SpringMVC源码情操陶冶-AnnotationDrivenBeanDefinitionParser注解解析器

mvc:annotation-driven节点的解析器，是springmvc的核心解析器

官方注释

Open Declaration   org.springframework.web.servlet.config.AnnotationDrivenBeanDefinitionParser

A BeanDefinitionParser that provides the configuration for the <annotation-driven/> MVC namespace element. 

This class registers the following <<HandlerMappings>>:
•RequestMappingHandlerMapping ordered at 0 for mapping requests to annotated controller methods.
•BeanNameUrlHandlerMapping ordered at 2 to map URL paths to controller bean names. 

Note: Additional HandlerMappings may be registered as a result of using the <view-controller> or the <resources> MVC namespace elements. 

This class registers the following <<HandlerAdapters>>:
•RequestMappingHandlerAdapter for processing requests with annotated controller methods.
•HttpRequestHandlerAdapter for processing requests with HttpRequestHandlers.
•SimpleControllerHandlerAdapter for processing requests with interface-based Controllers. 

This class registers the following <<HandlerExceptionResolvers>>:
•ExceptionHandlerExceptionResolver for handling exceptions through @ExceptionHandler methods.
•ResponseStatusExceptionResolver for exceptions annotated with @ResponseStatus.
•DefaultHandlerExceptionResolver for resolving known Spring exception types 

This class registers an org.springframework.util.<<AntPathMatcher>> and a org.springframework.web.util.<<UrlPathHelper>> to be used by:
•the RequestMappingHandlerMapping,
•the HandlerMapping for ViewControllers
•and the HandlerMapping for serving resources
Note that those beans can be configured by using the path-matching MVC namespace element.
Both the RequestMappingHandlerAdapter and the ExceptionHandlerExceptionResolver are configured with instances of the following by default:
•A ContentNegotiationManager
•A DefaultFormattingConversionService
•A org.springframework.validation.beanvalidation.LocalValidatorFactoryBean if a JSR-303 implementation is available on the classpath
•A range of HttpMessageConverters depending on what 3rd party libraries are available on the classpath. 

主要注册HandlerMappings-路径匹配器、HandlerAdapters-路径匹配适配器、HandlerExceptionResolvers-异常解析器、AntPathMatcher-路径解析器、UrlPathHelper-请求路径获取帮助类等beans，提前为mvc做好基础的准备

AnnotationDrivenBeanDefinitionParser#parse

从此方法中，提炼实现的最主要代码片段，代码如下

		parserContext.registerComponent(new BeanComponentDefinition(handlerMappingDef, HANDLER_MAPPING_BEAN_NAME));
		parserContext.registerComponent(new BeanComponentDefinition(handlerAdapterDef, HANDLER_ADAPTER_BEAN_NAME));
		parserContext.registerComponent(new BeanComponentDefinition(uriCompContribDef, uriCompContribName));
		parserContext.registerComponent(new BeanComponentDefinition(exceptionHandlerExceptionResolver, methodExceptionResolverName));
		parserContext.registerComponent(new BeanComponentDefinition(responseStatusExceptionResolver, responseStatusExceptionResolverName));
		parserContext.registerComponent(new BeanComponentDefinition(defaultExceptionResolver, defaultExceptionResolverName));
		//格式转换处理拦截类，比如时间、数字等
		parserContext.registerComponent(new BeanComponentDefinition(mappedCsInterceptorDef, mappedInterceptorName));

		// Ensure BeanNameUrlHandlerMapping (SPR-8289) and default HandlerAdapters are not "turned off"
		MvcNamespaceUtils.registerDefaultComponents(parserContext, source);

跟官方注释提及的一样，主要目的是注册与mvc处理有关的相关beans以及默认的mvc组件，下面我们将从以上代码的不同组件生成进行逐个分析

HandlerMappings组件注册

对应parse()方法的代码片段如下

		//生成RequestMappingHandlerMapping组件对象
		RootBeanDefinition handlerMappingDef = new RootBeanDefinition(RequestMappingHandlerMapping.class);
		handlerMappingDef.setSource(source);
		handlerMappingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		//优先级设置为最高
		handlerMappingDef.getPropertyValues().add("order", 0);
//添加contentNegotiationManager属性，处理media type		handlerMappingDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);

		//查看mvc:annotation-driven有无enable-matrix-variables/enableMatrixVariables，表示是否开启多变量映射比如/cars;a=1;b=1
		//具体使用可查阅相关文档，默认removeSemicolonContent为false
		if (element.hasAttribute("enable-matrix-variables")) {
			Boolean enableMatrixVariables = Boolean.valueOf(element.getAttribute("enable-matrix-variables"));
			handlerMappingDef.getPropertyValues().add("removeSemicolonContent", !enableMatrixVariables);
		}
		else if (element.hasAttribute("enableMatrixVariables")) {
			Boolean enableMatrixVariables = Boolean.valueOf(element.getAttribute("enableMatrixVariables"));
			handlerMappingDef.getPropertyValues().add("removeSemicolonContent", !enableMatrixVariables);
		}
		//配置路径匹配解析器等属性
		configurePathMatchingProperties(handlerMappingDef, element, parserContext);
//将RequestMappingHandlerMapping注册为bean对象放置bean工厂中		readerContext.getRegistry().registerBeanDefinition(HANDLER_MAPPING_BEAN_NAME , handlerMappingDef);

RequestMappingHandlerMapping主要是处理@Controller和@RequestMapping注解的，另外再看下configurePathMatchingProperties()配置路径解析器方法

AnnotationDrivenBeanDefinitionParser#configurePathMatchingProperties-路径匹配解析器配置

代码如下

	private void configurePathMatchingProperties(RootBeanDefinition handlerMappingDef, Element element,
			ParserContext parserContext) {
		//获取mvc:annotation-driven下子节点mvc:path-matching
		Element pathMatchingElement = DomUtils.getChildElementByTagName(element, "path-matching");

		if (pathMatchingElement != null) {
			Object source = parserContext.extractSource(element);
			//是否采用suffix-pattern，即.*,比如/user也匹配/user.*。默认为true
			if (pathMatchingElement.hasAttribute("suffix-pattern")) {
				Boolean useSuffixPatternMatch = Boolean.valueOf(pathMatchingElement.getAttribute("suffix-pattern"));
				handlerMappingDef.getPropertyValues().add("useSuffixPatternMatch", useSuffixPatternMatch);
			}
			//是否采用分隔符，特指/，比如/user也匹配/user/。默认为true
			if (pathMatchingElement.hasAttribute("trailing-slash")) {
				Boolean useTrailingSlashMatch = Boolean.valueOf(pathMatchingElement.getAttribute("trailing-slash"));
				handlerMappingDef.getPropertyValues().add("useTrailingSlashMatch", useTrailingSlashMatch);
			}
			//是否采用contentNegotiationManager中的格式，比如*.json/*.xml。默认为false
			if (pathMatchingElement.hasAttribute("registered-suffixes-only")) {
				Boolean useRegisteredSuffixPatternMatch = Boolean.valueOf(pathMatchingElement.getAttribute("registered-suffixes-only"));
				handlerMappingDef.getPropertyValues().add("useRegisteredSuffixPatternMatch", useRegisteredSuffixPatternMatch);
			}
			RuntimeBeanReference pathHelperRef = null;
			//路径解析帮助类，可指定，默认为UrlPathHelper
			if (pathMatchingElement.hasAttribute("path-helper")) {
				pathHelperRef = new RuntimeBeanReference(pathMatchingElement.getAttribute("path-helper"));
			}
			pathHelperRef = MvcNamespaceUtils.registerUrlPathHelper(pathHelperRef, parserContext, source);
			handlerMappingDef.getPropertyValues().add("urlPathHelper", pathHelperRef);

			RuntimeBeanReference pathMatcherRef = null;
			//路径解析器，默认为AntPathMatcher解析器
			if (pathMatchingElement.hasAttribute("path-matcher")) {
				pathMatcherRef = new RuntimeBeanReference(pathMatchingElement.getAttribute("path-matcher"));
			}
			pathMatcherRef = MvcNamespaceUtils.registerPathMatcher(pathMatcherRef, parserContext, source);
			handlerMappingDef.getPropertyValues().add("pathMatcher", pathMatcherRef);
		}
	}

看代码逻辑，主要是通过mvc:annotation-driven下的mvc:path-matching节点来配置

1. suffix-pattern-是否启用后缀匹配，默认为true，即对指定的url会再新增.*，比如/user实际匹配/user.*->/user匹配/user.html,/user.jsp
2. trailing-slash-是否启动尾部斜线匹配，默认为true，即对指定的url会新增/，比如/user也会匹配/user/
3. registered-suffixes-only-是否启用media type类型的匹配，即对指定的url新增*.json/*.xml等匹配，默认为false
4. path-helper-路径获取帮助类，默认为UrlPathHelper类
5. path-matcher-路径匹配解析器，默认为AntPathMather

HandlerAdapters组件注册

相应的代码片段如下

		//获取conversion-service属性，默认为FormattingConversionServiceFactoryBean
		//处理一些基本类的格式与转换，比如时间、数字等
		RuntimeBeanReference conversionService = getConversionService(element, source, parserContext);
		//获取validator,默认为OptionalValidatorFactoryBean，基于java自带的Validator接口，表示校验器，可用于javabean的参数校验等
		RuntimeBeanReference validator = getValidator(element, source, parserContext);
		//获取message-codes-resolver属性，默认为null。
		RuntimeBeanReference messageCodesResolver = getMessageCodesResolver(element);
		//设置ConfigurableWebBindingInitializer类 用于数据绑定
		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);

		//获取message-converters子节点的配置，消息转换器，可用于向前端发送数据再次自定义组装
		//比如MappingJackson2HttpMessageConverter json转字符串
		ManagedList<?> messageConverters = getMessageConverters(element, source, parserContext);
		//argument-resolvers子节点配置，参数解析
		ManagedList<?> argumentResolvers = getArgumentResolvers(element, parserContext);
		//return-value-handlers子节点解析
		ManagedList<?> returnValueHandlers = getReturnValueHandlers(element, parserContext);
		//async-support子节点解析，获取其中的default-timeout属性，作为异步处理超时时间，默认null
		String asyncTimeout = getAsyncTimeout(element);
		//async-support子节点解析，获取其中的task-executor属性。异步任务线程池
		RuntimeBeanReference asyncExecutor = getAsyncExecutor(element);
		//async-support子节点解析，获取其中的callable-interceptors节点。异步处理callable类型拦截器
		ManagedList<?> callableInterceptors = getCallableInterceptors(element, source, parserContext);
		ManagedList<?> deferredResultInterceptors = getDeferredResultInterceptors(element, source, parserContext);

		//将上述的属性添加到RequestMappingHandlerAdapter中
		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);
		addRequestBodyAdvice(handlerAdapterDef);
		addResponseBodyAdvice(handlerAdapterDef);

		//ignoreDefaultModelOnRedirect属性配置
		if (element.hasAttribute("ignore-default-model-on-redirect")) {
			Boolean ignoreDefaultModel = Boolean.valueOf(element.getAttribute("ignore-default-model-on-redirect"));
			handlerAdapterDef.getPropertyValues().add("ignoreDefaultModelOnRedirect", ignoreDefaultModel);
		}
		else if (element.hasAttribute("ignoreDefaultModelOnRedirect")) {
			// "ignoreDefaultModelOnRedirect" spelling is deprecated
			Boolean ignoreDefaultModel = Boolean.valueOf(element.getAttribute("ignoreDefaultModelOnRedirect"));
			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);
		readerContext.getRegistry().registerBeanDefinition(HANDLER_ADAPTER_BEAN_NAME , handlerAdapterDef);

配置的主要是RequestMappingHandlerAdapter对象，其中的属性较多，读者可查看>>>SpringMVC源码情操陶冶-RequestMappingHandlerAdapter适配器。其主要支持HandlerMethod类，而这些类都是由RequestMappingHandlerMapping来生成的，而这又是通过AbstractHandlerMethodMapping#initHandlerMethods来实现的，有兴趣的可以自行去查阅

ExceptionResolver组件注册

默认采用ExceptionHandlerExceptionResolver、ResponseStatusExceptionResolver、DefaultHandlerExceptionResolver作为异常处理类

		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);
		addResponseBodyAdvice(exceptionHandlerExceptionResolver);

		String methodExceptionResolverName = readerContext.registerWithGeneratedName(exceptionHandlerExceptionResolver);

		RootBeanDefinition responseStatusExceptionResolver = new RootBeanDefinition(ResponseStatusExceptionResolver.class);
		responseStatusExceptionResolver.setSource(source);
		responseStatusExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		responseStatusExceptionResolver.getPropertyValues().add("order", 1);
		String responseStatusExceptionResolverName =
				readerContext.registerWithGeneratedName(responseStatusExceptionResolver);

		RootBeanDefinition defaultExceptionResolver = new RootBeanDefinition(DefaultHandlerExceptionResolver.class);
		defaultExceptionResolver.setSource(source);
		defaultExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		defaultExceptionResolver.getPropertyValues().add("order", 2);
		String defaultExceptionResolverName =
				readerContext.registerWithGeneratedName(defaultExceptionResolver);

• ExceptionHandlerExceptionResolver-处理@ExceptionHandler方法注解

• ResponseStatusExceptionResolver-处理@ResponseStatus类型、方法注解

• DefaultHandlerExceptionResolver-处理普通的spring异常

更准确的可查看官方注释说明

小结

mvc:annotation-driven一句话便囊括了springmvc的基本处理组件注册成bean到springmvc上下文，结合此处再去理解springmvc的逻辑源码就简单了