JAVA防止重复提交Web表单的方法

本文实例讲述了JAVA防止重复提交Web表单的方法。分享给大家供大家参考，具体如下：

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									package cn.com.form;

									import java.io.IOException;

									import java.security.MessageDigest;

									import java.security.NoSuchAlgorithmException;

									import java.util.Random;

									import javax.servlet.ServletException;

									import javax.servlet.http.HttpServlet;

									import javax.servlet.http.HttpServletRequest;

									import javax.servlet.http.HttpServletResponse;

									import sun.misc.BASE64Encoder;

									//产生表单

									public class FormServlet extends HttpServlet {

									  private static final long serialVersionUID = 1L;

									  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

									    //产生随机数

									    TokenProcessor tp=TokenProcessor.getInstance();

									    String token=tp.generateToken();

									    request.getSession().setAttribute("token", token);

									    request.getRequestDispatcher("/form.jsp").forward(request, response);

									  }

									  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

									    doGet(request,response);

									  }

									}

									class TokenProcessor//令牌

									{

									  /*

									   * 1.把构造函数私有

									   * 2.自己创建一个

									   * 3.对外暴露一个方法，允许获取上面创建的对象

									   * */

									  private static final TokenProcessor instance=new TokenProcessor();

									  private TokenProcessor(){}

									  public static TokenProcessor getInstance()

									  {

									    return instance;

									  }

									  public String generateToken()

									  {

									    String token=System.currentTimeMillis()+new Random().nextInt()+"";

									    try {

									      MessageDigest md=MessageDigest.getInstance("md5");

									      byte[] md5=md.digest(token.getBytes());

									      //base64编码

									      BASE64Encoder encoder=new BASE64Encoder();

									      return encoder.encode(md5);

									    } catch (NoSuchAlgorithmException e) {

									      // TODO Auto-generated catch block

									      throw new RuntimeException(e);

									    }

									  }

									}

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

									<%

									String path = request.getContextPath();

									String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

									%>

									<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

									<html>

									 <head>

									 <base href="<%=basePath%>">

									 <title>My JSP 'form.jsp' starting page</title>

									  <meta http-equiv="pragma" content="no-cache">

									  <meta http-equiv="cache-control" content="no-cache">

									  <meta http-equiv="expires" content="0"> 

									  <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

									  <meta http-equiv="description" content="This is my page">

									  <!--

									  <link rel="stylesheet" type="text/css" href="styles.css">

									  -->

									 </head>

									 <body>

									   <form action="/Session/DoForm" method="post">

									     <input type="hidden" name="token" value="${token}">

									     用户名：<input type="text" name="userName">

									     <input type="submit" value="提交">

									   </form>

									 </body>

									</html>

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									package cn.com.form;

									import java.io.IOException;

									import javax.servlet.ServletException;

									import javax.servlet.http.HttpServlet;

									import javax.servlet.http.HttpServletRequest;

									import javax.servlet.http.HttpServletResponse;

									/**

									 * Servlet implementation class DoForm

									 * 处理表单提交的请求

									 * 

									 */

									public class DoForm extends HttpServlet {

									  private static final long serialVersionUID = 1L;

									  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

									    /*String userName=request.getParameter("userName");

									    try {

									      Thread.sleep(1000*3);

									    } catch (InterruptedException e) {

									      // TODO Auto-generated catch block

									      e.printStackTrace();

									    }

									    System.out.println("向数据库提交注册用户...");

									    */

									    boolean b=isTokenValid(request);

									    if(!b)

									    {

									      System.out.println("请不要重复提交！");

									      return;

									    }

									    request.getSession().removeAttribute("token");

									    System.out.println("向数据库中注册用户==");

									  }

									  private boolean isTokenValid(HttpServletRequest request) {

									    String client_token=request.getParameter("token");

									    if(client_token==null)

									    {

									      return false;

									    }

									    String server_token=(String)request.getSession().getAttribute("token");

									    if(server_token==null)

									    {

									      return false;

									    }

									    if(!client_token.equals(server_token))

									    {

									      return false;

									    }

									    return true;

									  }

									  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

									    doGet(request,response);

									  }

									}