【封装】实体类(entity)

一、ORM

ORM（Object Relational Mapping）

从数据库查询到的结果集(ResultSet)在进行遍历时，逐行遍历，取出的都是零散的数据。在实际应用开发中，我们需要将零散的数据进行封装整理

1.1 ORM 实体类(entity)：零散数据的载体

• 一行数据中，多个零散的数据进行整理
• 通过entity的规则对表中的数据进行对象的封装
• 表名=类名；列名=属性名；提供各个属性的get、set方法
• 提供无参构造方法、(视情况添加有参构造)

1.1.1 ORM应用

public class User {
    private int id;
    private String username;
    private String password;
    private String sex;
    private String email;
    private String address;
    public User(){}

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", sex='" + sex + '\'' +
                ", email='" + email + '\'' +
                ", address='" + address + '\'' +
                '}';
    }

    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;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public User(int id, String username, String password, String sex, String email, String address) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.sex = sex;
        this.email = email;
        this.address = address;
    }
}

在src目录下新建db.properties文件

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/companydb?useUnicode=true&characterEncoding=utf8
username=root
password=123456    

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class DBUtils {
   
    private static final Properties properties