1.Action 代码
/*
* $Id: ShowFileAction.java 471754 2006-11-06 14:55:09Z husted $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.    See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.    The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.    You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.    See the License for the
* specific language governing permissions and limitations
* under the License.
*/


package org.apache.struts.webapp.validator;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.commons.logging.LogFactory;
import org.apache.commons.logging.Log;

/**
* Action which retrieves a file specified in the parameter
* and stores its contents in the request, so that they
* can be displayed.
*/

public class ShowFileAction extends Action {

        /** Logging Instance. */
        private static final Log log = LogFactory.getLog(ShowFileAction.class);

        public ActionForward execute(ActionMapping mapping,
                                                                 ActionForm form,
                                                                 HttpServletRequest request,
                                                                 HttpServletResponse response)
                                                    throws Exception {

                // Get the file name
                String fileName = mapping.getParameter();
                StringBuffer fileContents = new StringBuffer();

                if(fileName != null) {

                        InputStream input = servlet.getServletContext().getResourceAsStream(fileName);
                        if (input == null) {
                                log.warn("File Not Found: "+fileName);
                        } else {
                                InputStreamReader inputReader = new InputStreamReader(input);
                                char[] buffer = new char[1000];
                                while (true) {
                                        int lth = inputReader.read(buffer);
                                        if (lth < 0) {
                                                break;
                                        } else {
                                                fileContents.append(buffer, 0, lth);
                                        }
                                }
                        }
                } else {
                        log.error("No file name specified.");
                }


                // Store the File contents and name in the Request
                request.setAttribute("fileName", fileName);
                request.setAttribute("fileContents", fileContents.toString());

                return mapping.findForward("success");
        }
}
分析:
 
 String fileName = mapping.getParameter();
其中mapping 是ActionMapping 对象,是ActionConfig的子对象。 其中ActionConfig封装了Struts-config.xml 中的配置信息。
 
inputStream input = servlet.getServletContext().getResourceAsStream(fileName);
每个Web应用程序都是一个独立的Servlet容器,每个Web应用程序分别用一个ServletContext对象。ServletContext对象包含在ServletConfig对象中,
调用ServletConfig.getServletContext()方法获取ServletContext对象。
1、    getResourcePath    返回一个包含该目录和文件路径名称的Set集合
2、    getResource        返回映射到资源上的URL对象。
3、    getResourceAsStream 返回连接到某资源上的InputStream对象
 
 
 InputStreamReader inputReader = new InputStreamReader(input);
需要重新包装成字符处理。
 
【2】配置文件
        <!-- Show validations.xml -->
        <action path="/showValidation"    
                        type="org.apache.struts.webapp.validator.ShowFileAction"    
                        scope="request"    
                        parameter="/WEB-INF/validator/validation.xml">
                <forward name="success" path="/showFile.jsp" />
        </action>
 
通过传递不同的parameter,读取不同的文件。
 
【3】在JSP页面 读取信息
    <body bgcolor="white">

        <h2>File: <i><bean:write name="fileName" scope="request" /></i></h2>
        <hr />
        <pre>
                <bean:write name="fileContents" scope="request" filter="true"/>
        </pre>
        <hr />
    </body>
 
bean:write 标签 有个filter属性。如果为true 的话,则表示
将把输出内容中的特殊HTML符号作为普通字符串来显示;如果filter属性为false,则不会把输出内容中的HTML符号转化为普通字符串.