spring中http请求流程源码

 入口-->org.springframework.web.servlet.DispatcherServlet

DispatcherServlet中没有service方法，在其父类FrameworkServlet中找到service

@Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String method = request.getMethod();
        if (method.equalsIgnoreCase(RequestMethod.PATCH.name())) {
            processRequest(request, response);
        }
        else {
            super.service(request, response);
        }
    }

调用主流程processRequest-->doService(request, response);-->doDispatch(request, response);

doDispatch方法

    /**
     * Process the actual dispatching to the handler.
     * <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
     * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
     * to find the first that supports the handler class.
     * <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
     * themselves to decide which methods are acceptable.
     * @param request current HTTP request
     * @param response current HTTP response
     * @throws Exception in case of any kind of processing failure
     */
    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.
                mappedHandler = getHandler(processedRequest);
                if (mappedHandler == null || mappedHandler.getHandler() == null) {
                    noHandlerFound(processedRequest, response);
                    return;
                }

                // Determine handler adapter for the current request.
                HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());//获取对应的适配器

                // 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()) {
                        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;
                }

                try {
                    // Actually invoke the handler.
                    mv = ha.handle(processedRequest, response, mappedHandler.getHandler());//反射执行业务方法
                }
                finally {
                    if (asyncManager.isConcurrentHandlingStarted()) {
                        return;
                    }
                }

                applyDefaultViewName(request, mv);
                mappedHandler.applyPostHandle(processedRequest, response, mv);
            }
            catch (Exception ex) {
                dispatchException = ex;
            }
            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);
            }
        }
    }

 

获取适配器代码

    /**
     * Return the HandlerAdapter for this handler object.
     * @param handler the handler object to find an adapter for
     * @throws ServletException if no HandlerAdapter can be found for the handler. This is a fatal error.
     */
    protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
        for (HandlerAdapter ha : this.handlerAdapters) {
            if (logger.isTraceEnabled()) {
                logger.trace("Testing handler adapter [" + ha + "]");
            }
            if (ha.supports(handler)) {
                return ha;
            }
        }
        throw new ServletException("No adapter for handler [" + handler +
                "]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
    }

 

执行业务方法invokeHandleMethod

/**
     * Invoke the {@link RequestMapping} handler method preparing a {@link ModelAndView}
     * if view resolution is required.
     */
    private ModelAndView invokeHandleMethod(HttpServletRequest request,
            HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {

        ServletWebRequest webRequest = new ServletWebRequest(request, response);

        WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);//创建@InitBinder注解的方法工厂类，进行缓存
        ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);//创建@ModelAttribute@ControllerAdvice注解方法工厂并缓存

        ServletInvocableHandlerMethod requestMappingMethod = createRequestMappingMethod(handlerMethod, binderFactory);

        ModelAndViewContainer mavContainer = new ModelAndViewContainer();//创建结果容器

        //初始化结果容器参数
        mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
        modelFactory.initModel(webRequest, mavContainer, requestMappingMethod);执行@ModelAttribute注解的方法，将结果放到结果容器中

        mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);

        AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
        asyncWebRequest.setTimeout(this.asyncRequestTimeout);

        final 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();

            if (logger.isDebugEnabled()) {
                logger.debug("Found concurrent result value [" + result + "]");
            }
            requestMappingMethod = requestMappingMethod.wrapConcurrentResult(result);
        }

        requestMappingMethod.invokeAndHandle(webRequest, mavContainer);

        if (asyncManager.isConcurrentHandlingStarted()) {
            return null;
        }

        return getModelAndView(mavContainer, modelFactory, webRequest);
    }

 

 

public final void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
        Object returnValue = this.invokeForRequest(webRequest, mavContainer, providedArgs); //执行方法，获取返回值
        this.setResponseStatus(webRequest);
        if (returnValue == null) {
            if (this.isRequestNotModified(webRequest) || this.hasResponseStatus() || mavContainer.isRequestHandled()) {
                mavContainer.setRequestHandled(true);
                return;
            }
        } else if (StringUtils.hasText(this.responseReason)) {
            mavContainer.setRequestHandled(true);
            return;
        }

        mavContainer.setRequestHandled(false);

        try { //处理返回值 ，封装结果集
            this.returnValueHandlers.handleReturnValue(returnValue, this.getReturnValueType(returnValue), mavContainer, webRequest);
        } catch (Exception var6) {
            if (this.logger.isTraceEnabled()) {
                this.logger.trace(this.getReturnValueHandlingErrorMessage("Error handling return value", returnValue), var6);
            }

            throw var6;
        }
    }

 

public final Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
        Object[] args = this.getMethodArgumentValues(request, mavContainer, providedArgs); //处理 参数
        if (this.logger.isTraceEnabled()) {
            StringBuilder builder = new StringBuilder("Invoking [");
            builder.append(this.getMethod().getName()).append("] method with arguments ");
            builder.append(Arrays.asList(args));
            this.logger.trace(builder.toString());
        }

        Object returnValue = this.invoke(args); //反射执行方法
        if (this.logger.isTraceEnabled()) {
            this.logger.trace("Method [" + this.getMethod().getName() + "] returned [" + returnValue + "]");
        }

        return returnValue;
    }

 

private Object[] getMethodArgumentValues(NativeWebRequest request, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
        MethodParameter[] parameters = this.getMethodParameters();
        Object[] args = new Object[parameters.length];

        for(int i = 0; i < parameters.length; ++i) { //遍历方法的所有参数
            MethodParameter parameter = parameters[i];
            parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
            GenericTypeResolver.resolveParameterType(parameter, this.getBean().getClass()); //获取设置参数类型
            args[i] = this.resolveProvidedArgument(parameter, providedArgs);
            if (args[i] == null) {
                if (this.argumentResolvers.supportsParameter(parameter)) { //这块是遍历预置的参数解析器，就是前面说的责任链模式，**composite负责查找和执行
                    try { //由找到的参数解析器，来解析参数
                        args[i] = this.argumentResolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
                    } catch (Exception var9) {
                        if (this.logger.isTraceEnabled()) {
                            this.logger.trace(this.getArgumentResolutionErrorMessage("Error resolving argument", i), var9);
                        }

                        throw var9;
                    }
                } else if (args[i] == null) {
                    String msg = this.getArgumentResolutionErrorMessage("No suitable resolver for argument", i);
                    throw new IllegalStateException(msg);
                }
            }
        }

        return args;
    }