JAVA Web防止表单重复提交范例 _Web前端

JAVA Web防止表单重复提交实例
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);
	}

}