1.表单由Servlet生成一个token,用户提交表单时候,会提交token,服务端根据token判断,如果在session中有token和表单提交的相同,则让用户正确提交,并且删除session中的token,
如果用户提交的token错误或者token为null则拒绝提交
a. 生成token类 generateProcessor.java
package com.luowen.formRepeat;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Random;
import sun.misc.BASE64Encoder;
public class TokenProcessor {
private static final TokenProcessor gp = new TokenProcessor();
private TokenProcessor(){};
//单例模式
public static TokenProcessor getInstance(){
return gp;
}
public String generateToken(){
String token = System.currentTimeMillis() + " " + new Random().nextInt();
try {
//拿到数据指纹
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] byt = md.digest(token.getBytes());
//用Base64编码确保token是可认识的字符
BASE64Encoder be = new BASE64Encoder();
return be.encode(byt);
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException();
}
}
}
b.给表单分配一个token FormSerlve.java
package com.luowen.formRepeat;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* Servlet implementation class FormRepeat
*/
@WebServlet("/FormServlet")
public class FormServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public FormServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
TokenProcessor gp = TokenProcessor.getInstance();
String token = gp.generateToken();
HttpSession session = request.getSession();
session.setAttribute("token", token);
request.getRequestDispatcher("/formRepeat.jsp").forward(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
c.表单jsp页面 formRepeat.jsp
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>form repeat submit</title>
</head>
<body>
<h1>Form submit</h1>
<hr/>
<form action="/webDemo/JudgeSubmit" method="post" onsubmit="return doSubmit()">
Username:<input type="text" name="username" /><br/>
<input type="submit" value="submit" id="sub" />
<input type="hidden" name="token" value="${token}" />
</form>
<script>
function doSubmit(){
var sub = document.getElementById("sub");
sub.disabled = 'disabled';
return true;
}
</script>
</body>
</html>
d.判断用户提交的JudgeSevlet.java
package com.luowen.formRepeat;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class JudgeSubmit
*/
@WebServlet("/JudgeSubmit")
public class JudgeSubmit extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public JudgeSubmit() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
boolean flag = isRepeat(request);
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
if(!flag){
response.getWriter().print("表单请勿重复提交");
return;
}
response.getWriter().print("提交成功弄!");
return;
}
private boolean isRepeat(HttpServletRequest request) {
String clientToken = request.getParameter("token");
String serverToken = (String) request.getSession().getAttribute("token");
//判断客服端是否来了token
if(clientToken == null)return false;
//判断服务端是否含有token
if(serverToken == null)return false;
//判断客户端token和服务端是否相等
if(!clientToken.equals(serverToken))return false;
//删除服务端token
request.getSession().removeAttribute("token");
return true;
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
e.jsp通过javascript限制了重复提交,serlvet通过token限制了重复提交.