struts2源码分析StrutsPrepareAndExecuteFilter

这个是struts2的核心过滤器(Filter)，代码如下：

  1 /*
  2  * $Id: DefaultActionSupport.java 651946 2008-04-27 13:41:38Z apetrelli $
  3  *
  4  * Licensed to the Apache Software Foundation (ASF) under one
  5  * or more contributor license agreements.  See the NOTICE file
  6  * distributed with this work for additional information
  7  * regarding copyright ownership.  The ASF licenses this file
  8  * to you under the Apache License, Version 2.0 (the
  9  * "License"); you may not use this file except in compliance
 10  * with the License.  You may obtain a copy of the License at
 11  *
 12  *  http://www.apache.org/licenses/LICENSE-2.0
 13  *
 14  * Unless required by applicable law or agreed to in writing,
 15  * software distributed under the License is distributed on an
 16  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 17  * KIND, either express or implied.  See the License for the
 18  * specific language governing permissions and limitations
 19  * under the License.
 20  */
 21 package org.apache.struts2.dispatcher.ng.filter;
 22 
 23 import org.apache.struts2.StrutsStatics;
 24 import org.apache.struts2.dispatcher.Dispatcher;
 25 import org.apache.struts2.dispatcher.mapper.ActionMapping;
 26 import org.apache.struts2.dispatcher.ng.ExecuteOperations;
 27 import org.apache.struts2.dispatcher.ng.InitOperations;
 28 import org.apache.struts2.dispatcher.ng.PrepareOperations;
 29 
 30 import javax.servlet.*;
 31 import javax.servlet.http.HttpServletRequest;
 32 import javax.servlet.http.HttpServletResponse;
 33 import java.io.IOException;
 34 import java.util.List;
 35 import java.util.regex.Pattern;
 36 
 37 /**
 38  * Handles both the preparation and execution phases of the Struts dispatching process.  This filter is better to use
 39  * when you don't have another filter that needs access to action context information, such as Sitemesh.
 40  */
 41 public class StrutsPrepareAndExecuteFilter implements StrutsStatics, Filter {
 42     protected PrepareOperations prepare;
 43     protected ExecuteOperations execute;
 44     protected List<Pattern> excludedPatterns = null;
 45 
 46     public void init(FilterConfig filterConfig) throws ServletException {
 47         InitOperations init = new InitOperations();
 48         try {
 49             FilterHostConfig config = new FilterHostConfig(filterConfig);
 50             init.initLogging(config);
 51             Dispatcher dispatcher = init.initDispatcher(config);
 52             init.initStaticContentLoader(config, dispatcher);
 53 
 54             prepare = new PrepareOperations(filterConfig.getServletContext(), dispatcher);
 55             execute = new ExecuteOperations(filterConfig.getServletContext(), dispatcher);
 56             this.excludedPatterns = init.buildExcludedPatternsList(dispatcher);
 57 
 58             postInit(dispatcher, filterConfig);
 59         } finally {
 60             init.cleanup();
 61         }
 62 
 63     }
 64 
 65     /**
 66      * Callback for post initialization
 67      */
 68     protected void postInit(Dispatcher dispatcher, FilterConfig filterConfig) {
 69     }
 70 
 71     public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
 72 
 73         HttpServletRequest request = (HttpServletRequest) req;
 74         HttpServletResponse response = (HttpServletResponse) res;
 75 
 76         try {
 77             prepare.setEncodingAndLocale(request, response);
 78             prepare.createActionContext(request, response);
 79             prepare.assignDispatcherToThread();
 80             if ( excludedPatterns != null && prepare.isUrlExcluded(request, excludedPatterns)) {
 81                 chain.doFilter(request, response);
 82             } else {
 83                 request = prepare.wrapRequest(request);
 84                 ActionMapping mapping = prepare.findActionMapping(request, response, true);
 85                 if (mapping == null) {
 86                     boolean handled = execute.executeStaticResourceRequest(request, response);
 87                     if (!handled) {
 88                         chain.doFilter(request, response);
 89                     }
 90                 } else {
 91                     execute.executeAction(request, response, mapping);
 92                 }
 93             }
 94         } finally {
 95             prepare.cleanupRequest(request);
 96         }
 97     }
 98 
 99     public void destroy() {
100         prepare.cleanupDispatcher();
101     }
102 }

doFilter方法的作用是捕获以.action为结尾的请求，然后给他分配action，处理request，返回response！