一次请求在SpringMVC核心执行流程

 

org.springframework.web.servlet.DispatcherServlet#doDispatch

1.1 获取执行调用链HandlerExecutionChain
1.2 获取处理器适配器HandlerAdapter
1.3 调用拦截器preHandle
1.4 调用适配器的handle方法
1.5 处理视图名
1.6 调用postHandle方法
1.7 视图渲染

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 {

// 检查是否多模块请求
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);

// Determine handler for the current request.

// 通过HandlerMapping根据url获取HandlerMethod, 再获取拦截器, 组合起来创建出调用执行链HandlerExecutionChain对象(HandlerMethod + 拦截器)
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}

// Determine handler adapter for the current request.

// 获取处理器适配器, 根据不同种类的适配器支持程度supports方法, 获取到合适的适配器, 处理的核心方法为handle方法
// mappedHandler.getHandler()获取的是HandlerMethod对象
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 (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}

// 处理拦截器preHandle方法
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}

// Actually invoke the handler.

// 调用HandlerAdapter的handle方法
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

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

// 处理视图名字
applyDefaultViewName(processedRequest, mv);

// 处理拦截器postHandle方法
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException = new NestedServletException("Handler dispatch failed", err);
}

// 处理视图渲染
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new NestedServletException("Handler processing failed", err));
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}
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文章来源: 博客园

原文链接: https://www.cnblogs.com/xiaoyusheng/p/13446412.html

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