【Java】servlet用户登录案例

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

项目结构
【Java】servlet用户登录案例_第1张图片

  1. 创建项目,导入html页面,配置文件,jar包
    【Java】servlet用户登录案例_第2张图片
  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
);
  1. 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;

    private String gender;

    public void setHehe(String gender){
        this.gender = gender;
    }

    public String getHehe(){
        return gender;
    }

    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 + '\'' +
                ", gender='" + gender + '\'' +
                '}';
    }
}
  1. 创建包cn.itcast.util,编写工具类JDBCUtils
package cn.itcast.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import javax.xml.crypto.Data;
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();
    }
}

上述代码读取的配置文件druid.properties的内容如下
【Java】servlet用户登录案例_第3张图片

  1. 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.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;
        }
    }
}

测试UserDao类

package cn.itcast.test;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import org.junit.Test;

public class UserDaoTest {



    @Test
    public void testLogin(){
        User loginuser = new User();
        loginuser.setUsername("superbaby");
        loginuser.setPassword("123111");


        UserDao dao = new UserDao();
        User user = dao.login(loginuser);

        System.out.println(user);
    }
}

  1. 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.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();
        //3.2使用BeanUtils封装
        try {
            BeanUtils.populate(loginUser,map);     //用 BeanUtils把存储请求参数的map封装为User对象
        } 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);
    }
}

  1. 编写FailServlet和SuccessServlet类

failServlet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 {
    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");

    }

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

SuccessServlet类

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 {
    protected void doPost(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");
        }


    }

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

  1. login.html中form表单的action路径的写法
    * 虚拟目录+Servlet的资源路径
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="/day14_test/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">

    </form>
</body>
</html>
  1. 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     这里的username成为属性
		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

要用BeanUtils需要先导入jar包
【Java】servlet用户登录案例_第4张图片
示例代码
setProperty是设置属性,而不是设置成员变量

package cn.itcast.test;

import cn.itcast.domain.User;
import org.apache.commons.beanutils.BeanUtils;
import org.testng.annotations.AfterTest;

import java.lang.reflect.InvocationTargetException;

public class BeanUtilsTest {

    @org.junit.Test
    public void test(){

        User user = new User();
        try {
            BeanUtils.setProperty(user,"hehe","male");
            System.out.println(user);

            String gender = BeanUtils.getProperty(user, "hehe");
            System.out.println(gender);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }
        
    }
}

【Java】servlet用户登录案例_第5张图片

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