原理
本质是将DispatcherServlet及关联的Spring上下文环境的初始化工作织入Servlet的生命周期内,将外部WEB请求转换为Spring Bean能处理的形式,然后将处理后的结果借助于符合J2EE规范组件,呈现给客户端。
步骤
HttpServletBean: init(),内部调用initServletBean完成Servlet的初始化
FrameworkServlet 重写 initServletBean()方法,方法内部调用 initWebApplicationContext()方法完成与DispatcherServlet关联的web应用上下文的初始化工作,应用环境的基础环境的初始化工作由子类DispatcherServlet的onRefresh方法完成。
DispatcherServlet.onRefresh方法内部调用:initStrategies方法完成Springmvc需要的各种组件的初始化工作,至此springmvc可提供完整的外部应用访问功能。
protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
}
springmvc 默认配置文件:DispatcherServlet.properties
Springmvc 客户端请求处理过程
核心方法:doService,本质是对Serlvet接口的service方法的最终实现。
doService:完成应用请求的数据封装封装,内部调用doDispatch方法完成请求调度调度处理
源码分析:
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 {
//判断外部请求是否是多部分请求(一般用于文件上传)
processedRequest = checkMultipart(request);
multipartRequestParsed = processedRequest != request;
// 根据请求请求获取请求处理器:注意这里会返回对应的处理器以及潜在的拦截器
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null || mappedHandler.getHandler() == null) {
noHandlerFound(processedRequest, response);
return;
}
// 获取能够支持请求处理器的处理器适配器
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 www.yongshiyule178.com= ha.getLastModified(request, mappedHandler.getHandler());
if (logger.isDebugEnabled()) {
String requestUri = urlPathHelper.getRequestUri(request);
logger.debug("Last-Modified www.xinghaiyule1.com value for [" + requestUri + "] is: " + lastModified);
}
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
//前置拦截器拦截请求
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
try {
// 处理器适配器将请求传递给控制器处理,获取ModelView对象
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
}
finally {
if (asyncManager.isConcurrentHandlingStarted(dasheng178.com )) {
return;
}
}
//设置视图名
applyDefaultViewName(request, mv);
//后置拦截器拦截请求
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
//处理控制器返回的结果ModelAndView,主要是讲model的数据填充view,渲染后将数据返回给客户端显示
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception www.tiaotiaoylzc.com 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)www.mytxyl1.com {
cleanupMultipart(processedRequest);
}
}
}
springmvc 请求响应:
主要是将MappingHandler返回的ModelAndView种的Model数据填充到view,并借助于servlet容器(例如tomcat)呈现给客户端。
AbstractView. render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response):
//具体执行代码
renderMergedOutputModel(mergedModel, request, response);
案例分析:内部资源视图(例JSP) InternalResourceView. renderMergedOutputModel
protected void renderMergedOutputModel(
Map<String, Object>www.jtujbo.com model, HttpServletRequest request, HttpServletResponse response) throws Exception {
//封装客户端可视的请求资源数据
HttpServletRequest requestToExpose = getRequestToExpose(request);
exposeModelAsRequestAttributes(model, requestToExpose);
//客户端请求添加辅助信息
exposeHelpers(requestToExpose);
// 获取请求转发路径
String dispatcherPath = prepareForRendering(requestToExpose, response);
//获取目标资源的请求调度器
RequestDispatcher rd = getRequestDispatcher(requestToExpose, dispatcherPath);
if (rd == null) {
throw new ServletException(www.yongshi123.cn"Could not get RequestDispatcher for [" + getUrl() +
"]: Check that the corresponding file exists within your web application archive!");
}
//如果一个URL的内部请求则进行响应资源追加,例如网页内的图片链接等
if (useInclude(requestToExpose, response)) {
response.setContentType(getContentType());
if (logger.isDebugEnabled()) {
logger.debug("Including resource [" + getUrl() + "] in InternalResourceView '" + getBeanName() + "'");
}
rd.include(requestToExpose, response);
}
else {
// Note: The forwarded resource is supposed to determine the content type itself.
if (logger.isDebugEnabled(www.fengshen157.com)) {
logger.debug("Forwarding to resource [" + getUrl(www.xtd912.com) + "] in InternalResourceView '" + getBeanName() + "'");
}
//repuest请求转发,说明springmvc采用的转发而不是重定向的方式
rd.forward(requestToExpose, response);
}
【spring】- springmvc 工作原理
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转载自www.cnblogs.com/qwangxiao/p/10425643.html
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