带有过滤器的小型留言系统（非常小）

一个用户名和一个留言框的JSP页面：

    
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<html>
  <head>
   
    
    <title>My JSP 'CommentLogin.jsp' starting page</title>


  </head>
  
  <body>
    <form action="CommentServlet">
        username:<input type="text" name="username"><br>
        Comment:<textarea name="comment" rows="7" cols="7"></textarea>
        <input type="submit" value="submit">
    </form>
  </body>
</html>

非常挫的界面见谅

一个过滤器类，用于过滤名字中出zhangsan并将它换成lisi 以及留言中出现zhongguo的字眼并将它替换成****

    
package FilterPackege;

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

public class CommentFilter implements Filter{

	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest req=(HttpServletRequest)request;
        HttpServletResponse resp=(HttpServletResponse)response;
        
        String username=req.getParameter("username");
        String comment=req.getParameter("comment");
        
        username=username.replace("zhangsan", "lisi");
        comment =comment.replace("zhongguo", "****");
        
        req.setAttribute("username",username);
        req.setAttribute("comment", comment);
        
        chain.doFilter(request, response);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		System.out.println("CommentFilter Start");
		
	}
   
}

一个Servlet类用于接收过滤后的

    
package com.mison;

import java.io.IOException;
import java.io.PrintWriter;

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

public class CommentServlet extends HttpServlet {

	/**
	 * 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 {
          
		  String username=(String)request.getAttribute("username");
          
		  String comment=(String)request.getAttribute("comment");
		  
		  request.getRequestDispatcher("commentout.jsp").forward(request, response);
		    
	}

}

一个显示结果的JSP页面

    
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<html>
  <head>
  
    
    <title>My JSP 'commentout.jsp' starting page</title>

  </head>
  
  <body>
       username:<%=request.getAttribute("username") %><br>
       comment:<%=request.getAttribute("comment") %>
       
  </body>
</html>

web.xml中的配置

    
<filter>
   <filter-name>CommentFilter</filter-name>
   <filter-class>FilterPackege.CommentFilter</filter-class>
</filter>
<filter-mapping>
   <filter-name>CommentFilter</filter-name>
   <url-pattern>/CommentServlet</url-pattern>
</filter-mapping>

显示结果分别为：

带有过滤器的小型留言系统（非常小）

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