springmvc

1.springmvc 首先会在初始化的时候将我们的Controller（@Controller）、Mehtod（@RequestMapping）、参数解析成一个HandlerMethod对象
2.在用户发起请求的时候,springmvc会通过DispatcherServlet进行转发：由于DispatcherServlet重写了HttpServelt中的Service方法，然后调用doDispatch
3.通过Request请求的映射路径找到对应的处理方法：返回HandlerMethod对象，然后通过bean的名字通过beanFactory把bean给创建出来，再返回新的HandlerMethod
4.然后便利找handler的适配器，如果有拦截器，先调用拦截器,如果没有，就调用hander
5.调用完hander之后，返回modelandview

image.png

请求分发控制器

  1. protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
  2.     HttpServletRequest processedRequest = request;
  3.     HandlerExecutionChain mappedHandler = null;
  4.     boolean multipartRequestParsed = false;
  6.     WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
  8.     try {
  9.         ModelAndView mv = null;
  10.         Exception dispatchException = null;
  12.         try {
  13.             //检查是否是二进制文件请求：如图片上传等
  14.             processedRequest = checkMultipart(request);
  15.             multipartRequestParsed = (processedRequest != request);
  17.             //1.寻找Controller处理类的方法和拦截器封装到执行链中HandlerExecutionChain
  18.             mappedHandler = getHandler(processedRequest);
  19.             if (mappedHandler == null) {
  20.                 noHandlerFound(processedRequest, response);
  21.                 return;
  22.             }
  24.             //2.寻找处理器Controller的适配器
  25.             HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
  27.             // Process last-modified header, if supported by the handler.
  28.             String method = request.getMethod();
  29.             boolean isGet = "GET".equals(method);
  30.             if (isGet || "HEAD".equals(method)) {
  31.                 long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
  32.                 if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
  33.                     return;
  34.                 }
  35.             }
  36.             //3.执行拦截器
  37.             if (!mappedHandler.applyPreHandle(processedRequest, response)) {
  38.                 return;
  39.             }
  41.             //4.执行Controller
  42.             mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
  44.             if (asyncManager.isConcurrentHandlingStarted()) {
  45.                 return;
  46.             }
  48.             applyDefaultViewName(processedRequest, mv);
  49.             mappedHandler.applyPostHandle(processedRequest, response, mv);
  50.         }
  51.         catch (Exception ex) {
  52.             dispatchException = ex;
  53.         }
  54.         catch (Throwable err) {
  55.             // As of 4.3, we're processing Errors thrown from handler methods as well,
  56.             // making them available for @ExceptionHandler methods and other scenarios.
  57.             dispatchException = new NestedServletException("Handler dispatch failed", err);
  58.         }
  59.         processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
  60.     }
  61.     catch (Exception ex) {
  62.         triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
  63.     }
  64.     catch (Throwable err) {
  65.         triggerAfterCompletion(processedRequest, response, mappedHandler,
  66.                                new NestedServletException("Handler processing failed", err));
  67.     }
  68.     finally {
  69.         if (asyncManager.isConcurrentHandlingStarted()) {
  70.             // Instead of postHandle and afterCompletion
  71.             if (mappedHandler != null) {
  72.                 mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
  73.             }
  74.         }
  75.         else {
  76.             // Clean up any resources used by a multipart request.
  77.             if (multipartRequestParsed) {
  78.                 cleanupMultipart(processedRequest);
  79.             }
  80.         }
  81.     }
  82. }

寻找Controller处理类的方法

image.png

SpringMVC实现方式

1.注解
2.BeanName

BeanNameUrlHandlerMapping

BeanName方式的实现接口

RequestMappingHandlerMapping

注解方式的实现接口

  1. protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
  2.     //handlerMappings记录了BeanName和注解方式的映射
  3.     if (this.handlerMappings != null) {
  4.         for (HandlerMapping mapping : this.handlerMappings) {
  5.             //便利查找Controller,因为有可能是通过BeanName方式实现的Controller,也有可能是通过注解
  6.             //HandlerExecutionChain 执行链,在调用Controller的时候，有可能存在拦截器的
  7.             HandlerExecutionChain handler = mapping.getHandler(request);
  8.             if (handler != null) {
  9.                 return handler;
  10.             }
  11.         }
  12.     }
  13.     return null;
  14. }

org.springframework.web.servlet.HandlerMapping#getHandler
org.springframework.web.servlet.handler.AbstractHandlerMapping#getHandler

  1. public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
  2.     //private final Map<String, Object> handlerMap = new LinkedHashMap<>();
  3.     //拿到请求的Controller
  4.     Object handler = getHandlerInternal(request);
  5.     if (handler == null) {
  6.         handler = getDefaultHandler();
  7.     }
  8.     if (handler == null) {
  9.         return null;
  10.     }
  11.     // Bean name or resolved handler?
  12.     if (handler instanceof String) {
  13.         String handlerName = (String) handler;
  14.         handler = obtainApplicationContext().getBean(handlerName);
  15.     }
  17.     HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
  19.     if (logger.isTraceEnabled()) {
  20.         logger.trace("Mapped to " + handler);
  21.     }
  22.     else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
  23.         logger.debug("Mapped to " + executionChain.getHandler());
  24.     }
  26.     if (hasCorsConfigurationSource(handler) || CorsUtils.isPreFlightRequest(request)) {
  27.         CorsConfiguration config = (this.corsConfigurationSource != null ? this.corsConfigurationSource.getCorsConfiguration(request) : null);
  28.         CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
  29.         config = (config != null ? config.combine(handlerConfig) : handlerConfig);
  30.         executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
  31.     }
  33.     return executionChain;
  34. }

org.springframework.web.servlet.HandlerMapping#getHandler
org.springframework.web.servlet.handler.AbstractHandlerMapping#getHandler
org.springframework.web.servlet.handler.AbstractUrlHandlerMapping#getHandlerInternal

  1. protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
  2.     //拿到请求的url
  3.     String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
  4.     request.setAttribute(LOOKUP_PATH, lookupPath);
  5.     //通过url拿到请求的Controller
  6.     Object handler = lookupHandler(lookupPath, request);
  7.     if (handler == null) {
  8.         // We need to care for the default handler directly, since we need to
  9.         // expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.
  10.         Object rawHandler = null;
  11.         if ("/".equals(lookupPath)) {
  12.             rawHandler = getRootHandler();
  13.         }
  14.         if (rawHandler == null) {
  15.             rawHandler = getDefaultHandler();
  16.         }
  17.         if (rawHandler != null) {
  18.             // Bean name or resolved handler?
  19.             if (rawHandler instanceof String) {
  20.                 String handlerName = (String) rawHandler;
  21.                 rawHandler = obtainApplicationContext().getBean(handlerName);
  22.             }
  23.             validateHandler(rawHandler, request);
  24.             handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);
  25.         }
  26.     }
  27.     return handler;
  28.     }

寻找Controller的适配器

org.springframework.web.servlet.DispatcherServlet#getHandlerAdapter
SpringMVC有三种不同的实现方式
1.implements Controller
2.implements HttpRequestHandler
3.注解@Controller
image.png

  1. protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
  2.     if (this.handlerAdapters != null) {
  3.         for (HandlerAdapter adapter : this.handlerAdapters) {
  4.             //判断一下是不是HandlerMethod
  5.             //三种实现方式
  6.             if (adapter.supports(handler)) {
  7.                 return adapter;
  8.             }
  9.         }
  10.     }
  11.     throw new ServletException("No adapter for handler [" + handler +
  12.                                "]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
  13. }

implements Controller方式

  1. public class SimpleControllerHandlerAdapter implements HandlerAdapter {
  3.     @Override
  4.     public boolean supports(Object handler) {
  5.         return (handler instanceof Controller);
  6.     }
  7. }

implements HttpRequestHandler

  1. public class HttpRequestHandlerAdapter implements HandlerAdapter {
  3.     @Override
  4.     public boolean supports(Object handler) {
  5.         return (handler instanceof HttpRequestHandler);
  6.     }
  7. }

注解@Controller

  1. public abstract class AbstractHandlerMethodAdapter extends WebContentGenerator implements HandlerAdapter, Ordered {
  2.     @Override
  3.     public final boolean supports(Object handler) {
  4.         return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
  5.     }
  6. }

执行拦截器

org.springframework.web.servlet.HandlerExecutionChain#applyPreHandle

  1. protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
  2.     //执行拦截器
  3.     if (!mappedHandler.applyPreHandle(processedRequest, response)) {
  4.         return;
  5.     }
  7.     // 执行Controller
  8.     mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
  10. }

执行Controller

  1. protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
  2.     //执行拦截器
  3.     if (!mappedHandler.applyPreHandle(processedRequest, response)) {
  4.         return;
  5.     }
  7.     // 执行Controller
  8.     mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
  10. }

org.springframework.web.servlet.HandlerAdapter#handle

  1. public interface HandlerAdapter {
  3.     //判断处理3种实现方式的接口
  4.     boolean supports(Object handler);
  6.     //执行Controller
  7.     @Nullable
  8.     ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
  10.     long getLastModified(HttpServletRequest request, Object handler);
  11. }

AbstractHandlerMethodAdapter

org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter

  1. @Override
  2. protected ModelAndView handleInternal(HttpServletRequest request,
  3.                                       HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
  5.     ModelAndView mav;
  6.     checkRequest(request);
  8.     if (this.synchronizeOnSession) {
  9.         HttpSession session = request.getSession(false);
  10.         if (session != null) {
  11.             Object mutex = WebUtils.getSessionMutex(session);
  12.             synchronized (mutex) {
  13.                 mav = invokeHandlerMethod(request, response, handlerMethod);
  14.             }
  15.         }
  16.         else {
  17.             mav = invokeHandlerMethod(request, response, handlerMethod);
  18.         }
  19.     }
  20.     else {
  21.         //关键代码,调用Controller
  22.         mav = invokeHandlerMethod(request, response, handlerMethod);
  23.     }
  25.     if (!response.containsHeader(HEADER_CACHE_CONTROL)) {
  26.         if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
  27.             applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
  28.         }
  29.         else {
  30.             prepareResponse(response);
  31.         }
  32.     }
  34.     return mav;
  35. }

org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#invokeHandlerMethod
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod#invokeAndHandle

  1. public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
  2.                             Object... providedArgs) throws Exception {
  4.     //设置参数,参数赋值
  5.     Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
  6.     setResponseStatus(webRequest);
  8.     if (returnValue == null) {
  9.         if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
  10.             disableContentCachingIfNecessary(webRequest);
  11.             mavContainer.setRequestHandled(true);
  12.             return;
  13.         }
  14.     }
  15.     else if (StringUtils.hasText(getResponseStatusReason())) {
  16.         mavContainer.setRequestHandled(true);
  17.         return;
  18.     }
  20.     mavContainer.setRequestHandled(false);
  21.     Assert.state(this.returnValueHandlers != null, "No return value handlers");
  22.     try {
  23.         this.returnValueHandlers.handleReturnValue(
  24.             returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
  25.     }
  26.     catch (Exception ex) {
  27.         if (logger.isTraceEnabled()) {
  28.             logger.trace(formatErrorForReturnValue(returnValue), ex);
  29.         }
  30.         throw ex;
  31.     }
  32. }

参数赋值，返回实参数组,调用Controller

  1. public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
  2.     //参数赋值
  3.     Object[] args = this.getMethodArgumentValues(request, mavContainer, providedArgs);
  4.     if (this.logger.isTraceEnabled()) {
  5.         this.logger.trace("Arguments: " + Arrays.toString(args));
  6.     }
  7.     //反射调用Controller方法
  8.     return this.doInvoke(args);
  9. }

执行链路