SpringMVC源码介绍

1.http://localhost:8000/hello这个路径的执行流程是怎么走的

流程大致分析一下：首先会请求会进入前端控制器的doService方法->调用doDispatch方法->调用handle方法->这个handle方法需要从RequestMappingHandlerAdapter的父类找到AbstractHandlerMethodAdapter里面的handle方法，这个方法又调用RequestMappingHandlerAdapter的handleInternal方法->调用this的invokeHandlerMethod->invokeAndHandle->invokeForRequest->doInvoke方法->doInvoke里面调用this.getBridgedMethod().invoke其中this.getBridgedMethod()这个就是controller里面的那个方法，这就利用了反射机制，这就是MVC的执行流程，期间经历了RequestMappingHandlerAdapter这个处理器适配器，ServletInvocableHandlerMethod Servlet处理控制方法，InvocableHandlerMethod执行方法反射这主要的三个类

下面将用截图代码分析MVC的执行流程

首先进入前端控制器的doservice方法，调用doDispatch方法

SpringMVC面试题总结「建议收藏」 xa

下面看下doDispatch方法干了啥事吧

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

        try {
            try {
                //返回modelAndView对象
                ModelAndView mv = null;
                Object dispatchException = null;
                //做检查
                try {
                    processedRequest = this.checkMultipart(request);
                    multipartRequestParsed = processedRequest != request;
                    mappedHandler = this.getHandler(processedRequest);
                    if (mappedHandler == null) {
                        this.noHandlerFound(processedRequest, response);
                        return;
                    }
                    //这个比较重要，创建一个请求的处理器适配器
                    HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());
                    String method = request.getMethod();
                    boolean isGet = "GET".equals(method);
                    if (isGet || "HEAD".equals(method)) {
                        long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
                        if (this.logger.isDebugEnabled()) {
                            this.logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
                        }

                        if ((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {
                            return;
                        }
                    }

                    if (!mappedHandler.applyPreHandle(processedRequest, response)) {
                        return;
                    }
                    //这个就比较重要了，调用处理器适配器来处理
                    mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
                    if (asyncManager.isConcurrentHandlingStarted()) {
                        return;
                    }

                    this.applyDefaultViewName(processedRequest, mv);
                    mappedHandler.applyPostHandle(processedRequest, response, mv);
                } catch (Exception var20) {
                    dispatchException = var20;
                } catch (Throwable var21) {
                    dispatchException = new NestedServletException("Handler dispatch failed", var21);
                }

                this.processDispatchResult(processedRequest, response, mappedHandler, mv, (Exception)dispatchException);
            } catch (Exception var22) {
                this.triggerAfterCompletion(processedRequest, response, mappedHandler, var22);
            } catch (Throwable var23) {
                this.triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException("Handler processing failed", var23));
            }

        } finally {
            if (asyncManager.isConcurrentHandlingStarted()) {
                if (mappedHandler != null) {
                    mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
                }
            } else if (multipartRequestParsed) {
                this.cleanupMultipart(processedRequest);
            }

        }
    }

下面我们来看下mv = ha.handle(processedRequest, response, mappedHandler.getHandler());做了什么事吧

SpringMVC面试题总结「建议收藏」

说白了，这就是调用了RequestMappingHandlerAdapter里面的handleInternal方法

SpringMVC面试题总结「建议收藏」

可以看下invokeForRequest方法,最后调用doInvok方法

SpringMVC面试题总结「建议收藏」

第二种介绍：springmvc的流程图分析：

SpringMVC面试题总结「建议收藏」

1.用户请求进入前端控制器，调用doservice在调用doDispatch方法，调用getHandler方法，返回一个HandlerExecutionChain，里面包含一个你自己写的controller和mvc的拦截器，获得这个执行链mappedHandler之后，调用getHandlerAdapter(mappedHandler.getHandler())方法，获取适配器，这就是上图右半部分的分析，左半部分暂时未做分析

代码截图分析:

不要意思，纠正下错误，默认提供的映射器只有两种

SpringMVC面试题总结「建议收藏」