一、用户登录案例需求

1.编写login.html登录页面
username & password 两个输入框
2.使用Druid数据库连接池技术,操作mysql，heima数据库中user表
3.使用JdbcTemplate技术封装JDBC
4.登录成功跳转到SuccessServlet展示：登录成功！用户名,欢迎您
5.登录失败跳转到FailServlet展示：登录失败，用户名或密码错误

本案例用到了Tomcat、Servlet、druid、junit知识

二、案例分析

三、代码展示

百度网盘完整源码文件：
链接：https://pan.baidu.com/s/1_iv2zUa77pYmhV816e-WZg
提取码：0fig

下面仅为部分代码展示，完整代码请下载网盘文件。

1.案例文件目录结构

2.数据库SQL语句

CREATE DATABASE heima;
USE heima;
CREATE TABLE USER(
			
	id INT PRIMARY KEY AUTO_INCREMENT,
	username VARCHAR(32) UNIQUE NOT NULL,
	PASSWORD VARCHAR(32) NOT NULL
);

加一条测试数据

3.登录页面HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录首页</title>
</head>
<body>
    <form action="/day14_test_war_exploded/loginServlet" method="post">
        用户名:<input type="text" name="username"> <br>
        密码:<input type="password" name="password"><br>

        <input type="submit" value="登录">/day14_test_war_exploded
        test1界面
    </form>
</body>
</html>

4.druid连接池配置

注意改成自己的数据库名，以及数据库的用户密码
druid.properties文件

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///heima
username=root
password=
initialSize=5
maxActive=10
maxWait=3000

5.案例所需jar包

都在百度网盘中（web目录下的lib目录）

6.domain用户实体类

package cn.itcast.domain;

/**
 * 用户实体类
 */
public class User {
    private int id;
    private String username;
    private String password;

    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;
    }

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

7.dao层-操作数据库中User表的类

package cn.itcast.dao;

import cn.itcast.domain.User;
import cn.itcast.util.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

/**
 * 操作数据库中User表的类
 */
public class UserDao {

    //声明JDBCTemplate对象共用
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    /**
     * 登录方法
     * @param loginUser 只有用户名和密码
     * @return user包含用户全部数据,没有查询到，返回null
     */
    public User login(User loginUser){
        try {
            //1.编写sql
            String sql = "select * from user where username = ? and password = ?";
            //2.调用query方法
            User user = template.queryForObject(sql,
                    new BeanPropertyRowMapper<User>(User.class),
                    loginUser.getUsername(), loginUser.getPassword());


            return user;
        } catch (DataAccessException e) {
            e.printStackTrace();  //记录日志
            return null;
        }
    }
}

登录实现Servlet

package cn.itcast.web.servlet;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import com.sun.net.httpserver.HttpServer;

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
{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{
        //1.设置编码
        req.setCharacterEncoding("utf-8");
        //2.获取请求参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //3.封装user对象
        User loginUser = new User();
        loginUser.setUsername(username);
        loginUser.setPassword(password);

        //4.调用UserDao的login方法
        UserDao dao = new UserDao();
        User user = dao.login(loginUser);

        //5.判断user
        if(user == null){
            //登录失败
            req.getRequestDispatcher("/failServlet").forward(req,resp);
        }else{
            //登录成功
            //存储数据
            req.setAttribute("user",user);
            //转发
            req.getRequestDispatcher("/successServlet").forward(req,resp);
        }
    }


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