案例（一）：request用户登录-阿里云开发者社区

✔ 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：

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cn.itcast.domain,创建类User

package cn.itcast.domain;
/*
   用户的实体类
 */
public class User {
    private int id ;
    private String username ;
    private String password ;
    public int getId() {
        return id;
    }
    public String getUsername() {
        return username;
    }
    public String getPassword() {
        return 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 + '\'' +
                '}';
    }
}

4. 创建包cn.itcast.util，编写工具类JDBCUtils

package cn.itcast.utils;
/*
   JDBC工具类，使用的是druid数据库连接池
 */
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;
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
            try {
                ds = DruidDataSourceFactory.createDataSource(pro);
            } catch (Exception e) {
                e.printStackTrace();
            }
        } catch (IOException 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cn.itcast.dao，创建类UserDao,提供login方法

package cn.itcast.dao;
import cn.itcast.domain.User;
import cn.itcast.utils.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,没有查询到数据，返回null
     */
    public User login(User loginUser){
        //1.编写sql
        try {
            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();
            return null ;
        }
    }
}

6. 编写cn.itcast.web.servlet.LoginServlet类

package cn.itcast.web.servlet;
import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import org.apache.commons.beanutils.BeanUtils;
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.DataOutput;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;
@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);
        //2.获取所有请求参数
        Map<String,String[]> map = req.getParameterMap();
        //3.创建User对象
        User loginuser = new User() ;
        //使用BeanUtils封装
        try {
            BeanUtils.populate(loginuser,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        //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{
            //登陆成功
            req.setAttribute("user",user);
            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 cn.itcast.web.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 req, HttpServletResponse resp) throws ServletException, IOException {
        //给页面写一句话
        //设置编码
        resp.setContentType("text/html;charset=utf-8");
        //输出
        resp.getWriter().write(" 登录失败，用户名或密码错误 ");
    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }
}

package cn.itcast.web.servlet;
import cn.itcast.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 {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取request域中共享的user对象
        User user = (User)req.getAttribute("user");
        if(user != null) {
            // 给页面写一句话
            //设置编码
            resp.setContentType("text/html;charset = utf-8");
            //输出
            resp.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

* 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

* 概念：

成员变量：

属性：setter和getter方法截取后的产物

例如：getUsername() --> Username--> username

* 方法：

setProperty()

@Test
    public void test(){
        User user = new User() ;
        try {
            BeanUtils.setProperty(user,"username","xiaochichi");
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        System.out.println(user);
    }

getProperty()

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

案例（一）：request用户登录

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