Mybatis(五) resultType 多表查询 (包装类)

来源：互联网发布：三维凸包算法编辑：程序博客网时间：2024/06/05 11:59

查看这张时必须有上一张的基础

这里使用了包装类，将多个表查询数来的复杂结果存储在包装类中返回回来

CREATE DATABASE my_db;CREATE TABLE user(        id INT(11) PRIMARY KEY AUTO_INCREMENT,        parentId INT(11),        sonId INT(11),        name VARCHAR(255),        birthday DATE        )DEFAULT CHARSET=utf8;CREATE TABLE `orders` (          `id` INTEGER NOT NULL AUTO_INCREMENT,          `userId` INTEGER NOT NULL,          `create` DATETIME DEFAULT NULL,          `detailId` INTEGER DEFAULT NULL,          PRIMARY KEY (`id`)        )DEFAULT CHARSET=utf8;

目录结构。
这里写图片描述

这里我新创建了：

Orders.java : Orders对象。
OrdersCustem.java: Order包装对象。（重点）
OrderDao.java : 数据接口
OrderDao.xml： mapper映射文件。（重点）

OrdersCustem对象和OrderDao 必须一一对应。

代码如下：
OrdersCustem.java:

package com.zll.mybatis.bean;import java.util.Date;public class OrderCustem extends Orders{    private String username;    private Date userBirthday;    public String getUsername() {        return username;    }    public void setUsername(String username) {        this.username = username;    }    public Date getUserBirthday() {        return userBirthday;    }    public void setUserBirthday(Date userBirthday) {        this.userBirthday = userBirthday;    }    @Override    public String toString() {        return "OrderCustem [username=" + username + ", userBirthday=" + userBirthday + ", getId()=" + getId() + ", getDetailId()=" + getDetailId() + ", getCreate()="                + getCreate() + ", getUserId()=" + getUserId() + "]";    }}

OrderDao.java :

package com.zll.mybatis.dao;import com.zll.mybatis.bean.OrderCustem;public interface OrderDao {    public List<OrderCustem> findOrderById() throws Exception;}

OrderDao.xml（重点）

<?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="com.zll.mybatis.dao.OrderDao">    <!-- 模糊查询     ${}符号表示sql使用拼接方式，这样会参数sql注入露点，所以大家要注意 -->    <select id="findOrderById" resultType="com.zll.mybatis.bean.OrderCustem">        select orders.*,user.name username,user.birthday userBirthday        from orders,user         where orders.userId = user.id;    </select></mapper>

测试代码：

/** * Unit test for simple App. */public class TestResultTypeMap extends TestCase {    SqlSessionFactory sqlSessionFactory;    @Override    protected void setUp() throws Exception {        super.setUp();        String resource = "mybatis-config.xml";        InputStream inputStream = Resources.getResourceAsStream(resource);        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);    }    public void findOrderById() throws Exception {        SqlSession openSession = sqlSessionFactory.openSession();        OrderDao mapper = openSession.getMapper(OrderDao.class);        List<OrderCustem> findOrderById = mapper.findOrderById();        for(int i=0; i<findOrderById.size(); i++){            System.out.println(findOrderById.get(i));        }        openSession.close();    }}

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