MyDispatcherServlet.java

package com.xiaozhi.blog.web;



import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.servlet.DispatcherServlet;
import org.springframework.web.servlet.HandlerAdapter;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.HandlerExecutionChain;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.ModelAndViewDefiningException;
import org.springframework.web.util.NestedServletException;
import org.springframework.web.util.UrlPathHelper;
import org.springframework.web.util.WebUtils;



@SuppressWarnings("serial")
public class MyDispatcherServlet extends DispatcherServlet{

    private static final UrlPathHelper urlPathHelper = new UrlPathHelper();

    protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HttpServletRequest processedRequest = request;
        HandlerExecutionChain mappedHandler = null;
        int interceptorIndex = -1;

        try {
            ModelAndView mv;
            boolean errorView = false;

            try {

                processedRequest = checkMultipart(request);

                // Determine handler for the current request.
                mappedHandler = getHandler(processedRequest, false);

                if (mappedHandler == null || mappedHandler.getHandler() == null) {
                    noHandlerFound(processedRequest, response);
                    return;
                }

                // Determine handler adapter for the current request.
                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;
                    }
                }

                // Apply preHandle methods of registered interceptors.
                HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();
                if (interceptors != null) {
                    for (int i = 0; i < interceptors.length; i++) {
                        HandlerInterceptor interceptor = interceptors[i];
                        if (!interceptor.preHandle(processedRequest, response, mappedHandler.getHandler())) {
                            triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);
                            return;
                        }
                        interceptorIndex = i;
                    }
                }

                // Actually invoke the handler.
                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

                // Do we need view name translation?
                if (mv != null && !mv.hasView()) {
                    mv.setViewName(getDefaultViewName(request));
                }

                // Apply postHandle methods of registered interceptors.
                if (interceptors != null) {
                    for (int i = interceptors.length - 1; i >= 0; i--) {
                        HandlerInterceptor interceptor = interceptors[i];
                        interceptor.postHandle(processedRequest, response, mappedHandler.getHandler(), mv);
                    }
                }
            }
            catch (ModelAndViewDefiningException ex) {
                logger.debug("ModelAndViewDefiningException encountered", ex);
                mv = ex.getModelAndView();
            }
            catch (Exception ex) {

                logger.debug("----------------->mappedHandler2");
               // mv = null;
              Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
              mv = processHandlerException(processedRequest, response, handler, ex);
              logger.debug("----------------->mv :"+ mv);
              errorView = (mv != null);
            }

            // Did the handler return a view to render?
            if (mv != null && !mv.wasCleared()) {
                render(mv, processedRequest, response);
                if (errorView) {
                    WebUtils.clearErrorRequestAttributes(request);
                }
            }
            else {
                if (logger.isDebugEnabled()) {
                    logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() +
                            "': assuming HandlerAdapter completed request handling");
                }
                //response.sendRedirect("http://tianji.com");//空ModelAndView
            }

            // Trigger after-completion for successful outcome.
            triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);
        }

        catch (Exception ex) {
            // Trigger after-completion for thrown exception.
            triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, ex);
            throw ex;
        }
        catch (Error err) {
            ServletException ex = new NestedServletException("Handler processing failed", err);
            // Trigger after-completion for thrown exception.
            triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, ex);
            throw ex;
        }

        finally {
            // Clean up any resources used by a multipart request.
            if (processedRequest != request) {
                cleanupMultipart(processedRequest);
            }
        }
    }


    private void triggerAfterCompletion(HandlerExecutionChain mappedHandler,
            int interceptorIndex,
            HttpServletRequest request,
            HttpServletResponse response,
            Exception ex) throws Exception {

        // Apply afterCompletion methods of registered interceptors.
        if (mappedHandler != null) {
            HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();
            if (interceptors != null) {
                for (int i = interceptorIndex; i >= 0; i--) {
                    HandlerInterceptor interceptor = interceptors[i];
                    try {
                        interceptor.afterCompletion(request, response, mappedHandler.getHandler(), ex);
                    }
                    catch (Throwable ex2) {
                        logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
                    }
                }
            }
        }
    }


    protected void noHandlerFound(HttpServletRequest request, HttpServletResponse response) throws Exception {
        if (pageNotFoundLogger.isWarnEnabled()) {
            String requestUri = urlPathHelper.getRequestUri(request);
            pageNotFoundLogger.warn("No mapping found for HTTP request with URI [" + requestUri +
                    "] in DispatcherServlet with name '" + getServletName() + "'");
        }
        //response.sendError(HttpServletResponse.SC_NOT_FOUND);
        response.sendRedirect("http://tianji.com");//404错误
    }

}