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session防止表单重复提交

2012-11-07 11:37 246 查看

（1）包含有Form表单得页面必须通过一个服务器程序动态生成，服务器程序为每次产生得页面中的form表单都分配一个唯一得随机标识号，并在form表单得一个隐藏域保存

（2）当用户提交form得时候，负责接受这一请求得服务器程序比较form表单隐藏字段中的标识号与存贮在session中的是否相同，当下列情情况时候，服务器程序将忽略提交请求：

a.当前用户session不存在表单标识
b.用户提交得表单数据并没有标识号字段
c.存贮在当前用户的session中得标识号与表单数据中的不同

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

<html>

<head>

<title>RepeateForm.html</title>

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

<metahttp-equiv="description"content="this is my page">

<metahttp-equiv="content-type"content="text/html; charset=UTF-8">



<scripttype="text/javascript">

var iscommitted = false;

function checkPost(){

if(!iscommitted){

document.getElementById("sub").disabled =turn;

iscimmitted = turn;

return trun;

}else{

// alert("不能重复提交表单！");

return false;

}

}

</script>

</head>

<body>

<formaction="/BookHistory/serlevt/RepeateFormServlet"method="poss"onsubmit="return checkPost()">

用户名:<inputtype="text"name="username"/><br>

<inputtype="submit"value="提交"id="sub"/>

</form>

</body>

</html>

package com.hbsi.servlet;

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 FormDealServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

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

if(client_token==null){

return false;*/

boolean b = isTokenValidate(request);

if(!b){

System.out.print("请不要重复提交");

return;

}

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

System.out.print("项数据库注册用户信息。。。");

}

private boolean isTokenValidate(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;

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

}

}

package com.hbsi.servlet;

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 ForeGenerateServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

response.setContentType("text/heml;charset=UTF-8");

PrintWriter out = response.getWriter();

//产生表单号

TokenProcessor tp = TokenProcessor.getInstance();

String token= tp.generateToken();

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

out.print("<formaction='/BookHistory/servlet/FormDealServlet'method='post'/>");

out.print("<inputtype='hidden'name='token'value='"+token+"'/>");

out.print("用户名：<inputtype='text'name='username'/>");

out.print("<inputtype='submit'value='提交'/>");

out.print("</form>");

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

}

}

package com.hbsi.servlet;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.util.Random;

import sun.misc.BASE64Encoder;

public class TokenProcessor {

private TokenProcessor(){

}

private static final TokenProcessor instance=new TokenProcessor();

public static TokenProcessor getInstance(){

return instance;

}

public String generateToken(){

int i= new Random().nextInt();

String token= System.currentTimeMillis()+i+"";

try {

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

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

//base64编码

BASE64Encoder encoder = new BASE64Encoder();

encoder.encode(md5);

//return new String(md5);

} catch (NoSuchAlgorithmException e) {

// TODO Auto-generated catch block

//e.printStackTrace();

throw new RuntimeException(e);

}

return null;

}

}

package com.hbsi.servlet;

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 RepeateFormServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

response.setContentType("text/html;charset=UTF-8");

PrintWriter out = response.getWriter();

String username = request.getParameter("username");

try {

Thread.sleep(5*1000);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

out.print("以处理你的信息");

System.out.println("向数据库注册信息……");

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request,response);

}

}

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