idea 配置java_home Idea 配置Dadabase自动登录

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mob6454cc70863a 2023-07-28 08:38:18

文章标签 idea 配置java_home java User 用户名 文章分类 Java 后端开发

用户登录案例需求：

1.编写login.html登陆页面

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技术封装到JDBC
4.登录成功跳转到SuccessServlet展示：登陆成功！用户名，欢迎您
5.登陆失败跳转到FailServlet展示：登陆失败，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，导入jar包 (注意：导入jar包的lib目录要添加到Library中)
2.创建数据库环境：在mysql上新建查询，创建数据库和数据表

CREATE DATABASE Login;

USE Login;

CREATE TABLE USER(
		id INT PRIMARY KEY AUTO_INCREMENT,
		username VARCHAR(32) UNIQUE NOT NULL,
		password VARCHAR(32) NOT NULL
);

3.在src目录下创建包cn.itcast.domain，创建类User

package cn.itcast.domain;

/**
 * 用户的实体类（javaBean）
 */

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.在src目录下创建包cn.itcast.util，创建JDBCUtils类，JDBC工具类，使用Durid连接池

package cn.itcast.utli;

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

5.在src目录下创建包cn.itcast.dao，创建UserDao类，提供login方法

package cn.itcast.dao;

import cn.itcast.domain.User;
import cn.itcast.utli.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());

    /**
     * 登陆方法
     * @param loginUser 只有用户名和密码
     * @return user包含用户的全部数据,若没有查询到，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.在src目录下创建包cn.itcast.test，创建UserDaoTest类,测试代码

package cn.itcast.test;

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

public class UserDaoTest {
    @Test
    public void testLogin(){
        User loginuser = new User();
        loginuser.setUsername("superman");
        loginuser.setPassword("123");

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

        System.out.println(user);
    }
}

7.运行 UserDaoTest类，输出如下：
8.编写cn.itcast.web.servlet，创LoginServlet类

package cn.itcast.web.servlet;

import cn.itcast.dao.UserDao;
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("/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){
            //登陆失败
            req.getRequestDispatcher("/failServlet").forward(req,resp);
        }else {
            //登陆成功
            //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);
    }
}

9.在cn.itcast.web.servlet下分别创建FailServlet类和SuccessServlet类,分别表示登录成功和登录失败时在页面上打印的结果。

FileServlet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("登陆失败，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("登陆成功！"+user.getUsername()+"，欢迎你");
        }
    }

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

10.启动服务器，在浏览器地址栏输入：http://localhost:8080/day14_test/login.html,跳转到登录页面，在form表单中输入正确的用户名和密码，会跳转到如下页面，输出如图：

若输入错误：

且服务器后台会抛出异常：

抛出该异常的原因是输入的用户名或密码不正确，在数据库中找不到与之对应的用户名和密码，故抛出异常。一般来说，这样的异常不会打印到控制台，都用log日志保存到文件上。
11.login.html中form表单的action路径的写法