关于近期开发中遇到的同一账户多人登录造成数据库数据不一致的思考和解决（避开了数据库存状态的常用处理手段）

1.问题：近期开发了工单系统，开发结束项目上线测试过程中，发现同一账户多人同时登录如果不进行限制，该用户的操作就不是唯一的，导致数据库存放的数据出现了问题，项目整个就出问题了，经过本人再三思考，网上好多方案都是通过数据库存一个登录状态做处理，这样的话又得对数据库进行更改，很难受，那还有什么其他的处理方案吗？经思考，想出了以下处理方案：

1.采用servelet的application对象存放所有登录用户的信息，存放方式为sessionid-username存储

　　2.在用户登录时从application对象中取出所有的键，对应得值——即username与登录用户名进行匹配，匹配成功说明已经登录，不让该用户登录，否则返给前台登录成功的状态。

　　3.前台拿到数据后根据是否登录决定是否保存sessionid及是否进行成功跳转

　　4.用户下线时从appication中移除该sessionid的键

2.具体代码：

2-1.index.jsp登录页面：

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
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 'index.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>
    name:<input  type=text id='name'/>
    <button>login in</button>
    <script type="text/javascript" src='js/jquery-1.8.3.js'></script>
    <script type="text/javascript" src='js/cookie.js'></script>
    <script type="text/javascript">
    $('button').on('click',function(){
        $.post('<%=path%>/loginservlet',{name:$('#name').val()},function(data){
            console.dir(data);
            var json = eval("("+data+")");
            if (!json.islogin&&json.flag==1){
                console.dir('login is permited!');
                setCookie("sessionId",json.sessionId,1);
                console.dir('set cookie success!it is'+json.sessionId);
                alert(json.sessionId);
                window.location.href='success.jsp';
            }else{
                alert('the account you are using is logined');
            }
        
        })
    
    });
    
    
    </script>
  </body>
</html>

View Code

　2-2.homepage.jsp登录成功页面：

<%@ 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>login success</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="sso login success page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
  <a href="javascript:void(0);" onclick='logout()'>logout</a><br/>
    ${name } ,welcome!!!<br>
    <script type="text/javascript" src='js/jquery-1.8.3.js'></script>
    <script type="text/javascript" src='js/cookie.js'></script>
    <script type="text/javascript">
    function logout(){
    var sessionId = getCookie("sessionId");
    console.dir(sessionId);
    $.post('<%=path%>/logout',{sessionId:sessionId},function(data){
         var json = eval("("+data+")");
         console.dir(json);
         if (json.logout){
             alert('logout success!');
             window.location.href = "index.jsp";
         }else{
             alert('logout fail!');
         }
    });
    }
    
    
    </script>
    
  </body>
</html>

View Code

　2-3.loginservlet.java后台登录逻辑处理：

package com.java.gwb.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.json.JSONObject;

public class loginservlet extends HttpServlet {

    
    private static final long serialVersionUID = 1L;

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String username = request.getParameter("name");
        ServletContext application = request.getSession().getServletContext();
        Enumeration<String> en = application.getAttributeNames();
        boolean islogin = false;
        String sessionIds = request.getSession().getId();
        JSONObject json = new JSONObject();
        if (username.equals("gwb")||username.equals("ls")){
            request.getSession().setAttribute("name", username);
            json.accumulate("flag", 1);
            while(en.hasMoreElements()){
                String sessionId = en.nextElement();
                if (application.getAttribute(sessionId).equals(username)){
                    islogin = true;
                }
            }
            json.accumulate("islogin", islogin);
            if (islogin){//如果已经登录，就不再存
                json.accumulate("sessionId", "");
            }else{
                application.setAttribute(sessionIds, username);
                json.accumulate("sessionId", sessionIds);
            }
        }else{
            json.accumulate("flag", 0);
            json.accumulate("sessionId", "");
        }
        out.write(json.toString());
        out.flush();
        out.close();
    }

}

View Code

　2-4.logoutservlet.java后台退出逻辑处理：

package com.java.gwb.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.json.JSONObject;

public class logoutservlet extends HttpServlet {


    private static final long serialVersionUID = 1L;

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String sessionid = request.getParameter("sessionId");
        ServletContext application = request.getSession().getServletContext();
        boolean logout = false;
        JSONObject json = new JSONObject();
        try{
            application.removeAttribute(sessionid);
            logout = true;
        }catch (Exception e) {
            System.out.println("下线失败"); 
        }
        json.accumulate("logout", logout);
        out.write(json.toString());
        out.flush();
        out.close();
    }

}

View Code

　2-5.web.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <display-name></display-name>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>loginservlet</servlet-name>
    <servlet-class>com.java.gwb.servlet.loginservlet</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>logoutservlet</servlet-name>
    <servlet-class>com.java.gwb.servlet.logoutservlet</servlet-class>
  </servlet>


  <servlet-mapping>
    <servlet-name>loginservlet</servlet-name>
    <url-pattern>/loginservlet</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>logoutservlet</servlet-name>
    <url-pattern>/logout</url-pattern>
  </servlet-mapping>    
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>