J2EE 通过Filter替换返回页面的内容

一个历史项目，客户要求改ip，由于系统较为久远，没有源代码，通过反编译后发现ip写死在类中，反编译后的代码基本没法进行修改，分析了代码后，发现与ip相关的内容为返回到页面中的字符串，所以，想到了使用Filter，在Filter中处理这些字符串，觉得可行，便查询了一些资料，试验成功。以下这个类是从网上找到的，试验成功后发现页面已经关了，对原作者表示抱歉的同时表示感谢。

package org.mice.ipchange;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.OutputStreamWriter;import java.io.PrintWriter;import java.io.UnsupportedEncodingException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpServletResponseWrapper;public class ResponseWrapper extends HttpServletResponseWrapper {private ByteArrayOutputStream buffer = null;private ServletOutputStream out = null;private PrintWriter writer = null;public ResponseWrapper(HttpServletResponse resp) throws IOException {super(resp);buffer = new ByteArrayOutputStream();// 真正存储数据的流out = new WapperedOutputStream(buffer);writer = new PrintWriter(new OutputStreamWriter(buffer,this.getCharacterEncoding()));}// 重载父类获取outputstream的方法public ServletOutputStream getOutputStream() throws IOException {return out;}// 重载父类获取writer的方法public PrintWriter getWriter() throws UnsupportedEncodingException {return writer;}// 重载父类获取flushBuffer的方法public void flushBuffer() throws IOException {if (out != null) {out.flush();}if (writer != null) {writer.flush();}}public void reset() {buffer.reset();}public byte[] getResponseData() throws IOException {// 将out、writer中的数据强制输出到WapperedResponse的buffer里面，否则取不到数据flushBuffer();return buffer.toByteArray();} //内部类，对ServletOutputStream进行包装      private class WapperedOutputStream extends ServletOutputStream{          private ByteArrayOutputStream bos=null;          public WapperedOutputStream(ByteArrayOutputStream stream) throws IOException{              bos=stream;          }          public void write(int b) throws IOException{              bos.write(b);          }      }  }

编写具体的Filter，内容如下

package org.mice.ipchange;import java.io.IOException;import java.io.PrintWriter;import java.util.Enumeration;import java.util.MissingResourceException;import java.util.ResourceBundle;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class IPChangeFilter implements Filter {public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {// 需要设置这个，以防乱码response.setContentType("text/html;charset=GBK");HttpServletRequest httpReq = (HttpServletRequest) request;HttpServletResponse httpResp = (HttpServletResponse) response;ResponseWrapper respWrapper = new ResponseWrapper(httpResp);chain.doFilter(request, respWrapper);// weblogic8不支持response.setCharacterEncoding// response.setCharacterEncoding("GBK");String content = new String(respWrapper.getResponseData());String result = replaceText(content);httpResp.setContentType("text/html;charset=GBK");PrintWriter out = httpResp.getWriter();out.println(result);out.close();}/** * 替换内容 */private String replaceText(String content) {Enumeration enumes = RESOURCE_BUNDLE.getKeys();while (enumes.hasMoreElements()) {String o = enumes.nextElement().toString();content = content.replaceAll(o, RESOURCE_BUNDLE.getString(o));}return content;}// 替换文字的配置文件路径private static final String BUNDLE_NAME = "org.mice.ipchange.ipchange";// 加载配置文件private static final ResourceBundle RESOURCE_BUNDLE = ResourceBundle.getBundle(BUNDLE_NAME);// 获取替换文字public static String getString(String key) {try {return RESOURCE_BUNDLE.getString(key);} catch (MissingResourceException e) {e.printStackTrace();}return key;}public void init(FilterConfig arg0) throws ServletException {// TODO Auto-generated method stub}public void destroy() {// TODO Auto-generated method stub}}

最后，在配置文件ipchange.properties中配置好你要替换的键值对就可以了，对了，别忘了在你的web.xml中定义Filter，并使用Filter。