HandlerAdapter处理适配器
HandlerMapping通过request找到了handler，HandlerAdapter是具体使用Handler来干活的，每个HandlerAdapter封装了一种Handler的具体使用方法
由于Spring经过很长时间的版本迭代，为了适配老版本，Spring 中的处理器的实现有很多种方式，比如可以实现 Controller 接口，也可以用 @Controller+@RequestMapping 注解将方法作为一个处理器等，这就导致 Spring 不知道怎么调用用户的处理器逻辑。因此需要一个处理器适配器，由处理器适配器去调用处理器的逻辑
HandlerAdapter按照特定规则去执行Handler，通过扩展适配器可以对更多类型的处理器进行执行
java
public interface HandlerAdapter {
// 判断是否可以使用某个Handler
boolean supports(Object handler);
// 具体使用handler完成工作
ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
// 获取Last-Modified资源最后一次修改时间
long getLastModified(HttpServletRequest request, Object handler);
}
xml
<bean id="annotationMethodHandlerAdapter"
class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping" />-
HttpRequestHandlerAdapter 用于适配HttpRequestHandler，处理实现了HttpRequestHandler接口的handler
javapublic class HttpRequestHandlerAdapter implements HandlerAdapter { @Override public boolean supports(Object handler) { return (handler instanceof HttpRequestHandler); } @Override public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { ((HttpRequestHandler) handler).handleRequest(request, response); return null; } @Override public long getLastModified(HttpServletRequest request, Object handler) { if (handler instanceof LastModified) { return ((LastModified) handler).getLastModified(request); } return -1L; } } -
SimpleControllerHandlerAdapter 用于适配Controller，处理实现了Controller接口的handler
javapublic class SimpleControllerHandlerAdapter implements HandlerAdapter { @Override public boolean supports(Object handler) { return (handler instanceof Controller); } @Override public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { return ((Controller) handler).handleRequest(request, response); } @Override public long getLastModified(HttpServletRequest request, Object handler) { if (handler instanceof LastModified) { return ((LastModified) handler).getLastModified(request); } return -1L; } } -
SimpleServletHandlerAdapter 用于适配Servlet，处理实现了Servlet接口的handler
javapublic class SimpleServletHandlerAdapter implements HandlerAdapter { @Override public boolean supports(Object handler) { return (handler instanceof Servlet); } @Override public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { ((Servlet) handler).service(request, response); return null; } @Override public long getLastModified(HttpServletRequest request, Object handler) { return -1; } } -
RequestMappingHandlerAdapter 用于适配HandlerMethod，这个就比较复杂了，下边单独拿出来说明
RequestMappingHandlerAdapter
平常使用最多的也是RequestMappingHandlerAdapter，可以看到它是处理HandlerMethod类的
java
public final boolean supports(Object handler) {
return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
}就是使用@Controller和@RequestMapping来进行映射的方法
该类实现了InitializingBean接口，会执行afterPropertiesSet方法
java
public void afterPropertiesSet() {
// Do this first, it may add ResponseBody advice beans
// @ControllerAdvice的bean
initControllerAdviceCache();
if (this.argumentResolvers == null) {
// 一些参数解析器，如解析@RequestParam、@PathVariable、@RequestBody等
List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers();
this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);
}
if (this.initBinderArgumentResolvers == null) {
// initBinder的参数解析器
List<HandlerMethodArgumentResolver> resolvers = getDefaultInitBinderArgumentResolvers();
this.initBinderArgumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);
}
if (this.returnValueHandlers == null) {
// 返回值的参数解析器，如ModelAndView、ResponseEntity、HttpEntity、@ResponseBody注解等
List<HandlerMethodReturnValueHandler> handlers = getDefaultReturnValueHandlers();
this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers);
}
}处理请求
java
protected ModelAndView handleInternal(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ModelAndView mav;
checkRequest(request);
// Execute invokeHandlerMethod in synchronized block if required.
if (this.synchronizeOnSession) {
HttpSession session = request.getSession(false);
if (session != null) {
Object mutex = WebUtils.getSessionMutex(session);
synchronized (mutex) {
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else {
// No HttpSession available -> no mutex necessary
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else {
// No synchronization on session demanded at all...
// 具体的执行逻辑
mav = invokeHandlerMethod(request, response, handlerMethod);
}
// 处理缓存
if (!response.containsHeader(HEADER_CACHE_CONTROL)) {
if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
}
else {
prepareResponse(response);
}
}
return mav;
}invokeHandlerMethod
java
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ServletWebRequest webRequest = new ServletWebRequest(request, response);
try {
// 将注解@InitBinder的方法找出来
WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
// 用来处理Model的，在处理器具体处理之前对Model进行初始化，在处理万请求之后对Model参数进行更新
ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);
// 用于参数绑定、处理请求以及返回值处理
ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
invocableMethod.setDataBinderFactory(binderFactory);
invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
// 用于保存Model和View的
ModelAndViewContainer mavContainer = new ModelAndViewContainer();
// 先将FlashMap中的数据添加进ModelAndViewContainer中
mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
// 初始化Model，处理@SessionAttributes注解和WebDataBinder定义的全局数据
modelFactory.initModel(webRequest, mavContainer, invocableMethod);
mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);
// 异步请求
AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
asyncWebRequest.setTimeout(this.asyncRequestTimeout);
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.setTaskExecutor(this.taskExecutor);
asyncManager.setAsyncWebRequest(asyncWebRequest);
asyncManager.registerCallableInterceptors(this.callableInterceptors);
asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);
if (asyncManager.hasConcurrentResult()) {
Object result = asyncManager.getConcurrentResult();
mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];
asyncManager.clearConcurrentResult();
invocableMethod = invocableMethod.wrapConcurrentResult(result);
}
// 执行请求
invocableMethod.invokeAndHandle(webRequest, mavContainer);
if (asyncManager.isConcurrentHandlingStarted()) {
return null;
}
// 请求执行完之后进行处理
// ①modelFactory.updateModel 更新Model
// ②根据mavContainer创建modelAndView
// ③如果model是RedirectAttributes类型，需要设置到FlashMap中
return getModelAndView(mavContainer, modelFactory, webRequest);
}
finally {
webRequest.requestCompleted();
}
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