案例：用户登录

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

* 分析

 

 

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

　　*添加一条数据，登录所需的用户名和密码

3. 创建包com.atwang.pojo,创建类User

package com.atwang.pojo;

/**
 * 用户的实体类
 */
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com.atwang.util,编写工具类JDBCUtils

*druid.properties

driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mytest?useSSL=true&useUnicode=true&characterEncoding=UTF-8
username=root
password=root

 

package com.atwang.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 {
//        1.加载配置文件
        try {
            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();
    }

}

5. 创建包com.atwang.dao,创建类UserDao,提供login方法

package com.atwang.dao;

import com.atwang.pojo.User;
import com.atwang.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 final 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;
        }
    }

}

 

6. 编写com.atwang.servlet.LoginServlet类

 

package com.atwang.servlet;

import com.atwang.dao.UserDao;
import com.atwang.pojo.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 {
    @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);
    }
}

7. 编写FailServlet和SuccessServlet类

package com.atwang.servlet;

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 {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //给页面写一句话

        //设置编码
        response.setContentType("text/html;charset=utf-8");
        //输出
        response.getWriter().write("登录失败，用户名或密码错误");
    }

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


}

 

package com.atwang.servlet;

import com.atwang.pojo.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 {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取request域中共享的user对象
        User user = (User) request.getAttribute("user");

        if(user != null){
            //给页面写一句话

            //设置编码
            response.setContentType("text/html;charset=utf-8");
            //输出
            response.getWriter().write("登录成功！"+user.getUsername()+",欢迎您");
        }
    }
    
}

 

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

　　* 用于封装JavaBean的
　　1. JavaBean：标准的Java类
　　　　1. 要求：
　　　　　　1. 类必须被public修饰
　　　　　　2. 必须提供空参的构造器
　　　　　　3. 成员变量必须使用private修饰
　　　　　　4. 提供公共setter和getter方法
　　　　2. 功能：封装数据

2. 概念：
　　　　成员变量：
　　　　属性：setter和getter方法截取后的产物
　　　　　　例如：getUsername() --> Username--> username

3. 方法：
　　1. setProperty()
　　2. getProperty()
3. populate(Object obj , Map map):将map集合的键值对信息，封装到对应的JavaBean对象中

所依赖的包

 <dependencies>
        
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.2.6</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>5.2.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.3.9</version>
        </dependency>
        <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.5.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.25</version>
        </dependency>
        <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>mchange-commons-java</artifactId>
            <version>0.2.19</version>
        </dependency>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.2</version>
        </dependency>


    </dependencies>

问题总结：

一定要先把所有依赖的包都部署进项目在运行，否则会出现BUG！