Add options to configure content negotiation

The MVC Java config and the MVC namespace now support options to
configure content negotiation. By default both support checking path
extensions first and the "Accept" header second. For path extensions
.json, .xml, .atom, and .rss are recognized out of the box if the
Jackson, JAXB2, or Rome libraries are available. The ServletContext
and the Java Activation Framework may be used as fallback options
for path extension lookups.

Issue: SPR-8420

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/accept/ContentNegotiationManager.java

@@ -30,10 +30,19 @@
 
 /**
  * This class is used to determine the requested {@linkplain MediaType media types}
- * in a request by delegating to a list of {@link ContentNegotiationStrategy} instances.
+ * of a request by delegating to a list of ContentNegotiationStrategy instances.
+ * The strategies must be provided at instantiation or alternatively if using
+ * the default constructor, an instance of {@link HeaderContentNegotiationStrategy}
+ * will be configured by default.
  *
- * <p>It may also be used to determine the extensions associated with a MediaType by
- * delegating to a list of {@link MediaTypeFileExtensionResolver} instances.
+ * <p>This class may also be used to look up file extensions associated with a
+ * MediaType. This is done by consulting the list of configured
+ * {@link MediaTypeFileExtensionResolver} instances. Note that some
+ * ContentNegotiationStrategy implementations also implement
+ * MediaTypeFileExtensionResolver and the class constructor accepting the former
+ * will also detect if they implement the latter. If you need to register additional
+ * resolvers, you can use the method
+ * {@link #addFileExtensionResolvers(MediaTypeFileExtensionResolver...)}.
  *
  * @author Rossen Stoyanchev
  * @since 3.2
@@ -50,6 +59,7 @@ public class ContentNegotiationManager implements ContentNegotiationStrategy, Me
 	 * Create an instance with the given ContentNegotiationStrategy instances.
 	 * <p>Each instance is checked to see if it is also an implementation of
 	 * MediaTypeFileExtensionResolver, and if so it is registered as such.
+	 * @param strategies one more more ContentNegotiationStrategy instances
 	 */
 	public ContentNegotiationManager(ContentNegotiationStrategy... strategies) {
 		Assert.notEmpty(strategies, "At least one ContentNegotiationStrategy is expected");
@@ -70,6 +80,11 @@ public ContentNegotiationManager() {
 
 	/**
 	 * Add MediaTypeFileExtensionResolver instances.
+	 * <p>Note that some {@link ContentNegotiationStrategy} implementations also
+	 * implement {@link MediaTypeFileExtensionResolver} and the class constructor
+	 * accepting the former will also detect implementations of the latter. Therefore
+	 * you only need to use this method to register additional instances.
+	 * @param one more resolvers
 	 */
 	public void addFileExtensionResolvers(MediaTypeFileExtensionResolver... resolvers) {
 		this.fileExtensionResolvers.addAll(Arrays.asList(resolvers));

spring-webmvc/src/main/java/org/springframework/web/servlet/config/AnnotationDrivenBeanDefinitionParser.java

@@ -16,7 +16,10 @@
 
 package org.springframework.web.servlet.config;
 
+import java.util.Arrays;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.BeanDefinitionHolder;
@@ -29,6 +32,7 @@
 import org.springframework.beans.factory.xml.ParserContext;
 import org.springframework.format.support.DefaultFormattingConversionService;
 import org.springframework.format.support.FormattingConversionServiceFactoryBean;
+import org.springframework.http.MediaType;
 import org.springframework.http.converter.ByteArrayHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.http.converter.ResourceHttpMessageConverter;
@@ -44,6 +48,9 @@
 import org.springframework.util.xml.DomUtils;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
 import org.springframework.web.HttpRequestHandler;
+import org.springframework.web.accept.ContentNegotiationManager;
+import org.springframework.web.accept.HeaderContentNegotiationStrategy;
+import org.springframework.web.accept.PathExtensionContentNegotiationStrategy;
 import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.ResponseStatus;
 import org.springframework.web.bind.support.ConfigurableWebBindingInitializer;
@@ -102,9 +109,10 @@
  * </ul>
  *
  * <p>Both the {@link RequestMappingHandlerAdapter} and the
- * {@link ExceptionHandlerExceptionResolver} are configured with default
- * instances of the following kind, unless custom instances are provided:
+ * {@link ExceptionHandlerExceptionResolver} are configured with instances of
+ * the following by default:
  * <ul>
+ * 	<li>A {@link ContentNegotiationManager}
  * 	<li>A {@link DefaultFormattingConversionService}
  * 	<li>A {@link LocalValidatorFactoryBean} if a JSR-303 implementation is
  * 	available on the classpath
@@ -143,11 +151,14 @@ public BeanDefinition parse(Element element, ParserContext parserContext) {
 		CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);
 		parserContext.pushContainingComponent(compDefinition);
 
-		RootBeanDefinition methodMappingDef = new RootBeanDefinition(RequestMappingHandlerMapping.class);
-		methodMappingDef.setSource(source);
-		methodMappingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
-		methodMappingDef.getPropertyValues().add("order", 0);
-		String methodMappingName = parserContext.getReaderContext().registerWithGeneratedName(methodMappingDef);
+		RuntimeBeanReference contentNegotiationManager = getContentNegotiationManager(element, source, parserContext);
+
+		RootBeanDefinition handlerMappingDef = new RootBeanDefinition(RequestMappingHandlerMapping.class);
+		handlerMappingDef.setSource(source);
+		handlerMappingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
+		handlerMappingDef.getPropertyValues().add("order", 0);
+		handlerMappingDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
+		String methodMappingName = parserContext.getReaderContext().registerWithGeneratedName(handlerMappingDef);
 
 		RuntimeBeanReference conversionService = getConversionService(element, source, parserContext);
 		RuntimeBeanReference validator = getValidator(element, source, parserContext);
@@ -164,22 +175,23 @@ public BeanDefinition parse(Element element, ParserContext parserContext) {
 		ManagedList<?> argumentResolvers = getArgumentResolvers(element, source, parserContext);
 		ManagedList<?> returnValueHandlers = getReturnValueHandlers(element, source, parserContext);
 
-		RootBeanDefinition methodAdapterDef = new RootBeanDefinition(RequestMappingHandlerAdapter.class);
-		methodAdapterDef.setSource(source);
-		methodAdapterDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
-		methodAdapterDef.getPropertyValues().add("webBindingInitializer", bindingDef);
-		methodAdapterDef.getPropertyValues().add("messageConverters", messageConverters);
+		RootBeanDefinition handlerAdapterDef = new RootBeanDefinition(RequestMappingHandlerAdapter.class);
+		handlerAdapterDef.setSource(source);
+		handlerAdapterDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
+		handlerAdapterDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
+		handlerAdapterDef.getPropertyValues().add("webBindingInitializer", bindingDef);
+		handlerAdapterDef.getPropertyValues().add("messageConverters", messageConverters);
 		if (element.hasAttribute("ignoreDefaultModelOnRedirect")) {
 			Boolean ignoreDefaultModel = Boolean.valueOf(element.getAttribute("ignoreDefaultModelOnRedirect"));
-			methodAdapterDef.getPropertyValues().add("ignoreDefaultModelOnRedirect", ignoreDefaultModel);
+			handlerAdapterDef.getPropertyValues().add("ignoreDefaultModelOnRedirect", ignoreDefaultModel);
 		}
 		if (argumentResolvers != null) {
-			methodAdapterDef.getPropertyValues().add("customArgumentResolvers", argumentResolvers);
+			handlerAdapterDef.getPropertyValues().add("customArgumentResolvers", argumentResolvers);
 		}
 		if (returnValueHandlers != null) {
-			methodAdapterDef.getPropertyValues().add("customReturnValueHandlers", returnValueHandlers);
+			handlerAdapterDef.getPropertyValues().add("customReturnValueHandlers", returnValueHandlers);
 		}
-		String methodAdapterName = parserContext.getReaderContext().registerWithGeneratedName(methodAdapterDef);
+		String handlerAdapterName = parserContext.getReaderContext().registerWithGeneratedName(handlerAdapterDef);
 
 		RootBeanDefinition csInterceptorDef = new RootBeanDefinition(ConversionServiceExposingInterceptor.class);
 		csInterceptorDef.setSource(source);
@@ -191,13 +203,14 @@ public BeanDefinition parse(Element element, ParserContext parserContext) {
 		mappedCsInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(1, csInterceptorDef);
 		String mappedInterceptorName = parserContext.getReaderContext().registerWithGeneratedName(mappedCsInterceptorDef);
 
-		RootBeanDefinition methodExceptionResolver = new RootBeanDefinition(ExceptionHandlerExceptionResolver.class);
-		methodExceptionResolver.setSource(source);
-		methodExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
-		methodExceptionResolver.getPropertyValues().add("messageConverters", messageConverters);
-		methodExceptionResolver.getPropertyValues().add("order", 0);
+		RootBeanDefinition exceptionHandlerExceptionResolver = new RootBeanDefinition(ExceptionHandlerExceptionResolver.class);
+		exceptionHandlerExceptionResolver.setSource(source);
+		exceptionHandlerExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
+		exceptionHandlerExceptionResolver.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
+		exceptionHandlerExceptionResolver.getPropertyValues().add("messageConverters", messageConverters);
+		exceptionHandlerExceptionResolver.getPropertyValues().add("order", 0);
 		String methodExceptionResolverName =
-				parserContext.getReaderContext().registerWithGeneratedName(methodExceptionResolver);
+				parserContext.getReaderContext().registerWithGeneratedName(exceptionHandlerExceptionResolver);
 
 		RootBeanDefinition responseStatusExceptionResolver = new RootBeanDefinition(ResponseStatusExceptionResolver.class);
 		responseStatusExceptionResolver.setSource(source);
@@ -213,9 +226,9 @@ public BeanDefinition parse(Element element, ParserContext parserContext) {
 		String defaultExceptionResolverName =
 				parserContext.getReaderContext().registerWithGeneratedName(defaultExceptionResolver);
 
-		parserContext.registerComponent(new BeanComponentDefinition(methodMappingDef, methodMappingName));
-		parserContext.registerComponent(new BeanComponentDefinition(methodAdapterDef, methodAdapterName));
-		parserContext.registerComponent(new BeanComponentDefinition(methodExceptionResolver, methodExceptionResolverName));
+		parserContext.registerComponent(new BeanComponentDefinition(handlerMappingDef, methodMappingName));
+		parserContext.registerComponent(new BeanComponentDefinition(handlerAdapterDef, handlerAdapterName));
+		parserContext.registerComponent(new BeanComponentDefinition(exceptionHandlerExceptionResolver, methodExceptionResolverName));
 		parserContext.registerComponent(new BeanComponentDefinition(responseStatusExceptionResolver, responseStatusExceptionResolverName));
 		parserContext.registerComponent(new BeanComponentDefinition(defaultExceptionResolver, defaultExceptionResolverName));
 		parserContext.registerComponent(new BeanComponentDefinition(mappedCsInterceptorDef, mappedInterceptorName));
@@ -261,6 +274,42 @@ else if (jsr303Present) {
 		}
 	}
 
+	private RuntimeBeanReference getContentNegotiationManager(Element element, Object source, ParserContext parserContext) {
+		RuntimeBeanReference contentNegotiationManagerRef;
+		if (element.hasAttribute("content-negotiation-manager")) {
+			contentNegotiationManagerRef = new RuntimeBeanReference(element.getAttribute("content-negotiation-manager"));
+		}
+		else {
+			RootBeanDefinition managerDef = new RootBeanDefinition(ContentNegotiationManager.class);
+			managerDef.setSource(source);
+			managerDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
+			PathExtensionContentNegotiationStrategy strategy1 = new PathExtensionContentNegotiationStrategy(getDefaultMediaTypes());
+			HeaderContentNegotiationStrategy strategy2 = new HeaderContentNegotiationStrategy();
+			managerDef.getConstructorArgumentValues().addIndexedArgumentValue(0, Arrays.asList(strategy1,strategy2));
+
+			String beanName = "mvcContentNegotiationManager";
+			parserContext.getReaderContext().getRegistry().registerBeanDefinition(beanName , managerDef);
+			parserContext.registerComponent(new BeanComponentDefinition(managerDef, beanName));
+			contentNegotiationManagerRef = new RuntimeBeanReference(beanName);
+		}
+		return contentNegotiationManagerRef;
+	}
+
+	private Map<String, MediaType> getDefaultMediaTypes() {
+		Map<String, MediaType> map = new HashMap<String, MediaType>();
+		if (romePresent) {
+			map.put("atom", MediaType.APPLICATION_ATOM_XML);
+			map.put("rss", MediaType.valueOf("application/rss+xml"));
+		}
+		if (jackson2Present || jacksonPresent) {
+			map.put("json", MediaType.APPLICATION_JSON);
+		}
+		if (jaxb2Present) {
+			map.put("xml", MediaType.APPLICATION_XML);
+		}
+		return map;
+	}
+
 	private RuntimeBeanReference getMessageCodesResolver(Element element, Object source, ParserContext parserContext) {
 		if (element.hasAttribute("message-codes-resolver")) {
 			return new RuntimeBeanReference(element.getAttribute("message-codes-resolver"));