Set the given single value under the given key.

spring-core/src/main/java/org/springframework/util/ReflectionUtils.java

@@ -119,7 +119,7 @@ public abstract class ReflectionUtils {
 	 * @param target the target object on which to set the field
 	 * @param value the value to set (may be {@code null})
 	 */
-	public static void setField(Field field, Object target, @Nullable Object value) {
+	public static void setField(Field field, @Nullable Object target, @Nullable Object value) {
 		try {
 			field.set(target, value);
 		}

spring-core/src/test/java/org/springframework/core/ResolvableTypeTests.java

@@ -56,6 +56,7 @@ import org.springframework.util.MultiValueMap;
 
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
+import static org.mockito.BDDMockito.any;
 import static org.mockito.BDDMockito.*;
 
 /**
@@ -86,7 +87,7 @@ public class ResolvableTypeTests {
 		assertThat(none.getGenerics().length, equalTo(0));
 		assertThat(none.getInterfaces().length, equalTo(0));
 		assertThat(none.getSuperType(), equalTo(ResolvableType.NONE));
-		assertThat(none.getType(), nullValue());
+		assertThat(none.getType(), equalTo(ResolvableType.EmptyType.INSTANCE));
 		assertThat(none.hasGenerics(), equalTo(false));
 		assertThat(none.isArray(), equalTo(false));
 		assertThat(none.resolve(), nullValue());

spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/InvocableHandlerMethod.java

@@ -28,7 +28,6 @@ import org.springframework.core.ResolvableType;
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.handler.HandlerMethod;
-import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
 
@@ -289,9 +288,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 
 		@Override
 		public Type getGenericParameterType() {
-			Type returnType = this.returnType.getType();
-			Assert.state(returnType != null, "No return type");
-			return returnType;
+			return this.returnType.getType();
 		}
 
 		@Override

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompHeaders.java

@@ -417,7 +417,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	}
 
 	@Override
-	public void addAll(String headerName, List<String> headerValues) {
+	public void addAll(String headerName, List<? extends String> headerValues) {
 		List<String> currentValues = headers.computeIfAbsent(headerName, k -> new LinkedList<>());
 		currentValues.addAll(headerValues);
 	}

spring-test/src/main/java/org/springframework/mock/http/client/MockClientHttpResponse.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -72,10 +72,7 @@ public class MockClientHttpResponse extends MockHttpInputMessage implements Clie
 	@Override
 	public void close() {
 		try {
-			InputStream body = getBody();
-			if (body != null) {
-				body.close();
-			}
+			getBody().close();
 		}
 		catch (IOException ex) {
 			// ignore

spring-test/src/main/java/org/springframework/mock/http/server/reactive/MockServerHttpRequest.java

@@ -72,7 +72,7 @@ public class MockServerHttpRequest extends AbstractServerHttpRequest {
 
 		super(uri, headers);
 		this.httpMethod = httpMethod;
-		this.contextPath = (contextPath != null ? contextPath : "");
+		this.contextPath = contextPath;
 		this.cookies = cookies;
 		this.remoteAddress = remoteAddress;
 		this.body = Flux.from(body);

spring-test/src/main/java/org/springframework/mock/jndi/SimpleNamingContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,6 +33,7 @@ import javax.naming.OperationNotSupportedException;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
 /**
@@ -80,7 +81,9 @@ public class SimpleNamingContext implements Context {
 	 * Create a new naming context with the given naming root,
 	 * the given name/object map, and the JNDI environment entries.
 	 */
-	public SimpleNamingContext(String root, Hashtable<String, Object> boundObjects, Hashtable<String, Object> env) {
+	public SimpleNamingContext(
+			String root, Hashtable<String, Object> boundObjects, @Nullable Hashtable<String, Object> env) {
+
 		this.root = root;
 		this.boundObjects = boundObjects;
 		if (env != null) {

spring-test/src/main/java/org/springframework/mock/jndi/SimpleNamingContextBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,6 @@
 package org.springframework.mock.jndi;
 
 import java.util.Hashtable;
-
 import javax.naming.Context;
 import javax.naming.NamingException;
 import javax.naming.spi.InitialContextFactory;
@@ -195,7 +194,7 @@ public class SimpleNamingContextBuilder implements InitialContextFactoryBuilder
 	 * @see SimpleNamingContext
 	 */
 	@Override
-	public InitialContextFactory createInitialContextFactory(Hashtable<?,?> environment) {
+	public InitialContextFactory createInitialContextFactory(@Nullable Hashtable<?,?> environment) {
 		if (activated == null && environment != null) {
 			Object icf = environment.get(Context.INITIAL_CONTEXT_FACTORY);
 			if (icf != null) {

spring-test/src/main/java/org/springframework/mock/web/HeaderValueHolder.java

@@ -68,10 +68,12 @@ class HeaderValueHolder {
 		return Collections.unmodifiableList(stringList);
 	}
 
+	@Nullable
 	public Object getValue() {
 		return (!this.values.isEmpty() ? this.values.get(0) : null);
 	}
 
+	@Nullable
 	public String getStringValue() {
 		return (!this.values.isEmpty() ? String.valueOf(this.values.get(0)) : null);
 	}

spring-test/src/main/java/org/springframework/mock/web/MockAsyncContext.java

@@ -55,7 +55,7 @@ public class MockAsyncContext implements AsyncContext {
 	private final List<Runnable> dispatchHandlers = new ArrayList<>();
 
 
-	public MockAsyncContext(ServletRequest request, ServletResponse response) {
+	public MockAsyncContext(ServletRequest request, @Nullable ServletResponse response) {
 		this.request = (HttpServletRequest) request;
 		this.response = (HttpServletResponse) response;
 	}

spring-test/src/main/java/org/springframework/mock/web/MockBodyContent.java

@@ -24,6 +24,8 @@ import javax.servlet.http.HttpServletResponse;
 import javax.servlet.jsp.JspWriter;
 import javax.servlet.jsp.tagext.BodyContent;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Mock implementation of the {@link javax.servlet.jsp.tagext.BodyContent} class.
  * Only necessary for testing applications when testing custom JSP tags.
@@ -60,12 +62,12 @@ public class MockBodyContent extends BodyContent {
 	 * @param response the servlet response to wrap
 	 * @param targetWriter the target Writer to wrap
 	 */
-	public MockBodyContent(String content, HttpServletResponse response, Writer targetWriter) {
+	public MockBodyContent(String content, @Nullable HttpServletResponse response, @Nullable Writer targetWriter) {
 		super(adaptJspWriter(targetWriter, response));
 		this.content = content;
 	}
 
-	private static JspWriter adaptJspWriter(Writer targetWriter, HttpServletResponse response) {
+	private static JspWriter adaptJspWriter(@Nullable Writer targetWriter, @Nullable HttpServletResponse response) {
 		if (targetWriter instanceof JspWriter) {
 			return (JspWriter) targetWriter;
 		}

spring-test/src/main/java/org/springframework/mock/web/MockFilterConfig.java

@@ -23,6 +23,7 @@ import java.util.Map;
 import javax.servlet.FilterConfig;
 import javax.servlet.ServletContext;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -64,7 +65,7 @@ public class MockFilterConfig implements FilterConfig {
 	 * Create a new MockFilterConfig.
 	 * @param servletContext the ServletContext that the servlet runs in
 	 */
-	public MockFilterConfig(ServletContext servletContext) {
+	public MockFilterConfig(@Nullable ServletContext servletContext) {
 		this(servletContext, "");
 	}
 
@@ -73,7 +74,7 @@ public class MockFilterConfig implements FilterConfig {
 	 * @param servletContext the ServletContext that the servlet runs in
 	 * @param filterName the name of the filter
 	 */
-	public MockFilterConfig(ServletContext servletContext, String filterName) {
+	public MockFilterConfig(@Nullable ServletContext servletContext, String filterName) {
 		this.servletContext = (servletContext != null ? servletContext : new MockServletContext());
 		this.filterName = filterName;
 	}

spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -41,7 +41,6 @@ import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.TimeZone;
-
 import javax.servlet.AsyncContext;
 import javax.servlet.DispatcherType;
 import javax.servlet.RequestDispatcher;
@@ -64,6 +63,7 @@ import org.springframework.util.Assert;
 import org.springframework.util.LinkedCaseInsensitiveMap;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StreamUtils;
 import org.springframework.util.StringUtils;
 
@@ -370,6 +370,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public String getCharacterEncoding() {
 		return this.characterEncoding;
 	}
@@ -449,7 +450,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 		return getContentLength();
 	}
 
-	public void setContentType(String contentType) {
+	public void setContentType(@Nullable String contentType) {
 		this.contentType = contentType;
 		if (contentType != null) {
 			try {
@@ -470,6 +471,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public String getContentType() {
 		return this.contentType;
 	}
@@ -530,7 +532,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	 * <p>If there are already one or more values registered for the given
 	 * parameter name, the given value will be added to the end of the list.
 	 */
-	public void addParameter(String name, String value) {
+	public void addParameter(String name, @Nullable String value) {
 		addParameter(name, new String[] {value});
 	}
 
@@ -591,8 +593,10 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public String getParameter(String name) {
-		String[] arr = (name != null ? this.parameters.get(name) : null);
+		Assert.notNull(name, "Parameter name must not be null");
+		String[] arr = this.parameters.get(name);
 		return (arr != null && arr.length > 0 ? arr[0] : null);
 	}
 
@@ -603,7 +607,8 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	@Override
 	public String[] getParameterValues(String name) {
-		return (name != null ? this.parameters.get(name) : null);
+		Assert.notNull(name, "Parameter name must not be null");
+		return this.parameters.get(name);
 	}
 
 	@Override
@@ -709,7 +714,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
-	public void setAttribute(String name, Object value) {
+	public void setAttribute(String name, @Nullable Object value) {
 		checkActive();
 		Assert.notNull(name, "Attribute name must not be null");
 		if (value != null) {
@@ -903,6 +908,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public AsyncContext getAsyncContext() {
 		return this.asyncContext;
 	}
@@ -930,17 +936,18 @@ public class MockHttpServletRequest implements HttpServletRequest {
 		return this.authType;
 	}
 
-	public void setCookies(Cookie... cookies) {
-		this.cookies = cookies;
+	public void setCookies(@Nullable Cookie... cookies) {
+		this.cookies = (ObjectUtils.isEmpty(cookies) ? null : cookies);
 		this.headers.remove(HttpHeaders.COOKIE);
-		if (cookies != null) {
-			Arrays.stream(cookies)
+		if (this.cookies != null) {
+			Arrays.stream(this.cookies)
 					.map(c -> c.getName() + '=' + (c.getValue() == null ? "" : c.getValue()))
 					.forEach(value -> doAddHeaderValue(HttpHeaders.COOKIE, value, false));
 		}
 	}
 
 	@Override
+	@Nullable
 	public Cookie[] getCookies() {
 		return this.cookies;
 	}
@@ -978,7 +985,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 		}
 	}
 
-	private void doAddHeaderValue(String name, Object value, boolean replace) {
+	private void doAddHeaderValue(String name, @Nullable Object value, boolean replace) {
 		HeaderValueHolder header = HeaderValueHolder.getByName(this.headers, name);
 		Assert.notNull(value, "Header value must not be null");
 		if (header == null || replace) {
@@ -1045,6 +1052,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public String getHeader(String name) {
 		HeaderValueHolder header = HeaderValueHolder.getByName(this.headers, name);
 		return (header != null ? header.getStringValue() : null);
@@ -1098,6 +1106,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public String getPathTranslated() {
 		return (this.pathInfo != null ? getRealPath(this.pathInfo) : null);
 	}
@@ -1111,7 +1120,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 		return this.contextPath;
 	}
 
-	public void setQueryString(String queryString) {
+	public void setQueryString(@Nullable String queryString) {
 		this.queryString = queryString;
 	}
 
@@ -1120,7 +1129,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 		return this.queryString;
 	}
 
-	public void setRemoteUser(String remoteUser) {
+	public void setRemoteUser(@Nullable String remoteUser) {
 		this.remoteUser = remoteUser;
 	}
 
@@ -1197,6 +1206,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public HttpSession getSession(boolean create) {
 		checkActive();
 		// Reset session if invalidated.
@@ -1211,6 +1221,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public HttpSession getSession() {
 		return getSession(true);
 	}
@@ -1284,6 +1295,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
+	@Nullable
 	public Part getPart(String name) throws IOException, IllegalStateException, ServletException {
 		return this.parts.getFirst(name);
 	}

spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java

@@ -33,7 +33,6 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.TimeZone;
-
 import javax.servlet.ServletOutputStream;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletResponse;
@@ -171,6 +170,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	}
 
 	@Override
+	@Nullable
 	public String getCharacterEncoding() {
 		return this.characterEncoding;
 	}
@@ -224,7 +224,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	}
 
 	@Override
-	public void setContentType(String contentType) {
+	public void setContentType(@Nullable String contentType) {
 		this.contentType = contentType;
 		if (contentType != null) {
 			try {
@@ -247,6 +247,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	}
 
 	@Override
+	@Nullable
 	public String getContentType() {
 		return this.contentType;
 	}
@@ -302,7 +303,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	}
 
 	@Override
-	public void setLocale(Locale locale) {
+	public void setLocale(@Nullable Locale locale) {
 		this.locale = locale;
 		if (locale != null) {
 			doAddHeaderValue(HttpHeaders.ACCEPT_LANGUAGE, locale.toLanguageTag(), true);
@@ -357,6 +358,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		return this.cookies.toArray(new Cookie[this.cookies.size()]);
 	}
 
+	@Nullable
 	public Cookie getCookie(String name) {
 		Assert.notNull(name, "Cookie name must not be null");
 		for (Cookie cookie : this.cookies) {
@@ -502,6 +504,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		setCommitted(true);
 	}
 
+	@Nullable
 	public String getRedirectedUrl() {
 		return getHeader(HttpHeaders.LOCATION);
 	}
@@ -639,17 +642,19 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		this.forwardedUrl = forwardedUrl;
 	}
 
+	@Nullable
 	public String getForwardedUrl() {
 		return this.forwardedUrl;
 	}
 
-	public void setIncludedUrl(String includedUrl) {
+	public void setIncludedUrl(@Nullable String includedUrl) {
 		this.includedUrls.clear();
 		if (includedUrl != null) {
 			this.includedUrls.add(includedUrl);
 		}
 	}
 
+	@Nullable
 	public String getIncludedUrl() {
 		int count = this.includedUrls.size();
 		Assert.state(count <= 1,

spring-test/src/main/java/org/springframework/mock/web/MockHttpSession.java

@@ -29,6 +29,7 @@ import javax.servlet.http.HttpSession;
 import javax.servlet.http.HttpSessionBindingEvent;
 import javax.servlet.http.HttpSessionBindingListener;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -79,7 +80,7 @@ public class MockHttpSession implements HttpSession {
 	 * Create a new MockHttpSession.
 	 * @param servletContext the ServletContext that the session runs in
 	 */
-	public MockHttpSession(ServletContext servletContext) {
+	public MockHttpSession(@Nullable ServletContext servletContext) {
 		this(servletContext, null);
 	}
 
@@ -88,7 +89,7 @@ public class MockHttpSession implements HttpSession {
 	 * @param servletContext the ServletContext that the session runs in
 	 * @param id a unique identifier for this session
 	 */
-	public MockHttpSession(ServletContext servletContext, String id) {
+	public MockHttpSession(@Nullable ServletContext servletContext, @Nullable String id) {
 		this.servletContext = (servletContext != null ? servletContext : new MockServletContext());
 		this.id = (id != null ? id : Integer.toString(nextId++));
 	}
@@ -171,7 +172,7 @@ public class MockHttpSession implements HttpSession {
 	}
 
 	@Override
-	public void setAttribute(String name, Object value) {
+	public void setAttribute(String name, @Nullable Object value) {
 		assertIsValid();
 		Assert.notNull(name, "Attribute name must not be null");
 		if (value != null) {

spring-test/src/main/java/org/springframework/mock/web/MockJspWriter.java

@@ -22,6 +22,8 @@ import java.io.Writer;
 import javax.servlet.http.HttpServletResponse;
 import javax.servlet.jsp.JspWriter;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Mock implementation of the {@link javax.servlet.jsp.JspWriter} class.
  * Only necessary for testing applications when testing custom JSP tags.
@@ -58,7 +60,7 @@ public class MockJspWriter extends JspWriter {
 	 * @param response the servlet response to wrap
 	 * @param targetWriter the target Writer to wrap
 	 */
-	public MockJspWriter(HttpServletResponse response, Writer targetWriter) {
+	public MockJspWriter(@Nullable HttpServletResponse response, @Nullable Writer targetWriter) {
 		super(DEFAULT_BUFFER, true);
 		this.response = (response != null ? response : new MockHttpServletResponse());
 		if (targetWriter instanceof PrintWriter) {

spring-test/src/main/java/org/springframework/mock/web/MockMultipartFile.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,6 +21,7 @@ import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.FileCopyUtils;
 import org.springframework.web.multipart.MultipartFile;
@@ -53,7 +54,7 @@ public class MockMultipartFile implements MultipartFile {
 	 * @param name the name of the file
 	 * @param content the content of the file
 	 */
-	public MockMultipartFile(String name, byte[] content) {
+	public MockMultipartFile(String name, @Nullable byte[] content) {
 		this(name, "", null, content);
 	}
 
@@ -74,7 +75,9 @@ public class MockMultipartFile implements MultipartFile {
 	 * @param contentType the content type (if known)
 	 * @param content the content of the file
 	 */
-	public MockMultipartFile(String name, String originalFilename, String contentType, byte[] content) {
+	public MockMultipartFile(
+			String name, @Nullable String originalFilename, @Nullable String contentType, @Nullable byte[] content) {
+
 		Assert.hasLength(name, "Name must not be null");
 		this.name = name;
 		this.originalFilename = (originalFilename != null ? originalFilename : "");
@@ -90,7 +93,8 @@ public class MockMultipartFile implements MultipartFile {
 	 * @param contentStream the content of the file as stream
 	 * @throws IOException if reading from the stream failed
 	 */
-	public MockMultipartFile(String name, String originalFilename, String contentType, InputStream contentStream)
+	public MockMultipartFile(
+			String name, @Nullable String originalFilename, @Nullable String contentType, InputStream contentStream)
 			throws IOException {
 
 		this(name, originalFilename, contentType, FileCopyUtils.copyToByteArray(contentStream));

spring-test/src/main/java/org/springframework/mock/web/MockPageContext.java

@@ -36,6 +36,7 @@ import javax.servlet.http.HttpSession;
 import javax.servlet.jsp.JspWriter;
 import javax.servlet.jsp.PageContext;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -79,7 +80,7 @@ public class MockPageContext extends PageContext {
 	 * @param servletContext the ServletContext that the JSP page runs in
 	 * (only necessary when actually accessing the ServletContext)
 	 */
-	public MockPageContext(ServletContext servletContext) {
+	public MockPageContext(@Nullable ServletContext servletContext) {
 		this(servletContext, null, null, null);
 	}
 
@@ -90,7 +91,7 @@ public class MockPageContext extends PageContext {
 	 * @param request the current HttpServletRequest
 	 * (only necessary when actually accessing the request)
 	 */
-	public MockPageContext(ServletContext servletContext, HttpServletRequest request) {
+	public MockPageContext(@Nullable ServletContext servletContext, @Nullable HttpServletRequest request) {
 		this(servletContext, request, null, null);
 	}
 
@@ -101,7 +102,9 @@ public class MockPageContext extends PageContext {
 	 * @param response the current HttpServletResponse
 	 * (only necessary when actually writing to the response)
 	 */
-	public MockPageContext(ServletContext servletContext, HttpServletRequest request, HttpServletResponse response) {
+	public MockPageContext(@Nullable ServletContext servletContext, @Nullable HttpServletRequest request,
+			@Nullable HttpServletResponse response) {
+
 		this(servletContext, request, response, null);
 	}
 
@@ -112,8 +115,8 @@ public class MockPageContext extends PageContext {
 	 * @param response the current HttpServletResponse
 	 * @param servletConfig the ServletConfig (hardly ever accessed from within a tag)
 	 */
-	public MockPageContext(ServletContext servletContext, HttpServletRequest request,
-			HttpServletResponse response, ServletConfig servletConfig) {
+	public MockPageContext(@Nullable ServletContext servletContext, @Nullable HttpServletRequest request,
+			@Nullable HttpServletResponse response, @Nullable ServletConfig servletConfig) {
 
 		this.servletContext = (servletContext != null ? servletContext : new MockServletContext());
 		this.request = (request != null ? request : new MockHttpServletRequest(servletContext));
@@ -135,7 +138,7 @@ public class MockPageContext extends PageContext {
 	}
 
 	@Override
-	public void setAttribute(String name, Object value) {
+	public void setAttribute(String name, @Nullable Object value) {
 		Assert.notNull(name, "Attribute name must not be null");
 		if (value != null) {
 			this.attributes.put(name, value);
@@ -146,7 +149,7 @@ public class MockPageContext extends PageContext {
 	}
 
 	@Override
-	public void setAttribute(String name, Object value, int scope) {
+	public void setAttribute(String name, @Nullable Object value, int scope) {
 		Assert.notNull(name, "Attribute name must not be null");
 		switch (scope) {
 			case PAGE_SCOPE:
@@ -167,12 +170,14 @@ public class MockPageContext extends PageContext {
 	}
 
 	@Override
+	@Nullable
 	public Object getAttribute(String name) {
 		Assert.notNull(name, "Attribute name must not be null");
 		return this.attributes.get(name);
 	}
 
 	@Override
+	@Nullable
 	public Object getAttribute(String name, int scope) {
 		Assert.notNull(name, "Attribute name must not be null");
 		switch (scope) {
@@ -191,6 +196,7 @@ public class MockPageContext extends PageContext {
 	}
 
 	@Override
+	@Nullable
 	public Object findAttribute(String name) {
 		Object value = getAttribute(name);
 		if (value == null) {
@@ -267,7 +273,7 @@ public class MockPageContext extends PageContext {
 				return this.request.getAttributeNames();
 			case SESSION_SCOPE:
 				HttpSession session = this.request.getSession(false);
-				return (session != null ? session.getAttributeNames() : null);
+				return (session != null ? session.getAttributeNames() : Collections.emptyEnumeration());
 			case APPLICATION_SCOPE:
 				return this.servletContext.getAttributeNames();
 			default:
@@ -290,12 +296,14 @@ public class MockPageContext extends PageContext {
 	}
 
 	@Override
+	@Nullable
 	public ELContext getELContext() {
 		return null;
 	}
 
 	@Override
 	@Deprecated
+	@Nullable
 	public javax.servlet.jsp.el.VariableResolver getVariableResolver() {
 		return null;
 	}
@@ -321,6 +329,7 @@ public class MockPageContext extends PageContext {
 	}
 
 	@Override
+	@Nullable
 	public Exception getException() {
 		return null;
 	}

spring-test/src/main/java/org/springframework/mock/web/MockPart.java

@@ -20,14 +20,15 @@ import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Collection;
+import java.util.Collections;
 import javax.servlet.http.Part;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.FileCopyUtils;
 
-
 /**
  * Mock implementation of {@code javax.servlet.http.Part}.
  *
@@ -55,7 +56,7 @@ public class MockPart implements Part {
 	/**
 	 * Constructor for a part with a filename.
 	 */
-	public MockPart(String name, String filename, InputStream content) throws IOException {
+	public MockPart(String name, @Nullable String filename, InputStream content) throws IOException {
 		this(name, filename, FileCopyUtils.copyToByteArray(content));
 	}
 
@@ -63,7 +64,7 @@ public class MockPart implements Part {
 	 * Constructor for a part with byte[] content only.
 	 * @see #getHeaders()
 	 */
-	private MockPart(String name, String filename, byte[] content) {
+	private MockPart(String name, @Nullable String filename, @Nullable byte[] content) {
 		Assert.hasLength(name, "Name must not be null");
 		this.name = name;
 		this.filename = filename;
@@ -83,6 +84,7 @@ public class MockPart implements Part {
 	}
 
 	@Override
+	@Nullable
 	public String getContentType() {
 		MediaType contentType = this.headers.getContentType();
 		return (contentType != null ? contentType.toString() : null);
@@ -99,13 +101,15 @@ public class MockPart implements Part {
 	}
 
 	@Override
+	@Nullable
 	public String getHeader(String name) {
 		return this.headers.getFirst(name);
 	}
 
 	@Override
 	public Collection<String> getHeaders(String name) {
-		return this.headers.get(name);
+		Collection<String> headerValues = this.headers.get(name);
+		return (headerValues != null ? headerValues : Collections.emptyList());
 	}
 
 	@Override

spring-test/src/main/java/org/springframework/mock/web/MockServletConfig.java

@@ -23,6 +23,7 @@ import java.util.Map;
 import javax.servlet.ServletConfig;
 import javax.servlet.ServletContext;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -60,7 +61,7 @@ public class MockServletConfig implements ServletConfig {
 	 * Create a new MockServletConfig.
 	 * @param servletContext the ServletContext that the servlet runs in
 	 */
-	public MockServletConfig(ServletContext servletContext) {
+	public MockServletConfig(@Nullable ServletContext servletContext) {
 		this(servletContext, "");
 	}
 
@@ -69,7 +70,7 @@ public class MockServletConfig implements ServletConfig {
 	 * @param servletContext the ServletContext that the servlet runs in
 	 * @param servletName the name of the servlet
 	 */
-	public MockServletConfig(ServletContext servletContext, String servletName) {
+	public MockServletConfig(@Nullable ServletContext servletContext, String servletName) {
 		this.servletContext = (servletContext != null ? servletContext : new MockServletContext());
 		this.servletName = servletName;
 	}

spring-test/src/main/java/org/springframework/mock/web/MockServletContext.java

@@ -182,7 +182,7 @@ public class MockServletContext implements ServletContext {
 	 */
 	public MockServletContext(String resourceBasePath, @Nullable ResourceLoader resourceLoader) {
 		this.resourceLoader = (resourceLoader != null ? resourceLoader : new DefaultResourceLoader());
-		this.resourceBasePath = (resourceBasePath != null ? resourceBasePath : "");
+		this.resourceBasePath = resourceBasePath;
 
 		// Use JVM temp dir as ServletContext temp dir.
 		String tempDir = System.getProperty(TEMP_DIR_SYSTEM_PROPERTY);
@@ -207,7 +207,7 @@ public class MockServletContext implements ServletContext {
 	}
 
 	public void setContextPath(String contextPath) {
-		this.contextPath = (contextPath != null ? contextPath : "");
+		this.contextPath = contextPath;
 	}
 
 	@Override
@@ -287,6 +287,7 @@ public class MockServletContext implements ServletContext {
 	}
 
 	@Override
+	@Nullable
 	public Set<String> getResourcePaths(String path) {
 		String actualPath = (path.endsWith("/") ? path : path + "/");
 		Resource resource = this.resourceLoader.getResource(getResourceLocation(actualPath));
@@ -313,6 +314,7 @@ public class MockServletContext implements ServletContext {
 	}
 
 	@Override
+	@Nullable
 	public URL getResource(String path) throws MalformedURLException {
 		Resource resource = this.resourceLoader.getResource(getResourceLocation(path));
 		if (!resource.exists()) {
@@ -331,6 +333,7 @@ public class MockServletContext implements ServletContext {
 	}
 
 	@Override
+	@Nullable
 	public InputStream getResourceAsStream(String path) {
 		Resource resource = this.resourceLoader.getResource(getResourceLocation(path));
 		if (!resource.exists()) {
@@ -410,6 +413,7 @@ public class MockServletContext implements ServletContext {
 
 	@Override
 	@Deprecated
+	@Nullable
 	public Servlet getServlet(String name) {
 		return null;
 	}
@@ -443,6 +447,7 @@ public class MockServletContext implements ServletContext {
 	}
 
 	@Override
+	@Nullable
 	public String getRealPath(String path) {
 		Resource resource = this.resourceLoader.getResource(getResourceLocation(path));
 		try {
@@ -486,6 +491,7 @@ public class MockServletContext implements ServletContext {
 	}
 
 	@Override
+	@Nullable
 	public Object getAttribute(String name) {
 		Assert.notNull(name, "Attribute name must not be null");
 		return this.attributes.get(name);
@@ -497,7 +503,7 @@ public class MockServletContext implements ServletContext {
 	}
 
 	@Override
-	public void setAttribute(String name, Object value) {
+	public void setAttribute(String name, @Nullable Object value) {
 		Assert.notNull(name, "Attribute name must not be null");
 		if (value != null) {
 			this.attributes.put(name, value);
@@ -523,6 +529,7 @@ public class MockServletContext implements ServletContext {
 	}
 
 	@Override
+	@Nullable
 	public ClassLoader getClassLoader() {
 		return ClassUtils.getDefaultClassLoader();
 	}

spring-test/src/main/java/org/springframework/mock/web/reactive/function/server/MockServerRequest.java

@@ -47,6 +47,7 @@ import org.springframework.web.server.WebSession;
 
 /**
  * Mock implementation of {@link ServerRequest}.
+ *
  * @author Arjen Poutsma
  * @since 5.0
  */
@@ -70,9 +71,9 @@ public class MockServerRequest implements ServerRequest {
 
 	private Principal principal;
 
-	private MockServerRequest(HttpMethod method, URI uri,
-			MockHeaders headers, @Nullable Object body, Map<String, Object> attributes,
-			MultiValueMap<String, String> queryParams,
+
+	private MockServerRequest(HttpMethod method, URI uri, MockHeaders headers, @Nullable Object body,
+			Map<String, Object> attributes, MultiValueMap<String, String> queryParams,
 			Map<String, String> pathVariables, WebSession session, Principal principal) {
 
 		this.method = method;
@@ -104,25 +105,29 @@ public class MockServerRequest implements ServerRequest {
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public <S> S body(BodyExtractor<S, ? super ServerHttpRequest> extractor){
+	public <S> S body(BodyExtractor<S, ? super ServerHttpRequest> extractor) {
+		Assert.state(this.body != null, "No body");
 		return (S) this.body;
 	}
 
 	@Override
 	@SuppressWarnings("unchecked")
 	public <S> S body(BodyExtractor<S, ? super ServerHttpRequest> extractor, Map<String, Object> hints) {
+		Assert.state(this.body != null, "No body");
 		return (S) this.body;
 	}
 
 	@Override
 	@SuppressWarnings("unchecked")
 	public <S> Mono<S> bodyToMono(Class<? extends S> elementClass) {
+		Assert.state(this.body != null, "No body");
 		return (Mono<S>) this.body;
 	}
 
 	@Override
 	@SuppressWarnings("unchecked")
 	public <S> Flux<S> bodyToFlux(Class<? extends S> elementClass) {
+		Assert.state(this.body != null, "No body");
 		return (Flux<S>) this.body;
 	}
 

spring-test/src/main/java/org/springframework/test/annotation/ProfileValueUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -77,6 +77,7 @@ public abstract class ProfileValueUtils {
 		}
 		else {
 			profileValueSourceType = (Class<? extends ProfileValueSource>) AnnotationUtils.getDefaultValue(annotationType);
+			Assert.state(profileValueSourceType != null, "No default ProfileValueSource class");
 		}
 		if (logger.isDebugEnabled()) {
 			logger.debug("Retrieved ProfileValueSource type [" + profileValueSourceType + "] for class [" +

spring-test/src/main/java/org/springframework/test/context/ContextConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -158,7 +158,7 @@ public @interface ContextConfiguration {
 	 * @see #inheritInitializers
 	 * @see #loader
 	 */
-	Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>[] initializers() default {};
+	Class<? extends ApplicationContextInitializer<?>>[] initializers() default {};
 
 	/**
 	 * Whether or not {@link #locations resource locations} or <em>annotated

spring-test/src/main/java/org/springframework/test/context/ContextConfigurationAttributes.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -58,7 +58,7 @@ public class ContextConfigurationAttributes {
 
 	private final boolean inheritLocations;
 
-	private final Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>[] initializers;
+	private final Class<? extends ApplicationContextInitializer<?>>[] initializers;
 
 	private final boolean inheritInitializers;
 
@@ -101,9 +101,10 @@ public class ContextConfigurationAttributes {
 	 */
 	@SuppressWarnings("unchecked")
 	public ContextConfigurationAttributes(Class<?> declaringClass, AnnotationAttributes annAttrs) {
-		this(declaringClass, annAttrs.getStringArray("locations"), annAttrs.getClassArray("classes"), annAttrs.getBoolean("inheritLocations"),
-				(Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>[]) annAttrs.getClassArray("initializers"),
-				annAttrs.getBoolean("inheritInitializers"), annAttrs.getString("name"), (Class<? extends ContextLoader>) annAttrs.getClass("loader"));
+		this(declaringClass, annAttrs.getStringArray("locations"), annAttrs.getClassArray("classes"),
+				annAttrs.getBoolean("inheritLocations"),
+				(Class<? extends ApplicationContextInitializer<?>>[]) annAttrs.getClassArray("initializers"),
+				annAttrs.getBoolean("inheritInitializers"), annAttrs.getString("name"), annAttrs.getClass("loader"));
 	}
 
 	/**
@@ -123,7 +124,7 @@ public class ContextConfigurationAttributes {
 	 */
 	public ContextConfigurationAttributes(
 			Class<?> declaringClass, String[] locations, Class<?>[] classes, boolean inheritLocations,
-			Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>[] initializers,
+			Class<? extends ApplicationContextInitializer<?>>[] initializers,
 			boolean inheritInitializers, Class<? extends ContextLoader> contextLoaderClass) {
 
 		this(declaringClass, locations, classes, inheritLocations, initializers, inheritInitializers, null,
@@ -148,11 +149,11 @@ public class ContextConfigurationAttributes {
 	 */
 	public ContextConfigurationAttributes(
 			Class<?> declaringClass, String[] locations, Class<?>[] classes, boolean inheritLocations,
-			Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>[] initializers,
-			boolean inheritInitializers, String name, Class<? extends ContextLoader> contextLoaderClass) {
+			Class<? extends ApplicationContextInitializer<?>>[] initializers,
+			boolean inheritInitializers, @Nullable String name, Class<? extends ContextLoader> contextLoaderClass) {
 
-		Assert.notNull(declaringClass, "declaringClass must not be null");
-		Assert.notNull(contextLoaderClass, "contextLoaderClass must not be null");
+		Assert.notNull(declaringClass, "'declaringClass' must not be null");
+		Assert.notNull(contextLoaderClass, "'contextLoaderClass' must not be null");
 
 		if (!ObjectUtils.isEmpty(locations) && !ObjectUtils.isEmpty(classes) && logger.isDebugEnabled()) {
 			logger.debug(String.format(
@@ -199,13 +200,12 @@ public class ContextConfigurationAttributes {
 	 * <p>Note: this is a mutable property. The returned value may therefore
 	 * represent a <em>processed</em> value that does not match the original value
 	 * declared via {@link ContextConfiguration @ContextConfiguration}.
-	 * @return the annotated classes; potentially {@code null} or <em>empty</em>
+	 * @return the annotated classes (potentially {<em>empty</em>)
 	 * @see ContextConfiguration#classes
 	 * @see #setClasses(Class[])
 	 */
-	@Nullable
 	public Class<?>[] getClasses() {
-		return this.classes;
+		return (this.classes != null ? this.classes : new Class<?>[0]);
 	}
 
 	/**
@@ -234,14 +234,13 @@ public class ContextConfigurationAttributes {
 	 * <p>Note: this is a mutable property. The returned value may therefore
 	 * represent a <em>processed</em> value that does not match the original value
 	 * declared via {@link ContextConfiguration @ContextConfiguration}.
-	 * @return the resource locations; potentially {@code null} or <em>empty</em>
+	 * @return the resource locations (potentially <em>empty</em>)
 	 * @see ContextConfiguration#value
 	 * @see ContextConfiguration#locations
-	 * @see #setLocations(String[])
+	 * @see #setLocations
 	 */
-	@Nullable
 	public String[] getLocations() {
-		return this.locations;
+		return (this.locations != null ? this.locations : new String[0]);
 	}
 
 	/**
@@ -283,7 +282,7 @@ public class ContextConfigurationAttributes {
 	 * @return the {@code ApplicationContextInitializer} classes
 	 * @since 3.2
 	 */
-	public Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>[] getInitializers() {
+	public Class<? extends ApplicationContextInitializer<?>>[] getInitializers() {
 		return this.initializers;
 	}
 

spring-test/src/main/java/org/springframework/test/context/ContextLoader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -60,7 +60,7 @@ public interface ContextLoader {
 	 * application context (can be {@code null} or empty)
 	 * @return an array of application context resource locations
 	 */
-	String[] processLocations(Class<?> clazz, @Nullable String... locations);
+	String[] processLocations(Class<?> clazz, String... locations);
 
 	/**
 	 * Loads a new {@link ApplicationContext context} based on the supplied

spring-test/src/main/java/org/springframework/test/context/MergedContextConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,7 +24,6 @@ import java.util.Set;
 
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextInitializer;
-import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.core.style.ToStringCreator;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -73,8 +72,8 @@ public class MergedContextConfiguration implements Serializable {
 
 	private static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
 
-	private static final Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> EMPTY_INITIALIZER_CLASSES =
-			Collections.<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> emptySet();
+	private static final Set<Class<? extends ApplicationContextInitializer<?>>> EMPTY_INITIALIZER_CLASSES =
+			Collections.<Class<? extends ApplicationContextInitializer<?>>> emptySet();
 
 	private static final Set<ContextCustomizer> EMPTY_CONTEXT_CUSTOMIZERS = Collections.<ContextCustomizer> emptySet();
 
@@ -85,7 +84,7 @@ public class MergedContextConfiguration implements Serializable {
 
 	private final Class<?>[] classes;
 
-	private final Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> contextInitializerClasses;
+	private final Set<Class<? extends ApplicationContextInitializer<?>>> contextInitializerClasses;
 
 	private final String[] activeProfiles;
 
@@ -102,52 +101,9 @@ public class MergedContextConfiguration implements Serializable {
 	private final MergedContextConfiguration parent;
 
 
-	private static String[] processStrings(String[] array) {
-		return (array != null ? array : EMPTY_STRING_ARRAY);
-	}
-
-	private static Class<?>[] processClasses(Class<?>[] classes) {
-		return (classes != null ? classes : EMPTY_CLASS_ARRAY);
-	}
-
-	private static Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> processContextInitializerClasses(
-			Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> contextInitializerClasses) {
-
-		return (contextInitializerClasses != null ?
-				Collections.unmodifiableSet(contextInitializerClasses) : EMPTY_INITIALIZER_CLASSES);
-	}
-
-	private static Set<ContextCustomizer> processContextCustomizers(Set<ContextCustomizer> contextCustomizers) {
-		return (contextCustomizers != null ?
-				Collections.unmodifiableSet(contextCustomizers) : EMPTY_CONTEXT_CUSTOMIZERS);
-	}
-
-	private static String[] processActiveProfiles(String[] activeProfiles) {
-		if (activeProfiles == null) {
-			return EMPTY_STRING_ARRAY;
-		}
-
-		// Active profiles must be unique
-		Set<String> profilesSet = new LinkedHashSet<>(Arrays.asList(activeProfiles));
-		return StringUtils.toStringArray(profilesSet);
-	}
-
-	/**
-	 * Generate a null-safe {@link String} representation of the supplied
-	 * {@link ContextLoader} based solely on the fully qualified name of the
-	 * loader or &quot;null&quot; if the supplied loader is {@code null}.
-	 */
-	@Nullable
-	protected static String nullSafeToString(@Nullable ContextLoader contextLoader) {
-		return (contextLoader != null ? contextLoader.getClass().getName() : "null");
-	}
-
-
 	/**
 	 * Create a new {@code MergedContextConfiguration} instance for the
 	 * supplied parameters.
-	 * <p>Delegates to
-	 * {@link #MergedContextConfiguration(Class, String[], Class[], Set, String[], String[], String[], ContextLoader, CacheAwareContextLoaderDelegate, MergedContextConfiguration)}.
 	 * @param testClass the test class for which the configuration was merged
 	 * @param locations the merged context resource locations
 	 * @param classes the merged annotated classes
@@ -163,18 +119,15 @@ public class MergedContextConfiguration implements Serializable {
 	/**
 	 * Create a new {@code MergedContextConfiguration} instance for the
 	 * supplied parameters.
-	 * <p>Delegates to
-	 * {@link #MergedContextConfiguration(Class, String[], Class[], Set, String[], String[], String[], ContextLoader, CacheAwareContextLoaderDelegate, MergedContextConfiguration)}.
 	 * @param testClass the test class for which the configuration was merged
 	 * @param locations the merged context resource locations
 	 * @param classes the merged annotated classes
 	 * @param contextInitializerClasses the merged context initializer classes
 	 * @param activeProfiles the merged active bean definition profiles
 	 * @param contextLoader the resolved {@code ContextLoader}
-	 * @see #MergedContextConfiguration(Class, String[], Class[], Set, String[], ContextLoader, CacheAwareContextLoaderDelegate, MergedContextConfiguration)
 	 */
 	public MergedContextConfiguration(Class<?> testClass, String[] locations, Class<?>[] classes,
-			Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> contextInitializerClasses,
+			@Nullable Set<Class<? extends ApplicationContextInitializer<?>>> contextInitializerClasses,
 			String[] activeProfiles, ContextLoader contextLoader) {
 
 		this(testClass, locations, classes, contextInitializerClasses, activeProfiles, contextLoader, null, null);
@@ -183,8 +136,6 @@ public class MergedContextConfiguration implements Serializable {
 	/**
 	 * Create a new {@code MergedContextConfiguration} instance for the
 	 * supplied parameters.
-	 * <p>Delegates to
-	 * {@link #MergedContextConfiguration(Class, String[], Class[], Set, String[], String[], String[], ContextLoader, CacheAwareContextLoaderDelegate, MergedContextConfiguration)}.
 	 * @param testClass the test class for which the configuration was merged
 	 * @param locations the merged context resource locations
 	 * @param classes the merged annotated classes
@@ -197,12 +148,13 @@ public class MergedContextConfiguration implements Serializable {
 	 * @since 3.2.2
 	 */
 	public MergedContextConfiguration(Class<?> testClass, String[] locations, Class<?>[] classes,
-			Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> contextInitializerClasses,
+			@Nullable Set<Class<? extends ApplicationContextInitializer<?>>> contextInitializerClasses,
 			String[] activeProfiles, ContextLoader contextLoader,
-			CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate, @Nullable MergedContextConfiguration parent) {
+			@Nullable CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate,
+			@Nullable MergedContextConfiguration parent) {
 
-		this(testClass, locations, classes, contextInitializerClasses, activeProfiles, null, null, contextLoader,
-			cacheAwareContextLoaderDelegate, parent);
+		this(testClass, locations, classes, contextInitializerClasses, activeProfiles, null, null,
+				contextLoader, cacheAwareContextLoaderDelegate, parent);
 	}
 
 	/**
@@ -212,9 +164,9 @@ public class MergedContextConfiguration implements Serializable {
 	 */
 	public MergedContextConfiguration(MergedContextConfiguration mergedConfig) {
 		this(mergedConfig.testClass, mergedConfig.locations, mergedConfig.classes,
-			mergedConfig.contextInitializerClasses, mergedConfig.activeProfiles, mergedConfig.propertySourceLocations,
-			mergedConfig.propertySourceProperties, mergedConfig.contextCustomizers,
-			mergedConfig.contextLoader, mergedConfig.cacheAwareContextLoaderDelegate, mergedConfig.parent);
+				mergedConfig.contextInitializerClasses, mergedConfig.activeProfiles, mergedConfig.propertySourceLocations,
+				mergedConfig.propertySourceProperties, mergedConfig.contextCustomizers,
+				mergedConfig.contextLoader, mergedConfig.cacheAwareContextLoaderDelegate, mergedConfig.parent);
 	}
 
 	/**
@@ -241,10 +193,12 @@ public class MergedContextConfiguration implements Serializable {
 	 * @since 4.1
 	 */
 	public MergedContextConfiguration(Class<?> testClass, @Nullable String[] locations, @Nullable Class<?>[] classes,
-			@Nullable Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> contextInitializerClasses,
-			@Nullable String[] activeProfiles, @Nullable String[] propertySourceLocations, @Nullable String[] propertySourceProperties,
-			ContextLoader contextLoader, CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate,
+			@Nullable Set<Class<? extends ApplicationContextInitializer<?>>> contextInitializerClasses,
+			@Nullable String[] activeProfiles, @Nullable String[] propertySourceLocations,
+			@Nullable String[] propertySourceProperties, ContextLoader contextLoader,
+			@Nullable CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate,
 			@Nullable MergedContextConfiguration parent) {
+
 		this(testClass, locations, classes, contextInitializerClasses, activeProfiles,
 				propertySourceLocations, propertySourceProperties,
 				EMPTY_CONTEXT_CUSTOMIZERS, contextLoader,
@@ -276,10 +230,11 @@ public class MergedContextConfiguration implements Serializable {
 	 * @since 4.3
 	 */
 	public MergedContextConfiguration(Class<?> testClass, @Nullable String[] locations, @Nullable Class<?>[] classes,
-			@Nullable Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> contextInitializerClasses,
-			@Nullable String[] activeProfiles, @Nullable String[] propertySourceLocations, @Nullable String[] propertySourceProperties,
-			@Nullable Set<ContextCustomizer> contextCustomizers, ContextLoader contextLoader,
-			CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate, @Nullable MergedContextConfiguration parent) {
+			@Nullable Set<Class<? extends ApplicationContextInitializer<?>>> contextInitializerClasses,
+			@Nullable String[] activeProfiles, @Nullable String[] propertySourceLocations,
+			@Nullable String[] propertySourceProperties, @Nullable Set<ContextCustomizer> contextCustomizers,
+			ContextLoader contextLoader, @Nullable CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate,
+			@Nullable MergedContextConfiguration parent) {
 
 		this.testClass = testClass;
 		this.locations = processStrings(locations);
@@ -361,7 +316,7 @@ public class MergedContextConfiguration implements Serializable {
 	 * Get the merged {@code ApplicationContextInitializer} classes for the
 	 * {@linkplain #getTestClass() test class}.
 	 */
-	public Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> getContextInitializerClasses() {
+	public Set<Class<? extends ApplicationContextInitializer<?>>> getContextInitializerClasses() {
 		return this.contextInitializerClasses;
 	}
 
@@ -455,7 +410,7 @@ public class MergedContextConfiguration implements Serializable {
 	 * {@link #getContextLoader() ContextLoaders}.
 	 */
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (this == other) {
 			return true;
 		}
@@ -495,7 +450,7 @@ public class MergedContextConfiguration implements Serializable {
 			return false;
 		}
 
-		if (!nullSafeToString(this.contextLoader).equals(nullSafeToString(otherConfig.contextLoader))) {
+		if (!nullSafeClassName(this.contextLoader).equals(nullSafeClassName(otherConfig.contextLoader))) {
 			return false;
 		}
 
@@ -517,7 +472,7 @@ public class MergedContextConfiguration implements Serializable {
 		result = 31 * result + Arrays.hashCode(this.propertySourceProperties);
 		result = 31 * result + this.contextCustomizers.hashCode();
 		result = 31 * result + (this.parent != null ? this.parent.hashCode() : 0);
-		result = 31 * result + nullSafeToString(this.contextLoader).hashCode();
+		result = 31 * result + nullSafeClassName(this.contextLoader).hashCode();
 		return result;
 	}
 
@@ -543,9 +498,51 @@ public class MergedContextConfiguration implements Serializable {
 				.append("propertySourceLocations", ObjectUtils.nullSafeToString(this.propertySourceLocations))
 				.append("propertySourceProperties", ObjectUtils.nullSafeToString(this.propertySourceProperties))
 				.append("contextCustomizers", this.contextCustomizers)
-				.append("contextLoader", nullSafeToString(this.contextLoader))
+				.append("contextLoader", nullSafeClassName(this.contextLoader))
 				.append("parent", this.parent)
 				.toString();
 	}
 
+
+	private static String[] processStrings(@Nullable String[] array) {
+		return (array != null ? array : EMPTY_STRING_ARRAY);
+	}
+
+	private static Class<?>[] processClasses(@Nullable Class<?>[] classes) {
+		return (classes != null ? classes : EMPTY_CLASS_ARRAY);
+	}
+
+	private static Set<Class<? extends ApplicationContextInitializer<?>>> processContextInitializerClasses(
+			@Nullable Set<Class<? extends ApplicationContextInitializer<?>>> contextInitializerClasses) {
+
+		return (contextInitializerClasses != null ?
+				Collections.unmodifiableSet(contextInitializerClasses) : EMPTY_INITIALIZER_CLASSES);
+	}
+
+	private static Set<ContextCustomizer> processContextCustomizers(
+			@Nullable Set<ContextCustomizer> contextCustomizers) {
+
+		return (contextCustomizers != null ?
+				Collections.unmodifiableSet(contextCustomizers) : EMPTY_CONTEXT_CUSTOMIZERS);
+	}
+
+	private static String[] processActiveProfiles(@Nullable String[] activeProfiles) {
+		if (activeProfiles == null) {
+			return EMPTY_STRING_ARRAY;
+		}
+
+		// Active profiles must be unique
+		Set<String> profilesSet = new LinkedHashSet<>(Arrays.asList(activeProfiles));
+		return StringUtils.toStringArray(profilesSet);
+	}
+
+	/**
+	 * Generate a null-safe {@link String} representation of the supplied
+	 * {@link ContextLoader} based solely on the fully qualified name of the
+	 * loader or &quot;null&quot; if the supplied loader is {@code null}.
+	 */
+	protected static String nullSafeClassName(@Nullable ContextLoader contextLoader) {
+		return (contextLoader != null ? contextLoader.getClass().getName() : "null");
+	}
+
 }

spring-test/src/main/java/org/springframework/test/context/TestContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -65,24 +65,21 @@ public interface TestContext extends AttributeAccessor, Serializable {
 	 * @return the current test instance (may be {@code null})
 	 * @see #updateState(Object, Method, Throwable)
 	 */
-	@Nullable
 	Object getTestInstance();
 
 	/**
 	 * Get the current {@linkplain Method test method} for this test context.
 	 * <p>Note: this is a mutable property.
-	 * @return the current test method (may be {@code null})
+	 * @return the current test method
 	 * @see #updateState(Object, Method, Throwable)
 	 */
-	@Nullable
 	Method getTestMethod();
 
 	/**
 	 * Get the {@linkplain Throwable exception} that was thrown during execution
 	 * of the {@linkplain #getTestMethod() test method}.
 	 * <p>Note: this is a mutable property.
-	 * @return the exception that was thrown, or {@code null} if no
-	 * exception was thrown
+	 * @return the exception that was thrown, or {@code null} if no exception was thrown
 	 * @see #updateState(Object, Method, Throwable)
 	 */
 	@Nullable
@@ -101,14 +98,13 @@ public interface TestContext extends AttributeAccessor, Serializable {
 	void markApplicationContextDirty(@Nullable HierarchyMode hierarchyMode);
 
 	/**
-	 * Update this test context to reflect the state of the currently executing
-	 * test.
+	 * Update this test context to reflect the state of the currently executing test.
 	 * <p>Caution: concurrent invocations of this method might not be thread-safe,
 	 * depending on the underlying implementation.
 	 * @param testInstance the current test instance (may be {@code null})
 	 * @param testMethod the current test method (may be {@code null})
-	 * @param testException the exception that was thrown in the test method, or
-	 * {@code null} if no exception was thrown
+	 * @param testException the exception that was thrown in the test method,
+	 * or {@code null} if no exception was thrown
 	 */
 	void updateState(@Nullable Object testInstance, @Nullable Method testMethod, @Nullable Throwable testException);
 

spring-test/src/main/java/org/springframework/test/context/TestContextManager.java

@@ -233,7 +233,6 @@ public class TestContextManager {
 	 * @see #getTestExecutionListeners()
 	 */
 	public void prepareTestInstance(Object testInstance) throws Exception {
-		Assert.notNull(testInstance, "Test instance must not be null");
 		if (logger.isTraceEnabled()) {
 			logger.trace("prepareTestInstance(): instance [" + testInstance + "]");
 		}
@@ -501,7 +500,6 @@ public class TestContextManager {
 	}
 
 	private void prepareForBeforeCallback(String callbackName, Object testInstance, Method testMethod) {
-		Assert.notNull(testInstance, "Test instance must not be null");
 		if (logger.isTraceEnabled()) {
 			logger.trace(String.format("%s(): instance [%s], method [%s]", callbackName, testInstance, testMethod));
 		}
@@ -509,8 +507,8 @@ public class TestContextManager {
 	}
 
 	private void prepareForAfterCallback(String callbackName, Object testInstance, Method testMethod,
-			Throwable exception) {
-		Assert.notNull(testInstance, "Test instance must not be null");
+			@Nullable Throwable exception) {
+
 		if (logger.isTraceEnabled()) {
 			logger.trace(String.format("%s(): instance [%s], method [%s], exception [%s]", callbackName, testInstance,
 					testMethod, exception));

spring-test/src/main/java/org/springframework/test/context/cache/DefaultContextCache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -160,12 +160,14 @@ public class DefaultContextCache implements ContextCache {
 	public void remove(MergedContextConfiguration key, @Nullable HierarchyMode hierarchyMode) {
 		Assert.notNull(key, "Key must not be null");
 
-		// startKey is the level at which to begin clearing the cache, depending
-		// on the configured hierarchy mode.
+		// startKey is the level at which to begin clearing the cache,
+		// depending on the configured hierarchy mode.s
 		MergedContextConfiguration startKey = key;
 		if (hierarchyMode == HierarchyMode.EXHAUSTIVE) {
-			while (startKey.getParent() != null) {
-				startKey = startKey.getParent();
+			MergedContextConfiguration parent = startKey.getParent();
+			while (parent != null) {
+				startKey = parent;
+				parent = startKey.getParent();
 			}
 		}
 

spring-test/src/main/java/org/springframework/test/context/junit/jupiter/AbstractExpressionEvaluatingCondition.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,7 +23,6 @@ import java.util.function.Function;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-
 import org.junit.jupiter.api.extension.ConditionEvaluationResult;
 import org.junit.jupiter.api.extension.ContainerExecutionCondition;
 import org.junit.jupiter.api.extension.ExtensionContext;
@@ -142,7 +141,8 @@ abstract class AbstractExpressionEvaluatingCondition implements ContainerExecuti
 
 		if (loadContext) {
 			applicationContext = SpringExtension.getApplicationContext(extensionContext);
-		} else {
+		}
+		else {
 			gac = new GenericApplicationContext();
 			gac.refresh();
 			applicationContext = gac;
@@ -150,7 +150,7 @@ abstract class AbstractExpressionEvaluatingCondition implements ContainerExecuti
 
 		if (!(applicationContext instanceof ConfigurableApplicationContext)) {
 			if (logger.isWarnEnabled()) {
-				String contextType = (applicationContext != null ? applicationContext.getClass().getName() : "null");
+				String contextType = applicationContext.getClass().getName();
 				logger.warn(String.format("@%s(\"%s\") could not be evaluated on [%s] since the test " +
 						"ApplicationContext [%s] is not a ConfigurableApplicationContext",
 						annotationType.getSimpleName(), expression, element, contextType));
@@ -160,17 +160,18 @@ abstract class AbstractExpressionEvaluatingCondition implements ContainerExecuti
 
 		ConfigurableBeanFactory configurableBeanFactory = ((ConfigurableApplicationContext) applicationContext).getBeanFactory();
 		BeanExpressionResolver expressionResolver = configurableBeanFactory.getBeanExpressionResolver();
+		Assert.state(expressionResolver != null, "No BeanExpressionResolver");
 		BeanExpressionContext beanExpressionContext = new BeanExpressionContext(configurableBeanFactory, null);
 
-		Object result = expressionResolver.evaluate(configurableBeanFactory.resolveEmbeddedValue(expression),
-			beanExpressionContext);
+		Object result = expressionResolver.evaluate(
+				configurableBeanFactory.resolveEmbeddedValue(expression), beanExpressionContext);
 
 		if (gac != null) {
 			gac.close();
 		}
 
 		if (result instanceof Boolean) {
-			return ((Boolean) result).booleanValue();
+			return (Boolean) result;
 		}
 		else if (result instanceof String) {
 			String str = ((String) result).trim().toLowerCase();

spring-test/src/main/java/org/springframework/test/context/junit/jupiter/SpringExtension.java

@@ -39,6 +39,7 @@ import org.junit.jupiter.api.extension.TestInstancePostProcessor;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.ApplicationContext;
 import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.test.context.TestContextManager;
 import org.springframework.util.Assert;
 
@@ -168,6 +169,7 @@ public class SpringExtension implements BeforeAllCallback, AfterAllCallback, Tes
 	 * @see ParameterAutowireUtils#resolveDependency
 	 */
 	@Override
+	@Nullable
 	public Object resolve(ParameterContext parameterContext, ExtensionContext extensionContext) {
 		Parameter parameter = parameterContext.getParameter();
 		Class<?> testClass = extensionContext.getTestClass().get();

spring-test/src/main/java/org/springframework/test/context/junit/jupiter/SpringJUnitConfig.java

@@ -73,7 +73,7 @@ public @interface SpringJUnitConfig {
 	 * Alias for {@link ContextConfiguration#initializers}.
 	 */
 	@AliasFor(annotation = ContextConfiguration.class)
-	Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>[] initializers() default {};
+	Class<? extends ApplicationContextInitializer<?>>[] initializers() default {};
 
 	/**
 	 * Alias for {@link ContextConfiguration#inheritLocations}.

spring-test/src/main/java/org/springframework/test/context/junit/jupiter/web/SpringJUnitWebConfig.java

@@ -78,7 +78,7 @@ public @interface SpringJUnitWebConfig {
 	 * Alias for {@link ContextConfiguration#initializers}.
 	 */
 	@AliasFor(annotation = ContextConfiguration.class)
-	Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>[] initializers() default {};
+	Class<? extends ApplicationContextInitializer<?>>[] initializers() default {};
 
 	/**
 	 * Alias for {@link ContextConfiguration#inheritLocations}.

spring-test/src/main/java/org/springframework/test/context/junit4/AbstractTransactionalJUnit4SpringContextTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,6 +31,7 @@ import org.springframework.test.context.transaction.TransactionalTestExecutionLi
 import org.springframework.test.jdbc.JdbcTestUtils;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.annotation.Transactional;
+import org.springframework.util.Assert;
 
 /**
  * Abstract {@linkplain Transactional transactional} extension of
@@ -201,8 +202,10 @@ public abstract class AbstractTransactionalJUnit4SpringContextTests extends Abst
 	 * @see #setSqlScriptEncoding
 	 */
 	protected void executeSqlScript(String sqlResourcePath, boolean continueOnError) throws DataAccessException {
+		DataSource ds = this.jdbcTemplate.getDataSource();
+		Assert.state(ds != null, "No DataSource set");
 		Resource resource = this.applicationContext.getResource(sqlResourcePath);
-		new ResourceDatabasePopulator(continueOnError, false, this.sqlScriptEncoding, resource).execute(jdbcTemplate.getDataSource());
+		new ResourceDatabasePopulator(continueOnError, false, this.sqlScriptEncoding, resource).execute(ds);
 	}
 
 }

spring-test/src/main/java/org/springframework/test/context/junit4/SpringJUnit4ClassRunner.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,7 +22,6 @@ import java.util.concurrent.TimeUnit;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-
 import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.internal.runners.model.ReflectiveCallable;
@@ -107,7 +106,7 @@ public class SpringJUnit4ClassRunner extends BlockJUnit4ClassRunner {
 
 		withRulesMethod = ReflectionUtils.findMethod(SpringJUnit4ClassRunner.class, "withRules",
 				FrameworkMethod.class, Object.class, Statement.class);
-		Assert.state(withRulesMethod != null, "SpringJUnit4ClassRunner requires JUnit 4.12 or higher.");
+		Assert.state(withRulesMethod != null, "SpringJUnit4ClassRunner requires JUnit 4.12 or higher");
 		ReflectionUtils.makeAccessible(withRulesMethod);
 	}
 
@@ -310,7 +309,9 @@ public class SpringJUnit4ClassRunner extends BlockJUnit4ClassRunner {
 	 * Invoke JUnit's private {@code withRules()} method using reflection.
 	 */
 	private Statement withRulesReflectively(FrameworkMethod frameworkMethod, Object testInstance, Statement statement) {
-		return (Statement) ReflectionUtils.invokeMethod(withRulesMethod, this, frameworkMethod, testInstance, statement);
+		Object result = ReflectionUtils.invokeMethod(withRulesMethod, this, frameworkMethod, testInstance, statement);
+		Assert.state(result instanceof Statement, "withRules mismatch");
+		return (Statement) result;
 	}
 
 	/**

spring-test/src/main/java/org/springframework/test/context/junit4/rules/SpringMethodRule.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,7 +23,6 @@ import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-
 import org.junit.ClassRule;
 import org.junit.rules.MethodRule;
 import org.junit.runners.model.FrameworkMethod;
@@ -233,7 +232,9 @@ public class SpringMethodRule implements MethodRule {
 				"SpringClassRule field [%s] must be annotated with JUnit's @ClassRule annotation. " +
 				"Consult the javadoc for SpringClassRule for details.", ruleField));
 
-		return (SpringClassRule) ReflectionUtils.getField(ruleField, null);
+		Object result = ReflectionUtils.getField(ruleField, null);
+		Assert.state(result instanceof SpringClassRule, "SpringClassRule field mismatch");
+		return (SpringClassRule) result;
 	}
 
 	private static Optional<Field> findSpringClassRuleField(Class<?> testClass) {

spring-test/src/main/java/org/springframework/test/context/support/AbstractContextLoader.java

@@ -91,7 +91,7 @@ public abstract class AbstractContextLoader implements SmartContextLoader {
 	 * @see #processLocations(Class, String...)
 	 */
 	@Override
-	public void processContextConfiguration(@Nullable ContextConfigurationAttributes configAttributes) {
+	public void processContextConfiguration(ContextConfigurationAttributes configAttributes) {
 		String[] processedLocations =
 				processLocations(configAttributes.getDeclaringClass(), configAttributes.getLocations());
 		configAttributes.setLocations(processedLocations);
@@ -143,7 +143,7 @@ public abstract class AbstractContextLoader implements SmartContextLoader {
 	private void invokeApplicationContextInitializers(ConfigurableApplicationContext context,
 			MergedContextConfiguration mergedConfig) {
 
-		Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> initializerClasses =
+		Set<Class<? extends ApplicationContextInitializer<?>>> initializerClasses =
 				mergedConfig.getContextInitializerClasses();
 		if (initializerClasses.isEmpty()) {
 			// no ApplicationContextInitializers have been declared -> nothing to do
@@ -153,7 +153,7 @@ public abstract class AbstractContextLoader implements SmartContextLoader {
 		List<ApplicationContextInitializer<ConfigurableApplicationContext>> initializerInstances = new ArrayList<>();
 		Class<?> contextClass = context.getClass();
 
-		for (Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>> initializerClass : initializerClasses) {
+		for (Class<? extends ApplicationContextInitializer<?>> initializerClass : initializerClasses) {
 			Class<?> initializerContextClass =
 					GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class);
 			if (initializerContextClass != null && !initializerContextClass.isInstance(context)) {
@@ -213,7 +213,7 @@ public abstract class AbstractContextLoader implements SmartContextLoader {
 	 * @see #processContextConfiguration(ContextConfigurationAttributes)
 	 */
 	@Override
-	public final String[] processLocations(Class<?> clazz, @Nullable String... locations) {
+	public final String[] processLocations(Class<?> clazz, String... locations) {
 		return (ObjectUtils.isEmpty(locations) && isGenerateDefaultLocations()) ?
 				generateDefaultLocations(clazz) : modifyLocations(clazz, locations);
 	}

spring-test/src/main/java/org/springframework/test/context/support/AbstractTestContextBootstrapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -300,6 +300,7 @@ public abstract class AbstractTestContextBootstrapper implements TestContextBoot
 			}
 
 			// Return the last level in the context hierarchy
+			Assert.state(mergedConfig != null, "No merged context configuration");
 			return mergedConfig;
 		}
 		else {
@@ -462,7 +463,6 @@ public abstract class AbstractTestContextBootstrapper implements TestContextBoot
 		Class<? extends ContextLoader> contextLoaderClass = resolveExplicitContextLoaderClass(configAttributesList);
 		if (contextLoaderClass == null) {
 			contextLoaderClass = getDefaultContextLoaderClass(testClass);
-			Assert.state(contextLoaderClass != null, "getDefaultContextLoaderClass() must not return null");
 		}
 		if (logger.isTraceEnabled()) {
 			logger.trace(String.format("Using ContextLoader class [%s] for test class [%s]",

spring-test/src/main/java/org/springframework/test/context/support/ActiveProfilesUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,6 +31,7 @@ import org.springframework.test.context.ActiveProfilesResolver;
 import org.springframework.test.util.MetaAnnotationUtils;
 import org.springframework.test.util.MetaAnnotationUtils.AnnotationDescriptor;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
@@ -107,16 +108,10 @@ abstract class ActiveProfilesUtils {
 			}
 
 			String[] profiles = resolver.resolve(rootDeclaringClass);
-			if (profiles == null) {
-				String msg = String.format(
-						"ActiveProfilesResolver [%s] returned a null array of bean definition profiles",
-						resolverClass.getName());
-				logger.error(msg);
-				throw new IllegalStateException(msg);
+			if (!ObjectUtils.isEmpty(profiles)) {
+				profileArrays.add(profiles);
 			}
 
-			profileArrays.add(profiles);
-
 			descriptor = (annotation.inheritProfiles() ? MetaAnnotationUtils.findAnnotationDescriptor(
 					rootDeclaringClass.getSuperclass(), annotationType) : null);
 		}

spring-test/src/main/java/org/springframework/test/context/support/AnnotationConfigContextLoader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,7 +22,6 @@ import org.apache.commons.logging.LogFactory;
 import org.springframework.beans.factory.support.BeanDefinitionReader;
 import org.springframework.context.annotation.AnnotatedBeanDefinitionReader;
 import org.springframework.context.support.GenericApplicationContext;
-import org.springframework.lang.Nullable;
 import org.springframework.test.context.ContextConfigurationAttributes;
 import org.springframework.test.context.MergedContextConfiguration;
 import org.springframework.util.ObjectUtils;
@@ -79,7 +78,7 @@ public class AnnotationConfigContextLoader extends AbstractGenericContextLoader
 	 * @see #detectDefaultConfigurationClasses(Class)
 	 */
 	@Override
-	public void processContextConfiguration(@Nullable ContextConfigurationAttributes configAttributes) {
+	public void processContextConfiguration(ContextConfigurationAttributes configAttributes) {
 		if (!configAttributes.hasClasses() && isGenerateDefaultLocations()) {
 			configAttributes.setClasses(detectDefaultConfigurationClasses(configAttributes.getDeclaringClass()));
 		}

spring-test/src/main/java/org/springframework/test/context/support/AnnotationConfigContextLoaderUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +25,7 @@ import org.apache.commons.logging.LogFactory;
 
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.test.context.SmartContextLoader;
 import org.springframework.util.Assert;
 
@@ -101,7 +102,7 @@ public abstract class AnnotationConfigContextLoaderUtils {
 	 * @param clazz the class to check
 	 * @return {@code true} if the supplied class meets the candidate criteria
 	 */
-	private static boolean isDefaultConfigurationClassCandidate(Class<?> clazz) {
+	private static boolean isDefaultConfigurationClassCandidate(@Nullable Class<?> clazz) {
 		return (clazz != null && isStaticNonPrivateAndNonFinal(clazz) &&
 				AnnotatedElementUtils.hasAnnotation(clazz, Configuration.class));
 	}

spring-test/src/main/java/org/springframework/test/context/support/ApplicationContextInitializerUtils.java

@@ -69,11 +69,11 @@ abstract class ApplicationContextInitializerUtils {
 	 * superclasses if appropriate (never {@code null})
 	 * @since 3.2
 	 */
-	static Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> resolveInitializerClasses(
+	static Set<Class<? extends ApplicationContextInitializer<?>>> resolveInitializerClasses(
 			List<ContextConfigurationAttributes> configAttributesList) {
 		Assert.notEmpty(configAttributesList, "ContextConfigurationAttributes list must not be empty");
 
-		final Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> initializerClasses = //
+		final Set<Class<? extends ApplicationContextInitializer<?>>> initializerClasses = //
 				new HashSet<>();
 
 		for (ContextConfigurationAttributes configAttributes : configAttributesList) {

spring-test/src/main/java/org/springframework/test/context/support/ContextLoaderUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -130,9 +130,11 @@ abstract class ContextLoaderUtils {
 			}
 			else if (contextHierarchyDeclaredLocally) {
 				ContextHierarchy contextHierarchy = getAnnotation(declaringClass, contextHierarchyType);
-				for (ContextConfiguration contextConfiguration : contextHierarchy.value()) {
-					convertContextConfigToConfigAttributesAndAddToList(
-							contextConfiguration, rootDeclaringClass, configAttributesList);
+				if (contextHierarchy != null) {
+					for (ContextConfiguration contextConfiguration : contextHierarchy.value()) {
+						convertContextConfigToConfigAttributesAndAddToList(
+								contextConfiguration, rootDeclaringClass, configAttributesList);
+					}
 				}
 			}
 			else {

spring-test/src/main/java/org/springframework/test/context/support/DefaultTestContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -74,15 +74,16 @@ public class DefaultTestContext implements TestContext {
 
 	/**
 	 * Construct a new {@code DefaultTestContext} from the supplied arguments.
-	 * @param testClass the test class for this test context; never {@code null}
+	 * @param testClass the test class for this test context
 	 * @param mergedContextConfiguration the merged application context
-	 * configuration for this test context; never {@code null}
+	 * configuration for this test context
 	 * @param cacheAwareContextLoaderDelegate the delegate to use for loading
-	 * and closing the application context for this test context; never {@code null}
+	 * and closing the application context for this test context
 	 */
 	public DefaultTestContext(Class<?> testClass, MergedContextConfiguration mergedContextConfiguration,
 			CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate) {
-		Assert.notNull(testClass, "testClass must not be null");
+
+		Assert.notNull(testClass, "Test Class must not be null");
 		Assert.notNull(mergedContextConfiguration, "MergedContextConfiguration must not be null");
 		Assert.notNull(cacheAwareContextLoaderDelegate, "CacheAwareContextLoaderDelegate must not be null");
 		this.testClass = testClass;
@@ -132,10 +133,12 @@ public class DefaultTestContext implements TestContext {
 	}
 
 	public final Object getTestInstance() {
+		Assert.state(this.testInstance != null, "No test instance");
 		return this.testInstance;
 	}
 
 	public final Method getTestMethod() {
+		Assert.state(this.testMethod != null, "No test method");
 		return this.testMethod;
 	}
 

spring-test/src/main/java/org/springframework/test/context/support/DependencyInjectionTestExecutionListener.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

spring-test/src/main/java/org/springframework/test/context/support/TestPropertySourceAttributes.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -73,12 +73,11 @@ class TestPropertySourceAttributes {
 
 	private TestPropertySourceAttributes(Class<?> declaringClass, String[] locations, boolean inheritLocations,
 			String[] properties, boolean inheritProperties) {
-		Assert.notNull(declaringClass, "declaringClass must not be null");
 
+		Assert.notNull(declaringClass, "declaringClass must not be null");
 		if (ObjectUtils.isEmpty(locations) && ObjectUtils.isEmpty(properties)) {
 			locations = new String[] { detectDefaultPropertiesFile(declaringClass) };
 		}
-
 		this.declaringClass = declaringClass;
 		this.locations = locations;
 		this.inheritLocations = inheritLocations;
@@ -86,44 +85,38 @@ class TestPropertySourceAttributes {
 		this.inheritProperties = inheritProperties;
 	}
 
+
 	/**
 	 * Get the {@linkplain Class class} that declared {@code @TestPropertySource}.
-	 *
 	 * @return the declaring class; never {@code null}
 	 */
 	Class<?> getDeclaringClass() {
-		return declaringClass;
+		return this.declaringClass;
 	}
 
 	/**
 	 * Get the resource locations that were declared via {@code @TestPropertySource}.
-	 *
 	 * <p>Note: The returned value may represent a <em>detected default</em>
 	 * that does not match the original value declared via {@code @TestPropertySource}.
-	 *
-	 * @return the resource locations; potentially {@code null} or <em>empty</em>
+	 * @return the resource locations; potentially <em>empty</em>
 	 * @see TestPropertySource#value
 	 * @see TestPropertySource#locations
-	 * @see #setLocations(String[])
 	 */
-	@Nullable
 	String[] getLocations() {
-		return locations;
+		return this.locations;
 	}
 
 	/**
 	 * Get the {@code inheritLocations} flag that was declared via {@code @TestPropertySource}.
-	 *
 	 * @return the {@code inheritLocations} flag
 	 * @see TestPropertySource#inheritLocations
 	 */
 	boolean isInheritLocations() {
-		return inheritLocations;
+		return this.inheritLocations;
 	}
 
 	/**
 	 * Get the inlined properties that were declared via {@code @TestPropertySource}.
-	 *
 	 * @return the inlined properties; potentially {@code null} or <em>empty</em>
 	 * @see TestPropertySource#properties
 	 */
@@ -134,7 +127,6 @@ class TestPropertySourceAttributes {
 
 	/**
 	 * Get the {@code inheritProperties} flag that was declared via {@code @TestPropertySource}.
-	 *
 	 * @return the {@code inheritProperties} flag
 	 * @see TestPropertySource#inheritProperties
 	 */
@@ -157,6 +149,7 @@ class TestPropertySourceAttributes {
 		.toString();
 	}
 
+
 	/**
 	 * Detect a default properties file for the supplied class, as specified
 	 * in the class-level Javadoc for {@link TestPropertySource}.
@@ -174,10 +167,10 @@ class TestPropertySourceAttributes {
 			return prefixedResourcePath;
 		}
 		else {
-			String msg = String.format("Could not detect default properties file for test [%s]: "
-					+ "%s does not exist. Either declare the 'locations' or 'properties' attributes "
-					+ "of @TestPropertySource or make the default properties file available.", testClass.getName(),
-				classPathResource);
+			String msg = String.format("Could not detect default properties file for test [%s]: " +
+					"%s does not exist. Either declare the 'locations' or 'properties' attributes " +
+					"of @TestPropertySource or make the default properties file available.", testClass.getName(),
+					classPathResource);
 			logger.error(msg);
 			throw new IllegalStateException(msg);
 		}

spring-test/src/main/java/org/springframework/test/context/support/TestPropertySourceUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -132,7 +132,10 @@ public abstract class TestPropertySourceUtils {
 			if (logger.isTraceEnabled()) {
 				logger.trace(String.format("Processing inlined properties for TestPropertySource attributes %s", attrs));
 			}
-			properties.addAll(0, Arrays.asList(attrs.getProperties()));
+			String[] attrProps = attrs.getProperties();
+			if (attrProps != null) {
+				properties.addAll(0, Arrays.asList(attrProps));
+			}
 			if (!attrs.isInheritProperties()) {
 				break;
 			}

spring-test/src/main/java/org/springframework/test/context/testng/AbstractTransactionalTestNGSpringContextTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,6 +30,7 @@ import org.springframework.test.context.transaction.TransactionalTestExecutionLi
 import org.springframework.test.jdbc.JdbcTestUtils;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.annotation.Transactional;
+import org.springframework.util.Assert;
 
 /**
  * Abstract {@linkplain Transactional transactional} extension of
@@ -185,8 +186,10 @@ public abstract class AbstractTransactionalTestNGSpringContextTests extends Abst
 	 * @see #setSqlScriptEncoding
 	 */
 	protected void executeSqlScript(String sqlResourcePath, boolean continueOnError) throws DataAccessException {
+		DataSource ds = this.jdbcTemplate.getDataSource();
+		Assert.state(ds != null, "No DataSource set");
 		Resource resource = this.applicationContext.getResource(sqlResourcePath);
-		new ResourceDatabasePopulator(continueOnError, false, this.sqlScriptEncoding, resource).execute(jdbcTemplate.getDataSource());
+		new ResourceDatabasePopulator(continueOnError, false, this.sqlScriptEncoding, resource).execute(ds);
 	}
 
 }

spring-test/src/main/java/org/springframework/test/context/transaction/TransactionContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ package org.springframework.test.context.transaction;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.lang.Nullable;
 import org.springframework.test.context.TestContext;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.TransactionDefinition;
@@ -56,6 +57,7 @@ class TransactionContext {
 
 	TransactionContext(TestContext testContext, PlatformTransactionManager transactionManager,
 			TransactionDefinition transactionDefinition, boolean defaultRollback) {
+
 		this.testContext = testContext;
 		this.transactionManager = transactionManager;
 		this.transactionDefinition = transactionDefinition;
@@ -63,6 +65,8 @@ class TransactionContext {
 		this.flaggedForRollback = defaultRollback;
 	}
 
+
+	@Nullable
 	TransactionStatus getTransactionStatus() {
 		return this.transactionStatus;
 	}
@@ -83,7 +87,7 @@ class TransactionContext {
 	}
 
 	/**
-	 * Start a new transaction for the configured {@linkplain #getTestContext test context}.
+	 * Start a new transaction for the configured test context.
 	 * <p>Only call this method if {@link #endTransaction} has been called or if no
 	 * transaction has been previously started.
 	 * @throws TransactionException if starting the transaction fails
@@ -102,9 +106,8 @@ class TransactionContext {
 	}
 
 	/**
-	 * Immediately force a <em>commit</em> or <em>rollback</em> of the transaction
-	 * for the configured {@linkplain #getTestContext test context}, according to
-	 * the {@linkplain #isFlaggedForRollback rollback flag}.
+	 * Immediately force a <em>commit</em> or <em>rollback</em> of the transaction for the
+	 * configured test context, according to the {@linkplain #isFlaggedForRollback rollback flag}.
 	 */
 	void endTransaction() {
 		if (logger.isTraceEnabled()) {
@@ -133,4 +136,4 @@ class TransactionContext {
 		}
 	}
 
-}
+}

spring-test/src/main/java/org/springframework/test/context/transaction/TransactionContextHolder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package org.springframework.test.context.transaction;
 
 import org.springframework.core.NamedInheritableThreadLocal;
+import org.springframework.lang.Nullable;
 
 /**
  * {@link InheritableThreadLocal}-based holder for the current {@link TransactionContext}.
@@ -26,18 +27,20 @@ import org.springframework.core.NamedInheritableThreadLocal;
  */
 class TransactionContextHolder {
 
-	private static final ThreadLocal<TransactionContext> currentTransactionContext = new NamedInheritableThreadLocal<>(
-			"Test Transaction Context");
+	private static final ThreadLocal<TransactionContext> currentTransactionContext =
+			new NamedInheritableThreadLocal<>("Test Transaction Context");
 
 
-	static TransactionContext getCurrentTransactionContext() {
-		return currentTransactionContext.get();
+	static void setCurrentTransactionContext(@Nullable TransactionContext transactionContext) {
+		currentTransactionContext.set(transactionContext);
 	}
 
-	static void setCurrentTransactionContext(TransactionContext transactionContext) {
-		currentTransactionContext.set(transactionContext);
+	@Nullable
+	static TransactionContext getCurrentTransactionContext() {
+		return currentTransactionContext.get();
 	}
 
+	@Nullable
 	static TransactionContext removeCurrentTransactionContext() {
 		synchronized (currentTransactionContext) {
 			TransactionContext transactionContext = currentTransactionContext.get();

spring-test/src/main/java/org/springframework/test/context/transaction/TransactionalTestExecutionListener.java

@@ -31,6 +31,7 @@ import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.annotation.BeanFactoryAnnotationUtils;
 import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.test.annotation.Commit;
 import org.springframework.test.annotation.Rollback;
 import org.springframework.test.context.TestContext;
@@ -156,8 +157,8 @@ public class TransactionalTestExecutionListener extends AbstractTestExecutionLis
 	 */
 	@Override
 	public void beforeTestMethod(final TestContext testContext) throws Exception {
-		final Method testMethod = testContext.getTestMethod();
-		final Class<?> testClass = testContext.getTestClass();
+		Method testMethod = testContext.getTestMethod();
+		Class<?> testClass = testContext.getTestClass();
 		Assert.notNull(testMethod, "The test method of the supplied TestContext must not be null");
 
 		TransactionContext txContext = TransactionContextHolder.removeCurrentTransactionContext();
@@ -180,7 +181,6 @@ public class TransactionalTestExecutionListener extends AbstractTestExecutionLis
 			}
 
 			tm = getTransactionManager(testContext, transactionAttribute.getQualifier());
-
 			Assert.state(tm != null, () -> String.format(
 					"Failed to retrieve PlatformTransactionManager for @Transactional test for test context %s.",
 					testContext));
@@ -212,7 +212,7 @@ public class TransactionalTestExecutionListener extends AbstractTestExecutionLis
 			TransactionStatus transactionStatus = txContext.getTransactionStatus();
 			try {
 				// If the transaction is still active...
-				if ((transactionStatus != null) && !transactionStatus.isCompleted()) {
+				if (transactionStatus != null && !transactionStatus.isCompleted()) {
 					txContext.endTransaction();
 				}
 			}
@@ -306,6 +306,7 @@ public class TransactionalTestExecutionListener extends AbstractTestExecutionLis
 	 * @throws BeansException if an error occurs while retrieving the transaction manager
 	 * @see #getTransactionManager(TestContext)
 	 */
+	@Nullable
 	protected PlatformTransactionManager getTransactionManager(TestContext testContext, String qualifier) {
 		// Look up by type and qualifier from @Transactional
 		if (StringUtils.hasText(qualifier)) {
@@ -344,6 +345,7 @@ public class TransactionalTestExecutionListener extends AbstractTestExecutionLis
 	 * exists in the ApplicationContext
 	 * @see #getTransactionManager(TestContext, String)
 	 */
+	@Nullable
 	protected PlatformTransactionManager getTransactionManager(TestContext testContext) {
 		return TestContextTransactionUtils.retrieveTransactionManager(testContext, null);
 	}

spring-test/src/main/java/org/springframework/test/context/util/TestContextResourceUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -47,10 +47,6 @@ public abstract class TestContextResourceUtils {
 	private static final String SLASH = "/";
 
 
-	private TestContextResourceUtils() {
-		/* prevent instantiation */
-	}
-
 	/**
 	 * Convert the supplied paths to classpath resource paths.
 	 *
@@ -65,7 +61,6 @@ public abstract class TestContextResourceUtils {
 	 * {@link ResourceUtils#CLASSPATH_URL_PREFIX classpath:},
 	 * {@link ResourceUtils#FILE_URL_PREFIX file:}, {@code http:}, etc.) will be
 	 * {@link StringUtils#cleanPath cleaned} but otherwise unmodified.
-	 *
 	 * @param clazz the class with which the paths are associated
 	 * @param paths the paths to be converted
 	 * @return a new array of converted resource paths
@@ -79,8 +74,8 @@ public abstract class TestContextResourceUtils {
 				convertedPaths[i] = ResourceUtils.CLASSPATH_URL_PREFIX + path;
 			}
 			else if (!ResourcePatternUtils.isUrl(path)) {
-				convertedPaths[i] = ResourceUtils.CLASSPATH_URL_PREFIX + SLASH
-						+ StringUtils.cleanPath(ClassUtils.classPackageAsResourcePath(clazz) + SLASH + path);
+				convertedPaths[i] = ResourceUtils.CLASSPATH_URL_PREFIX + SLASH +
+						StringUtils.cleanPath(ClassUtils.classPackageAsResourcePath(clazz) + SLASH + path);
 			}
 			else {
 				convertedPaths[i] = StringUtils.cleanPath(path);
@@ -92,7 +87,6 @@ public abstract class TestContextResourceUtils {
 	/**
 	 * Convert the supplied paths to an array of {@link Resource} handles using
 	 * the given {@link ResourceLoader}.
-	 *
 	 * @param resourceLoader the {@code ResourceLoader} to use to convert the paths
 	 * @param paths the paths to be converted
 	 * @return a new array of resources
@@ -106,7 +100,6 @@ public abstract class TestContextResourceUtils {
 	/**
 	 * Convert the supplied paths to a list of {@link Resource} handles using
 	 * the given {@link ResourceLoader}.
-	 *
 	 * @param resourceLoader the {@code ResourceLoader} to use to convert the paths
 	 * @param paths the paths to be converted
 	 * @return a new list of resources

spring-test/src/main/java/org/springframework/test/context/web/AnnotationConfigWebContextLoader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,6 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
 import org.springframework.context.annotation.AnnotatedBeanDefinitionReader;
-import org.springframework.lang.Nullable;
 import org.springframework.test.context.ContextConfigurationAttributes;
 import org.springframework.test.context.MergedContextConfiguration;
 import org.springframework.test.context.support.AnnotationConfigContextLoaderUtils;
@@ -80,7 +79,7 @@ public class AnnotationConfigWebContextLoader extends AbstractGenericWebContextL
 	 * @see #detectDefaultConfigurationClasses(Class)
 	 */
 	@Override
-	public void processContextConfiguration(@Nullable ContextConfigurationAttributes configAttributes) {
+	public void processContextConfiguration(ContextConfigurationAttributes configAttributes) {
 		if (!configAttributes.hasClasses() && isGenerateDefaultLocations()) {
 			configAttributes.setClasses(detectDefaultConfigurationClasses(configAttributes.getDeclaringClass()));
 		}

spring-test/src/main/java/org/springframework/test/context/web/WebMergedContextConfiguration.java

@@ -99,7 +99,7 @@ public class WebMergedContextConfiguration extends MergedContextConfiguration {
 	 * @since 4.1
 	 */
 	public WebMergedContextConfiguration(Class<?> testClass, @Nullable String[] locations, @Nullable Class<?>[] classes,
-			@Nullable Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> contextInitializerClasses,
+			@Nullable Set<Class<? extends ApplicationContextInitializer<?>>> contextInitializerClasses,
 			@Nullable String[] activeProfiles, @Nullable String[] propertySourceLocations, @Nullable String[] propertySourceProperties,
 			String resourceBasePath, ContextLoader contextLoader,
 			CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate, @Nullable MergedContextConfiguration parent) {
@@ -135,7 +135,7 @@ public class WebMergedContextConfiguration extends MergedContextConfiguration {
 	 * @since 4.3
 	 */
 	public WebMergedContextConfiguration(Class<?> testClass, @Nullable String[] locations, @Nullable Class<?>[] classes,
-			@Nullable Set<Class<? extends ApplicationContextInitializer<? extends ConfigurableApplicationContext>>> contextInitializerClasses,
+			@Nullable Set<Class<? extends ApplicationContextInitializer<?>>> contextInitializerClasses,
 			@Nullable String[] activeProfiles, @Nullable String[] propertySourceLocations, @Nullable String[] propertySourceProperties,
 			@Nullable Set<ContextCustomizer> contextCustomizers, String resourceBasePath, ContextLoader contextLoader,
 			CacheAwareContextLoaderDelegate cacheAwareContextLoaderDelegate, @Nullable MergedContextConfiguration parent) {
@@ -206,7 +206,7 @@ public class WebMergedContextConfiguration extends MergedContextConfiguration {
 				.append("propertySourceProperties", ObjectUtils.nullSafeToString(getPropertySourceProperties()))
 				.append("contextCustomizers", getContextCustomizers())
 				.append("resourceBasePath", getResourceBasePath())
-				.append("contextLoader", nullSafeToString(getContextLoader()))
+				.append("contextLoader", nullSafeClassName(getContextLoader()))
 				.append("parent", getParent())
 				.toString();
 	}

spring-test/src/main/java/org/springframework/test/context/web/socket/MockServerContainerContextCustomizer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,7 +16,10 @@
 
 package org.springframework.test.context.web.socket;
 
+import javax.servlet.ServletContext;
+
 import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.lang.Nullable;
 import org.springframework.test.context.ContextCustomizer;
 import org.springframework.test.context.MergedContextConfiguration;
 import org.springframework.web.context.WebApplicationContext;
@@ -35,12 +38,15 @@ class MockServerContainerContextCustomizer implements ContextCustomizer {
 	public void customizeContext(ConfigurableApplicationContext context, MergedContextConfiguration mergedConfig) {
 		if (context instanceof WebApplicationContext) {
 			WebApplicationContext wac = (WebApplicationContext) context;
-			wac.getServletContext().setAttribute("javax.websocket.server.ServerContainer", new MockServerContainer());
+			ServletContext sc = wac.getServletContext();
+			if (sc != null) {
+				sc.setAttribute("javax.websocket.server.ServerContainer", new MockServerContainer());
+			}
 		}
 	}
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		return (this == other || (other != null && getClass() == other.getClass()));
 	}
 

spring-test/src/main/java/org/springframework/test/jdbc/JdbcTestUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -50,7 +50,8 @@ public class JdbcTestUtils {
 	 * @return the number of rows in the table
 	 */
 	public static int countRowsInTable(JdbcTemplate jdbcTemplate, String tableName) {
-		return jdbcTemplate.queryForObject("SELECT COUNT(0) FROM " + tableName, Integer.class);
+		Integer result = jdbcTemplate.queryForObject("SELECT COUNT(0) FROM " + tableName, Integer.class);
+		return (result != null ? result : 0);
 	}
 
 	/**
@@ -72,7 +73,8 @@ public class JdbcTestUtils {
 		if (StringUtils.hasText(whereClause)) {
 			sql += " WHERE " + whereClause;
 		}
-		return jdbcTemplate.queryForObject(sql, Integer.class);
+		Integer result = jdbcTemplate.queryForObject(sql, Integer.class);
+		return (result != null ? result : 0);
 	}
 
 	/**
@@ -112,14 +114,14 @@ public class JdbcTestUtils {
 	 * optionally the scale.
 	 * @return the number of rows deleted from the table
 	 */
-	public static int deleteFromTableWhere(JdbcTemplate jdbcTemplate, String tableName, String whereClause,
-			Object... args) {
+	public static int deleteFromTableWhere(
+			JdbcTemplate jdbcTemplate, String tableName, String whereClause, Object... args) {
 
 		String sql = "DELETE FROM " + tableName;
 		if (StringUtils.hasText(whereClause)) {
 			sql += " WHERE " + whereClause;
 		}
-		int rowCount = (args != null && args.length > 0 ? jdbcTemplate.update(sql, args) : jdbcTemplate.update(sql));
+		int rowCount = (args.length > 0 ? jdbcTemplate.update(sql, args) : jdbcTemplate.update(sql));
 		if (logger.isInfoEnabled()) {
 			logger.info("Deleted " + rowCount + " rows from table " + tableName);
 		}

spring-test/src/main/java/org/springframework/test/util/AssertionErrors.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.test.util;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -50,7 +51,7 @@ public abstract class AssertionErrors {
 	 * @param expected expected value
 	 * @param actual actual value
 	 */
-	public static void fail(String message, Object expected, Object actual) {
+	public static void fail(String message, @Nullable Object expected, @Nullable Object actual) {
 		throw new AssertionError(message + " expected:<" + expected + "> but was:<" + actual + ">");
 	}
 
@@ -76,7 +77,7 @@ public abstract class AssertionErrors {
 	 * @param expected the expected value
 	 * @param actual the actual value
 	 */
-	public static void assertEquals(String message, Object expected, Object actual) {
+	public static void assertEquals(String message, @Nullable Object expected, @Nullable Object actual) {
 		if (!ObjectUtils.nullSafeEquals(expected, actual)) {
 			fail(message, ObjectUtils.nullSafeToString(expected), ObjectUtils.nullSafeToString(actual));
 		}
@@ -92,7 +93,7 @@ public abstract class AssertionErrors {
 	 * @param expected the expected value
 	 * @param actual the actual value
 	 */
-	public static void assertNotEquals(String message, Object expected, Object actual) {
+	public static void assertNotEquals(String message, @Nullable Object expected, @Nullable Object actual) {
 		if (ObjectUtils.nullSafeEquals(expected, actual)) {
 			throw new AssertionError(message + " was not expected to be:" +
 					"<" + ObjectUtils.nullSafeToString(actual) + ">");

spring-test/src/main/java/org/springframework/test/util/JsonExpectationsHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,7 +34,6 @@ public class JsonExpectationsHelper {
 	 * are "similar" - i.e. they contain the same attribute-value pairs
 	 * regardless of formatting with a lenient checking (extensible, and non-strict
 	 * array ordering).
-	 *
 	 * @param expected the expected JSON content
 	 * @param actual the actual JSON content
 	 * @since 4.1
@@ -48,13 +47,11 @@ public class JsonExpectationsHelper {
 	 * Parse the expected and actual strings as JSON and assert the two
 	 * are "similar" - i.e. they contain the same attribute-value pairs
 	 * regardless of formatting.
-	 *
 	 * <p>Can compare in two modes, depending on {@code strict} parameter value:
 	 * <ul>
-	 *     <li>{@code true}: strict checking. Not extensible, and strict array ordering.</li>
-	 *     <li>{@code false}: lenient checking. Extensible, and non-strict array ordering.</li>
+	 * <li>{@code true}: strict checking. Not extensible, and strict array ordering.</li>
+	 * <li>{@code false}: lenient checking. Extensible, and non-strict array ordering.</li>
 	 * </ul>
-	 *
 	 * @param expected the expected JSON content
 	 * @param actual the actual JSON content
 	 * @param strict enables strict checking
@@ -69,7 +66,6 @@ public class JsonExpectationsHelper {
 	 * are "not similar" - i.e. they contain different attribute-value pairs
 	 * regardless of formatting with a lenient checking (extensible, and non-strict
 	 * array ordering).
-	 *
 	 * @param expected the expected JSON content
 	 * @param actual the actual JSON content
 	 * @since 4.1
@@ -83,13 +79,11 @@ public class JsonExpectationsHelper {
 	 * Parse the expected and actual strings as JSON and assert the two
 	 * are "not similar" - i.e. they contain different attribute-value pairs
 	 * regardless of formatting.
-	 *
 	 * <p>Can compare in two modes, depending on {@code strict} parameter value:
 	 * <ul>
-	 *     <li>{@code true}: strict checking. Not extensible, and strict array ordering.</li>
-	 *     <li>{@code false}: lenient checking. Extensible, and non-strict array ordering.</li>
+	 * <li>{@code true}: strict checking. Not extensible, and strict array ordering.</li>
+	 * <li>{@code false}: lenient checking. Extensible, and non-strict array ordering.</li>
 	 * </ul>
-	 *
 	 * @param expected the expected JSON content
 	 * @param actual the actual JSON content
 	 * @param strict enables strict checking

spring-test/src/main/java/org/springframework/test/util/JsonPathExpectationsHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,6 +22,7 @@ import java.util.Map;
 import com.jayway.jsonpath.JsonPath;
 import org.hamcrest.Matcher;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
@@ -95,7 +96,7 @@ public class JsonPathExpectationsHelper {
 	 * @param content the JSON content
 	 * @param expectedValue the expected value
 	 */
-	public void assertValue(String content, Object expectedValue) {
+	public void assertValue(String content, @Nullable Object expectedValue) {
 		Object actualValue = evaluateJsonPath(content);
 		if ((actualValue instanceof List) && !(expectedValue instanceof List)) {
 			@SuppressWarnings("rawtypes")
@@ -231,11 +232,12 @@ public class JsonPathExpectationsHelper {
 		assertTrue(failureReason("a non-empty value", value), !ObjectUtils.isEmpty(value));
 	}
 
-	private String failureReason(String expectedDescription, Object value) {
+	private String failureReason(String expectedDescription, @Nullable Object value) {
 		return String.format("Expected %s at JSON path \"%s\" but found: %s", expectedDescription, this.expression,
 				ObjectUtils.nullSafeToString(StringUtils.quoteIfString(value)));
 	}
 
+	@Nullable
 	private Object evaluateJsonPath(String content) {
 		String message = "No value at JSON path \"" + this.expression + "\"";
 		try {
@@ -256,6 +258,7 @@ public class JsonPathExpectationsHelper {
 		}
 	}
 
+	@Nullable
 	private Object assertExistsAndReturn(String content) {
 		Object value = evaluateJsonPath(content);
 		String reason = "No value at JSON path \"" + this.expression + "\"";

spring-test/src/main/java/org/springframework/test/util/MetaAnnotationUtils.java

@@ -100,7 +100,7 @@ public abstract class MetaAnnotationUtils {
 	 */
 	@Nullable
 	private static <T extends Annotation> AnnotationDescriptor<T> findAnnotationDescriptor(
-			Class<?> clazz, Set<Annotation> visited, Class<T> annotationType) {
+			@Nullable Class<?> clazz, Set<Annotation> visited, Class<T> annotationType) {
 
 		Assert.notNull(annotationType, "Annotation type must not be null");
 		if (clazz == null || Object.class == clazz) {
@@ -187,7 +187,7 @@ public abstract class MetaAnnotationUtils {
 	 */
 	@SuppressWarnings("unchecked")
 	@Nullable
-	private static UntypedAnnotationDescriptor findAnnotationDescriptorForTypes(Class<?> clazz,
+	private static UntypedAnnotationDescriptor findAnnotationDescriptorForTypes(@Nullable Class<?> clazz,
 			Set<Annotation> visited, Class<? extends Annotation>... annotationTypes) {
 
 		assertNonEmptyAnnotationTypeArray(annotationTypes, "The list of annotation types must not be empty");
@@ -298,7 +298,7 @@ public abstract class MetaAnnotationUtils {
 		}
 
 		public AnnotationDescriptor(Class<?> rootDeclaringClass, Class<?> declaringClass,
-				Annotation composedAnnotation, T annotation) {
+				@Nullable Annotation composedAnnotation, T annotation) {
 
 			Assert.notNull(rootDeclaringClass, "'rootDeclaringClass' must not be null");
 			Assert.notNull(annotation, "Annotation must not be null");
@@ -349,6 +349,7 @@ public abstract class MetaAnnotationUtils {
 			return this.composedAnnotation;
 		}
 
+		@Nullable
 		public Class<? extends Annotation> getComposedAnnotationType() {
 			return (this.composedAnnotation != null ? this.composedAnnotation.annotationType() : null);
 		}
@@ -380,7 +381,7 @@ public abstract class MetaAnnotationUtils {
 		}
 
 		public UntypedAnnotationDescriptor(Class<?> rootDeclaringClass, Class<?> declaringClass,
-				Annotation composedAnnotation, Annotation annotation) {
+				@Nullable Annotation composedAnnotation, Annotation annotation) {
 
 			super(rootDeclaringClass, declaringClass, composedAnnotation, annotation);
 		}

spring-test/src/main/java/org/springframework/test/util/ReflectionTestUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -81,7 +81,7 @@ public class ReflectionTestUtils {
 	 * @param name the name of the field to set; never {@code null}
 	 * @param value the value to set
 	 */
-	public static void setField(Object targetObject, String name, Object value) {
+	public static void setField(Object targetObject, String name, @Nullable Object value) {
 		setField(targetObject, name, value, null);
 	}
 
@@ -97,7 +97,7 @@ public class ReflectionTestUtils {
 	 * @param type the type of the field to set; may be {@code null} if
 	 * {@code name} is specified
 	 */
-	public static void setField(Object targetObject, @Nullable String name, Object value, Class<?> type) {
+	public static void setField(Object targetObject, @Nullable String name, @Nullable Object value, @Nullable Class<?> type) {
 		setField(targetObject, null, name, value, type);
 	}
 
@@ -112,7 +112,7 @@ public class ReflectionTestUtils {
 	 * @param value the value to set
 	 * @since 4.2
 	 */
-	public static void setField(Class<?> targetClass, String name, Object value) {
+	public static void setField(Class<?> targetClass, String name, @Nullable Object value) {
 		setField(null, targetClass, name, value, null);
 	}
 
@@ -131,7 +131,9 @@ public class ReflectionTestUtils {
 	 * {@code name} is specified
 	 * @since 4.2
 	 */
-	public static void setField(Class<?> targetClass, @Nullable String name, Object value, @Nullable Class<?> type) {
+	public static void setField(
+			Class<?> targetClass, @Nullable String name, @Nullable Object value, @Nullable Class<?> type) {
+
 		setField(null, targetClass, name, value, type);
 	}
 
@@ -161,9 +163,11 @@ public class ReflectionTestUtils {
 	 * @see ReflectionUtils#setField(Field, Object, Object)
 	 * @see AopTestUtils#getUltimateTargetObject(Object)
 	 */
-	public static void setField(@Nullable Object targetObject, @Nullable Class<?> targetClass, @Nullable String name, Object value, @Nullable Class<?> type) {
+	public static void setField(@Nullable Object targetObject, @Nullable Class<?> targetClass,
+			@Nullable String name, @Nullable Object value, @Nullable Class<?> type) {
+
 		Assert.isTrue(targetObject != null || targetClass != null,
-			"Either targetObject or targetClass for the field must be specified");
+				"Either targetObject or targetClass for the field must be specified");
 
 		Object ultimateTarget = (targetObject != null ? AopTestUtils.getUltimateTargetObject(targetObject) : null);
 
@@ -198,6 +202,7 @@ public class ReflectionTestUtils {
 	 * @return the field's current value
 	 * @see #getField(Class, String)
 	 */
+	@Nullable
 	public static Object getField(Object targetObject, String name) {
 		return getField(targetObject, null, name);
 	}
@@ -214,6 +219,7 @@ public class ReflectionTestUtils {
 	 * @since 4.2
 	 * @see #getField(Object, String)
 	 */
+	@Nullable
 	public static Object getField(Class<?> targetClass, String name) {
 		return getField(null, targetClass, name);
 	}
@@ -242,6 +248,7 @@ public class ReflectionTestUtils {
 	 * @see ReflectionUtils#getField(Field, Object)
 	 * @see AopTestUtils#getUltimateTargetObject(Object)
 	 */
+	@Nullable
 	public static Object getField(@Nullable Object targetObject, @Nullable Class<?> targetClass, String name) {
 		Assert.isTrue(targetObject != null || targetClass != null,
 			"Either targetObject or targetClass for the field must be specified");
@@ -311,7 +318,7 @@ public class ReflectionTestUtils {
 	 * @see ReflectionUtils#makeAccessible(Method)
 	 * @see ReflectionUtils#invokeMethod(Method, Object, Object[])
 	 */
-	public static void invokeSetterMethod(Object target, String name, Object value, Class<?> type) {
+	public static void invokeSetterMethod(Object target, String name, @Nullable Object value, @Nullable Class<?> type) {
 		Assert.notNull(target, "Target object must not be null");
 		Assert.hasText(name, "Method name must not be empty");
 		Class<?>[] paramTypes = (type != null ? new Class<?>[] {type} : null);
@@ -361,6 +368,7 @@ public class ReflectionTestUtils {
 	 * @see ReflectionUtils#makeAccessible(Method)
 	 * @see ReflectionUtils#invokeMethod(Method, Object, Object[])
 	 */
+	@Nullable
 	public static Object invokeGetterMethod(Object target, String name) {
 		Assert.notNull(target, "Target object must not be null");
 		Assert.hasText(name, "Method name must not be empty");
@@ -404,7 +412,7 @@ public class ReflectionTestUtils {
 	 */
 	@SuppressWarnings("unchecked")
 	@Nullable
-	public static <T> T invokeMethod(Object target, String name, @Nullable Object... args) {
+	public static <T> T invokeMethod(Object target, String name, Object... args) {
 		Assert.notNull(target, "Target object must not be null");
 		Assert.hasText(name, "Method name must not be empty");
 
@@ -428,13 +436,13 @@ public class ReflectionTestUtils {
 		}
 	}
 
-	private static String safeToString(Object target) {
+	private static String safeToString(@Nullable Object target) {
 		try {
 			return String.format("target object [%s]", target);
 		}
 		catch (Exception ex) {
 			return String.format("target of type [%s] whose toString() method threw [%s]",
-				(target != null ? target.getClass().getName() : "unknown"), ex);
+					(target != null ? target.getClass().getName() : "unknown"), ex);
 		}
 	}
 

spring-test/src/main/java/org/springframework/test/util/XpathExpectationsHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,6 @@ package org.springframework.test.util;
 import java.io.ByteArrayInputStream;
 import java.util.Collections;
 import java.util.Map;
-
 import javax.xml.namespace.QName;
 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.DocumentBuilderFactory;
@@ -75,7 +74,7 @@ public class XpathExpectationsHelper {
 	}
 
 
-	private XPathExpression compileXpathExpression(String expression, Map<String, String> namespaces)
+	private XPathExpression compileXpathExpression(String expression, @Nullable Map<String, String> namespaces)
 			throws XPathExpressionException {
 
 		SimpleNamespaceContext namespaceContext = new SimpleNamespaceContext();
@@ -96,7 +95,9 @@ public class XpathExpectationsHelper {
 	 * Parse the content, evaluate the XPath expression as a {@link Node},
 	 * and assert it with the given {@code Matcher<Node>}.
 	 */
-	public void assertNode(byte[] content, String encoding, final Matcher<? super Node> matcher) throws Exception {
+	public void assertNode(byte[] content, @Nullable String encoding, final Matcher<? super Node> matcher)
+			throws Exception {
+
 		Document document = parseXmlByteArray(content, encoding);
 		Node node = evaluateXpath(document, XPathConstants.NODE, Node.class);
 		assertThat("XPath " + this.expression, node, matcher);
@@ -108,7 +109,7 @@ public class XpathExpectationsHelper {
 	 * @param encoding optional content encoding, if provided as metadata (e.g. in HTTP headers)
 	 * @return the parsed document
 	 */
-	protected Document parseXmlByteArray(byte[] xml, String encoding) throws Exception {
+	protected Document parseXmlByteArray(byte[] xml, @Nullable String encoding) throws Exception {
 		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
 		factory.setNamespaceAware(this.hasNamespaces);
 		DocumentBuilder documentBuilder = factory.newDocumentBuilder();
@@ -124,6 +125,7 @@ public class XpathExpectationsHelper {
 	 * @throws XPathExpressionException
 	 */
 	@SuppressWarnings("unchecked")
+	@Nullable
 	protected <T> T evaluateXpath(Document document, QName evaluationType, Class<T> expectedClass)
 			throws XPathExpressionException {
 
@@ -134,7 +136,7 @@ public class XpathExpectationsHelper {
 	 * Apply the XPath expression and assert the resulting content exists.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void exists(byte[] content, String encoding) throws Exception {
+	public void exists(byte[] content, @Nullable String encoding) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		Node node = evaluateXpath(document, XPathConstants.NODE, Node.class);
 		assertTrue("XPath " + this.expression + " does not exist", node != null);
@@ -144,7 +146,7 @@ public class XpathExpectationsHelper {
 	 * Apply the XPath expression and assert the resulting content does not exist.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void doesNotExist(byte[] content, String encoding) throws Exception {
+	public void doesNotExist(byte[] content, @Nullable String encoding) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		Node node = evaluateXpath(document, XPathConstants.NODE, Node.class);
 		assertTrue("XPath " + this.expression + " exists", node == null);
@@ -155,20 +157,22 @@ public class XpathExpectationsHelper {
 	 * given Hamcrest matcher.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void assertNodeCount(byte[] content, String encoding, Matcher<Integer> matcher) throws Exception {
+	public void assertNodeCount(byte[] content, @Nullable String encoding, Matcher<Integer> matcher) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		NodeList nodeList = evaluateXpath(document, XPathConstants.NODESET, NodeList.class);
-		assertThat("nodeCount for XPath " + this.expression, nodeList.getLength(), matcher);
+		assertThat("nodeCount for XPath " + this.expression,
+				(nodeList != null ? nodeList.getLength() : 0), matcher);
 	}
 
 	/**
 	 * Apply the XPath expression and assert the resulting content as an integer.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void assertNodeCount(byte[] content, String encoding, int expectedCount) throws Exception {
+	public void assertNodeCount(byte[] content, @Nullable String encoding, int expectedCount) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		NodeList nodeList = evaluateXpath(document, XPathConstants.NODESET, NodeList.class);
-		assertEquals("nodeCount for XPath " + this.expression, expectedCount, nodeList.getLength());
+		assertEquals("nodeCount for XPath " + this.expression, expectedCount,
+				(nodeList != null ? nodeList.getLength() : 0));
 	}
 
 	/**
@@ -176,7 +180,7 @@ public class XpathExpectationsHelper {
 	 * given Hamcrest matcher.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void assertString(byte[] content, String encoding, Matcher<? super String> matcher) throws Exception {
+	public void assertString(byte[] content, @Nullable String encoding, Matcher<? super String> matcher) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		String result = evaluateXpath(document,  XPathConstants.STRING, String.class);
 		assertThat("XPath " + this.expression, result, matcher);
@@ -186,7 +190,7 @@ public class XpathExpectationsHelper {
 	 * Apply the XPath expression and assert the resulting content as a String.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void assertString(byte[] content, String encoding, String expectedValue) throws Exception {
+	public void assertString(byte[] content, @Nullable String encoding, String expectedValue) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		String actual = evaluateXpath(document,  XPathConstants.STRING, String.class);
 		assertEquals("XPath " + this.expression, expectedValue, actual);
@@ -197,7 +201,7 @@ public class XpathExpectationsHelper {
 	 * given Hamcrest matcher.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void assertNumber(byte[] content, String encoding, Matcher<? super Double> matcher) throws Exception {
+	public void assertNumber(byte[] content, @Nullable String encoding, Matcher<? super Double> matcher) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		Double result = evaluateXpath(document, XPathConstants.NUMBER, Double.class);
 		assertThat("XPath " + this.expression, result, matcher);
@@ -207,7 +211,7 @@ public class XpathExpectationsHelper {
 	 * Apply the XPath expression and assert the resulting content as a Double.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void assertNumber(byte[] content, String encoding, Double expectedValue) throws Exception {
+	public void assertNumber(byte[] content, @Nullable String encoding, Double expectedValue) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		Double actual = evaluateXpath(document, XPathConstants.NUMBER, Double.class);
 		assertEquals("XPath " + this.expression, expectedValue, actual);
@@ -217,7 +221,7 @@ public class XpathExpectationsHelper {
 	 * Apply the XPath expression and assert the resulting content as a Boolean.
 	 * @throws Exception if content parsing or expression evaluation fails
 	 */
-	public void assertBoolean(byte[] content, String encoding, boolean expectedValue) throws Exception {
+	public void assertBoolean(byte[] content, @Nullable String encoding, boolean expectedValue) throws Exception {
 		Document document = parseXmlByteArray(content, encoding);
 		String actual = evaluateXpath(document, XPathConstants.STRING, String.class);
 		assertEquals("XPath " + this.expression, expectedValue, Boolean.parseBoolean(actual));

spring-test/src/main/java/org/springframework/test/web/ModelAndViewAssert.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -48,30 +48,30 @@ public abstract class ModelAndViewAssert {
 	 * Checks whether the model value under the given {@code modelName}
 	 * exists and checks it type, based on the {@code expectedType}. If the
 	 * model entry exists and the type matches, the model value is returned.
-	 *
 	 * @param mav ModelAndView to test against (never {@code null})
-	 * @param modelName name of the object to add to the model (never
-	 * {@code null})
+	 * @param modelName name of the object to add to the model (never {@code null})
 	 * @param expectedType expected type of the model value
 	 * @return the model value
 	 */
 	@SuppressWarnings("unchecked")
 	public static <T> T assertAndReturnModelAttributeOfType(ModelAndView mav, String modelName, Class<T> expectedType) {
-		assertTrue("ModelAndView is null", mav != null);
-		assertTrue("Model is null", mav.getModel() != null);
-		Object obj = mav.getModel().get(modelName);
-		assertTrue("Model attribute with name '" + modelName + "' is null", obj != null);
-		assertTrue("Model attribute is not of expected type '" + expectedType.getName() + "' but rather of type '"
-				+ obj.getClass().getName() + "'", expectedType.isAssignableFrom(obj.getClass()));
+		if (mav == null) {
+			fail("ModelAndView is null");
+		}
+		Map<String, Object> model = mav.getModel();
+		Object obj = model.get(modelName);
+		if (obj == null) {
+			fail("Model attribute with name '" + modelName + "' is null");
+		}
+		assertTrue("Model attribute is not of expected type '" + expectedType.getName() + "' but rather of type '" +
+				obj.getClass().getName() + "'", expectedType.isAssignableFrom(obj.getClass()));
 		return (T) obj;
 	}
 
 	/**
 	 * Compare each individual entry in a list, without first sorting the lists.
-	 *
 	 * @param mav ModelAndView to test against (never {@code null})
-	 * @param modelName name of the object to add to the model (never
-	 * {@code null})
+	 * @param modelName name of the object to add to the model (never {@code null})
 	 * @param expectedList the expected list
 	 */
 	@SuppressWarnings("rawtypes")
@@ -87,55 +87,53 @@ public abstract class ModelAndViewAssert {
 
 	/**
 	 * Assert whether or not a model attribute is available.
-	 *
 	 * @param mav ModelAndView to test against (never {@code null})
-	 * @param modelName name of the object to add to the model (never
-	 * {@code null})
+	 * @param modelName name of the object to add to the model (never {@code null})
 	 */
 	public static void assertModelAttributeAvailable(ModelAndView mav, String modelName) {
-		assertTrue("ModelAndView is null", mav != null);
-		assertTrue("Model is null", mav.getModel() != null);
-		assertTrue("Model attribute with name '" + modelName + "' is not available",
-			mav.getModel().containsKey(modelName));
+		if (mav == null) {
+			fail("ModelAndView is null");
+		}
+		Map<String, Object> model = mav.getModel();
+		assertTrue("Model attribute with name '" + modelName + "' is not available", model.containsKey(modelName));
 	}
 
 	/**
 	 * Compare a given {@code expectedValue} to the value from the model
 	 * bound under the given {@code modelName}.
-	 *
 	 * @param mav ModelAndView to test against (never {@code null})
-	 * @param modelName name of the object to add to the model (never
-	 * {@code null})
+	 * @param modelName name of the object to add to the model (never {@code null})
 	 * @param expectedValue the model value
 	 */
 	public static void assertModelAttributeValue(ModelAndView mav, String modelName, Object expectedValue) {
 		assertTrue("ModelAndView is null", mav != null);
 		Object modelValue = assertAndReturnModelAttributeOfType(mav, modelName, Object.class);
-		assertTrue("Model value with name '" + modelName + "' is not the same as the expected value which was '"
-				+ expectedValue + "'", modelValue.equals(expectedValue));
+		assertTrue("Model value with name '" + modelName + "' is not the same as the expected value which was '" +
+				expectedValue + "'", modelValue.equals(expectedValue));
 	}
 
 	/**
 	 * Inspect the {@code expectedModel} to see if all elements in the
 	 * model appear and are equal.
-	 *
 	 * @param mav ModelAndView to test against (never {@code null})
 	 * @param expectedModel the expected model
 	 */
 	public static void assertModelAttributeValues(ModelAndView mav, Map<String, Object> expectedModel) {
-		assertTrue("ModelAndView is null", mav != null);
-		assertTrue("Model is null", mav.getModel() != null);
+		if (mav == null) {
+			fail("ModelAndView is null");
+		}
+		Map<String, Object> model = mav.getModel();
 
-		if (!mav.getModel().keySet().equals(expectedModel.keySet())) {
+		if (!model.keySet().equals(expectedModel.keySet())) {
 			StringBuilder sb = new StringBuilder("Keyset of expected model does not match.\n");
-			appendNonMatchingSetsErrorMessage(expectedModel.keySet(), mav.getModel().keySet(), sb);
+			appendNonMatchingSetsErrorMessage(expectedModel.keySet(), model.keySet(), sb);
 			fail(sb.toString());
 		}
 
 		StringBuilder sb = new StringBuilder();
-		for (String modelName : mav.getModel().keySet()) {
+		for (String modelName : model.keySet()) {
 			Object assertionValue = expectedModel.get(modelName);
-			Object mavValue = mav.getModel().get(modelName);
+			Object mavValue = model.get(modelName);
 			if (!assertionValue.equals(mavValue)) {
 				sb.append("Value under name '").append(modelName).append("' differs, should have been '").append(
 					assertionValue).append("' but was '").append(mavValue).append("'\n");
@@ -151,18 +149,15 @@ public abstract class ModelAndViewAssert {
 	/**
 	 * Compare each individual entry in a list after having sorted both lists
 	 * (optionally using a comparator).
-	 *
 	 * @param mav ModelAndView to test against (never {@code null})
-	 * @param modelName name of the object to add to the model (never
-	 * {@code null})
+	 * @param modelName name of the object to add to the model (never {@code null})
 	 * @param expectedList the expected list
-	 * @param comparator the comparator to use (may be {@code null}). If
-	 * not specifying the comparator, both lists will be sorted not using any
-	 * comparator.
+	 * @param comparator the comparator to use (may be {@code null}). If not
+	 * specifying the comparator, both lists will be sorted not using any comparator.
 	 */
 	@SuppressWarnings({ "unchecked", "rawtypes" })
-	public static void assertSortAndCompareListModelAttribute(ModelAndView mav, String modelName, List expectedList,
-			Comparator comparator) {
+	public static void assertSortAndCompareListModelAttribute(
+			ModelAndView mav, String modelName, List expectedList, Comparator comparator) {
 
 		assertTrue("ModelAndView is null", mav != null);
 		List modelList = assertAndReturnModelAttributeOfType(mav, modelName, List.class);
@@ -187,18 +182,20 @@ public abstract class ModelAndViewAssert {
 	/**
 	 * Check to see if the view name in the ModelAndView matches the given
 	 * {@code expectedName}.
-	 *
 	 * @param mav ModelAndView to test against (never {@code null})
 	 * @param expectedName the name of the model value
 	 */
 	public static void assertViewName(ModelAndView mav, String expectedName) {
-		assertTrue("ModelAndView is null", mav != null);
+		if (mav == null) {
+			fail("ModelAndView is null");
+		}
 		assertTrue("View name is not equal to '" + expectedName + "' but was '" + mav.getViewName() + "'",
 			ObjectUtils.nullSafeEquals(expectedName, mav.getViewName()));
 	}
 
-	private static void appendNonMatchingSetsErrorMessage(Set<String> assertionSet, Set<String> incorrectSet,
-			StringBuilder sb) {
+
+	private static void appendNonMatchingSetsErrorMessage(
+			Set<String> assertionSet, Set<String> incorrectSet, StringBuilder sb) {
 
 		Set<String> tempSet = new HashSet<>();
 		tempSet.addAll(incorrectSet);

spring-test/src/main/java/org/springframework/test/web/client/match/ContentRequestMatchers.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -98,8 +98,10 @@ public class ContentRequestMatchers {
 			public void match(ClientHttpRequest request) throws IOException, AssertionError {
 				MediaType actualContentType = request.getHeaders().getContentType();
 				assertTrue("Content type not set", actualContentType != null);
-				assertTrue("Content type [" + actualContentType + "] is not compatible with [" + contentType + "]",
-						actualContentType.isCompatibleWith(contentType));
+				if (actualContentType != null) {
+					assertTrue("Content type [" + actualContentType + "] is not compatible with [" + contentType + "]",
+							actualContentType.isCompatibleWith(contentType));
+				}
 			}
 		};
 	}

spring-test/src/main/java/org/springframework/test/web/client/match/MockRestRequestMatchers.java

@@ -180,8 +180,10 @@ public abstract class MockRestRequestMatchers {
 			@Override
 			public void match(ClientHttpRequest request) {
 				assertValueCount("header", name, request.getHeaders(), matchers.length);
-				for (int i = 0 ; i < matchers.length; i++) {
-					assertThat("Request header", request.getHeaders().get(name).get(i), matchers[i]);
+				List<String> headerValues = request.getHeaders().get(name);
+				Assert.state(headerValues != null, "No header values");
+				for (int i = 0; i < matchers.length; i++) {
+					assertThat("Request header [" + name + "]", headerValues.get(i), matchers[i]);
 				}
 			}
 		};
@@ -195,9 +197,10 @@ public abstract class MockRestRequestMatchers {
 			@Override
 			public void match(ClientHttpRequest request) {
 				assertValueCount("header", name, request.getHeaders(), expectedValues.length);
+				List<String> headerValues = request.getHeaders().get(name);
+				Assert.state(headerValues != null, "No header values");
 				for (int i = 0 ; i < expectedValues.length; i++) {
-					assertEquals("Request header + [" + name + "]",
-							expectedValues[i], request.getHeaders().get(name).get(i));
+					assertEquals("Request header [" + name + "]", expectedValues[i], headerValues.get(i));
 				}
 			}
 		};

spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultRouterFunctionSpec.java

@@ -43,9 +43,7 @@ class DefaultRouterFunctionSpec extends AbstractMockServerSpec<WebTestClient.Rou
 
 	@Override
 	public WebTestClient.RouterFunctionSpec handlerStrategies(HandlerStrategies handlerStrategies) {
-		if (handlerStrategies != null) {
-			this.handlerStrategies = handlerStrategies;
-		}
+		this.handlerStrategies = handlerStrategies;
 		return this;
 	}
 

spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultWebTestClient.java

@@ -50,11 +50,9 @@ import org.springframework.web.reactive.function.client.ExchangeFilterFunction;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.util.UriBuilder;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
-import static org.springframework.test.util.AssertionErrors.assertEquals;
-import static org.springframework.test.util.AssertionErrors.assertTrue;
-import static org.springframework.web.reactive.function.BodyExtractors.toFlux;
-import static org.springframework.web.reactive.function.BodyExtractors.toMono;
+import static java.nio.charset.StandardCharsets.*;
+import static org.springframework.test.util.AssertionErrors.*;
+import static org.springframework.web.reactive.function.BodyExtractors.*;
 
 /**
  * Default implementation of {@link WebTestClient}.
@@ -73,7 +71,7 @@ class DefaultWebTestClient implements WebTestClient {
 	private final AtomicLong requestIndex = new AtomicLong();
 
 
-	DefaultWebTestClient(WebClient.Builder clientBuilder, ClientHttpConnector connector, Duration timeout) {
+	DefaultWebTestClient(WebClient.Builder clientBuilder, ClientHttpConnector connector, @Nullable Duration timeout) {
 		Assert.notNull(clientBuilder, "WebClient.Builder is required");
 		this.wiretapConnector = new WiretapConnector(connector);
 		this.webClient = clientBuilder.clientConnector(this.wiretapConnector).build();
@@ -179,15 +177,13 @@ class DefaultWebTestClient implements WebTestClient {
 
 		private final String requestId;
 
-
-		DefaultRequestBodySpec(WebClient.RequestBodySpec spec, String uriTemplate) {
+		DefaultRequestBodySpec(WebClient.RequestBodySpec spec, @Nullable String uriTemplate) {
 			this.bodySpec = spec;
 			this.uriTemplate = uriTemplate;
 			this.requestId = String.valueOf(requestIndex.incrementAndGet());
 			this.bodySpec.header(WebTestClient.WEBTESTCLIENT_REQUEST_ID, this.requestId);
 		}
 
-
 		@Override
 		public RequestBodySpec header(String headerName, String... headerValues) {
 			this.bodySpec.header(headerName, headerValues);
@@ -276,7 +272,6 @@ class DefaultWebTestClient implements WebTestClient {
 			ExchangeResult exchangeResult = wiretapConnector.claimRequest(this.requestId);
 			return new DefaultResponseSpec(exchangeResult, clientResponse, this.uriTemplate, getTimeout());
 		}
-
 	}
 
 
@@ -286,7 +281,6 @@ class DefaultWebTestClient implements WebTestClient {
 
 		private final Duration timeout;
 
-
 		UndecodedExchangeResult(ExchangeResult result, ClientResponse response,
 				String uriTemplate, Duration timeout) {
 
@@ -295,7 +289,6 @@ class DefaultWebTestClient implements WebTestClient {
 			this.timeout = timeout;
 		}
 
-
 		@SuppressWarnings("unchecked")
 		public <T> EntityExchangeResult<T> decode(ResolvableType bodyType) {
 			T body = (T) this.response.body(toMono(bodyType)).block(this.timeout);
@@ -318,7 +311,6 @@ class DefaultWebTestClient implements WebTestClient {
 			byte[] body = (resource != null ? resource.getByteArray() : null);
 			return new EntityExchangeResult<>(this, body);
 		}
-
 	}
 
 
@@ -326,7 +318,6 @@ class DefaultWebTestClient implements WebTestClient {
 
 		private final UndecodedExchangeResult result;
 
-
 		DefaultResponseSpec(ExchangeResult result, ClientResponse response, String uriTemplate, Duration timeout) {
 			this.result = new UndecodedExchangeResult(result, response, uriTemplate, timeout);
 		}
@@ -342,13 +333,15 @@ class DefaultWebTestClient implements WebTestClient {
 		}
 
 		@Override
+		@SuppressWarnings("unchecked")
 		public <B> BodySpec<B, ?> expectBody(Class<B> bodyType) {
-			return expectBody(ResolvableType.forClass(bodyType));
+			return (BodySpec<B, ?>) expectBody(ResolvableType.forClass(bodyType));
 		}
 
 		@Override
+		@SuppressWarnings({"rawtypes", "unchecked"})
 		public <B> BodySpec<B, ?> expectBody(ResolvableType bodyType) {
-			return new DefaultBodySpec<>(this.result.decode(bodyType));
+			return new DefaultBodySpec(this.result.decode(bodyType));
 		}
 
 		@Override
@@ -375,7 +368,6 @@ class DefaultWebTestClient implements WebTestClient {
 		public <T> FluxExchangeResult<T> returnResult(ResolvableType elementType) {
 			return this.result.decodeToFlux(elementType);
 		}
-
 	}
 
 
@@ -383,26 +375,23 @@ class DefaultWebTestClient implements WebTestClient {
 
 		private final EntityExchangeResult<B> result;
 
-
 		DefaultBodySpec(EntityExchangeResult<B> result) {
 			this.result = result;
 		}
 
-
 		protected EntityExchangeResult<B> getResult() {
 			return this.result;
 		}
 
 		@Override
 		public <T extends S> T isEqualTo(B expected) {
-			B actual = this.result.getResponseBody();
-			this.result.assertWithDiagnostics(() -> assertEquals("Response body", expected, actual));
+			this.result.assertWithDiagnostics(() ->
+					assertEquals("Response body", expected, this.result.getResponseBody()));
 			return self();
 		}
 
 		@Override
 		public <T extends S> T consumeWith(Consumer<EntityExchangeResult<B>> consumer) {
-			B actual = this.result.getResponseBody();
 			this.result.assertWithDiagnostics(() -> consumer.accept(this.result));
 			return self();
 		}
@@ -416,24 +405,21 @@ class DefaultWebTestClient implements WebTestClient {
 		public EntityExchangeResult<B> returnResult() {
 			return this.result;
 		}
-
 	}
 
 
 	private static class DefaultListBodySpec<E> extends DefaultBodySpec<List<E>, ListBodySpec<E>>
 			implements ListBodySpec<E> {
 
-
 		DefaultListBodySpec(EntityExchangeResult<List<E>> result) {
 			super(result);
 		}
 
-
 		@Override
 		public ListBodySpec<E> hasSize(int size) {
 			List<E> actual = getResult().getResponseBody();
 			String message = "Response body does not contain " + size + " elements";
-			getResult().assertWithDiagnostics(() -> assertEquals(message, size, actual.size()));
+			getResult().assertWithDiagnostics(() -> assertEquals(message, size, (actual != null ? actual.size() : 0)));
 			return this;
 		}
 
@@ -443,7 +429,7 @@ class DefaultWebTestClient implements WebTestClient {
 			List<E> expected = Arrays.asList(elements);
 			List<E> actual = getResult().getResponseBody();
 			String message = "Response body does not contain " + expected;
-			getResult().assertWithDiagnostics(() -> assertTrue(message, actual.containsAll(expected)));
+			getResult().assertWithDiagnostics(() -> assertTrue(message, (actual != null && actual.containsAll(expected))));
 			return this;
 		}
 
@@ -452,8 +438,8 @@ class DefaultWebTestClient implements WebTestClient {
 		public ListBodySpec<E> doesNotContain(E... elements) {
 			List<E> expected = Arrays.asList(elements);
 			List<E> actual = getResult().getResponseBody();
-			String message = "Response body should have contained " + expected;
-			getResult().assertWithDiagnostics(() -> assertTrue(message, !actual.containsAll(expected)));
+			String message = "Response body should not have contained " + expected;
+			getResult().assertWithDiagnostics(() -> assertTrue(message, (actual == null || !actual.containsAll(expected))));
 			return this;
 		}
 
@@ -461,7 +447,6 @@ class DefaultWebTestClient implements WebTestClient {
 		public EntityExchangeResult<List<E>> returnResult() {
 			return getResult();
 		}
-
 	}
 
 
@@ -471,13 +456,11 @@ class DefaultWebTestClient implements WebTestClient {
 
 		private final boolean isEmpty;
 
-
 		DefaultBodyContentSpec(EntityExchangeResult<byte[]> result) {
 			this.result = result;
 			this.isEmpty = (result.getResponseBody() == null);
 		}
 
-
 		@Override
 		public EntityExchangeResult<Void> isEmpty() {
 			this.result.assertWithDiagnostics(() -> assertTrue("Expected empty body", this.isEmpty));
@@ -502,14 +485,14 @@ class DefaultWebTestClient implements WebTestClient {
 			return new JsonPathAssertions(this, getBodyAsString(), expression, args);
 		}
 
-		@Nullable
 		private String getBodyAsString() {
-			if (this.isEmpty) {
-				return null;
+			byte[] body = this.result.getResponseBody();
+			if (body == null || body.length == 0) {
+				return "";
 			}
 			MediaType mediaType = this.result.getResponseHeaders().getContentType();
 			Charset charset = Optional.ofNullable(mediaType).map(MimeType::getCharset).orElse(UTF_8);
-			return new String(this.result.getResponseBody(), charset);
+			return new String(body, charset);
 		}
 
 		@Override
@@ -522,7 +505,6 @@ class DefaultWebTestClient implements WebTestClient {
 		public EntityExchangeResult<byte[]> returnResult() {
 			return this.result;
 		}
-
 	}
 
 }

spring-test/src/main/java/org/springframework/test/web/reactive/server/EntityExchangeResult.java

@@ -16,6 +16,8 @@
 
 package org.springframework.test.web.reactive.server;
 
+import org.springframework.lang.Nullable;
+
 /**
  * {@code ExchangeResult} sub-class that exposes the response body fully
  * extracted to a representation of type {@code <T>}.
@@ -30,7 +32,7 @@ public class EntityExchangeResult<T> extends ExchangeResult {
 	private final T body;
 
 
-	EntityExchangeResult(ExchangeResult result, T body) {
+	EntityExchangeResult(ExchangeResult result, @Nullable T body) {
 		super(result);
 		this.body = body;
 	}
@@ -39,6 +41,7 @@ public class EntityExchangeResult<T> extends ExchangeResult {
 	/**
 	 * Return the entity extracted from the response body.
 	 */
+	@Nullable
 	public T getResponseBody() {
 		return this.body;
 	}

spring-test/src/main/java/org/springframework/test/web/reactive/server/ExchangeResult.java

@@ -31,6 +31,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseCookie;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 
@@ -110,6 +111,7 @@ public class ExchangeResult {
 	/**
 	 * Return the original URI template used to prepare the request, if any.
 	 */
+	@Nullable
 	public String getUriTemplate() {
 		return this.uriTemplate;
 	}
@@ -194,11 +196,7 @@ public class ExchangeResult {
 	}
 
 	private String getStatusReason() {
-		String reason = "";
-		if (getStatus() != null && getStatus().getReasonPhrase() != null) {
-			reason = getStatus().getReasonPhrase();
-		}
-		return reason;
+		return getStatus().getReasonPhrase();
 	}
 
 	private String formatHeaders(HttpHeaders headers, String delimiter) {
@@ -207,7 +205,7 @@ public class ExchangeResult {
 				.collect(Collectors.joining(delimiter));
 	}
 
-	private String formatBody(MediaType contentType, MonoProcessor<byte[]> body) {
+	private String formatBody(@Nullable MediaType contentType, MonoProcessor<byte[]> body) {
 		if (body.isSuccess()) {
 			byte[] bytes = body.block(Duration.ZERO);
 			if (bytes.length == 0) {

spring-test/src/main/java/org/springframework/test/web/reactive/server/HeaderAssertions.java

@@ -23,9 +23,9 @@ import org.springframework.http.CacheControl;
 import org.springframework.http.ContentDisposition;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
+import org.springframework.lang.Nullable;
 
-import static org.springframework.test.util.AssertionErrors.assertEquals;
-import static org.springframework.test.util.AssertionErrors.assertTrue;
+import static org.springframework.test.util.AssertionErrors.*;
 
 /**
  * Assertions on headers of the response.
@@ -62,7 +62,9 @@ public class HeaderAssertions {
 	 */
 	public WebTestClient.ResponseSpec valueMatches(String name, String pattern) {
 		String value = getHeaders().getFirst(name);
-		assertTrue(getMessage(name) + " not found", value != null);
+		if (value == null) {
+			fail(getMessage(name) + " not found");
+		}
 		boolean match = Pattern.compile(pattern).matcher(value).matches();
 		String message = getMessage(name) + "=\'" + value + "\' does not match \'" + pattern + "\'";
 		this.exchangeResult.assertWithDiagnostics(() -> assertTrue(message, match));
@@ -122,7 +124,7 @@ public class HeaderAssertions {
 		return "Response header [" + headerName + "]";
 	}
 
-	private WebTestClient.ResponseSpec assertHeader(String name, Object expected, Object actual) {
+	private WebTestClient.ResponseSpec assertHeader(String name, @Nullable Object expected, @Nullable Object actual) {
 		this.exchangeResult.assertWithDiagnostics(() -> assertEquals(getMessage(name), expected, actual));
 		return this.responseSpec;
 	}

spring-test/src/main/java/org/springframework/test/web/reactive/server/JsonPathAssertions.java

@@ -13,11 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.test.web.reactive.server;
 
 import org.springframework.test.util.JsonPathExpectationsHelper;
 
-
 /**
  * <a href="https://github.com/jayway/JsonPath">JsonPath</a> assertions.
  *

spring-test/src/main/java/org/springframework/test/web/servlet/DefaultMvcResult.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@ package org.springframework.test.web.servlet;
 
 import java.util.concurrent.atomic.AtomicReference;
 
+import org.springframework.lang.Nullable;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.mock.web.MockHttpServletResponse;
 import org.springframework.web.servlet.FlashMap;
@@ -71,7 +72,7 @@ class DefaultMvcResult implements MvcResult {
 		return this.mockResponse;
 	}
 
-	public void setHandler(Object handler) {
+	public void setHandler(@Nullable Object handler) {
 		this.handler = handler;
 	}
 
@@ -80,7 +81,7 @@ class DefaultMvcResult implements MvcResult {
 		return this.handler;
 	}
 
-	public void setInterceptors(HandlerInterceptor... interceptors) {
+	public void setInterceptors(@Nullable HandlerInterceptor... interceptors) {
 		this.interceptors = interceptors;
 	}
 
@@ -98,7 +99,7 @@ class DefaultMvcResult implements MvcResult {
 		return this.resolvedException;
 	}
 
-	public void setModelAndView(ModelAndView mav) {
+	public void setModelAndView(@Nullable ModelAndView mav) {
 		this.modelAndView = mav;
 	}
 

spring-test/src/main/java/org/springframework/test/web/servlet/MockMvc.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -79,18 +79,16 @@ public final class MockMvc {
 	 * Private constructor, not for direct instantiation.
 	 * @see org.springframework.test.web.servlet.setup.MockMvcBuilders
 	 */
-	MockMvc(TestDispatcherServlet servlet, Filter[] filters, ServletContext servletContext) {
-
+	MockMvc(TestDispatcherServlet servlet, Filter... filters) {
 		Assert.notNull(servlet, "DispatcherServlet is required");
-		Assert.notNull(filters, "filters cannot be null");
-		Assert.noNullElements(filters, "filters cannot contain null values");
-		Assert.notNull(servletContext, "A ServletContext is required");
-
+		Assert.notNull(filters, "Filters cannot be null");
+		Assert.noNullElements(filters, "Filters cannot contain null values");
 		this.servlet = servlet;
 		this.filters = filters;
-		this.servletContext = servletContext;
+		this.servletContext = servlet.getServletContext();
 	}
 
+
 	/**
 	 * A default request builder merged into every performed request.
 	 * @see org.springframework.test.web.servlet.setup.DefaultMockMvcBuilder#defaultRequest(RequestBuilder)
@@ -120,18 +118,14 @@ public final class MockMvc {
 	/**
 	 * Perform a request and return a type that allows chaining further
 	 * actions, such as asserting expectations, on the result.
-	 *
 	 * @param requestBuilder used to prepare the request to execute;
 	 * see static factory methods in
 	 * {@link org.springframework.test.web.servlet.request.MockMvcRequestBuilders}
-	 *
 	 * @return an instance of {@link ResultActions}; never {@code null}
-	 *
 	 * @see org.springframework.test.web.servlet.request.MockMvcRequestBuilders
 	 * @see org.springframework.test.web.servlet.result.MockMvcResultMatchers
 	 */
 	public ResultActions perform(RequestBuilder requestBuilder) throws Exception {
-
 		if (this.defaultRequestBuilder != null) {
 			if (requestBuilder instanceof Mergeable) {
 				requestBuilder = (RequestBuilder) ((Mergeable) requestBuilder).merge(this.defaultRequestBuilder);
@@ -156,28 +150,23 @@ public final class MockMvc {
 
 		if (DispatcherType.ASYNC.equals(request.getDispatcherType()) &&
 				request.getAsyncContext() != null & !request.isAsyncStarted()) {
-
 			request.getAsyncContext().complete();
 		}
 
 		applyDefaultResultActions(mvcResult);
-
 		RequestContextHolder.setRequestAttributes(previousAttributes);
 
 		return new ResultActions() {
-
 			@Override
 			public ResultActions andExpect(ResultMatcher matcher) throws Exception {
 				matcher.match(mvcResult);
 				return this;
 			}
-
 			@Override
 			public ResultActions andDo(ResultHandler handler) throws Exception {
 				handler.handle(mvcResult);
 				return this;
 			}
-
 			@Override
 			public MvcResult andReturn() {
 				return mvcResult;
@@ -185,6 +174,7 @@ public final class MockMvc {
 		};
 	}
 
+
 	private void applyDefaultResultActions(MvcResult mvcResult) throws Exception {
 
 		for (ResultMatcher matcher : this.defaultResultMatchers) {

spring-test/src/main/java/org/springframework/test/web/servlet/MockMvcBuilderSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,10 +18,10 @@ package org.springframework.test.web.servlet;
 
 import java.util.List;
 import javax.servlet.Filter;
-import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
 
 import org.springframework.core.NestedRuntimeException;
+import org.springframework.lang.Nullable;
 import org.springframework.mock.web.MockServletConfig;
 import org.springframework.web.context.WebApplicationContext;
 
@@ -43,9 +43,7 @@ public abstract class MockMvcBuilderSupport {
 	protected final MockMvc createMockMvc(Filter[] filters, MockServletConfig servletConfig,
 			WebApplicationContext webAppContext, RequestBuilder defaultRequestBuilder,
 			List<ResultMatcher> globalResultMatchers, List<ResultHandler> globalResultHandlers,
-			List<DispatcherServletCustomizer> dispatcherServletCustomizers) {
-
-		ServletContext servletContext = webAppContext.getServletContext();
+			@Nullable List<DispatcherServletCustomizer> dispatcherServletCustomizers) {
 
 		TestDispatcherServlet dispatcherServlet = new TestDispatcherServlet(webAppContext);
 		if (dispatcherServletCustomizers != null) {
@@ -61,7 +59,7 @@ public abstract class MockMvcBuilderSupport {
 			throw new MockMvcBuildException("Failed to initialize TestDispatcherServlet", ex);
 		}
 
-		MockMvc mockMvc = new MockMvc(dispatcherServlet, filters, servletContext);
+		MockMvc mockMvc = new MockMvc(dispatcherServlet, filters);
 		mockMvc.setDefaultRequest(defaultRequestBuilder);
 		mockMvc.setGlobalResultMatchers(globalResultMatchers);
 		mockMvc.setGlobalResultHandlers(globalResultHandlers);
@@ -69,6 +67,7 @@ public abstract class MockMvcBuilderSupport {
 		return mockMvc;
 	}
 
+
 	@SuppressWarnings("serial")
 	private static class MockMvcBuildException extends NestedRuntimeException {
 

spring-test/src/main/java/org/springframework/test/web/servlet/MvcResult.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License; Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -60,7 +60,7 @@ public interface MvcResult {
 
 	/**
 	 * Return the {@code ModelAndView} prepared by the handler.
-	 * @return a {@code ModelAndView}, or {@code null}
+	 * @return a {@code ModelAndView}, or {@code null} if none
 	 */
 	@Nullable
 	ModelAndView getModelAndView();
@@ -68,7 +68,7 @@ public interface MvcResult {
 	/**
 	 * Return any exception raised by a handler and successfully resolved
 	 * through a {@link HandlerExceptionResolver}.
-	 * @return an exception, possibly {@code null}
+	 * @return an exception, or {@code null} if none
 	 */
 	@Nullable
  	Exception getResolvedException();

spring-test/src/main/java/org/springframework/test/web/servlet/RequestBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,7 +34,6 @@ public interface RequestBuilder {
 
 	/**
 	 * Build the request.
-	 *
 	 * @param servletContext the {@link ServletContext} to use to create the request
 	 * @return the request
 	 */

spring-test/src/main/java/org/springframework/test/web/servlet/htmlunit/HtmlUnitRequestBuilder.java

@@ -107,11 +107,13 @@ final class HtmlUnitRequestBuilder implements RequestBuilder, Mergeable {
 		Charset charset = getCharset();
 		String httpMethod = this.webRequest.getHttpMethod().name();
 		UriComponents uriComponents = uriComponents();
+		String path = uriComponents.getPath();
 
 		MockHttpServletRequest request = new HtmlUnitMockHttpServletRequest(
-				servletContext, httpMethod, uriComponents.getPath());
+				servletContext, httpMethod, (path != null ? path : ""));
 		parent(request, this.parentBuilder);
-		request.setServerName(uriComponents.getHost());  // needs to be first for additional headers
+		String host = uriComponents.getHost();
+		request.setServerName(host != null ? host : "");  // needs to be first for additional headers
 		authType(request);
 		request.setCharacterEncoding(charset.name());
 		content(request, charset);
@@ -125,7 +127,8 @@ final class HtmlUnitRequestBuilder implements RequestBuilder, Mergeable {
 		ports(uriComponents, request);
 		request.setProtocol("HTTP/1.1");
 		request.setQueryString(uriComponents.getQuery());
-		request.setScheme(uriComponents.getScheme());
+		String scheme = uriComponents.getScheme();
+		request.setScheme(scheme != null ? scheme : "");
 		request.setPathInfo(null);
 
 		return postProcess(request);
@@ -146,7 +149,7 @@ final class HtmlUnitRequestBuilder implements RequestBuilder, Mergeable {
 		return request;
 	}
 
-	private void parent(MockHttpServletRequest request, RequestBuilder parent) {
+	private void parent(MockHttpServletRequest request, @Nullable RequestBuilder parent) {
 		if (parent == null) {
 			return;
 		}
@@ -156,11 +159,13 @@ final class HtmlUnitRequestBuilder implements RequestBuilder, Mergeable {
 		// session
 		HttpSession parentSession = parentRequest.getSession(false);
 		if (parentSession != null) {
+			HttpSession localSession = request.getSession();
+			Assert.state(localSession != null, "No local HttpSession");
 			Enumeration<String> attrNames = parentSession.getAttributeNames();
 			while (attrNames.hasMoreElements()) {
 				String attrName = attrNames.nextElement();
 				Object attrValue = parentSession.getAttribute(attrName);
-				request.getSession().setAttribute(attrName, attrValue);
+				localSession.setAttribute(attrName, attrValue);
 			}
 		}
 
@@ -254,7 +259,8 @@ final class HtmlUnitRequestBuilder implements RequestBuilder, Mergeable {
 			}
 		}
 		else {
-			Assert.isTrue(uriComponents.getPath().startsWith(this.contextPath),
+			String path = uriComponents.getPath();
+			Assert.isTrue(path != null && path.startsWith(this.contextPath),
 					() -> "\"" + uriComponents.getPath() +
 							"\" should start with context path \"" + this.contextPath + "\"");
 			request.setContextPath(this.contextPath);
@@ -302,6 +308,7 @@ final class HtmlUnitRequestBuilder implements RequestBuilder, Mergeable {
 		}
 	}
 
+	@Nullable
 	private String header(String headerName) {
 		return this.webRequest.getAdditionalHeaders().get(headerName);
 	}
@@ -376,9 +383,6 @@ final class HtmlUnitRequestBuilder implements RequestBuilder, Mergeable {
 
 	private void servletPath(MockHttpServletRequest request, String requestPath) {
 		String servletPath = requestPath.substring(request.getContextPath().length());
-		if ("".equals(servletPath)) {
-			servletPath = null;
-		}
 		request.setServletPath(servletPath);
 	}
 
@@ -386,7 +390,8 @@ final class HtmlUnitRequestBuilder implements RequestBuilder, Mergeable {
 		if ("".equals(request.getPathInfo())) {
 			request.setPathInfo(null);
 		}
-		servletPath(request, uriComponents.getPath());
+		String path = uriComponents.getPath();
+		servletPath(request, (path != null ? path : ""));
 	}
 
 	private void ports(UriComponents uriComponents, MockHttpServletRequest request) {

spring-test/src/main/java/org/springframework/test/web/servlet/htmlunit/MockMvcWebConnection.java

@@ -154,9 +154,6 @@ public final class MockMvcWebConnection implements WebConnection {
 	}
 
 	private void storeCookies(WebRequest webRequest, javax.servlet.http.Cookie[] cookies) {
-		if (cookies == null) {
-			return;
-		}
 		Date now = new Date();
 		CookieManager cookieManager = this.webClient.getCookieManager();
 		for (javax.servlet.http.Cookie cookie : cookies) {