Polishing (backported from 5.2.x)

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -94,8 +94,7 @@ import org.springframework.util.StringUtils;
  * operating on pre-resolved bean definition metadata objects.
  *
  * <p>Note that readers for specific bean definition formats are typically
- * implemented separately rather than as bean factory subclasses:
- * see for example {@link PropertiesBeanDefinitionReader} and
+ * implemented separately rather than as bean factory subclasses: see for example
  * {@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader}.
  *
  * <p>For an alternative implementation of the
@@ -182,7 +181,7 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 	private volatile String[] frozenBeanDefinitionNames;
 
 	/** Whether bean definition metadata may be cached for all beans. */
-	private volatile boolean configurationFrozen = false;
+	private volatile boolean configurationFrozen;
 
 
 	/**
@@ -354,12 +353,11 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 	}
 
 	@Override
-	public <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType) throws BeansException {
+	public <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType) {
 		Assert.notNull(requiredType, "Required type must not be null");
 		return getBeanProvider(ResolvableType.forRawClass(requiredType));
 	}
 
-	@SuppressWarnings("unchecked")
 	@Override
 	public <T> ObjectProvider<T> getBeanProvider(ResolvableType requiredType) {
 		return new BeanObjectProvider<T>() {
@@ -389,15 +387,20 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 			public T getIfUnique() throws BeansException {
 				return resolveBean(requiredType, null, true);
 			}
+			@SuppressWarnings("unchecked")
 			@Override
 			public Stream<T> stream() {
 				return Arrays.stream(getBeanNamesForTypedStream(requiredType))
 						.map(name -> (T) getBean(name))
 						.filter(bean -> !(bean instanceof NullBean));
 			}
+			@SuppressWarnings("unchecked")
 			@Override
 			public Stream<T> orderedStream() {
 				String[] beanNames = getBeanNamesForTypedStream(requiredType);
+				if (beanNames.length == 0) {
+					return Stream.empty();
+				}
 				Map<String, T> matchingBeans = new LinkedHashMap<>(beanNames.length);
 				for (String beanName : beanNames) {
 					Object beanInstance = getBean(beanName);
@@ -1352,9 +1355,11 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 			TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
 			Object result = converter.convertIfNecessary(matchingBeans.values(), type);
 			if (result instanceof List) {
-				Comparator<Object> comparator = adaptDependencyComparator(matchingBeans);
-				if (comparator != null) {
-					((List<?>) result).sort(comparator);
+				if (((List<?>) result).size() > 1) {
+					Comparator<Object> comparator = adaptDependencyComparator(matchingBeans);
+					if (comparator != null) {
+						((List<?>) result).sort(comparator);
+					}
 				}
 			}
 			return result;

spring-context/src/main/java/org/springframework/cache/support/AbstractValueAdaptingCache.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.
@@ -55,8 +55,7 @@ public abstract class AbstractValueAdaptingCache implements Cache {
 	@Override
 	@Nullable
 	public ValueWrapper get(Object key) {
-		Object value = lookup(key);
-		return toValueWrapper(value);
+		return toValueWrapper(lookup(key));
 	}
 
 	@Override
@@ -123,5 +122,4 @@ public abstract class AbstractValueAdaptingCache implements Cache {
 		return (storeValue != null ? new SimpleValueWrapper(fromStoreValue(storeValue)) : null);
 	}
 
-
 }

spring-core/src/main/java/org/springframework/core/io/FileUrlResource.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.
@@ -52,7 +52,7 @@ public class FileUrlResource extends UrlResource implements WritableResource {
 	/**
 	 * Create a new {@code FileUrlResource} based on the given URL object.
 	 * <p>Note that this does not enforce "file" as URL protocol. If a protocol
-	 * is known to be resolvable to a file,
+	 * is known to be resolvable to a file, it is acceptable for this purpose.
 	 * @param url a URL
 	 * @see ResourceUtils#isFileURL(URL)
 	 * @see #getFile()

spring-tx/src/main/java/org/springframework/dao/support/PersistenceExceptionTranslationInterceptor.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.
@@ -146,7 +146,8 @@ public class PersistenceExceptionTranslationInterceptor
 			else {
 				PersistenceExceptionTranslator translator = this.persistenceExceptionTranslator;
 				if (translator == null) {
-					Assert.state(this.beanFactory != null, "No PersistenceExceptionTranslator set");
+					Assert.state(this.beanFactory != null,
+							"Cannot use PersistenceExceptionTranslator autodetection without ListableBeanFactory");
 					translator = detectPersistenceExceptionTranslators(this.beanFactory);
 					this.persistenceExceptionTranslator = translator;
 				}
@@ -157,16 +158,15 @@ public class PersistenceExceptionTranslationInterceptor
 
 	/**
 	 * Detect all PersistenceExceptionTranslators in the given BeanFactory.
-	 * @param beanFactory the ListableBeanFactory to obtaining all
-	 * PersistenceExceptionTranslators from
+	 * @param bf the ListableBeanFactory to obtain PersistenceExceptionTranslators from
 	 * @return a chained PersistenceExceptionTranslator, combining all
-	 * PersistenceExceptionTranslators found in the factory
+	 * PersistenceExceptionTranslators found in the given bean factory
 	 * @see ChainedPersistenceExceptionTranslator
 	 */
-	protected PersistenceExceptionTranslator detectPersistenceExceptionTranslators(ListableBeanFactory beanFactory) {
+	protected PersistenceExceptionTranslator detectPersistenceExceptionTranslators(ListableBeanFactory bf) {
 		// Find all translators, being careful not to activate FactoryBeans.
 		Map<String, PersistenceExceptionTranslator> pets = BeanFactoryUtils.beansOfTypeIncludingAncestors(
-				beanFactory, PersistenceExceptionTranslator.class, false, false);
+				bf, PersistenceExceptionTranslator.class, false, false);
 		ChainedPersistenceExceptionTranslator cpet = new ChainedPersistenceExceptionTranslator();
 		for (PersistenceExceptionTranslator pet : pets.values()) {
 			cpet.addDelegate(pet);

spring-web/src/main/java/org/springframework/http/MediaType.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.
@@ -85,7 +85,6 @@ public class MediaType extends MimeType implements Serializable {
 
 	/**
 	 * Public constant media type for {@code application/json}.
-	 * @see #APPLICATION_JSON_UTF8
 	 */
 	public static final MediaType APPLICATION_JSON;
 
@@ -97,7 +96,6 @@ public class MediaType extends MimeType implements Serializable {
 
 	/**
 	 * Public constant media type for {@code application/json;charset=UTF-8}.
-	 *
 	 * <p>This {@link MediaType#APPLICATION_JSON} variant should be used to set JSON
 	 * content type because while
 	 * <a href="https://tools.ietf.org/html/rfc7159#section-11">RFC7159</a>
@@ -108,7 +106,6 @@ public class MediaType extends MimeType implements Serializable {
 
 	/**
 	 * A String equivalent of {@link MediaType#APPLICATION_JSON_UTF8}.
-	 *
 	 * <p>This {@link MediaType#APPLICATION_JSON_VALUE} variant should be used to set JSON
 	 * content type because while
 	 * <a href="https://tools.ietf.org/html/rfc7159#section-11">RFC7159</a>
@@ -407,7 +404,7 @@ public class MediaType extends MimeType implements Serializable {
 
 	/**
 	 * Copy-constructor that copies the type and subtype of the given {@code MediaType},
-	 * and allows for different parameter.
+	 * and allows for different parameters.
 	 * @param other the other media type
 	 * @param parameters the parameters, may be {@code null}
 	 * @throws IllegalArgumentException if any of the parameters contain illegal characters
@@ -454,7 +451,7 @@ public class MediaType extends MimeType implements Serializable {
 	 * <p>For instance, {@code text/*} includes {@code text/plain} and {@code text/html},
 	 * and {@code application/*+xml} includes {@code application/soap+xml}, etc.
 	 * This method is <b>not</b> symmetric.
-	 * <p>Simply calls {@link #includes(MimeType)} but declared with a
+	 * <p>Simply calls {@link MimeType#includes(MimeType)} but declared with a
 	 * {@code MediaType} parameter for binary backwards compatibility.
 	 * @param other the reference media type with which to compare
 	 * @return {@code true} if this media type includes the given media type;
@@ -469,7 +466,7 @@ public class MediaType extends MimeType implements Serializable {
 	 * <p>For instance, {@code text/*} is compatible with {@code text/plain},
 	 * {@code text/html}, and vice versa. In effect, this method is similar to
 	 * {@link #includes}, except that it <b>is</b> symmetric.
-	 * <p>Simply calls {@link #isCompatibleWith(MimeType)} but declared with a
+	 * <p>Simply calls {@link MimeType#isCompatibleWith(MimeType)} but declared with a
 	 * {@code MediaType} parameter for binary backwards compatibility.
 	 * @param other the reference media type with which to compare
 	 * @return {@code true} if this media type is compatible with the given media type;

spring-web/src/main/java/org/springframework/web/bind/support/WebExchangeDataBinder.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.
@@ -64,7 +64,7 @@ public class WebExchangeDataBinder extends WebDataBinder {
 
 	/**
 	 * Bind query params, form data, and or multipart form data to the binder target.
-	 * @param exchange the current exchange.
+	 * @param exchange the current exchange
 	 * @return a {@code Mono<Void>} when binding is complete
 	 */
 	public Mono<Void> bind(ServerWebExchange exchange) {

spring-web/src/main/java/org/springframework/web/bind/support/WebRequestDataBinder.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.
@@ -101,7 +101,7 @@ public class WebRequestDataBinder extends WebDataBinder {
 	 * <p>The type of the target property for a multipart file can be Part, MultipartFile,
 	 * byte[], or String. The latter two receive the contents of the uploaded file;
 	 * all metadata like original file name, content type, etc are lost in those cases.
-	 * @param request request with parameters to bind (can be multipart)
+	 * @param request the request with parameters to bind (can be multipart)
 	 * @see org.springframework.web.multipart.MultipartRequest
 	 * @see org.springframework.web.multipart.MultipartFile
 	 * @see javax.servlet.http.Part
@@ -109,12 +109,12 @@ public class WebRequestDataBinder extends WebDataBinder {
 	 */
 	public void bind(WebRequest request) {
 		MutablePropertyValues mpvs = new MutablePropertyValues(request.getParameterMap());
-		if (isMultipartRequest(request) && request instanceof NativeWebRequest) {
+		if (request instanceof NativeWebRequest) {
 			MultipartRequest multipartRequest = ((NativeWebRequest) request).getNativeRequest(MultipartRequest.class);
 			if (multipartRequest != null) {
 				bindMultipart(multipartRequest.getMultiFileMap(), mpvs);
 			}
-			else {
+			else if (isMultipartRequest(request)) {
 				HttpServletRequest servletRequest = ((NativeWebRequest) request).getNativeRequest(HttpServletRequest.class);
 				if (servletRequest != null) {
 					bindParts(servletRequest, mpvs);
@@ -126,11 +126,11 @@ public class WebRequestDataBinder extends WebDataBinder {
 
 	/**
 	 * Check if the request is a multipart request (by checking its Content-Type header).
-	 * @param request request with parameters to bind
+	 * @param request the request with parameters to bind
 	 */
 	private boolean isMultipartRequest(WebRequest request) {
 		String contentType = request.getHeader("Content-Type");
-		return (contentType != null && StringUtils.startsWithIgnoreCase(contentType, "multipart"));
+		return StringUtils.startsWithIgnoreCase(contentType, "multipart/");
 	}
 
 	private void bindParts(HttpServletRequest request, MutablePropertyValues mpvs) {

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/PathVariableMethodArgumentResolver.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.
@@ -85,7 +85,6 @@ public class PathVariableMethodArgumentResolver extends AbstractNamedValueSyncAr
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	protected Object resolveNamedValue(String name, MethodParameter parameter, ServerWebExchange exchange) {
 		String attributeName = HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE;
 		return exchange.getAttributeOrDefault(attributeName, Collections.emptyMap()).get(name);
@@ -97,7 +96,6 @@ public class PathVariableMethodArgumentResolver extends AbstractNamedValueSyncAr
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	protected void handleResolvedValue(
 			@Nullable Object arg, String name, MethodParameter parameter, Model model, ServerWebExchange exchange) {
 

spring-webmvc/src/main/java/org/springframework/web/servlet/HandlerExecutionChain.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.
@@ -88,10 +88,16 @@ public class HandlerExecutionChain {
 		return this.handler;
 	}
 
+	/**
+	 * Add the given interceptor to the end of this chain.
+	 */
 	public void addInterceptor(HandlerInterceptor interceptor) {
 		initInterceptorList().add(interceptor);
 	}
 
+	/**
+	 * Add the given interceptors to the end of this chain.
+	 */
 	public void addInterceptors(HandlerInterceptor... interceptors) {
 		if (!ObjectUtils.isEmpty(interceptors)) {
 			CollectionUtils.mergeArrayIntoCollection(interceptors, initInterceptorList());
@@ -188,13 +194,16 @@ public class HandlerExecutionChain {
 		HandlerInterceptor[] interceptors = getInterceptors();
 		if (!ObjectUtils.isEmpty(interceptors)) {
 			for (int i = interceptors.length - 1; i >= 0; i--) {
-				if (interceptors[i] instanceof AsyncHandlerInterceptor) {
+				HandlerInterceptor interceptor = interceptors[i];
+				if (interceptor instanceof AsyncHandlerInterceptor) {
 					try {
-						AsyncHandlerInterceptor asyncInterceptor = (AsyncHandlerInterceptor) interceptors[i];
+						AsyncHandlerInterceptor asyncInterceptor = (AsyncHandlerInterceptor) interceptor;
 						asyncInterceptor.afterConcurrentHandlingStarted(request, response, this.handler);
 					}
 					catch (Throwable ex) {
-						logger.error("Interceptor [" + interceptors[i] + "] failed in afterConcurrentHandlingStarted", ex);
+						if (logger.isErrorEnabled()) {
+							logger.error("Interceptor [" + interceptor + "] failed in afterConcurrentHandlingStarted", ex);
+						}
 					}
 				}
 			}

spring-webmvc/src/main/java/org/springframework/web/servlet/handler/AbstractHandlerMapping.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.
@@ -310,22 +310,22 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 	}
 
 	/**
-	 * Detect beans of type {@link MappedInterceptor} and add them to the list of mapped interceptors.
-	 * <p>This is called in addition to any {@link MappedInterceptor MappedInterceptors} that may have been provided
-	 * via {@link #setInterceptors}, by default adding all beans of type {@link MappedInterceptor}
-	 * from the current context and its ancestors. Subclasses can override and refine this policy.
-	 * @param mappedInterceptors an empty list to add {@link MappedInterceptor} instances to
+	 * Detect beans of type {@link MappedInterceptor} and add them to the list
+	 * of mapped interceptors.
+	 * <p>This is called in addition to any {@link MappedInterceptor}s that may
+	 * have been provided via {@link #setInterceptors}, by default adding all
+	 * beans of type {@link MappedInterceptor} from the current context and its
+	 * ancestors. Subclasses can override and refine this policy.
+	 * @param mappedInterceptors an empty list to add to
 	 */
 	protected void detectMappedInterceptors(List<HandlerInterceptor> mappedInterceptors) {
-		mappedInterceptors.addAll(
-				BeanFactoryUtils.beansOfTypeIncludingAncestors(
-						obtainApplicationContext(), MappedInterceptor.class, true, false).values());
+		mappedInterceptors.addAll(BeanFactoryUtils.beansOfTypeIncludingAncestors(
+				obtainApplicationContext(), MappedInterceptor.class, true, false).values());
 	}
 
 	/**
-	 * Initialize the specified interceptors, checking for {@link MappedInterceptor MappedInterceptors} and
-	 * adapting {@link HandlerInterceptor}s and {@link WebRequestInterceptor HandlerInterceptor}s and
-	 * {@link WebRequestInterceptor}s if necessary.
+	 * Initialize the specified interceptors adapting
+	 * {@link WebRequestInterceptor}s to {@link HandlerInterceptor}.
 	 * @see #setInterceptors
 	 * @see #adaptInterceptor
 	 */
@@ -342,13 +342,13 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 	}
 
 	/**
-	 * Adapt the given interceptor object to the {@link HandlerInterceptor} interface.
-	 * <p>By default, the supported interceptor types are {@link HandlerInterceptor}
-	 * and {@link WebRequestInterceptor}. Each given {@link WebRequestInterceptor}
-	 * will be wrapped in a {@link WebRequestHandlerInterceptorAdapter}.
-	 * Can be overridden in subclasses.
-	 * @param interceptor the specified interceptor object
-	 * @return the interceptor wrapped as HandlerInterceptor
+	 * Adapt the given interceptor object to {@link HandlerInterceptor}.
+	 * <p>By default, the supported interceptor types are
+	 * {@link HandlerInterceptor} and {@link WebRequestInterceptor}. Each given
+	 * {@link WebRequestInterceptor} is wrapped with
+	 * {@link WebRequestHandlerInterceptorAdapter}.
+	 * @param interceptor the interceptor
+	 * @return the interceptor downcast or adapted to HandlerInterceptor
 	 * @see org.springframework.web.servlet.HandlerInterceptor
 	 * @see org.springframework.web.context.request.WebRequestInterceptor
 	 * @see WebRequestHandlerInterceptorAdapter
@@ -367,7 +367,8 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 
 	/**
 	 * Return the adapted interceptors as {@link HandlerInterceptor} array.
-	 * @return the array of {@link HandlerInterceptor HandlerInterceptors}, or {@code null} if none
+	 * @return the array of {@link HandlerInterceptor HandlerInterceptor}s,
+	 * or {@code null} if none
 	 */
 	@Nullable
 	protected final HandlerInterceptor[] getAdaptedInterceptors() {
@@ -376,8 +377,8 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 	}
 
 	/**
-	 * Return all configured {@link MappedInterceptor MappedInterceptors} as an array.
-	 * @return the array of {@link MappedInterceptor MappedInterceptors}, or {@code null} if none
+	 * Return all configured {@link MappedInterceptor}s as an array.
+	 * @return the array of {@link MappedInterceptor}s, or {@code null} if none
 	 */
 	@Nullable
 	protected final MappedInterceptor[] getMappedInterceptors() {
@@ -456,7 +457,7 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 	 * Build a {@link HandlerExecutionChain} for the given handler, including
 	 * applicable interceptors.
 	 * <p>The default implementation builds a standard {@link HandlerExecutionChain}
-	 * with the given handler, the handler mapping's common interceptors, and any
+	 * with the given handler, the common interceptors of the handler mapping, and any
 	 * {@link MappedInterceptor MappedInterceptors} matching to the current request URL. Interceptors
 	 * are added in the order they were registered. Subclasses may override this
 	 * in order to extend/rearrange the list of interceptors.
@@ -527,12 +528,12 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 
 		if (CorsUtils.isPreFlightRequest(request)) {
 			HandlerInterceptor[] interceptors = chain.getInterceptors();
-			chain = new HandlerExecutionChain(new PreFlightHandler(config), interceptors);
+			return new HandlerExecutionChain(new PreFlightHandler(config), interceptors);
 		}
 		else {
 			chain.addInterceptor(new CorsInterceptor(config));
+			return chain;
 		}
-		return chain;
 	}
 
 

spring-webmvc/src/main/java/org/springframework/web/servlet/i18n/CookieLocaleResolver.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.
@@ -335,7 +335,6 @@ public class CookieLocaleResolver extends CookieGenerator implements LocaleConte
 	 * @see #setDefaultLocale
 	 * @see javax.servlet.http.HttpServletRequest#getLocale()
 	 */
-	@Nullable
 	protected Locale determineDefaultLocale(HttpServletRequest request) {
 		Locale defaultLocale = getDefaultLocale();
 		if (defaultLocale == null) {