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JavaWeb实现登录

更新时间:2021-12-07 10:30:20 来源:动力节点 浏览674次

JavaWeb中要怎么实现登录功能呢?小编来告诉大家。

1.项目说明

本项目实现了登录功能。点击首页的“我要登录”链接跳转到登录页面。在登录页面,输入用户名和密码,点击登录,提交给LoginServlet处理。查询数据库表中的数据。如果用户名和密码正确,会跳转到登录成功页面;如果用户名或密码错误,请求将被转发到登录页面。

2.开发环境

开发工具:spring-tool-suite-4

数据库:Mysql

服务器:tomcat7

jdk:1.8

3.数据库的结构和数据

/*
Navicat MySQL Data Transfer
Source Server         : localhost
Source Server Version : 50716
Source Host           : localhost:3306
Source Database       : test
Target Server Type    : MYSQL
Target Server Version : 50716
File Encoding         : 65001
Date: 2020-07-30 10:28:07
*/
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for users
-- ----------------------------
DROP TABLE IF EXISTS `users`;
CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(100) NOT NULL,
  `password` varchar(100) NOT NULL,
  `email` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of users
-- ----------------------------
INSERT INTO `users` VALUES ('1', 'admin', '123456', 'admin@atguigu.com');

4.项目实施

(1)在bean包中,我们实现了User实体类,定义了User对象的私有成员变量,封装了get和set方法,构造了带参数和不带参数的方法,重写了toString方法

package com.atguigu.bean;
public class User {    
    private int id;
    private String username;
    private String password;
    private String email;    
    public User() {
        super();
    }
    public User(int id, String username, String password, String email) {
        super();
        this.id = id;
        this.username = username;
        this.password = password;
        this.email = email;
    }
    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 getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", password=" + password + ", email=" + email + "]";
    }
}

(2)在dao包中定义了User dao接口,使用User daoimpl类继承该接口,重写了接口中的checkUsernameAndPassword方法。该方法可以根据用户名和密码查询数据库中的相应记录。如果是,则返回一个 User 对象;否则返回 null

用户道接口代码如下

package com.atguigu.dao;
import com.atguigu.bean.User;
public interface UserDao {
    /**
     * Query the corresponding records in the database according to the user name and password
     * @param username
     * @param Password
     * @return User This record is null, but there is no such record
     */
    User checkUsernameAndPassword(String username,String Password);
}

UserDaoImpl 代码如下

package com.atguigu.dao.impl;
import com.atguigu.bean.User;
import com.atguigu.dao.BasicDao;
import com.atguigu.dao.UserDao;
public class UserDaoImpl implements UserDao {
    //establish BasicDao object
    BasicDao basicDao = new BasicDao();    
    @Override
    public User checkUsernameAndPassword(String username, String password) {
        //write sql sentence
        String sql = "select id,username,password,email from users where username = ? and password = ?";
        User user = basicDao.getBean(User.class, sql, username,password);
        return user;
    }
}

BasicDao 类提供了用于添加、删除、修改和查询数据库的 Dao。代码如下

package com.atguigu.dao;
import java.sql.Connection;
import java.sql.SQLException;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import com.atguigu.utils.JDBCUtils;
public class BasicDao {
    /*
     * Dao is provided to add, delete and modify the database
     */    
    private QueryRunner queryRunner = new QueryRunner();    
    /**
     * General method of adding, deleting and modifying
     * @param sql
     * @param params
     * @return
     */
    public int update(String sql,Object... params) {
        //Get connection
        Connection connection = JDBCUtils.getConnection();
        int count = 0;
        try {
            count = queryRunner.update(connection, sql, params);
        }catch(SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtils.releaseConnection(connection);
        }
        return count;
    }    
    /**
     * Method to get an object
     * @param <T>
     * @param type
     * @param sql
     * @param params
     * @return
     */
    public <T> T getBean(Class<T> type,String sql,Object... params) {
        //Get connection
        Connection connection = JDBCUtils.getConnection();
        T t = null;
        try {
            t = queryRunner.query(connection, sql, new BeanHandler<T>(type), params);
        }catch(SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtils.releaseConnection(connection);
        }
        return t;
    }
}

(3)在servlet包下定义了一个servlet,LoginServlet。doGet 和 doPost 方法用于处理用户登录请求

package com.atguigu.servlet;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.atguigu.bean.User;
import com.atguigu.dao.UserDao;
import com.atguigu.dao.impl.UserDaoImpl;
/**
 * Servlet s that handle user login
 */
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;   
    public LoginServlet() {
        super();
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //Get user name and password
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //establish UserDao object
        UserDao userDao = new UserDaoImpl();
        //call UserDao The password and user name verification method
        User user = userDao.checkUsernameAndPassword(username, password);
        if(user != null) {
            //The user name and password are correct
            response.sendRedirect(request.getContextPath()+"/pages/login_success.html");
        }else {
            //Username or password incorrect 
            //Get transponder
            RequestDispatcher requestDispatcher = request.getRequestDispatcher("/pages/login.html");
            //Forward request
            requestDispatcher.forward(request, response);
        }
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

(4) 测试包,负责单元测试

ConnectionTest 类测试数据库是否连接成功

package com.atguigu.test;
import java.sql.Connection;
import org.junit.jupiter.api.Test;
import com.atguigu.utils.JDBCUtils;
class ConnectionTest {
    @Test
    void test() {
        Connection connection = JDBCUtils.getConnection();
        System.out.println(connection);
    }
}

UserdaoTest类测试UserDao接口的方法是否可以实现

package com.atguigu.test;
import org.junit.jupiter.api.Test;
import com.atguigu.bean.User;
import com.atguigu.dao.UserDao;
import com.atguigu.dao.impl.UserDaoImpl;
class UserDaoTest {
    UserDao userDao = new UserDaoImpl();   
    @Test
    void testCheckUsernameAndPassword() {
        User user = userDao.checkUsernameAndPassword("admin", "123456");
        System.out.println(user);
    }
}

(5)utils包下定义了JDBC utils工具类,用于获取和释放Connection连接

package com.atguigu.utils;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
import javax.sql.DataSource;
import com.alibaba.druid.pool.DruidDataSourceFactory;
/*
 * Tool class for getting and releasing connections
 */
public class JDBCUtils {
    private static DataSource dataSource;    
    static {
        try {
            //1,read druid.properties file
            Properties pro = new Properties();
            pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));            
            //2,Connection pool
            dataSource = DruidDataSourceFactory.createDataSource(pro);
        }catch(Exception e) {
            e.printStackTrace();
        }
    }    
    //Get connection
    public static Connection getConnection() {
        Connection connection = null;
        try {
            connection = dataSource.getConnection();
        }catch(SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }    
    //Release the connection
    public static void releaseConnection(Connection connection) {
        if(connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

(6)在config源文件中,定义druid配置文件,配置数据库连接池的相关属性

# key=value
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?rewriteBatchedStatements=true
username=root
password=root
initialSize=10
minIdle=5
maxActive=20
maxWait=5000

(7)jar包说明:对应的jar包可以从maven中央仓库下载,复制到WEB-INF下的lib文件夹下

(8)首页说明

索引,html页面代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<!-- base In the label href Property makes the relative path in the current page an absolute path -->
<base href="http://localhost:8080/Web_Ex/">
</head>
<body>
    <!-- 
        with / The first path is the absolute path
        In absolute path / What does it stand for
            If the path is resolved by the browser, then / On behalf of http://localhost:8080/
            Which paths are resolved by the browser?
                1)HTML The path in the label, such as a In the label href The path in the property, form In the label action Path in attribute, etc
                2)Paths in redirection
            If the path is resolved by the server, then / On behalf of http://localhost:8080/Web_Ex/
            Which paths are resolved by the server?
                1)web.xml In the configuration file url-pattern Path in label
                2)Path in forwarding
     -->
    <a href="pages/login.html">I want to log in</a><br><br>
    <a href="#">I want to register</a>
</body>
</html>

login.html 页面代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style type="text/css">
    body{
        background-color: pink;
    }
</style>
<!-- base In the label href Property makes the relative path in the current page an absolute path -->
<base href="http://localhost:8080/Web_Ex/">
</head>
<body>
    <h1>Welcome to login</h1>
    <form action="LoginServlet" method="post">
        User name:<input type="text" name="username" /><br>
        User password:<input type="password" name="password" /><br>
        <input type="submit" value="Sign in">
    </form>
</body>
</html>

login_success.html 代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<!-- base In the label href Property makes the relative path in the current page an absolute path -->
<base href="http://localhost:8080/Web_Ex/">
</head>
<body>
    <h1>Login successful</h1>
    <a href="index.html">Home </a>
</body>
</html>

 

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