登录案例_需求&登陆案例_分析&登录案例_代码实现

案例：用户登录

• 用户登陆案例需求：
• 编写Login.html登录页面
  • username&pawword两个输入框
• 使用Druid数据库连接池技术，操作mysql，day14数据库中的user表
• 使用JdbcTemplate技术封装到JDBC
• 登录成功跳转到SuccessServlet展示：登陆成功！用户名，欢迎你
• 登陆失败跳转到FailServlet展示：登录失败，用户名或密码错误

分析：

开发步骤：

• 创建项目，导入html页面，配置文件，jar包
• 创建数据库环境

create database day14;
USE day14;

create table user(

id int primary key auto_increment,
username varchar(32) UNIQUE not null,
password varchar(32) not null

);

• 创建包domain 创建类User

package com.ailyt.domain;

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

    public void setId(int id) {
        this.id = id;
    }
    
    public void setUsername(String username) {
        this.username = username;
    }

    public void setPassword(String password) {
        this.password = password;
    }

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

    public int getId() {
        return id;
    }

    public String getUsername() {
        return username;
    }

    public String getPassword() {
        return password;
    }

    public User() {
    }

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }
}

• 创建包dao 创建类UserDao

package com.ailyt.dao;

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

/**
 * 创建数据库中User表的类
 */
public class UserDao {
    //声明JDBCTemplate对象共用
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDs());
    /**
     * 登录方法
     * @param loginUser 只用用户名和密码
     * @return user包含用户全部数据
     */
    public User login(User loginUser) {
        //编写sql
        String sql = "select * from user where username = ? and password = ?";
        //调用query方法
        User user = template.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class), loginUser.getUsername(), loginUser.getPassword());
        return user;
    }
}

• 编写servlet.LoginServlet类

package com.ailyt.servlet;

import com.ailyt.dao.UserDao;
import com.ailyt.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(value = "/loginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.设置编码
        req.setCharacterEncoding("utf8");

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

        //5.判断User
        if (user == null) {
            //登陆失败
            //转发
            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);
    }
}

• login.html中form表单的action路径的写法
  • 虚拟目录+Servlet的资源路径