SpringMVC源碼解析系列3-HandleMapping

• SpringMVC源碼解析系列3-HandleMapping
  • 接口實現
  • RequestMappingHandlerMapping初始化過程
  • getHandler()實現

接口定義

/** * Interface to be implemented by objects that define a mapping between * requests and handler objects. */
public interface HandlerMapping {
  //根據request獲取處理鏈
   HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
}

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以RequestMappingHandlerMapping爲例來說

RequestMappingHandlerMapping初始化過程

定義: 請求路徑-處理過程映射管理

打個比方就是根據你的http請求的路徑獲得能夠處理的handler(你的Controller方法)

先看下他的繼承關係

看到3個Spring的生命週期接口

1. ServletContextAware:保存ServletContext

   #org.springframework.web.context.support.WebApplicationObjectSupport
   @Override
   public final void setServletContext(ServletContext servletContext) {
   	if (servletContext != this.servletContext) {
   		//保存ServletContext
   		this.servletContext = servletContext;
   		if (servletContext != null) {
   			//空實現
   			initServletContext(servletContext);
   		}
   	}
   }
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2. ApplicationContext:保存Spring上下文

   @Override
   public final void setApplicationContext(ApplicationContext context) throws BeansException {
   ...
     //保存SpringMVC上下文
     this.applicationContext = context;
     //保存資源訪問器
     this.messageSourceAccessor = new MessageSourceAccessor(context);
     //空實現
     initApplicationContext(context);
   	...
   }
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3. InitlizingBean:初始化映射關係

   #org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping
   //1.
   @Override
   public void afterPropertiesSet() {
      if (this.useRegisteredSuffixPatternMatch) {
         this.fileExtensions.addAll(this.contentNegotiationManager.getAllFileExtensions());
      }
      super.afterPropertiesSet();
   }
   //4.
   @Override
   protected boolean isHandler(Class<?> beanType) {
   	return ((AnnotationUtils.findAnnotation(beanType, Controller.class) != null) ||
   			(AnnotationUtils.findAnnotation(beanType, RequestMapping.class) != null));
   }
   //6.
   @Override
   protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
   	RequestMappingInfo info = null;
   	RequestMapping methodAnnotation = AnnotationUtils.findAnnotation(method, RequestMapping.class);
   	if (methodAnnotation != null) {
   		//組裝映射信息
   		RequestCondition<?> methodCondition = getCustomMethodCondition(method);
   		info = createRequestMappingInfo(methodAnnotation, methodCondition);
   		RequestMapping typeAnnotation = AnnotationUtils.findAnnotation(handlerType, RequestMapping.class);
   		if (typeAnnotation != null) {
   			RequestCondition<?> typeCondition = getCustomTypeCondition(handlerType);
   			info = createRequestMappingInfo(typeAnnotation, typeCondition).combine(info);
   		}
   	}
   	return info;
   }
   #org.springframework.web.servlet.handler.AbstractHandlerMethodMapping
   //2.
   @Override
   public void afterPropertiesSet() {
   	initHandlerMethods();
   }
   //3.
   protected void initHandlerMethods() {
   	if (logger.isDebugEnabled()) {
   		logger.debug("Looking for request mappings in application context: " + getApplicationContext());
   	}
   	//從容器中獲取全部object類型名
   	String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?
   			BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :
   			getApplicationContext().getBeanNamesForType(Object.class));
   	for (String beanName : beanNames) {
   		//抽象,過濾(在RequestMappingHandlerMapping中根據Controller和RequestMapping註解過濾)
   		if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX) &&
   				isHandler(getApplicationContext().getType(beanName))){
   			//探測類中定義的handler方法
   			detectHandlerMethods(beanName);
   		}
   	}
   	handlerMethodsInitialized(getHandlerMethods());
   }
   //5.
   protected void detectHandlerMethods(final Object handler) {
   	Class<?> handlerType =
   			(handler instanceof String ? getApplicationContext().getType((String) handler) : handler.getClass());
   	final Map<Method, T> mappings = new IdentityHashMap<Method, T>();
   	final Class<?> userType = ClassUtils.getUserClass(handlerType);
   	//獲得符合條件的handler方法
   	Set<Method> methods = HandlerMethodSelector.selectMethods(userType, new MethodFilter() {
   		@Override
   		public boolean matches(Method method) {
   			//抽象,獲得映射信息(如RequestMappingInfo)
   			T mapping = getMappingForMethod(method, userType);
   			if (mapping != null) {
   				mappings.put(method, mapping);
   				return true;
   			}
   			else {
   				return false;
   			}
   		}
   	});
   	//註冊handler映射關係
   	for (Method method : methods) {
   		//保存映射路徑和處理方法(還有跨域信息)
   		registerHandlerMethod(handler, method, mappings.get(method));
   	}
   }
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過程歸納:

1. 獲取全部object子類

2. 根據條件過濾出handle處理類

3. 解析handle類中定義的處理方法

4. 註冊映射關係

   public void register(T mapping, Object handler, Method method) {
   			try {
     	//保存handler和處理方法
   	HandlerMethod handlerMethod = createHandlerMethod(handler, method);
   	...
        //保存映射路徑和HandlerMethod
   	this.mappingLookup.put(mapping, handlerMethod);
   	//解析@CrossOrigin配置(跨域用)
   	CorsConfiguration corsConfig = initCorsConfiguration(handler, method, mapping);
     	//保存跨域信息
   	if (corsConfig != null) {
   		this.corsLookup.put(handlerMethod, corsConfig);
   	}
   	//保存映射關係
   	this.registry.put(mapping, new MappingRegistration<T>(mapping, handlerMethod, directUrls, name));
   }
   ...
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}

## getHandler()實現

```java
#org.springframework.web.servlet.handler.AbstractHandlerMapping
@Override
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
//抽象,調用子類實現獲得一個handler(能夠是任一對象,須要經過HandleAdapter來解析)
//RequestMappingInfoHandlerMapping中具體實現就是匹配請求路徑和RequestMapping註解
Object handler = getHandlerInternal(request);
...
//包裝handle成HandlerExecutionChain
 HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
 //若是是跨域請求 則根據@CrossOrigin配置添加前置Intercept
 if (CorsUtils.isCorsRequest(request)) {
 	CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);
 	CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
 	CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
 	executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
 }
 return executionChain;
}
#org.springframework.web.servlet.handler.AbstractHandlerMethodMapping
@Override
 protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
 //獲得映射路徑
 String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
 ...
 try {
 	//根據映射路徑獲取HandlerMethod
 	HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
 	return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
 }
 ...
}
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