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

时间:2021-12-27 15:32:34

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@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ExceptionHandlerExceptionResolverResponseStatusExceptionResolverDefaultHandlerExceptionResolver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