JavaWeb学习笔记——案例：用户登录

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，day14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

开发步骤：
1. 创建项目，导入html页面，配置文件，jar包

2. 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
);

3. 创建包domain,创建类User

package 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 + '\'' +
                '}';
    }
}

4.创建包dao,创建类UserDao,提供login方法

package dao;

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

/*
* 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());

    /**
     * 登陆方法
     * @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){
        //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.class),
                loginUser.getUsername(), loginUser.getPassword());

        return user;
    }
}

5. 创建包util,编写工具类JDBCUtils

package util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

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

/**
 * JDBC工具类 使用Durid连接池
 */
public class JDBCUtils {

    private static DataSource ds ;

    static {

        try {
            //1.加载配置文件
            Properties pro = new Properties();
            //使用ClassLoader加载配置文件，获取字节输入流
            InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
            pro.load(is);

            //2.初始化连接池对象
            ds = DruidDataSourceFactory.createDataSource(pro);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }


    }

    /**
     * 获取连接池对象
     */
    public static DataSource getDataSource(){
        return ds;
    }

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

6. 编写web.servlet.LoginServlet类

package web.servlet;

import dao.UserDao;
import domain.User;

import javax.jws.soap.SOAPBinding;
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.setUsername(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){
            //登陆失败
            req.getRequestDispatcher("failServlet").forward(req,resp);
        }else {
            //登录成功
            //存储
            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);
    }
}

7. 编写FailServlet和SuccessServlet类

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

9. BeanUtils工具类，简化数据封装