Mybatis学习4——一对一关联查询方法1--创建实体

创建一个实体继承两个实体之一，另一个实体作为属性

实体1.

order

package pojo;

import java.util.Date;

public class Order {
    private Integer id;

    private Integer userId;

    private String number;

    private Date createtime;

    private String note;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number == null ? null : number.trim();
    }

    public Date getCreatetime() {
        return createtime;
    }

    public void setCreatetime(Date createtime) {
        this.createtime = createtime;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note == null ? null : note.trim();
    }

    @Override
    public String toString() {
        return "Order [id=" + id + ", userId=" + userId + ", number=" + number + ", createtime=" + createtime
                + ", note=" + note + "]";
    }

}

实体2user

package pojo;

import java.util.Date;

public class User {

    private Integer id;
    private String username;// 鐢ㄦ埛濮撳悕
    private String sex;// 鎬у埆
    private Date birthday;// 鐢熸棩
    private String address;// 鍦板潃
    private String uuid2;

    public String getUuid2() {
        return uuid2;
    }

    public void setUuid2(String uuid2) {
        this.uuid2 = uuid2;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getSex() {
        return sex;
    }

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

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getAddress() {
        return address;
    }

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

    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", sex=" + sex + ", birthday=" + birthday + ", address="
                + address + ", uuid2=" + uuid2 + "]";
    }

}

创建实体OrderUser

package pojo;

import java.util.Date;

public class OrderUser extends Order {
    private String username;// 鐢ㄦ埛濮撳悕
    private String address;// 鍦板潃
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    @Override
    public String toString() {
        return "OrderUser [username=" + username + ", address=" + address + ", getId()=" + getId() + ", getUserId()="
                + getUserId() + ", getNumber()=" + getNumber() + ", getCreatetime()=" + getCreatetime() + ", getNote()="
                + getNote() + "]";
    }

}

mapper文件使用

resultType

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="mapper.OrderMapper">

<!-- 引用resultMap -->
    <select id="getOrderList"  resultMap="order_List_map">
     select id,
     user_id,
     number,
     createtime,
     note
     from order1
    </select>
    <!-- 一对一关联查询 -->
    <select id="getOrderUser"  resultType="orderuser">
     select
     o.id,
     o.user_id userId,
     o.number,
     o.createtime,
     o.note,
     u.username,
     u.address
     from order1 o left join user u on u.id = o.user_id
    </select>
</mapper>

测试

@Test
    public void getOrderUser() {
        SqlSession openSession = SqlSessionFactoryUtil.getSqlSessionFactory().openSession();
        //获得接口实现类
        OrderMapper mapper = openSession.getMapper(OrderMapper.class);
        List<OrderUser> orderUser = mapper.getOrderUser();
        for (OrderUser orderUser2 : orderUser) {
            System.out.println(orderUser2);
        }
        openSession.close();
    }