1. Frontier
In Spring MVC projects, we often use the configuration <mvc:annotation-driven> , so what exactly does this configuration do? Let's analyze it below. First find the definition of mvc's namespace, as shown in the figure below:
As can be seen from the above figure, the implementation class of the annotation-driven configuration should be defined in the MvcNamespaceHandler class. Isn’t that the case? Let's take a look at the source code of MvcNamespaceHandler
二、MvcNamespaceHandler
The source code of MvcNamespaceHandler is as follows:
/**
* {@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());
}
}From the above source code, we can see that the analysis class AnnotationDrivenBeanDefinitionParser corresponding to the annotation-driven configuration is indeed defined in the init method of MvcNamespaceHandler. Then the specific business implemented by the annotation-driven configuration must be in the AnnotationDrivenBeanDefinitionParser class. Let’s analyze the AnnotationDrivenBeanDefinitionParser source code.
三、AnnotationDrivenBeanDefinitionParser
The parse method of AnnotationDrivenBeanDefinitionParser implements the specific parsing logic. The source code is as follows:
/**
* 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;
}
}As can be seen from the above source code, the AnnotationDrivenBeanDefinitionParser mainly realizes the function of registering many beans. Among them, we are most concerned about the RequestMappingHandlerMapping and RequestMappingHandlerAdapter two classes, the functions are shown in the figure:
RequestMappingHandlerMapping : The implementation class of HandlerMapping, which handles the @RequestMapping annotation and registers it in the mapping table, that is, the method of the Controller corresponding to the url
RequestMappingHandlerAdapter : The implementation class of HandlerAdapter, it is the adapter that processes the request, which is to determine which method of which Controller to call
At this point, the source code of AnnotationDrivenBeanDefinitionParser has been analyzed. There is not much complicated logic in it, and the code comments are clearly written.
Four, annotation-driven role
By reading the source code of AnnotationDrivenBeanDefinitionParser, we can see that the function of annotation-driven configuration is as follows:
1), Mainly register RequestMappingHandlerMapping and RequestMappingHandlerAdapter beans, and store the mapping relationship between request url and Controller method
2), registered exception handler
Five, summary
If <mvc:annotation-driven> is configured in Spring MVC, all Controllers will be parsed, so the corresponding .do requests will be processed by the Controller , so this configuration is very important. When the request does not match the processing class (including no configuration of <mvc:annotation-driven> or access to static resource files), it will look for the configuration of <mvc:default-servlet-handler> (processing static resource files) The DefaultServletHttpRequestHandler is handled by the default processor