Explicit nullability declarations for all AOP Alliance methods

Includes consistent declarations in AOP Alliance related Spring AOP code.

Closes gh-24117

spring-aop/src/main/java/org/aopalliance/intercept/ConstructorInterceptor.java

@@ -16,6 +16,8 @@
 
 package org.aopalliance.intercept;
 
+import javax.annotation.Nonnull;
+
 /**
  * Intercepts the construction of a new object.
  *
@@ -54,6 +56,7 @@ public interface ConstructorInterceptor extends Interceptor  {
 	 * @throws Throwable if the interceptors or the target object
 	 * throws an exception
 	 */
+	@Nonnull
 	Object construct(ConstructorInvocation invocation) throws Throwable;
 
 }

spring-aop/src/main/java/org/aopalliance/intercept/ConstructorInvocation.java

@@ -18,6 +18,8 @@ package org.aopalliance.intercept;
 
 import java.lang.reflect.Constructor;
 
+import javax.annotation.Nonnull;
+
 /**
  * Description of an invocation to a constructor, given to an
  * interceptor upon constructor-call.
@@ -36,6 +38,7 @@ public interface ConstructorInvocation extends Invocation {
 	 * {@link Joinpoint#getStaticPart()} method (same result).
 	 * @return the constructor being called
 	 */
+	@Nonnull
 	Constructor<?> getConstructor();
 
 }

spring-aop/src/main/java/org/aopalliance/intercept/Invocation.java

@@ -16,6 +16,8 @@
 
 package org.aopalliance.intercept;
 
+import javax.annotation.Nonnull;
+
 /**
  * This interface represents an invocation in the program.
  *
@@ -32,6 +34,7 @@ public interface Invocation extends Joinpoint {
 	 * array to change the arguments.
 	 * @return the argument of the invocation
 	 */
+	@Nonnull
 	Object[] getArguments();
 
 }

spring-aop/src/main/java/org/aopalliance/intercept/Joinpoint.java

@@ -18,6 +18,9 @@ package org.aopalliance.intercept;
 
 import java.lang.reflect.AccessibleObject;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * This interface represents a generic runtime joinpoint (in the AOP
  * terminology).
@@ -46,6 +49,7 @@ public interface Joinpoint {
 	 * @return see the children interfaces' proceed definition
 	 * @throws Throwable if the joinpoint throws an exception
 	 */
+	@Nullable
 	Object proceed() throws Throwable;
 
 	/**
@@ -53,6 +57,7 @@ public interface Joinpoint {
 	 * <p>For instance, the target object for an invocation.
 	 * @return the object (can be null if the accessible object is static)
 	 */
+	@Nullable
 	Object getThis();
 
 	/**
@@ -60,6 +65,7 @@ public interface Joinpoint {
 	 * <p>The static part is an accessible object on which a chain of
 	 * interceptors are installed.
 	 */
+	@Nonnull
 	AccessibleObject getStaticPart();
 
 }

spring-aop/src/main/java/org/aopalliance/intercept/MethodInterceptor.java

@@ -16,6 +16,9 @@
 
 package org.aopalliance.intercept;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * Intercepts calls on an interface on its way to the target. These
  * are nested "on top" of the target.
@@ -52,6 +55,7 @@ public interface MethodInterceptor extends Interceptor {
 	 * @throws Throwable if the interceptors or the target object
 	 * throws an exception
 	 */
-	Object invoke(MethodInvocation invocation) throws Throwable;
+	@Nullable
+	Object invoke(@Nonnull MethodInvocation invocation) throws Throwable;
 
 }

spring-aop/src/main/java/org/aopalliance/intercept/MethodInvocation.java

@@ -18,6 +18,8 @@ package org.aopalliance.intercept;
 
 import java.lang.reflect.Method;
 
+import javax.annotation.Nonnull;
+
 /**
  * Description of an invocation to a method, given to an interceptor
  * upon method-call.
@@ -36,6 +38,7 @@ public interface MethodInvocation extends Invocation {
 	 * {@link Joinpoint#getStaticPart()} method (same result).
 	 * @return the method being called
 	 */
+	@Nonnull
 	Method getMethod();
 
 }

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAfterAdvice.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -23,6 +23,7 @@ import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
 
 import org.springframework.aop.AfterAdvice;
+import org.springframework.lang.Nullable;
 
 /**
  * Spring AOP advice wrapping an AspectJ after advice method.
@@ -42,6 +43,7 @@ public class AspectJAfterAdvice extends AbstractAspectJAdvice
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation mi) throws Throwable {
 		try {
 			return mi.proceed();

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAfterThrowingAdvice.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -23,6 +23,7 @@ import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
 
 import org.springframework.aop.AfterAdvice;
+import org.springframework.lang.Nullable;
 
 /**
  * Spring AOP advice wrapping an AspectJ after-throwing advice method.
@@ -57,6 +58,7 @@ public class AspectJAfterThrowingAdvice extends AbstractAspectJAdvice
 	}
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation mi) throws Throwable {
 		try {
 			return mi.proceed();

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAroundAdvice.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.aspectj.lang.ProceedingJoinPoint;
 import org.aspectj.weaver.tools.JoinPointMatch;
 
 import org.springframework.aop.ProxyMethodInvocation;
+import org.springframework.lang.Nullable;
 
 /**
  * Spring AOP around advice (MethodInterceptor) that wraps
@@ -60,6 +61,7 @@ public class AspectJAroundAdvice extends AbstractAspectJAdvice implements Method
 	}
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation mi) throws Throwable {
 		if (!(mi instanceof ProxyMethodInvocation)) {
 			throw new IllegalStateException("MethodInvocation is not a Spring ProxyMethodInvocation: " + mi);

spring-aop/src/main/java/org/springframework/aop/aspectj/MethodInvocationProceedingJoinPoint.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -84,11 +84,13 @@ public class MethodInvocationProceedingJoinPoint implements ProceedingJoinPoint,
 	}
 
 	@Override
+	@Nullable
 	public Object proceed() throws Throwable {
 		return this.methodInvocation.invocableClone().proceed();
 	}
 
 	@Override
+	@Nullable
 	public Object proceed(Object[] arguments) throws Throwable {
 		Assert.notNull(arguments, "Argument array passed to proceed cannot be null");
 		if (arguments.length != this.methodInvocation.getArguments().length) {

spring-aop/src/main/java/org/springframework/aop/framework/adapter/AfterReturningAdviceInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -23,6 +23,7 @@ import org.aopalliance.intercept.MethodInvocation;
 
 import org.springframework.aop.AfterAdvice;
 import org.springframework.aop.AfterReturningAdvice;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -51,6 +52,7 @@ public class AfterReturningAdviceInterceptor implements MethodInterceptor, After
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation mi) throws Throwable {
 		Object retVal = mi.proceed();
 		this.advice.afterReturning(retVal, mi.getMethod(), mi.getArguments(), mi.getThis());

spring-aop/src/main/java/org/springframework/aop/framework/adapter/MethodBeforeAdviceInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -23,6 +23,7 @@ import org.aopalliance.intercept.MethodInvocation;
 
 import org.springframework.aop.BeforeAdvice;
 import org.springframework.aop.MethodBeforeAdvice;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -51,6 +52,7 @@ public class MethodBeforeAdviceInterceptor implements MethodInterceptor, BeforeA
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation mi) throws Throwable {
 		this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis());
 		return mi.proceed();

spring-aop/src/main/java/org/springframework/aop/framework/adapter/ThrowsAdviceInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -107,6 +107,7 @@ public class ThrowsAdviceInterceptor implements MethodInterceptor, AfterAdvice {
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation mi) throws Throwable {
 		try {
 			return mi.proceed();

spring-aop/src/main/java/org/springframework/aop/interceptor/AbstractTraceInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.aop.support.AopUtils;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * Base {@code MethodInterceptor} implementation for tracing.
@@ -151,6 +152,7 @@ public abstract class AbstractTraceInterceptor implements MethodInterceptor, Ser
 		}
 		else {
 			Object target = invocation.getThis();
+			Assert.state(target != null, "Target must not be null");
 			return LogFactory.getLog(getClassForLogging(target));
 		}
 	}

spring-aop/src/main/java/org/springframework/aop/interceptor/ConcurrencyThrottleInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2020 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.Serializable;
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ConcurrencyThrottleSupport;
 
 /**
@@ -48,6 +49,7 @@ public class ConcurrencyThrottleInterceptor extends ConcurrencyThrottleSupport
 	}
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation methodInvocation) throws Throwable {
 		beforeAccess();
 		try {

spring-aop/src/main/java/org/springframework/aop/interceptor/CustomizableTraceInterceptor.java

@@ -296,6 +296,8 @@ public class CustomizableTraceInterceptor extends AbstractTraceInterceptor {
 			@Nullable Object returnValue, @Nullable Throwable throwable, long invocationTime) {
 
 		Matcher matcher = PATTERN.matcher(message);
+		Object target = methodInvocation.getThis();
+		Assert.state(target != null, "Target must not be null");
 
 		StringBuffer output = new StringBuffer();
 		while (matcher.find()) {
@@ -304,11 +306,11 @@ public class CustomizableTraceInterceptor extends AbstractTraceInterceptor {
 				matcher.appendReplacement(output, Matcher.quoteReplacement(methodInvocation.getMethod().getName()));
 			}
 			else if (PLACEHOLDER_TARGET_CLASS_NAME.equals(match)) {
-				String className = getClassForLogging(methodInvocation.getThis()).getName();
+				String className = getClassForLogging(target).getName();
 				matcher.appendReplacement(output, Matcher.quoteReplacement(className));
 			}
 			else if (PLACEHOLDER_TARGET_CLASS_SHORT_NAME.equals(match)) {
-				String shortName = ClassUtils.getShortName(getClassForLogging(methodInvocation.getThis()));
+				String shortName = ClassUtils.getShortName(getClassForLogging(target));
 				matcher.appendReplacement(output, Matcher.quoteReplacement(shortName));
 			}
 			else if (PLACEHOLDER_ARGUMENTS.equals(match)) {

spring-aop/src/main/java/org/springframework/aop/interceptor/DebugInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2020 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 +18,8 @@ package org.springframework.aop.interceptor;
 
 import org.aopalliance.intercept.MethodInvocation;
 
+import org.springframework.lang.Nullable;
+
 /**
  * AOP Alliance {@code MethodInterceptor} that can be introduced in a chain
  * to display verbose information about intercepted invocations to the logger.
@@ -56,6 +58,7 @@ public class DebugInterceptor extends SimpleTraceInterceptor {
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		synchronized (this) {
 			this.count++;

spring-aop/src/main/java/org/springframework/aop/interceptor/ExposeBeanNameAdvisors.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.springframework.aop.support.DefaultIntroductionAdvisor;
 import org.springframework.aop.support.DefaultPointcutAdvisor;
 import org.springframework.aop.support.DelegatingIntroductionInterceptor;
 import org.springframework.beans.factory.NamedBean;
+import org.springframework.lang.Nullable;
 
 /**
  * Convenient methods for creating advisors that may be used when autoproxying beans
@@ -110,6 +111,7 @@ public abstract class ExposeBeanNameAdvisors {
 		}
 
 		@Override
+		@Nullable
 		public Object invoke(MethodInvocation mi) throws Throwable {
 			if (!(mi instanceof ProxyMethodInvocation)) {
 				throw new IllegalStateException("MethodInvocation is not a Spring ProxyMethodInvocation: " + mi);
@@ -134,6 +136,7 @@ public abstract class ExposeBeanNameAdvisors {
 		}
 
 		@Override
+		@Nullable
 		public Object invoke(MethodInvocation mi) throws Throwable {
 			if (!(mi instanceof ProxyMethodInvocation)) {
 				throw new IllegalStateException("MethodInvocation is not a Spring ProxyMethodInvocation: " + mi);

spring-aop/src/main/java/org/springframework/aop/interceptor/ExposeInvocationInterceptor.java

@@ -25,6 +25,7 @@ import org.springframework.aop.Advisor;
 import org.springframework.aop.support.DefaultPointcutAdvisor;
 import org.springframework.core.NamedThreadLocal;
 import org.springframework.core.PriorityOrdered;
+import org.springframework.lang.Nullable;
 
 /**
  * Interceptor that exposes the current {@link org.aopalliance.intercept.MethodInvocation}
@@ -88,6 +89,7 @@ public final class ExposeInvocationInterceptor implements MethodInterceptor, Pri
 	}
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation mi) throws Throwable {
 		MethodInvocation oldInvocation = invocation.get();
 		invocation.set(mi);

spring-aop/src/main/java/org/springframework/aop/interceptor/SimpleTraceInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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 +19,8 @@ package org.springframework.aop.interceptor;
 import org.aopalliance.intercept.MethodInvocation;
 import org.apache.commons.logging.Log;
 
+import org.springframework.util.Assert;
+
 /**
  * Simple AOP Alliance {@code MethodInterceptor} that can be introduced
  * in a chain to display verbose trace information about intercepted method
@@ -73,7 +75,9 @@ public class SimpleTraceInterceptor extends AbstractTraceInterceptor {
 	 * @return the description
 	 */
 	protected String getInvocationDescription(MethodInvocation invocation) {
-		String className = invocation.getThis().getClass().getName();
+		Object target = invocation.getThis();
+		Assert.state(target != null, "Target must not be null");
+		String className = target.getClass().getName();
 		return "method '" + invocation.getMethod().getName() + "' of class [" + className + "]";
 	}
 

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

@@ -114,12 +114,13 @@ public class DelegatePerTargetObjectIntroductionInterceptor extends Introduction
 	 * that it is introduced into. This method is <strong>never</strong> called for
 	 * {@link MethodInvocation MethodInvocations} on the introduced interfaces.
 	 */
+	@Nullable
 	protected Object doProceed(MethodInvocation mi) throws Throwable {
 		// If we get here, just pass the invocation on.
 		return mi.proceed();
 	}
 
-	private Object getIntroductionDelegateFor(Object targetObject) {
+	private Object getIntroductionDelegateFor(@Nullable Object targetObject) {
 		synchronized (this.delegateMap) {
 			if (this.delegateMap.containsKey(targetObject)) {
 				return this.delegateMap.get(targetObject);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -131,6 +131,7 @@ public class DelegatingIntroductionInterceptor extends IntroductionInfoSupport
 	 * that it is introduced into. This method is <strong>never</strong> called for
 	 * {@link MethodInvocation MethodInvocations} on the introduced interfaces.
 	 */
+	@Nullable
 	protected Object doProceed(MethodInvocation mi) throws Throwable {
 		// If we get here, just pass the invocation on.
 		return mi.proceed();

spring-aop/src/test/java/org/springframework/aop/interceptor/ExposeInvocationInterceptorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -16,13 +16,11 @@
 
 package org.springframework.aop.interceptor;
 
-import org.aopalliance.intercept.MethodInvocation;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
 import org.springframework.beans.testfixture.beans.ITestBean;
-import org.springframework.beans.testfixture.beans.TestBean;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.core.testfixture.io.ResourceTestUtils.qualifiedResource;
@@ -48,33 +46,3 @@ public class ExposeInvocationInterceptorTests {
 	}
 
 }
-
-
-abstract class ExposedInvocationTestBean extends TestBean {
-
-	@Override
-	public String getName() {
-		MethodInvocation invocation = ExposeInvocationInterceptor.currentInvocation();
-		assertions(invocation);
-		return super.getName();
-	}
-
-	@Override
-	public void absquatulate() {
-		MethodInvocation invocation = ExposeInvocationInterceptor.currentInvocation();
-		assertions(invocation);
-		super.absquatulate();
-	}
-
-	protected abstract void assertions(MethodInvocation invocation);
-}
-
-
-class InvocationCheckExposedInvocationTestBean extends ExposedInvocationTestBean {
-
-	@Override
-	protected void assertions(MethodInvocation invocation) {
-		assertThat(invocation.getThis() == this).isTrue();
-		assertThat(ITestBean.class.isAssignableFrom(invocation.getMethod().getDeclaringClass())).as("Invocation should be on ITestBean: " + invocation.getMethod()).isTrue();
-	}
-}

spring-aop/src/test/java/org/springframework/aop/interceptor/ExposedInvocationTestBean.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2002-2020 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.aop.interceptor;
+
+import org.aopalliance.intercept.MethodInvocation;
+
+import org.springframework.beans.testfixture.beans.TestBean;
+
+abstract class ExposedInvocationTestBean extends TestBean {
+
+	@Override
+	public String getName() {
+		MethodInvocation invocation = ExposeInvocationInterceptor.currentInvocation();
+		assertions(invocation);
+		return super.getName();
+	}
+
+	@Override
+	public void absquatulate() {
+		MethodInvocation invocation = ExposeInvocationInterceptor.currentInvocation();
+		assertions(invocation);
+		super.absquatulate();
+	}
+
+	protected abstract void assertions(MethodInvocation invocation);
+}

spring-aop/src/test/java/org/springframework/aop/interceptor/InvocationCheckExposedInvocationTestBean.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2002-2020 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.aop.interceptor;
+
+import org.aopalliance.intercept.MethodInvocation;
+
+import org.springframework.beans.testfixture.beans.ITestBean;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class InvocationCheckExposedInvocationTestBean extends ExposedInvocationTestBean {
+
+	@Override
+	protected void assertions(MethodInvocation invocation) {
+		assertThat(invocation.getThis() == this).isTrue();
+		assertThat(ITestBean.class.isAssignableFrom(invocation.getMethod().getDeclaringClass())).as("Invocation should be on ITestBean: " + invocation.getMethod()).isTrue();
+	}
+}

spring-context-support/src/main/java/org/springframework/cache/jcache/interceptor/JCacheAspectSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -165,6 +165,7 @@ public class JCacheAspectSupport extends AbstractCacheInvoker implements Initial
 	 * @return the result of the invocation
 	 * @see CacheOperationInvoker#invoke()
 	 */
+	@Nullable
 	protected Object invokeOperation(CacheOperationInvoker invoker) {
 		return invoker.invoke();
 	}

spring-context-support/src/main/java/org/springframework/cache/jcache/interceptor/JCacheInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -27,6 +27,7 @@ import org.springframework.cache.interceptor.CacheErrorHandler;
 import org.springframework.cache.interceptor.CacheOperationInvoker;
 import org.springframework.cache.interceptor.SimpleCacheErrorHandler;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.function.SingletonSupplier;
 
 /**
@@ -78,8 +79,10 @@ public class JCacheInterceptor extends JCacheAspectSupport implements MethodInte
 			}
 		};
 
+		Object target = invocation.getThis();
+		Assert.state(target != null, "Target must not be null");
 		try {
-			return execute(aopAllianceInvoker, invocation.getThis(), method, invocation.getArguments());
+			return execute(aopAllianceInvoker, target, method, invocation.getArguments());
 		}
 		catch (CacheOperationInvoker.ThrowableWrapper th) {
 			throw th.getOriginal();

spring-context/src/main/java/org/springframework/cache/interceptor/CacheAspectSupport.java

@@ -361,6 +361,7 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	 * @return the result of the invocation
 	 * @see CacheOperationInvoker#invoke()
 	 */
+	@Nullable
 	protected Object invokeOperation(CacheOperationInvoker invoker) {
 		return invoker.invoke();
 	}
@@ -445,7 +446,7 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	}
 
 	@Nullable
-	private Object unwrapReturnValue(Object returnValue) {
+	private Object unwrapReturnValue(@Nullable Object returnValue) {
 		return ObjectUtils.unwrapOptional(returnValue);
 	}
 

spring-context/src/main/java/org/springframework/cache/interceptor/CacheInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -23,6 +23,7 @@ import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
 
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * AOP Alliance MethodInterceptor for declarative cache
@@ -57,8 +58,10 @@ public class CacheInterceptor extends CacheAspectSupport implements MethodInterc
 			}
 		};
 
+		Object target = invocation.getThis();
+		Assert.state(target != null, "Target must not be null");
 		try {
-			return execute(aopAllianceInvoker, invocation.getThis(), method, invocation.getArguments());
+			return execute(aopAllianceInvoker, target, method, invocation.getArguments());
 		}
 		catch (CacheOperationInvoker.ThrowableWrapper th) {
 			throw th.getOriginal();

spring-context/src/main/java/org/springframework/cache/interceptor/CacheOperationInvoker.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2020 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.cache.interceptor;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Abstract the invocation of a cache operation.
  *
@@ -36,6 +38,7 @@ public interface CacheOperationInvoker {
 	 * @return the result of the operation
 	 * @throws ThrowableWrapper if an error occurred while invoking the operation
 	 */
+	@Nullable
 	Object invoke() throws ThrowableWrapper;
 
 

spring-context/src/main/java/org/springframework/context/event/EventPublicationInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -94,6 +94,7 @@ public class EventPublicationInterceptor
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		Object retVal = invocation.proceed();
 

spring-context/src/main/java/org/springframework/jndi/JndiObjectFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -368,6 +368,7 @@ public class JndiObjectFactoryBean extends JndiObjectLocator
 		}
 
 		@Override
+		@Nullable
 		public Object invoke(MethodInvocation invocation) throws Throwable {
 			Context ctx = (isEligible(invocation.getMethod()) ? this.jndiTemplate.getContext() : null);
 			try {

spring-context/src/main/java/org/springframework/remoting/rmi/JndiRmiClientInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -268,6 +268,7 @@ public class JndiRmiClientInterceptor extends JndiObjectLocator implements Metho
 	 * @see java.rmi.NoSuchObjectException
 	 */
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		Object stub;
 		try {

spring-context/src/main/java/org/springframework/remoting/rmi/RmiClientInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -255,6 +255,7 @@ public class RmiClientInterceptor extends RemoteInvocationBasedAccessor
 	 * @see java.rmi.NoSuchObjectException
 	 */
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		Remote stub = getStub();
 		try {

spring-context/src/main/java/org/springframework/remoting/support/RemoteInvocationBasedAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2020 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 +18,8 @@ package org.springframework.remoting.support;
 
 import org.aopalliance.intercept.MethodInvocation;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Abstract base class for remote service accessors that are based
  * on serialization of {@link RemoteInvocation} objects.
@@ -81,6 +83,7 @@ public abstract class RemoteInvocationBasedAccessor extends UrlBasedRemoteAccess
 	 * @throws Throwable if the invocation result is an exception
 	 * @see RemoteInvocationResult#recreate()
 	 */
+	@Nullable
 	protected Object recreateRemoteInvocationResult(RemoteInvocationResult result) throws Throwable {
 		return result.recreate();
 	}

spring-context/src/main/java/org/springframework/remoting/support/RemoteInvocationTraceInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -23,6 +23,7 @@ import org.aopalliance.intercept.MethodInvocation;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -68,6 +69,7 @@ public class RemoteInvocationTraceInterceptor implements MethodInterceptor {
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		Method method = invocation.getMethod();
 		if (logger.isDebugEnabled()) {

spring-context/src/main/java/org/springframework/validation/beanvalidation/MethodValidationInterceptor.java

@@ -33,6 +33,8 @@ import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.SmartFactoryBean;
 import org.springframework.core.BridgeMethodResolver;
 import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.validation.annotation.Validated;
 
@@ -87,7 +89,7 @@ public class MethodValidationInterceptor implements MethodInterceptor {
 
 
 	@Override
-	@SuppressWarnings("unchecked")
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		// Avoid Validator invocation on FactoryBean.getObjectType/isSingleton
 		if (isFactoryBeanMetadataMethod(invocation.getMethod())) {
@@ -101,17 +103,18 @@ public class MethodValidationInterceptor implements MethodInterceptor {
 		Method methodToValidate = invocation.getMethod();
 		Set<ConstraintViolation<Object>> result;
 
+		Object target = invocation.getThis();
+		Assert.state(target != null, "Target must not be null");
+
 		try {
-			result = execVal.validateParameters(
-					invocation.getThis(), methodToValidate, invocation.getArguments(), groups);
+			result = execVal.validateParameters(target, methodToValidate, invocation.getArguments(), groups);
 		}
 		catch (IllegalArgumentException ex) {
 			// Probably a generic type mismatch between interface and impl as reported in SPR-12237 / HV-1011
 			// Let's try to find the bridged method on the implementation class...
 			methodToValidate = BridgeMethodResolver.findBridgedMethod(
-					ClassUtils.getMostSpecificMethod(invocation.getMethod(), invocation.getThis().getClass()));
-			result = execVal.validateParameters(
-					invocation.getThis(), methodToValidate, invocation.getArguments(), groups);
+					ClassUtils.getMostSpecificMethod(invocation.getMethod(), target.getClass()));
+			result = execVal.validateParameters(target, methodToValidate, invocation.getArguments(), groups);
 		}
 		if (!result.isEmpty()) {
 			throw new ConstraintViolationException(result);
@@ -119,7 +122,7 @@ public class MethodValidationInterceptor implements MethodInterceptor {
 
 		Object returnValue = invocation.proceed();
 
-		result = execVal.validateReturnValue(invocation.getThis(), methodToValidate, returnValue, groups);
+		result = execVal.validateReturnValue(target, methodToValidate, returnValue, groups);
 		if (!result.isEmpty()) {
 			throw new ConstraintViolationException(result);
 		}
@@ -158,7 +161,9 @@ public class MethodValidationInterceptor implements MethodInterceptor {
 	protected Class<?>[] determineValidationGroups(MethodInvocation invocation) {
 		Validated validatedAnn = AnnotationUtils.findAnnotation(invocation.getMethod(), Validated.class);
 		if (validatedAnn == null) {
-			validatedAnn = AnnotationUtils.findAnnotation(invocation.getThis().getClass(), Validated.class);
+			Object target = invocation.getThis();
+			Assert.state(target != null, "Target must not be null");
+			validatedAnn = AnnotationUtils.findAnnotation(target.getClass(), Validated.class);
 		}
 		return (validatedAnn != null ? validatedAnn.value() : new Class<?>[0]);
 	}

spring-orm/src/main/java/org/springframework/orm/hibernate5/support/OpenSessionInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -78,6 +78,7 @@ public class OpenSessionInterceptor implements MethodInterceptor, InitializingBe
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		SessionFactory sf = getSessionFactory();
 		Assert.state(sf != null, "No SessionFactory set");

spring-tx/src/main/java/org/springframework/dao/support/PersistenceExceptionTranslationInterceptor.java

@@ -134,6 +134,7 @@ public class PersistenceExceptionTranslationInterceptor
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation mi) throws Throwable {
 		try {
 			return mi.proceed();

spring-tx/src/main/java/org/springframework/jca/endpoint/GenericMessageEndpointFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -107,6 +107,7 @@ public class GenericMessageEndpointFactory extends AbstractMessageEndpointFactor
 	private class GenericMessageEndpoint extends AbstractMessageEndpoint implements MethodInterceptor {
 
 		@Override
+		@Nullable
 		public Object invoke(MethodInvocation methodInvocation) throws Throwable {
 			Throwable endpointEx = null;
 			boolean applyDeliveryCalls = !hasBeforeDeliveryBeenCalled();

spring-tx/src/main/java/org/springframework/transaction/interceptor/TransactionAspectSupport.java

@@ -375,7 +375,7 @@ public abstract class TransactionAspectSupport implements BeanFactoryAware, Init
 				cleanupTransactionInfo(txInfo);
 			}
 
-			if (vavrPresent && VavrDelegate.isVavrTry(retVal)) {
+			if (retVal != null && vavrPresent && VavrDelegate.isVavrTry(retVal)) {
 				// Set rollback-only in case of Vavr failure matching our rollback rules...
 				TransactionStatus status = txInfo.getTransactionStatus();
 				if (status != null && txAttr != null) {
@@ -396,7 +396,7 @@ public abstract class TransactionAspectSupport implements BeanFactoryAware, Init
 					TransactionInfo txInfo = prepareTransactionInfo(ptm, txAttr, joinpointIdentification, status);
 					try {
 						Object retVal = invocation.proceedWithInvocation();
-						if (vavrPresent && VavrDelegate.isVavrTry(retVal)) {
+						if (retVal != null && vavrPresent && VavrDelegate.isVavrTry(retVal)) {
 							// Set rollback-only in case of Vavr failure matching our rollback rules...
 							retVal = VavrDelegate.evaluateTryFailure(retVal, txAttr, status);
 						}
@@ -780,6 +780,7 @@ public abstract class TransactionAspectSupport implements BeanFactoryAware, Init
 	@FunctionalInterface
 	protected interface InvocationCallback {
 
+		@Nullable
 		Object proceedWithInvocation() throws Throwable;
 	}
 

spring-web/src/main/java/org/springframework/remoting/httpinvoker/HttpInvokerClientInterceptor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -142,6 +142,7 @@ public class HttpInvokerClientInterceptor extends RemoteInvocationBasedAccessor
 
 
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation methodInvocation) throws Throwable {
 		if (AopUtils.isToStringMethod(methodInvocation.getMethod())) {
 			return "HTTP invoker proxy for service URL [" + getServiceUrl() + "]";