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JAVA Web防止表单重复提交实例

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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);

}

}

}

<%@ 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">



</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>

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);

}

}

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