1.在我们的web开发中，常常会遇到表单的重复提交问题，那么我们的解决方案有两种：①重定向：response.sendrediect(); ②token的使用，即做个标记
下面写一个token的例子：（在tomcat上可以运行的。）
1.JSP页面，3个。
index.jsp
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<%@ page language="java"import="java.util.*"pageEncoding="UTF-8"%>
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>避免表单重复提交的例子</title>
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</head>
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<body>
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<h4>请支付：</h4>
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<%
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String token = (String)request.getAttribute("mytoken");
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out.print(token);
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%>
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<formaction="token.jspx?_m=pay"method="post">
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<inputtype="hidden"name="token"value="<%=token %>"/>
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<inputtype="text"name="money"/>
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<inputtype="submit"value="支付"/>
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</form>
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</body>
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</html>
suc.jsp
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<%@ page language="java"import="java.util.*"pageEncoding="UTF-8"%>
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>支付成功</title>
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</head>
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<body>
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<h2style="color:red;">支付成功！感谢您的使用！</h2>
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</body>
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</html>
error.jsp
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<%@ page language="java"import="java.util.*"pageEncoding="UTF-8"%>
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>重复提交了</title>
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</head>
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<body>
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<h2>系统正在处理，请勿重复提交！</h2>
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</body>
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</html>
2.com.hanchao.web.util是我们工具包
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package com.hanchao.web.util;
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import java.util.UUID;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpSession;
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/**
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* 工具类
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* @author hanlw
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* 2012-07-09
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*/
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publicclass TokenUtil {
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//定义一个常量，此常量只是为以后取值，传值方便
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privatestaticfinal String TOKEN = "TOKEN";
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/**
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* 获得唯一的token
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* @param request
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* @return
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*/
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public String getToken(HttpServletRequest request) {
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//UUID可以产生唯一的序列码
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UUID uuid = UUID.randomUUID();
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String token = uuid.toString();
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HttpSession session = request.getSession();
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session.setAttribute(TOKEN, token);
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return token;
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}
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/**
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* 验证token
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* @param request
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* @param requestToken
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* @return
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*/
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publicboolean validateToken(HttpServletRequest request,String requestToken) {
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HttpSession session = request.getSession();
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String sessionToken = (String) session.getAttribute(TOKEN);
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if(sessionToken != null &&
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requestToken != null &&
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sessionToken.equals(requestToken)) {
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session.removeAttribute(TOKEN);
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returntrue;
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} else {
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returnfalse;
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}
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}
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}
3.我们的servlet
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package com.hanchao.web.util;
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import java.io.IOException;
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import javax.servlet.ServletException;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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publicclass TokenServlet extends HttpServlet {
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privatestaticfinallong serialVersionUID = 1L;
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publicvoid doGet(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException {
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String method = request.getParameter("_m");
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if("pay".equals(method)) {
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pay(request,response);
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} elseif("tosave".equals(method)) {
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save(request,response);
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}
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}
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/**
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* 产生token
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* @param request
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* @param response
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* @throws ServletException
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* @throws IOException
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*/
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privatevoid save(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException{
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TokenUtil util = new TokenUtil();
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String token = util.getToken(request);
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request.setAttribute("mytoken", token);
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request.getRequestDispatcher("index.jsp").forward(request, response);
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}
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/**
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* 支付
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* @param request
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* @param response
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* @throws ServletException
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* @throws IOException
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*/
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privatevoid pay(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException{
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String token = request.getParameter("token");
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TokenUtil util = new TokenUtil();
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boolean result = util.validateToken(request, token);
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if(result) {
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String money = request.getParameter("money");
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System.out.println("支付"+money+"成功");
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request.getRequestDispatcher("suc.jsp").forward(request, response);
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} else {
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request.getRequestDispatcher("error.jsp").forward(request, response);
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}
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}
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publicvoid doPost(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException {
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doGet(request,response);
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}
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}
==================================================================
2013-06-21-add-han
昨天和我们的架构聊到这个问题，因为现在做的项目涉及到了。他说：对于分布式的大型互联网项目，这种token的方式，在高并发时可能会出现问题。所以，也建议用redirect最保险吧。谢谢
本文转自韩立伟 51CTO博客，原文链接：http://blog.51cto.com/hanchaohan/931145，如需转载请自行联系原作者
