SpringMVC执行流程

public class DispatcherServlet extends FrameworkServlet {
//定义了默认策略名字
private static final String DEFAULT_STRATEGIES_PATH = "DispatcherServlet.properties";
private static final Properties defaultStrategies;
static {
            //从Properties文件中加载默认策略实现
            ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class);
            defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
    }
private List<HandlerMapping> handlerMappings;
private List<HandlerAdapter> handlerAdapters;
private List<HandlerExceptionResolver> handlerExceptionResolvers;
private List<ViewResolver> viewResolvers;
//初始化策略
protected void initStrategies(ApplicationContext context) {
        initMultipartResolver(context);
        initLocaleResolver(context);
        initThemeResolver(context);
        initHandlerMappings(context);
        initHandlerAdapters(context);
        initHandlerExceptionResolvers(context);
        initRequestToViewNameTranslator(context);
        initViewResolvers(context);
        initFlashMapManager(context);
    }
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
            try {
            ModelAndView mv = null;
            Exception dispatchException = null;
            try {
                                //检查是否文件上传
                processedRequest = checkMultipart(request);
                multipartRequestParsed = (processedRequest != request);
                //通过HandlerMapping 获取Handler(返回的是HandlerExecutionChain)
               /**public class HandlerExecutionChain {
                       //HandlerExecutionChain封装了Handler(就是我们编写的Controller)跟interceptors
                       private final Object handler;
                       private HandlerInterceptor[] interceptors;
                **/
                HandlerExecutionChain mappedHandler = getHandler(processedRequest);
                //获取的Handler是Object类型,需要通过HandlerAdapter获取Handler真实类型
                HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

                // Process last-modified header, if supported by the handler.
                //调用Handlerinterceptor PreHandle(前置拦截器),返回false则停止执行
                if (!mappedHandler.applyPreHandle(processedRequest, response)) {
                    return;
                }

                // 调用真实handler逻辑并返回ModelAndView
                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
                                //将ModelAndView返回值DispatcherServlet后
                applyDefaultViewName(processedRequest, mv);
                                //调用Handlerinterceptor PostHandle(后置拦截器)    
                    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);
            }
            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) {
                                      //调用Handlerinterceptor afterCompletion
                    mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
                }
            }
            else {
                // Clean up any resources used by a multipart request.
                if (multipartRequestParsed) {
                    cleanupMultipart(processedRequest);
                }
            }
        }
    }}

    <bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="mappings">
            <props>
                <prop key="/hello">helloController</prop>
            </props>
        </property>
    </bean>
    <bean id="helloController" class="com.ckd.controller.HelloController"/>
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import org.springframework.web.servlet.mvc.Controller;
public class HelloController implements Controller {
    @Override
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView mv = new ModelAndView("index");
        mv.addObject("hello","world");
        return mv;
    }
}

<bean id="/beanname" class="com.ckd.controller.BeanNameController"/>
//需要继承HttpRequestHandler 此时可以把/beanname映射到handleRequest方法上
public class BeanNameControl implements HttpRequestHandler {
    @Override
    public void handleRequest(HttpServletRequest request, HttpServletResponse response)
            throws IOException, ServletException {
        request.getRequestDispatcher("/WEB-INF/page/userView.jsp").forward(request, response);
    }
}

<bean class="org.springframework.web.servlet.handler.SimpleServletHandlerAdapter"/>
<bean id="/helloservlet" class="com.ckd.controller.HelloServlet"/>
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public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().println("hello Servlet");
    }
}

<bean class="com.ckd.controller.ExceptionHandlerSample"/>
public class ExceptionHandlerSample implements HandlerExceptionResolver {
    @Override
    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
        return new ModelAndView("error");
    }
}

<mvc:interceptors>
        <mvc:interceptor>
            <!-- 拦截所有的请求，这个必须写在前面-->
            <mvc:mapping path="/**" />            
            <bean class="com.ckd.controller.SimpleHandlerInterceptor" />
        </mvc:interceptor>
    </mvc:interceptors>
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public class SimpleHandlerInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion");
    }
}