避免表单重复提交--用session实现token机制
直接拿例子来说吧！！
目录结构
web.xml
javaWeb_25
index.jsp
index.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
index.jsp
TokenServlet.java
package com.dao.chu;
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 TokenServlet
*/
@WebServlet("/tokenServlet")
public class TokenServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public TokenServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String name = request.getParameter("name");
System.out.println("name is :"+name);
request.getRequestDispatcher("/success.jsp").forward(request, response);
}
}success.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
success.jsp
success page
运行效果
提交表单一次，并且刷新三次页面
这就是表单的重复提交
重复提交的情况:
①在表单提交到一个Servlet而Servlet又通过请求转发的方式响应了一个jsp或者是html页面，此时地址栏还保留着Servlet的路径，在响应页面点击刷新。
②在响应页面没有到达时，重复点击提交按钮。
③点击返回，再点击提交
不是重复提交的情况
①点击返回，刷新原表单页面，再点击提交
如何避免表单的重复提交
在表单中做一个标记，提交到Servlet时，检查标记是否存在且是否和预定的标记一致，若一致，则受理请求，并销毁标记，若不一致，则直接响应提示信息:重复提交。
1.只写一个一个隐藏逾
，不行。因为无法销毁标记。
2.标记放在request中
各文件修改如下:
index.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
index.jsp
TokenServlet
package com.dao.chu;
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 TokenServlet
*/
@WebServlet("/tokenServlet")
public class TokenServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public TokenServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String name = request.getParameter("name");
Object token = request.getAttribute("token");
if (token!=null) {
request.removeAttribute("token");
}else {
response.sendRedirect(request.getContextPath()+"/token.jsp");;
}
}
} token.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
token.jsp
对不起，您已经提交过了
也不行，因为表单页面刷新后request已经被销毁,再提交表单是一个新的request。
3.标记放在session中.
index.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
index.jsp
TokenServlet.Java
package com.dao.chu;
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 TokenServlet
*/
@WebServlet("/tokenServlet")
public class TokenServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public TokenServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
HttpSession session = request.getSession();
Object token = session.getAttribute("token");
if (token!=null) {
session.removeAttribute("token");
}else {
response.sendRedirect(request.getContextPath()+"/token.jsp");;
}
}
}经过检测，此方法可行。
但是有时候我们需要往session中放一个随机值，后台如何取得该随机值呢，这时候需要和隐藏逾搭配使用。
index.jsp
<%@page import="java.util.Date"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
index.jsp
<%
String tokenValue = new Date().getTime() + "";
session.setAttribute("token", tokenValue);
%>
TokenServlet.java
package com.dao.chu;
import java.io.IOException;
import java.util.Date;
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 TokenServlet
*/
@WebServlet("/tokenServlet")
public class TokenServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public TokenServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
HttpSession session = request.getSession();
String tokenValue = request.getParameter("token");
String token = (String)session.getAttribute("token");
if (token!=null && token.equals(tokenValue)) {
session.removeAttribute("token");
}else {
response.sendRedirect(request.getContextPath()+"/token.jsp");;
}
}
}经过检测，此方法可行。并且更加满足需求。
步骤:
1.在原表单页面，生成一个随机数token
2.在原表单页面,把token放在session属性中
3.在原表单页面，把token值放在隐藏逾中
4.在目标Servlet中，获取session和隐藏逾中的token值
5.比较两个值是否一致，若一致，受理请求且把session中的token属性清除，若不一致则直接显示提示页面:重复提交
使用strus1的工具类来编写代码
strus1的工具类
下载地址
http://download.csdn.NET/download/zhangyw31/2706595
打开
G:\struts-1.2.9-src\src\share\org\apache\struts\util\TokenProcessor.java
将TokenProcessor复制到项目中,修改两个常量即可。如果好奇可以在G:\struts-1.2.9-src\src\share\org\apache\struts\Globals中可以搜索到。
最终我们修改成如下文件:
TokenProcessor.java
/*
* $Id: TokenProcessor.java 54929 2004-10-16 16:38:42Z germuska $
*
* Copyright 2003-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.dao.chu;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
/**
* TokenProcessor is responsible for handling all token related functionality. The
* methods in this class are synchronized to protect token processing from multiple
* threads. Servlet containers are allowed to return a different HttpSession object
* for two threads accessing the same session so it is not possible to synchronize
* on the session.
*
* @since Struts 1.1
*/
public class TokenProcessor {
private static final String TOKEN_KEY = null;
private static final String TRANSACTION_TOKEN_KEY = null;
/**
* The singleton instance of this class.
*/
private static TokenProcessor instance = new TokenProcessor();
/**
* Retrieves the singleton instance of this class.
*/
public static TokenProcessor getInstance() {
return instance;
}
/**
* Protected constructor for TokenProcessor. Use TokenProcessor.getInstance()
* to obtain a reference to the processor.
*/
protected TokenProcessor() {
super();
}
/**
* The timestamp used most recently to generate a token value.
*/
private long previous;
/**
* Return true if there is a transaction token stored in
* the user's current session, and the value submitted as a request
* parameter with this action matches it. Returns false
* under any of the following circumstances:
*
* - No session associated with this request
* - No transaction token saved in the session
* - No transaction token included as a request parameter
* - The included transaction token value does not match the
* transaction token in the user's session
*
*
* @param request The servlet request we are processing
*/
public synchronized boolean isTokenValid(HttpServletRequest request) {
return this.isTokenValid(request, false);
}
/**
* Return true if there is a transaction token stored in
* the user's current session, and the value submitted as a request
* parameter with this action matches it. Returns false
*
* - No session associated with this request
* - No transaction token saved in the session
* - No transaction token included as a request parameter
* - The included transaction token value does not match the
* transaction token in the user's session
*
*
* @param request The servlet request we are processing
* @param reset Should we reset the token after checking it?
*/
public synchronized boolean isTokenValid(
HttpServletRequest request,
boolean reset) {
// Retrieve the current session for this request
HttpSession session = request.getSession(false);
if (session == null) {
return false;
}
// Retrieve the transaction token from this session, and
// reset it if requested
String saved = (String) session.getAttribute(TRANSACTION_TOKEN_KEY);
if (saved == null) {
return false;
}
if (reset) {
this.resetToken(request);
}
// Retrieve the transaction token included in this request
String token = request.getParameter(TOKEN_KEY);
if (token == null) {
return false;
}
return saved.equals(token);
}
/**
* Reset the saved transaction token in the user's session. This
* indicates that transactional token checking will not be needed
* on the next request that is submitted.
*
* @param request The servlet request we are processing
*/
public synchronized void resetToken(HttpServletRequest request) {
HttpSession session = request.getSession(false);
if (session == null) {
return;
}
session.removeAttribute(TRANSACTION_TOKEN_KEY);
}
/**
* Save a new transaction token in the user's current session, creating
* a new session if necessary.
*
* @param request The servlet request we are processing
*/
public synchronized void saveToken(HttpServletRequest request) {
HttpSession session = request.getSession();
String token = generateToken(request);
if (token != null) {
session.setAttribute(TRANSACTION_TOKEN_KEY, token);
}
}
/**
* Generate a new transaction token, to be used for enforcing a single
* request for a particular transaction.
*
* @param request The request we are processing
*/
public synchronized String generateToken(HttpServletRequest request) {
HttpSession session = request.getSession();
try {
byte id[] = session.getId().getBytes();
long current = System.currentTimeMillis();
if (current == previous) {
current++;
}
previous = current;
byte now[] = new Long(current).toString().getBytes();
MessageDigest md = MessageDigest.getInstance("MD5");
md.update(id);
md.update(now);
return toHex(md.digest());
} catch (NoSuchAlgorithmException e) {
return null;
}
}
/**
* Convert a byte array to a String of hexadecimal digits and return it.
* @param buffer The byte array to be converted
*/
private String toHex(byte buffer[]) {
StringBuffer sb = new StringBuffer(buffer.length * 2);
for (int i = 0; i < buffer.length; i++) {
sb.append(Character.forDigit((buffer[i] & 0xf0) >> 4, 16));
sb.append(Character.forDigit(buffer[i] & 0x0f, 16));
}
return sb.toString();
}
} 项目结构
index.jsp
<%@page import="com.dao.chu.TokenProcessor"%>
<%@page import="java.util.Date"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
index.jsp
TokenServlet.java
package com.dao.chu;
import java.io.IOException;
import java.util.Date;
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 TokenServlet
*/
@WebServlet("/tokenServlet")
public class TokenServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public TokenServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
boolean tokenValid = TokenProcessor.getInstance().isTokenValid(request);
if (tokenValid) {
TokenProcessor.getInstance().resetToken(request);
}
else {
response.sendRedirect(request.getContextPath()+"/token.jsp");;
}
}
}可以看出这样写代码复用性很高。
运行效果
正常情况下可以提交，一旦发生重复提交，则会跳转到另外一个页面。
转自http://blog.csdn.net/daochuwenziyao/article/details/60592188