运行helloWorld示例进入调试界面。
DispatcherServlet：前端控制器
DispatcherServlet.doDispatch(HttpServletRequest, HttpServletResponse) line: 945 DispatcherServlet.doService(HttpServletRequest, HttpServletResponse) line: 876 DispatcherServlet(FrameworkServlet).processRequest(HttpServletRequest, HttpServletResponse) line: 931 DispatcherServlet(FrameworkServlet).doGet(HttpServletRequest, HttpServletResponse) line: 822 DispatcherServlet(HttpServlet).service(HttpServletRequest, HttpServletResponse) line: 624 DispatcherServlet(FrameworkServlet).service(HttpServletRequest, HttpServletResponse) line: 807 DispatcherServlet(HttpServlet).service(ServletRequest, ServletResponse) line: 731
由上进入源码查看
DispatcherServlet(FrameworkServlet).service(HttpServletRequest, HttpServletResponse) line: 807的
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware {
...
service();
}
HttpServletBean 的实现
public abstract class HttpServletBean extends HttpServlet implements EnvironmentCapable, EnvironmentAware {}
接下来重点关注doDispatch()
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.
//1、根据当前请求地址找到哪个处理器来处理请求
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null || mappedHandler.getHandler() == null) {
//2、如果找不到报错
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
//2\为当前请求确定适配器
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 = 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.
//真正执行方法
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;
}
//处理响应结果
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);
}
}
}
四步：
1）、所有请求进来都经过DispatcherServlet的900：doDispatch()方法（包含了处理请求以及响应的所有流程）
2）、916；getHandler(processedRequest);根据当前请求获取到能处理这个请求的Controller对象
3）、923：找到能执行这个Controller对象里面每一个方法的适配器
4）、945：ha.handle适配器调用目标方法（利用反射调用方法）
5）、959：转发到页面（处理响应结果）processDispatchResult
1、根据当前请求地址找到哪个处理器来处理请求
mappedHandler = getHandler(processedRequest);
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
for (HandlerMapping hm : this.handlerMappings) {
if (logger.isTraceEnabled()) {
logger.trace(
"Testing handler map [" + hm + "] in DispatcherServlet with name ‘" + getServletName() + "‘");
}
HandlerExecutionChain handler = hm.getHandler(request);
if (handler != null) {
return handler;
}
}
return null;
}
SpringfMVC启动的时候扫描所有的注解，将每一个类的每一个方法能处理什么请求都已经保存在handlerMapping中了；DefaultAnnotationHandlerMapping；
2、为当前请求确定适配器
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
找到能调用这个类里面每个方法的适配器；适配器利用反射调用方法；
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");
}
我们都使用注解模式的所以适配器使用第三个；
3、SpringMVC中DispatcherServlet的几个重要属性，以及赋值
SpringMVC九大组件；
/** MultipartResolver used by this servlet 文件上传解析器*/
private MultipartResolver multipartResolver;
/** LocaleResolver used by this servlet 国际化解析器*/
private LocaleResolver localeResolver;
/** ThemeResolver used by this servlet 主题解析器*/
private ThemeResolver themeResolver;
/** List of HandlerMappings used by this servlet 保存了请求与类的映射关系（哪个请求用哪个类来处理）*/
private List<HandlerMapping> handlerMappings;
/** List of HandlerAdapters used by this servlet适配器；用来执行控制器（处理器）目标方法的*/
private List<HandlerAdapter> handlerAdapters;
/** List of HandlerExceptionResolvers used by this servlet 异常解析器*/
private List<HandlerExceptionResolver> handlerExceptionResolvers;
/** RequestToViewNameTranslator used by this servlet 转化器*/
private RequestToViewNameTranslator viewNameTranslator;
/** FlashMapManager used by this servletFlashMap 管理器 */
private FlashMapManager flashMapManager;
/** List of ViewResolvers used by this servlet视图解析器 */
private List<ViewResolver> viewResolvers;
文件上传组件默认没值；
默认赋值；
protected void initStrategies(ApplicationContext context) {
//默认从ioc容器中获取id为multipartResolver的组件，如果没有获取到就赋值为null；
initMultipartResolver(context);
//按照id获取localeResolver；如果没有；
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
}
//1、有些组件是这么》？先获取用户配置的，如果没有可以使用默认的（MultipartResolver ）
//2、有些组件是拿id获取的；有些是拿类型获取的，
//3、给SpringMVC中配置九大之一的某个组件；如果是拿id‘获取的？id不要乱写，用指定id；
//如果是用类型获取，id可以不用写；
在于DispatcherServlet.class同目录下有一个properties文件，这里封装了所有组件默认的类型；
时间： 2024-11-09 02:07:57