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JAVA Web防止表单重复提交实例

2016-05-14 23:25 399 查看 
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">
<!--
<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>
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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