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！