spring MVC 请求响应流程_java springmvc yunxi-优快云博客

本文链接：https://blog.youkuaiyun.com/yunxiyiii/article/details/74857726

本文详细介绍了SpringMVC框架中的请求响应处理流程，包括请求如何被前端控制器接收、DispatcherServlet如何处理请求并调用相应的Controller，以及最终如何生成ModelAndView对象。还解释了ModelAndView对象后续的处理步骤。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Spring MVC 请求响应流程

这里写图片描述
通过tomcat 和 Spring对请求的处理过程的函数栈分析，可以看出Spring-MVC工作原理。
1、请求经过tomcat处理后，进入Spring MVC的前端控制器FrameworkServlet。
2、前端控制器处理完成后，让DispatcherServlet(继承FrameworkServlet,所以1和2的处理，也可以看成统一的处理器)对结果进行处理。在DispatcherServlet中doDispatch函数完成了spring mvc对请求的后续处理，包括：获取控制处理链（HandlerExecutionChain类的对象）、通过控制处理链查找对应的处理器适配器（HandlerAdapter对象）、执行执行对应的Controller和ModelAndView的后续处理。下面看看doDispatch的源代码。

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HttpServletRequest processedRequest = request;
        HandlerExecutionChain mappedHandler = null;
        boolean multipartRequestParsed = false;

        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

        try {
            ModelAndView mv = null;
            Exception dispatchException = null;

            try {
                processedRequest = checkMultipart(request);
                multipartRequestParsed = processedRequest != request;

                // Determine handler for the current request.
                //获取对应的控制处理链
                mappedHandler = getHandler(processedRequest);
                if (mappedHandler == null || mappedHandler.getHandler() == null) {
                    noHandlerFound(processedRequest, response);
                    return;
                }

                // Determine handler adapter for the current request.
                //获取对应的真正的执行
                HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

                // Process last-modified header, if supported by the handler.
                String method = request.getMethod();
                boolean isGet = "GET".equals(method);
                if (isGet || "HEAD".equals(method)) {
                    long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
                    if (logger.isDebugEnabled()) {
                        String requestUri = urlPathHelper.getRequestUri(request);
                        logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified);
                    }
                    if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
                        return;
                    }
                }

                if (!mappedHandler.applyPreHandle(processedRequest, response)) {
                    return;
                }

                try {
                    // Actually invoke the handler.
                    //处理器适配器的代理执行，返回ModelAndView
                    mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
                }
                finally {
                    if (asyncManager.isConcurrentHandlingStarted()) {
                        return;
                    }
                }

                applyDefaultViewName(request, mv);
                mappedHandler.applyPostHandle(processedRequest, response, mv);
            }
            catch (Exception ex) {
                dispatchException = ex;
            }
            //ModelAndView的后续处理
            processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
        }
        catch (Exception ex) {
            triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
        }
        catch (Error err) {
            triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err);
        }
        finally {
            if (asyncManager.isConcurrentHandlingStarted()) {
                // Instead of postHandle and afterCompletion
                mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
                return;
            }
            // Clean up any resources used by a multipart request.
            if (multipartRequestParsed) {
                cleanupMultipart(processedRequest);
            }
        }
    }