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

2023-07-21 17:41:58

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

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