SQL防止重复提交和Filter

/class User

package com.neuedu.bean;

import java.io.Serializable;

public class User implements Serializable{
    private static final long serialVersionUID = 1L;
private  int password;
   private  String name;

    public User() {
        super();
        
    }
    public User(int password, String name) {
        super();
        this.password = password;
        this.name = name;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getPassword() {
        return password;
    }
    public void setPassword(int password) {
        this.password = password;
    }
    @Override
    public String toString() {
        return "password=" + password + ", name=" + name;
    }
   
    
}

View Code

/class LoginDao

package com.neusoft.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.neuedu.bean.User;
import com.neusoft.utils.JDBCUtil;

public class LoginDao {
     public User getUser(String name,String password){
         User user=null;        
         PreparedStatement ps=null;
         ResultSet rs =null;
         Connection conn=JDBCUtil.getConnection();
         String sql="select * from t_user where password= ? and name =?";
         try {
              ps = conn.prepareStatement(sql);
              ps.setString(1, password);
              ps.setString(2, name);
              rs = ps.executeQuery();
            while (rs.next()) {
                String username = rs.getString("name");
                int password2 = rs.getInt("password");
                user=new User(password2,username);
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {            
            JDBCUtil.close(ps, rs, conn);
        }
        return user;
         
     }
     public void Add(String name,String password,String email){

         PreparedStatement ps=null;
         Connection conn=JDBCUtil.getConnection();
         String sql="insert into t_user values(?,?,?,?)";
         try {
              ps = conn.prepareStatement(sql);
              ps.setString(1, null);              
              ps.setString(2, name);
              ps.setString(3, password);
              ps.setString(4, email);
               ps.executeUpdate();
            System.out.println(ps.toString());
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {            
            
            if (ps !=null) {
                try {
                    ps.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if (conn !=null) {
                 try {
                    conn.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }     
     }
     public void Update(String name,String password,String email){

         PreparedStatement ps=null;
         Connection conn=JDBCUtil.getConnection();
         String sql="update t_user set name=?,pasword=?,mail=? where id=?";
         try {
              ps = conn.prepareStatement(sql);
              ps.setString(1, null);              
              ps.setString(2, name);
              ps.setString(3, password);
              ps.setString(4, email);
               ps.executeUpdate();
            System.out.println(ps.toString());
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {            
            
            if (ps !=null) {
                try {
                    ps.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if (conn !=null) {
                 try {
                    conn.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }     
     }
}

View Code

/class AFilter

package com.neusoft.servlet;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;


@WebFilter( "/LoginServlet" )
public class AFilter implements Filter {

   
    public void destroy() {
        // TODO Auto-generated method stub
    }

    
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("AFilter此路是我开，此树是我栽！");
        String name = request.getParameter("username");
        if (name.equals("qwe")) {
            chain.doFilter(request, response);
            System.out.println("AFilter要想从此过，留下买路财！");
        }else {
            request.getRequestDispatcher("/Login.jsp").forward(request, response);//转发
        }
        
    }

    
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

}

View Code

/class BFilter

package com.neusoft.servlet;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;


@WebFilter("/LoginServlet")
public class BFilter implements Filter {

   
    public void destroy() {
        // TODO Auto-generated method stub
    }

    
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("BFilter此路是我开，此树是我栽！");
        String psd = request.getParameter("pwd");
        if (psd.equals("123")) {
            chain.doFilter(request, response);
            System.out.println("BFilter要想从此过，留下买路财！");
        }else {
            request.getRequestDispatcher("/Login.jsp").forward(request, response);//转发
        }
        
    }

    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

}

View Code

/class LoginServlet

package com.neusoft.servlet;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

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;

import com.neuedu.bean.User;
import com.neusoft.dao.LoginDao;


@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
   
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String reqUUID = request.getParameter("uuid");
        HttpSession session = request.getSession();
        String sessUUID =(String)session.getAttribute("uuid");
        session.removeAttribute("uuid");//防止重复提交
        try {
            Thread.sleep(1000*3);//休眠3秒
        
        String name = request.getParameter("username");
        String psd = request.getParameter("pwd");
        System.out.println(name);
        User user=new LoginDao().getUser(name, psd);
        if (user !=null&&reqUUID.equals(sessUUID)) {
//            List<User>List=new ArrayList<User>();
//            List.add(user);
            request.setAttribute("user", user);
            System.out.println(user);
//            response.sendRedirect(request.getContextPath()+"/login-success.jsp");//重定向
            request.getRequestDispatcher("/login-success.jsp").forward(request, response);//转发
        }else {
            request.setAttribute("errorMsg", "不要重复提交！");
            request.getRequestDispatcher("/Login.jsp").forward(request, response);//转发
        }
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        doGet(request, response);
    }

}

View Code

/class OUTServlet

package com.neusoft.servlet;

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;
import javax.swing.JOptionPane;

@WebServlet("/OUTServlet")
public class OUTServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
   
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        session.invalidate();//清除会话，也就是清除参数
        JOptionPane.showMessageDialog(null,"您已退出，请重新登录");
        response.sendRedirect(request.getContextPath()+"/Login.jsp");//重定向
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        doGet(request, response);
    }

}

View Code

/class JDBCUtil

package com.neusoft.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCUtil {
    private static String driver="com.mysql.jdbc.Driver";
    private static String url="jdbc:mysql://localhost:3306/demo";
    private static String username="root";
    private static String password="123456";
    static{
        
        try {
            Class.forName(driver);            
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
    public static Connection getConnection(){
            try {
                return DriverManager.getConnection(url, username, password);
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                return null;
            }
        }
    
    public static void close(Statement st,ResultSet rs,Connection conn){
        if (conn !=null) {
             try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if (rs !=null) {
            try {
                rs.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if (st !=null) {
            try {
                st.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

View Code

/Login.jsp

<%@page import="java.util.UUID"%>
<%@ 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>Insert title here</title>
</head>
<body>
   <%
     String uuid=UUID.randomUUID().toString();
     session.setAttribute("uuid", uuid);
   %>
   ${errorMsg}
   <form action="${pageContext.request.contextPath}/LoginServlet" method="post">
            <input type="hidden" name="uuid" value="<%=uuid%>"/>
                   用户名：<input type="text" name="username"/>
                   密码：<input type="password" name="pwd"/>
       <input type="submit" value="提交"/>
   </form>
   <a href="Regist.html">去注册</a>
</body>
</html>

<%@page import= "com.neuedu.bean.User"%>
<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ 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>Insert title here</title>
</head>
<body>
   <table border="1" align="center" width="50%">
      <tr>
         <th>姓名 </th>
         <th>密码 </th>
         <th colspan="2"> </th>
      </tr>
      <%-- <% 
      List<User>stuList=new ArrayList<User>();
      stuList=(List<User>)request.getAttribute("stuList");
      for(int i=0;i<stuList.size();i++){
    	  User user=stuList.get(i);
    	  %> --%>
	        <tr>
	         <td><%-- <%=user.getName() %> --%>${user.name}</td>
	         <td><%-- <%=user.getPassword() %> --%>${user.password}</td>
	         <td><a href="#">修改</a></td>
	         <td><a href="#">删除</a></td>
	        </tr>
    	<%--   <%
         }
      %> --%>
      
   </table>
   <form action="${pageContext.request.contextPath}/OUTServlet" >
      <input type="submit"value="退出"/>
   </form>
</body>
</html>

　　写之前导包

相关阅读:
Javascript 创建对象的三种方法及比较【转载+整理】
Firebug Console Panel 控制台详解【转载+整理】
解剖 CPU（另）
解剖 CPU
关于 URL 编码及 JavaScript 编码函数【转载+整理】
基于用户投票的 6 个排名算法【转载+整理】
奥巴马筹款网站的制作过程【转载+整理】
CentOS 7.0关闭默认firewall防火墙启用iptables防火墙
 mybatis-generator 代码自动生成工具
 Linux中启动和停止jar包的运行
原文地址：https://www.cnblogs.com/lc-java/p/7400187.html