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annotation-driven 配置详解

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annotation-driven 配置详解一、前沿在SpringMVC的项目中，我们经常使用<mvc:annotation-driven>这个配置，那么这个配置到底是做什么的呢？下面来分析一下，首先找到mvc的命名空间的定义，如下图：从上述图中可知，annotation-driven配置的实现类应该是定义在了MvcNamespaceHandler类中，是不是这样的呢？下面我们看下MvcNa…

一、前沿

在 Spring MVC 的项目中，我们经常使用 <mvc:annotation-driven> 这个配置，那么这个配置到底是做什么的呢？下面来分析一下，首先找到 mvc 的命名空间的定义，如下图：

annotation-driven 配置详解

annotation-driven 配置详解

从上述图中可知，annotation-driven 配置的实现类应该是定义在了 MvcNamespaceHandler 类中，是不是这样的呢？下面我们看下 MvcNamespaceHandler 源码

二、MvcNamespaceHandler

MvcNamespaceHandler 源码如下：

/**
 * {@link NamespaceHandler} for Spring MVC configuration namespace.
 *
 * @author Keith Donald
 * @author Jeremy Grelle
 * @author Sebastien Deleuze
 * @since 3.0
 */
public class MvcNamespaceHandler extends NamespaceHandlerSupport {

	@Override
	public void init() {
		// 注册 annotation-driven 标签的解析器 AnnotationDrivenBeanDefinitionParser，用来解析 Controller
		registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
		// 注册 default-servlet-handler 标签的解析器 DefaultServletHandlerBeanDefinitionParser，用来解析静态资源文件（html、jsp、js和css等）
		registerBeanDefinitionParser("default-servlet-handler", new DefaultServletHandlerBeanDefinitionParser());
		// 注册 interceptors 标签的解析器 InterceptorsBeanDefinitionParser，用来解析拦截器
		registerBeanDefinitionParser("interceptors", new InterceptorsBeanDefinitionParser());
		// 注册 resources 标签的解析器 ResourcesBeanDefinitionParser，用来解析资源文件
		registerBeanDefinitionParser("resources", new ResourcesBeanDefinitionParser());
		// 注册 view-controller、redirect-view-controller、status-controller 标签的解析器 ViewControllerBeanDefinitionParser，用来解析视图view
		registerBeanDefinitionParser("view-controller", new ViewControllerBeanDefinitionParser());
		registerBeanDefinitionParser("redirect-view-controller", new ViewControllerBeanDefinitionParser());
		registerBeanDefinitionParser("status-controller", new ViewControllerBeanDefinitionParser());
		// 注册 view-resolvers 标签的解析器 ViewResolversBeanDefinitionParser，用来解析视图解析器
		registerBeanDefinitionParser("view-resolvers", new ViewResolversBeanDefinitionParser());
		registerBeanDefinitionParser("tiles-configurer", new TilesConfigurerBeanDefinitionParser());
		// 注册 freemarker-configurer 标签的解析器 FreeMarkerConfigurerBeanDefinitionParser，用来解析 freemarker 配置
		registerBeanDefinitionParser("freemarker-configurer", new FreeMarkerConfigurerBeanDefinitionParser());
		// 注册 groovy-configurer 标签的解析器 GroovyMarkupConfigurerBeanDefinitionParser，用来解析 groovy 配置
		registerBeanDefinitionParser("groovy-configurer", new GroovyMarkupConfigurerBeanDefinitionParser());
		// 注册 script-template-configurer 标签的解析器 ScriptTemplateConfigurerBeanDefinitionParser，用来解析 script 脚本模板配置
		registerBeanDefinitionParser("script-template-configurer", new ScriptTemplateConfigurerBeanDefinitionParser());
		// 注册 cors 标签的解析器 CorsBeanDefinitionParser，用来解析跨域
		registerBeanDefinitionParser("cors", new CorsBeanDefinitionParser());
	}

}

从上述源码中可知 annotation-driven 配置对应的解析类 AnnotationDrivenBeanDefinitionParser 确实是定义在 MvcNamespaceHandler 的 init 方法中，那么 annotation-driven 配置实现的具体业务肯定在 AnnotationDrivenBeanDefinitionParser 类中，下面我们分析一下 AnnotationDrivenBeanDefinitionParser 源码

三、AnnotationDrivenBeanDefinitionParser

AnnotationDrivenBeanDefinitionParser 的 parse 方法实现了具体的解析逻辑，源码如下：

/**
 * A {@link BeanDefinitionParser} that provides the configuration for the
 * {@code <annotation-driven/>} MVC namespace element.
 *
 * <p>This class registers the following {@link HandlerMapping HandlerMappings}:</p>
 * <ul>
 * <li>{@link RequestMappingHandlerMapping}
 * 将请求映射到带注解的控制器方法时，按照0排序，例如 @RequestMapping("/test")
 * ordered at 0 for mapping requests to annotated controller methods.
 * <li>{@link BeanNameUrlHandlerMapping}
 * 将URL路径映射到控制器bean名称时，按照2排序
 * ordered at 2 to map URL paths to controller bean names.
 * </ul>
 *
 * <p><strong>Note:</strong> Additional HandlerMappings may be registered
 * as a result of using the {@code <view-controller>} or the
 * {@code <resources>} MVC namespace elements.
 *
 * <p>This class registers the following {@link HandlerAdapter HandlerAdapters}:
 * <ul>
 * <li>{@link RequestMappingHandlerAdapter}
 * 处理带有@controller注解的适配器（支持自定义的参数和返回值），对应于 RequestMappingHandlerMapping，例如 @RequestMapping("/test")
 * for processing requests with annotated controller methods.
 * <li>{@link HttpRequestHandlerAdapter}
 * 处理带有 HttpRequestHandlers 的适配器
 * for processing requests with {@link HttpRequestHandler HttpRequestHandlers}.
 * <li>{@link SimpleControllerHandlerAdapter}
 * 处理基于 Controllers 接口的适配器
 * for processing requests with interface-based {@link Controller Controllers}.
 * </ul>
 *
 * 异常处理器
 * <p>This class registers the following {@link HandlerExceptionResolver HandlerExceptionResolvers}:
 * <ul>
 * <li>{@link ExceptionHandlerExceptionResolver} for handling exceptions through
 * {@link org.springframework.web.bind.annotation.ExceptionHandler} methods.
 * <li>{@link ResponseStatusExceptionResolver} for exceptions annotated
 * with {@link org.springframework.web.bind.annotation.ResponseStatus}.
 * <li>{@link DefaultHandlerExceptionResolver} for resolving known Spring
 * exception types
 * </ul>
 *
 * <p>This class registers an {@link org.springframework.util.AntPathMatcher}
 * and a {@link org.springframework.web.util.UrlPathHelper} to be used by:
 * <ul>
 * <li>the {@link RequestMappingHandlerMapping},
 * <li>the {@link HandlerMapping} for ViewControllers
 * <li>and the {@link HandlerMapping} for serving resources
 * </ul>
 * Note that those beans can be configured by using the {@code path-matching}
 * MVC namespace element.
 *
 * <p>Both the {@link RequestMappingHandlerAdapter} and the
 * {@link ExceptionHandlerExceptionResolver} are configured with instances of
 * the following by default:
 * <ul>
 * <li>A {@link ContentNegotiationManager}
 * <li>A {@link DefaultFormattingConversionService}
 * <li>A {@link org.springframework.validation.beanvalidation.LocalValidatorFactoryBean}
 * if a JSR-303 implementation is available on the classpath
 * <li>A range of {@link HttpMessageConverter HttpMessageConverters} depending on which third-party
 * libraries are available on the classpath.
 * </ul>
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @author Brian Clozel
 * @author Agim Emruli
 * @since 3.0
 */
class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
    @Override
	@Nullable
	public BeanDefinition parse(Element element, ParserContext context) {
		Object source = context.extractSource(element);
		XmlReaderContext readerContext = context.getReaderContext();

		CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);
		context.pushContainingComponent(compDefinition);

		RuntimeBeanReference contentNegotiationManager = getContentNegotiationManager(element, source, context);

		// 定义 RequestMappingHandlerMapping
		RootBeanDefinition handlerMappingDef = new RootBeanDefinition(RequestMappingHandlerMapping.class);
		handlerMappingDef.setSource(source);
		handlerMappingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		// 排序值为 0
		handlerMappingDef.getPropertyValues().add("order", 0);
		handlerMappingDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);

		if (element.hasAttribute("enable-matrix-variables")) {
			Boolean enableMatrixVariables = Boolean.valueOf(element.getAttribute("enable-matrix-variables"));
			handlerMappingDef.getPropertyValues().add("removeSemicolonContent", !enableMatrixVariables);
		}

		configurePathMatchingProperties(handlerMappingDef, element, context);
		// 注册 RequestMappingHandlerMapping 类型对应的 RootBeanDefinition
		readerContext.getRegistry().registerBeanDefinition(HANDLER_MAPPING_BEAN_NAME, handlerMappingDef);

		RuntimeBeanReference corsRef = MvcNamespaceUtils.registerCorsConfigurations(null, context, source);
		handlerMappingDef.getPropertyValues().add("corsConfigurations", corsRef);

		RuntimeBeanReference conversionService = getConversionService(element, source, context);
		RuntimeBeanReference validator = getValidator(element, source, context);
		RuntimeBeanReference messageCodesResolver = getMessageCodesResolver(element);

		RootBeanDefinition bindingDef = new RootBeanDefinition(ConfigurableWebBindingInitializer.class);
		bindingDef.setSource(source);
		bindingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		bindingDef.getPropertyValues().add("conversionService", conversionService);
		bindingDef.getPropertyValues().add("validator", validator);
		bindingDef.getPropertyValues().add("messageCodesResolver", messageCodesResolver);

		ManagedList<?> messageConverters = getMessageConverters(element, source, context);
		ManagedList<?> argumentResolvers = getArgumentResolvers(element, context);
		ManagedList<?> returnValueHandlers = getReturnValueHandlers(element, context);
		String asyncTimeout = getAsyncTimeout(element);
		RuntimeBeanReference asyncExecutor = getAsyncExecutor(element);
		ManagedList<?> callableInterceptors = getCallableInterceptors(element, source, context);
		ManagedList<?> deferredResultInterceptors = getDeferredResultInterceptors(element, source, context);

		// 定义 RequestMappingHandlerAdapter
		RootBeanDefinition handlerAdapterDef = new RootBeanDefinition(RequestMappingHandlerAdapter.class);
		handlerAdapterDef.setSource(source);
		handlerAdapterDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		handlerAdapterDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
		handlerAdapterDef.getPropertyValues().add("webBindingInitializer", bindingDef);
		// 消息转换器
		handlerAdapterDef.getPropertyValues().add("messageConverters", messageConverters);
		addRequestBodyAdvice(handlerAdapterDef);
		addResponseBodyAdvice(handlerAdapterDef);

		if (element.hasAttribute("ignore-default-model-on-redirect")) {
			Boolean ignoreDefaultModel = Boolean.valueOf(element.getAttribute("ignore-default-model-on-redirect"));
			handlerAdapterDef.getPropertyValues().add("ignoreDefaultModelOnRedirect", ignoreDefaultModel);
		}
		if (argumentResolvers != null) {
			handlerAdapterDef.getPropertyValues().add("customArgumentResolvers", argumentResolvers);
		}
		if (returnValueHandlers != null) {
			handlerAdapterDef.getPropertyValues().add("customReturnValueHandlers", returnValueHandlers);
		}
		if (asyncTimeout != null) {
			handlerAdapterDef.getPropertyValues().add("asyncRequestTimeout", asyncTimeout);
		}
		if (asyncExecutor != null) {
			handlerAdapterDef.getPropertyValues().add("taskExecutor", asyncExecutor);
		}

		handlerAdapterDef.getPropertyValues().add("callableInterceptors", callableInterceptors);
		handlerAdapterDef.getPropertyValues().add("deferredResultInterceptors", deferredResultInterceptors);
		// 注册 RequestMappingHandlerAdapter 对应的 RootBeanDefinition
		readerContext.getRegistry().registerBeanDefinition(HANDLER_ADAPTER_BEAN_NAME, handlerAdapterDef);

		RootBeanDefinition uriContributorDef =
				new RootBeanDefinition(CompositeUriComponentsContributorFactoryBean.class);
		uriContributorDef.setSource(source);
		uriContributorDef.getPropertyValues().addPropertyValue("handlerAdapter", handlerAdapterDef);
		uriContributorDef.getPropertyValues().addPropertyValue("conversionService", conversionService);
		String uriContributorName = MvcUriComponentsBuilder.MVC_URI_COMPONENTS_CONTRIBUTOR_BEAN_NAME;
		readerContext.getRegistry().registerBeanDefinition(uriContributorName, uriContributorDef);

		RootBeanDefinition csInterceptorDef = new RootBeanDefinition(ConversionServiceExposingInterceptor.class);
		csInterceptorDef.setSource(source);
		csInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(0, conversionService);
		RootBeanDefinition mappedInterceptorDef = new RootBeanDefinition(MappedInterceptor.class);
		mappedInterceptorDef.setSource(source);
		mappedInterceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		mappedInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(0, (Object) null);
		mappedInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(1, csInterceptorDef);
		String mappedInterceptorName = readerContext.registerWithGeneratedName(mappedInterceptorDef);

		// 定义 ExceptionHandlerExceptionResolver 异常处理器
		RootBeanDefinition methodExceptionResolver = new RootBeanDefinition(ExceptionHandlerExceptionResolver.class);
		methodExceptionResolver.setSource(source);
		methodExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		methodExceptionResolver.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
		methodExceptionResolver.getPropertyValues().add("messageConverters", messageConverters);
		// 排序值为 0
		methodExceptionResolver.getPropertyValues().add("order", 0);
		addResponseBodyAdvice(methodExceptionResolver);
		if (argumentResolvers != null) {
			methodExceptionResolver.getPropertyValues().add("customArgumentResolvers", argumentResolvers);
		}
		if (returnValueHandlers != null) {
			methodExceptionResolver.getPropertyValues().add("customReturnValueHandlers", returnValueHandlers);
		}
		String methodExResolverName = readerContext.registerWithGeneratedName(methodExceptionResolver);

		// 定义 ResponseStatusExceptionResolver 返回状态异常解析器
		RootBeanDefinition statusExceptionResolver = new RootBeanDefinition(ResponseStatusExceptionResolver.class);
		statusExceptionResolver.setSource(source);
		statusExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		// 排序值为 1
		statusExceptionResolver.getPropertyValues().add("order", 1);
		String statusExResolverName = readerContext.registerWithGeneratedName(statusExceptionResolver);

		// 定义Spring中已知的异常解析器
		RootBeanDefinition defaultExceptionResolver = new RootBeanDefinition(DefaultHandlerExceptionResolver.class);
		defaultExceptionResolver.setSource(source);
		defaultExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		// 排序值为 2
		defaultExceptionResolver.getPropertyValues().add("order", 2);
		String defaultExResolverName = readerContext.registerWithGeneratedName(defaultExceptionResolver);

		// 将上面所有的 bean 组件注册到上下文中
		context.registerComponent(new BeanComponentDefinition(handlerMappingDef, HANDLER_MAPPING_BEAN_NAME));
		context.registerComponent(new BeanComponentDefinition(handlerAdapterDef, HANDLER_ADAPTER_BEAN_NAME));
		context.registerComponent(new BeanComponentDefinition(uriContributorDef, uriContributorName));
		context.registerComponent(new BeanComponentDefinition(mappedInterceptorDef, mappedInterceptorName));
		context.registerComponent(new BeanComponentDefinition(methodExceptionResolver, methodExResolverName));
		context.registerComponent(new BeanComponentDefinition(statusExceptionResolver, statusExResolverName));
		context.registerComponent(new BeanComponentDefinition(defaultExceptionResolver, defaultExResolverName));

		// Ensure BeanNameUrlHandlerMapping (SPR-8289) and default HandlerAdapters are not "turned off"
		// 注册默认的一些组件，例如 BeanNameUrlHandlerMapping、HttpRequestHandlerAdapter、
		// SimpleControllerHandlerAdapter 和 HandlerMappingIntrospector
		MvcNamespaceUtils.registerDefaultComponents(context, source);

		context.popAndRegisterContainingComponent();

		return null;
	}
}

从上述源码中可以看出，在 AnnotationDrivenBeanDefinitionParser 中主要实现了注册了很多 bean 的功能，其中我们最关心的就是 RequestMappingHandlerMapping 和 RequestMappingHandlerAdapter 两个类，功能分别如图：

RequestMappingHandlerMapping ： HandlerMapping 的实现类，它处理的是 @RequestMapping 注解，并将其注册到映射表中，即 url 对应的 Controller 的 方法

RequestMappingHandlerAdapter ： HandlerAdapter 的实现类，它是处理请求的适配器，就是确定调用哪个 Controller 的 哪个方法

到这里，AnnotationDrivenBeanDefinitionParser 的源码就分析完了，其中没有什么太多复杂的逻辑，代码注释都写清楚了

四、annotation-driven 作用

通过阅读 AnnotationDrivenBeanDefinitionParser 的源码可知，annotation-driven 配置的作用如下：

1）、主要是注册了 RequestMappingHandlerMapping 和 RequestMappingHandlerAdapter bean，存储了请求url到Controller方法的映射关系

2）、注册了异常处理器

五、总结

Spring MVC 中如果配置了 <mvc:annotation-driven> ，则所有的 Controller 就会被解析，所以相应的 .do 请求就会被 Controller 处理，因此这个配置至关重要。当请求没有匹配到处理类（其中包括没有配置 <mvc:annotation-driven> 或者 访问的是静态资源文件）时，就会去找  <mvc:default-servlet-handler> （处理静态资源文件）配置的 DefaultServletHttpRequestHandler 默认处理器处理了

今天的文章annotation-driven 配置详解分享到此就结束了，感谢您的阅读，如果确实帮到您，您可以动动手指转发给其他人。

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