也是一个朋友要求帮忙，在整个网站的访问期间要过滤掉例如“法轮功”的非法字符，所以帮忙写了个。一下是一个测试的源程序。tomcat 5.0.28 , windows 2000 sp4 , jdk1.4中测试通过 Eclipse下工程源码下载（将文件后面的.jpg去掉即可，是个压缩包） /** * @author 李国庆 * @company leemenz (C) copyright * @time Dec 18, 2006 2:08:18 PM * @version 1.0.0.0 * @package com */package com; import java.io.IOException;import java.io.PrintWriter; 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; /** * @author Administrator * * 这个过滤器用来过滤黑名单中的用户不能留言 * */public class NoteFilter implements Filter { private FilterConfig config = null; private String blackList = null; /* * (non-Javadoc) * * @see javax.servlet.Filter#destroy() */ public void destroy() { // TODO Auto-generated method stub config = null; } /* * (non-Javadoc) * * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, * javax.servlet.ServletResponse, javax.servlet.FilterChain) */ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { // TODO Auto-generated method stub String username = request.getParameter("username"); if (username != null) username = new String(request.getParameter("username").getBytes( "ISO8859-1"), "GB2312"); if (username != null && username.indexOf(blackList) != -1) { response.setContentType("text/html;charset=GB2312"); PrintWriter out = response.getWriter(); out.println("<html><head></head><body>"); out.println("<h1>对不起，" + username + ",您没有留言的权限！"); out.println("</h1></body></html>"); out.flush(); return; } long before = System.currentTimeMillis(); config.getServletContext() .log("NoteFilter:before call chain.Filter();"); chain.doFilter(request, response); config.getServletContext().log("NoteFilter:after call chain.Filter();"); long end = System.currentTimeMillis(); String name = ""; if (request instanceof javax.servlet.http.HttpServletRequest) { name = ((HttpServletRequest) request).getRequestURI(); } config.getServletContext().log( "NoteFilter " + name + " : " + (end - before) + " ms"); } /* * (non-Javadoc) * * @see javax.servlet.Filter#init(javax.servlet.FilterConfig) */ public void init(FilterConfig arg0) throws ServletException { // TODO Auto-generated method stub this.config = arg0; this.blackList = config.getInitParameter("blackList"); } } /** * @author 李国庆 * @company leemenz (C) copyright * @time Dec 18, 2006 2:08:18 PM * @version 1.0.0.0 * @package com */package com; import java.io.IOException; import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse; /* *测试页面 */public class NoteServlet extends HttpServlet { public static final String CONTENT_TYPE = "text/html;charset=GB2312"; /** * Constructor of the object. */ public NoteServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doDelete method of the servlet. <br> * * This method is called when a HTTP delete request is received. * * @param request * the request send by the client to the server * @param response * the response send by the server to the client * @throws ServletException * if an error occurred * @throws IOException * if an error occurred */ public void doDelete(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request * the request send by the client to the server * @param response * the response send by the server to the client * @throws ServletException * if an error occurred * @throws IOException * if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType(CONTENT_TYPE); ServletOutputStream out = response.getOutputStream(); out .println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>留言簿</TITLE></HEAD>"); out.println(" <BODY>"); String name = request.getParameter("username"); String content = request.getParameter("content"); if (name != null) name = new String(name.getBytes("ISO-8859-1"), "GB2312"); if (content != null) content = new String(content.getBytes("ISO-8859-1"), "GB2312"); if (content != null) out.println("<p> " + name + "的留言为：" + content); out.println("<form method=\"post\" action=\"" + request.getContextPath() + "/servlet/NoteServlet\">"); out.println("<b>姓名：</b><input type=\"text\" name=\"username\"></br>"); out .println("<b>内容：</b><textArea name=\"content\" row=\"5\" cols=\"20\" wrap></textArea></br>"); out.println("<input type=\"submit\" name=\"提交\" value=\"提交\">"); out.println("<input type=\"reset\" name=\"重填\" value=\"重填\"></br>"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to * post. * * @param request * the request send by the client to the server * @param response * the response send by the server to the client * @throws ServletException * if an error occurred * @throws IOException * if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doGet(request, response); } /** * Initialization of the servlet. <br> * * @throws ServletException * if an error occure */ public void init() throws ServletException { // Put your code here } } /** * @author 李国庆 * @company leemenz (C) copyright * @time Dec 18, 2006 3:58:53 PM * @version 1.0.0.0 * @package com */package com; import java.io.IOException; import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpServletResponseWrapper; /** * @author Administrator * 这个类继承HttpServletResponseWrapper ，并重写相应的方法 */public class ReplaceServletWapper extends HttpServletResponseWrapper { private ReplaceTextStream tpStream; /** * @param arg0 */ public ReplaceServletWapper(HttpServletResponse arg0, String searchText, String replaceText) throws IOException { // TODO Auto-generated constructor stub super((HttpServletResponse)arg0); tpStream = new ReplaceTextStream(arg0.getOutputStream(),searchText,replaceText); } public ServletOutputStream getOutputStream() throws IOException { return tpStream; } } /** * @author 李国庆 * @company leemenz (C) copyright * @time Dec 18, 2006 2:08:18 PM * @version 1.0.0.0 * @package com */package com; import java.io.IOException; 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.HttpServletResponse; /** * @author Administrator * * 这个类用来过滤留言或者是用户名中的非法内容 * */public class ReplaceTextFilter implements Filter { private FilterConfig config; private String searchStr; private String replaceStr; /* * (non-Javadoc) * * @see javax.servlet.Filter#destroy() */ public void destroy() { // TODO Auto-generated method stub config = null; } /* * (non-Javadoc) * * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, * javax.servlet.ServletResponse, javax.servlet.FilterChain) */ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { // TODO Auto-generated method stub ReplaceServletWapper myWrappered = new ReplaceServletWapper( (HttpServletResponse) response, searchStr, replaceStr); config.getServletContext().log( "ReplaceTextFilter : before called doFilter"); chain.doFilter(request, myWrappered); config.getServletContext().log( "ReplaceTextFilter : after called doFilter"); myWrappered.getOutputStream().close(); } /* * (non-Javadoc) * * @see javax.servlet.Filter#init(javax.servlet.FilterConfig) */ public void init(FilterConfig arg0) throws ServletException { // TODO Auto-generated method stub this.config = arg0; this.searchStr = config.getInitParameter("search"); this.replaceStr = config.getInitParameter("replace"); } } /** * @author 李国庆 * @company leemenz (C) copyright * @time Dec 18, 2006 3:33:51 PM * @version 1.0.0.0 * @package com */package com; import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.OutputStream; import javax.servlet.ServletOutputStream; /** * @author Administrator * 这个类继承ServletOutputStream ，并重写相应的方法 */public class ReplaceTextStream extends ServletOutputStream { private OutputStream intStream; private ByteArrayOutputStream baStream; private boolean closed = false; private String newStr; private String oldStr; /** * */ public ReplaceTextStream(OutputStream outStream, String strSearch, String strReplace) { // TODO Auto-generated constructor stub intStream = outStream; baStream = new ByteArrayOutputStream(); oldStr = strSearch; newStr = strReplace; } /* * (non-Javadoc) * * @see java.io.OutputStream#write(int) */ public void write(int b) throws IOException { // TODO Auto-generated method stub baStream.write(b); } /** * 重写方法 */ public void println(String s) throws IOException { s = s + "\n"; byte[] bs = s.getBytes(); baStream.write(bs); } /** * 重写方法 */ public void close() throws IOException { if (!closed) { processStream(); intStream.close(); closed = true; } } /** * 重写方法 */ public void flush() throws IOException { if (baStream.size() != 0) { processStream(); baStream = new ByteArrayOutputStream(); } } /** * 重写 processStream 方法 * * @throws IOException */ public void processStream() throws IOException { intStream.write(replaceContent(baStream.toByteArray())); } /** * 替换所有的目的词语 * * @param inBytes * @return */ public byte[] replaceContent(byte[] inBytes) { String retVal = ""; String tpString = new String(inBytes); String srchString = (new String(inBytes)).toLowerCase(); int endBody = srchString.indexOf(oldStr); if (endBody != -1) { retVal = tpString.replaceAll(oldStr, newStr); } else retVal = tpString; return retVal.getBytes(); } } <?xml version="1.0" encoding="GB2312"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <!-- --> <filter> <filter-name>NoteFilter</filter-name> <filter-class>com.NoteFilter</filter-class> <init-param> <param-name>blackList</param-name> <param-value>毛泽东</param-value> </init-param> </filter> <filter-mapping> <filter-name>NoteFilter</filter-name> <url-pattern>/servlet/NoteServlet</url-pattern> </filter-mapping> <filter> <filter-name>ReplaceTextFilter</filter-name> <filter-class>com.ReplaceTextFilter</filter-class> <init-param> <param-name>search</param-name> <param-value>法轮功</param-value> </init-param> <init-param> <param-name>replace</param-name> <param-value>邪教</param-value> </init-param> </filter> <filter-mapping> <filter-name>ReplaceTextFilter</filter-name> <url-pattern>/servlet/NoteServlet</url-pattern> </filter-mapping> <servlet> <servlet-name>NoteServlet</servlet-name> <servlet-class>com.NoteServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>NoteServlet</servlet-name> <url-pattern>/servlet/NoteServlet</url-pattern> </servlet-mapping></web-app> 另外，要看到日志的输出信息，必须确保在server.xml文件中有如下代码：<Logger className="org.apache.catalina.logger.FileLogger" prefix="catalina_log." suffix=".txt" timestamp="true"/> enjoy it!!! :)
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