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javaWEB总结(25):避免表单的重复提交

2017-03-06 20:15 302 查看

什么是表单的重复提交?

目录结构

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>javaWeb_25</display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

index.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>index.jsp</title>
</head>
<body>
<form action="<%=request.getContextPath() %>/tokenServlet" method="post">
name: <input type="text" name="name"><br>
<input type="submit" value="提交">

</form>
</body>
</html>

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"%>
<!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>success.jsp</title>
</head>
<body>
<h1>success page</h1>
</body>
</html>

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

<input type="hidden" name="token" value="daochuwenziyao">，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"%>
<!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>index.jsp</title>
</head>
<body>

<form action="<%=request.getContextPath() %>/tokenServlet" method="post">

<%
request.setAttribute("token", "daochuwenizyao");
%>
name: <input type="text" name="name"><br>

<input type="submit" value="提交">

</form>
</body>
</html>

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"%>
<!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>token.jsp</title>
</head>
<body>

<h3>对不起，您已经提交过了</h3>
</body>
</html>

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"%>
<!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>index.jsp</title>
</head>
<body>

<form action="<%=request.getContextPath() %>/tokenServlet" method="post">

<%
session.setAttribute("token", "daochuwenizyao");
%>
name: <input type="text" name="name"><br>

<input type="submit" value="提交">

</form>
</body>
</html>

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"%>
<!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>index.jsp</title>
</head>
<body>
<%
String tokenValue = new Date().getTime() + "";
session.setAttribute("token", tokenValue);
%>

<form action="<%=request.getContextPath() %>/tokenServlet" method="post">

<input type="hidden" name="token" value="<%=tokenValue %>">

name: <input type="text" name="name"><br>

<input type="submit" value="提交">

</form>
</body>
</html>

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 <code>true</code> 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 <code>false</code>
* under any of the following circumstances:
* <ul>
* <li>No session associated with this request</li>
* <li>No transaction token saved in the session</li>
* <li>No transaction token included as a request parameter</li>
* <li>The included transaction token value does not match the
*     transaction token in the user's session</li>
* </ul>
*
* @param request The servlet request we are processing
*/
public synchronized boolean isTokenValid(HttpServletRequest request) {
return this.isTokenValid(request, false);
}

/**
* Return <code>true</code> 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 <code>false</code>
* <ul>
* <li>No session associated with this request</li>
* <li>No transaction token saved in the session</li>
* <li>No transaction token included as a request parameter</li>
* <li>The included transaction token value does not match the
*     transaction token in the user's session</li>
* </ul>
*
* @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"%>
<!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>index.jsp</title>
</head>
<body>

<form action="<%=request.getContextPath() %>/tokenServlet" method="post">

<!-- 两个作用
1.产生一个随机值
2.tokenValue放在session中

-->
<input type="hidden" name="TOKEN_KEY" value="<%=TokenProcessor.getInstance().saveToken(request) %>">

name: <input type="text" name="name"><br>

<input type="submit" value="提交">

</form>
</body>
</html>

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。

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标签： java web

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