Java实现用户登录Demo

一、环境

工具：Idea，mysql，Jdk9

二、工程目录

三、代码编写

1、数据库表 _ user

CREATE TABLE user(
id INT,
username VARCHAR(10),
password VARCHAR(10)
);
ALTER TABLE user MODIFY id INT PRIMARY KEY AUTO_INCREMENT;
ALTER TABLE user MODIFY username VARCHAR(10) NOT NULL;
ALTER TABLE user MODIFY password VARCHAR(10) NOT NULL;

2、JDBC工具类 _ JDBCUtils

package com.mollen.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

/**
 * @ClassName:      JDBCUtils
 * @Auther:         Mollen
 * @CreateTime:     2018-09-23  10:18:14
 * @Description:    JDBCUtils 数据库连接工具类
 */
public class JDBCUtils {

    /**
     * 1.定义成员变量datasource
     */
    private static DataSource ds;

    /**
     * 2.加载数据源
     */
    static {
        try {
            Properties pro = new Properties();
            pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("Druid.properties"));
            ds = DruidDataSourceFactory.createDataSource(pro);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 3.获取连接池对象
     * @return
     */
    public static DataSource getDatasource(){
        return ds;
    }

    /**
     * 4.获取连接池Connection对象
     * @return
     * @throws SQLException
     */
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }

    /**
     * 5.释放资源
     * @param st
     * @param conn
     */
    public static void close(PreparedStatement st, Connection conn) {
        close(null, st, conn);
    }

    /**
     * 5.释放资源重载方法
     * @param rs
     * @param st
     * @param conn
     */
    public static void close(ResultSet rs, PreparedStatement st, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (st != null) {
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

3、实体类 _ User

package com.mollen.domain;

/**
 * @ClassName:      User
 * @Auther:         Mollen
 * @CreateTime:     2018-09-23  10:12:41
 * @Description:
 *                  User实体类
 */
 
public class User {

    private String userName;
    private String password;

    public User() {
    }

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

    @Override
    public String toString() {
        return "User{" +
                "userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                '}';
    }

    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;
    }
}

4、用户操作类 _ UserDao

package com.mollen.dao;

import com.mollen.domain.User;
import com.mollen.util.JDBCUtils;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

/**
 * @ClassName: 	UserDao
 * @Auther:	Mollen
 * @CreateTime: 2018-09-23  10:17:31
 * @Description: UserDao类操作user数据
 */
public class UserDao {

    private JdbcTemplate jtl = new JdbcTemplate(JDBCUtils.getDatasource());

    public User login(User loginUser) {
        try {
            String sql = "SELECT * FROM user WHERE username=? and password = ?";
            User user = jtl.queryForObject(
                    sql, new BeanPropertyRowMapper(User.class),
                    loginUser.getUserName(), loginUser.getPassword());
            return user;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }

    }
}

5、Servlet类

1.登陆Serevlet _ LoginServlet

package com.mollen.web;

import com.mollen.dao.UserDao;
import com.mollen.domain.User;

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 java.io.IOException;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       this.doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        User loginUser = new User(username,password);

        UserDao userDao = new UserDao();
        User user = userDao.login(loginUser);

        if(user==null){
            request.getRequestDispatcher("/failServlet").forward(request,response);
        }else{
            request.setAttribute("user",user);
            request.getRequestDispatcher("/successServlet").forward(request,response);
        }
    }
}

2.失败跳转Servlet类 _ FailServlet

package com.mollen.web;

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 java.io.IOException;

@WebServlet("/failServlet")
public class FailServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().write("登陆失败! 用户名或者密码错误!");
    }

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

3.成功跳转 _ ServletSuccessServlet

package com.mollen.web;

import com.mollen.domain.User;

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 java.io.IOException;

@WebServlet("/successServlet")
public class SuccessServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        User user = (User) request.getAttribute("user");
        if (user != null) {
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("登陆成功!" + user.getUserName() + ",欢迎你!");
        }
    }

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

实现效果如下：

原文：https://blog.csdn.net/mollen/article/details/82822801