登录之JavaWeb

来源：互联网发布：香水时代的淘宝店怎么编辑：程序博客网时间：2024/06/05 20:10

开始，话不多说，直接上代码：

数据库：

数据库名为:db_login

表名为：t_user

注意：我用的MySql

前端代码：

<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>登录界面</title>
</head>
<body>
   <div align="center" style="padding-top: 50px;">
       <form action="login" method="post">
           <table>
               <tr>
                   <td>账号:</td>
                   <td><input type="text" name="userName" id="userName"/></td>
               </tr>
               <tr>
                   <td>密码:</td>
                   <td><input type="password" name="password" id="password"/></td>
               </tr>
               <tr>
                   <td><input type="submit" value="登录"/></td>
                   <font color="red">${error }</font>
               </tr>
           </table>
       </form>
   </div>
</body>
</html>

效果如下图：

main.jsp:

后台代码:

User.java

package model;

public class User {

   private int id;
   private String userName;
   private String passowrd;

   public User(String userName, String passowrd) {
       super();
       this.userName = userName;
       this.passowrd = passowrd;
   }

   public User() {
       super();
       // TODO Auto-generated constructor stub
   }

   public int getId() {
       return id;
   }
   public void setId(int id) {
       this.id = id;
   }
   public String getUserName() {
       return userName;
   }
   public void setUserName(String userName) {
       this.userName = userName;
   }
   public String getPassowrd() {
       return passowrd;
   }
   public void setPassowrd(String passowrd) {
       this.passowrd = passowrd;
   }

}

UserDao.java

package dao;

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

import model.User;

public class UserDao {

   public User userLogin(Connection con,User user)throws Exception{
       User resultUser=null;
       String sql="select * from t_user where userName=? and password=?";
       PreparedStatement pstmt=con.prepareStatement(sql);
       pstmt.setString(1, user.getUserName());
       pstmt.setString(2, user.getPassowrd());
       ResultSet rs=pstmt.executeQuery();
       if(rs.next()){
           resultUser=new User();
           resultUser.setUserName(rs.getString("userName"));
           resultUser.setPassowrd(rs.getString("password"));
       }
       return resultUser;
   }
}

DbUtil.java(注意：连接数据库记住导入相对应的jar包)

package util;

import java.sql.Connection;
import java.sql.DriverManager;

public class DbUtil {

   //数据库地址
   private String dbUrl="jdbc:mysql://localhost:3306/db_login";
   //账号
   private String userName="root";
   //密码
   private String password="123456";
   //驱动
   private String jdbcName="com.mysql.jdbc.Driver";

   //连接数据库
   public Connection getCon() throws Exception{
       Class.forName(jdbcName);
       Connection con=DriverManager.getConnection(dbUrl,userName,password);
       return con;
   }

   //关闭数据库
   public void closeCon(Connection con)throws Exception{
       if(con!=null){
           con.close();
       }
   }

   //测试
   public static void main(String[] args) {
       DbUtil dbUtil=new DbUtil();
       Connection con=null;
       try {
           //连接数据库
           con=dbUtil.getCon();
           System.out.println("连接数据库成功");
       } catch (Exception e) {
           e.printStackTrace();
       }finally{
           try {
               //关闭数据库
               dbUtil.closeCon(con);
               System.out.println("关闭数据库成功");
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }
}

LoginServlet.java

package web;

import java.io.IOException;
import java.sql.Connection;

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

import dao.UserDao;
import model.User;
import util.DbUtil;

public class LoginServlet extends HttpServlet{

   /**
   *
   */
   private static final long serialVersionUID = 1L;

   DbUtil dbUtil=new DbUtil();
   UserDao userDao=new UserDao();

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

   @Override
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       String userName=request.getParameter("userName");
       String password=request.getParameter("password");
       User user=new User(userName,password);
       Connection con=null;
       try {
           //连接数据库
           con=dbUtil.getCon();
           User currentUser=userDao.userLogin(con, user);
           if(currentUser==null){
               request.setAttribute("error", "账号或密码错误");
               request.getRequestDispatcher("login.jsp").forward(request, response);
           }else{
               request.getRequestDispatcher("main.jsp").forward(request, response);
           }
       } catch (Exception e) {
           e.printStackTrace();
       }finally{
           try {
               //关闭数据库
               dbUtil.closeCon(con);
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }

}

注意：写了Servlet要配置web.xml文件

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_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>Login</display-name>
<welcome-file-list>
    <welcome-file>login.jsp</welcome-file>
</welcome-file-list>

<servlet>
   <servlet-name>loginServlet</servlet-name>
   <servlet-class>web.LoginServlet</servlet-class>
</servlet>

<servlet-mapping>
   <servlet-name>loginServlet</servlet-name>
   <url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>

上一张项目图：

注意：大家写代码的时候一定要仔细，我在写连接数据库代码的时候写错了代码，导致报异常，找了好久才发现是自己不仔细，如下图：

运行项目效果如下图：

先输入账号和密码，然后点击登录：

输入账号或者密码会提示，效果见下图：

账号和密码正确就会跳到另外一个页面：

好了整个项目到这就结束了，如果大家发现有错误，请指正，谢谢！

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