mybatis快速入门

Posted 2020-10-08

今天写写user表和orders表的mybatis的高级映射,一对一映射和一对多映射

1.创建一个orders.java文件

 1.1一对一映射，一条订单对应一个用户

package cn.my.mybatis.entity;

import java.util.Date;

public class Orders {

    private int id;
    private int user_id;
    private String number;
    private Date createtime;
    private String note;
    private User user;//对应一个用户
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public int getUser_id() {
        return user_id;
    }
    public void setUser_id(int user_id) {
        this.user_id = user_id;
    }
    public String getNumber() {
        return number;
    }
    public void setNumber(String number) {
        this.number = number;
    }
    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;
    }
    public User getUser() {
        return user;
    }
    public void setUser(User user) {
        this.user = user;
    }
    @Override
    public String toString() {
        return "Orders [id=" + id + ", user_id=" + user_id + ", number=" + number + ", createtime=" + createtime
                + ", note=" + note + ", user=" + user + "]";
    }
}

1.2创建一个OrdersDaoMapper.java接口

新增一个查询方法

package cn.my.dao;

import java.util.List;

import cn.my.mybatis.entity.Orders;

public interface OrdersDaoMapper {

public List<Orders> findAll();
}

 

1.3.创建一个ordersMapper.xml映射文件

<?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="cn.my.dao.OrdersDaoMapper">
       
       <!-- 映射一对一  和前面的用户字段取别名类似-->
       <resultMap type="cn.my.mybatis.entity.Orders" id="oneOnone">
           <id column="id" property="id"/>
           <result column="user_id" property="user_id"/>
           <result column="number" property="number"/>
           <result column="createtime" property="createtime"/>
           <result column="note" property="note"/>
           
           <!-- 重点在这里，映射一对一的 -->
           <association property="user" javaType="cn.my.mybatis.entity.User">
               <id column="user_id" property="id"/>
               <result column="username" property="username"/>
               <result column="birthday" property="birthday"/>
               <result column="sex" property="sex"/>
               <result column="address" property="address"/>
           </association>
       </resultMap>
       
       <select id="findAll" resultMap="oneOnone">
           SELECT a.*,b.username,b.birthday,b.sex,b.address FROM `orders` a,`user` b WHERE a.user_id=b.id
       </select>
</mapper>

1.4.创建一个TestOrdersMapper.java文件

创建一个findAll的测试方法

package cn.my.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

import cn.my.dao.OrdersDaoMapper;
import cn.my.mybatis.entity.Orders;

public class TestOrdersMapper {
    private SqlSessionFactory factory;
    @Before
    public void setUp() throws IOException{
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        factory = new SqlSessionFactoryBuilder().build(inputStream);
    }
    
    @Test  
    public void testFindAll(){  
        SqlSession session = factory.openSession();
        OrdersDaoMapper dao = session.getMapper(OrdersDaoMapper.class);//获取mybatis的动态代码实现接口对象
        List<Orders> list = dao.findAll();
        session.close();  
        for (Orders orders : list) {
            System.out.println(orders);  
        }
    }  
}

 

以上都弄好了，最后记住一点很重要的，SqlMapConfig.xml需要引入<mapper resource="mapper/OrdersMapper.xml"/>

    <mappers>
        <mapper resource="User.xml"/>
        <mapper resource="mapper/UserMapper.xml"/>
        <mapper resource="mapper/OrdersMapper.xml"/>
    </mappers>

 

 运行结果：

Orders [id=3, user_id=1, number=1000010, createtime=Wed Feb 04 13:22:35 CST 2015, note=null, user=User [id=1, username=王五, sex=2, birthday=null, address=null]]
Orders [id=4, user_id=1, number=1000011, createtime=Tue Feb 03 13:22:41 CST 2015, note=null, user=User [id=1, username=王五, sex=2, birthday=null, address=null]]
Orders [id=5, user_id=10, number=1000012, createtime=Thu Feb 12 16:13:23 CST 2015, note=null, user=User [id=10, username=张三, sex=1, birthday=Thu Jul 10 00:00:00 CST 2014, address=北京市]]

 

2.一对多的映射，一个订单对应一个用户，一个订单对应多个详细

2.1创建一个Ordersdetail.java文件

package cn.my.mybatis.entity;

public class Ordersdetail {

    private int id;
    private int items_id;
    private int items_num;
    private int orders_id;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public int getItems_id() {
        return items_id;
    }
    public void setItems_id(int items_id) {
        this.items_id = items_id;
    }
    public int getItems_num() {
        return items_num;
    }
    public void setItems_num(int items_num) {
        this.items_num = items_num;
    }
    public int getOrders_id() {
        return orders_id;
    }
    public void setOrders_id(int orders_id) {
        this.orders_id = orders_id;
    }
    @Override
    public String toString() {
        return "Ordersdetail [id=" + id + ", items_id=" + items_id + ", items_num=" + items_num + ", orders_id="
                + orders_id + "]";
    }
}

 

2.2在ordersMapper.xml里面添加映射代码

<!-- extends="oneOnone"这里需要注意的是继承了上面的id名称为oneOnone的resultMap,
           因为这里也包含了一对一映射，所以不需要在写了直接继承过来就好了 -->
       <resultMap type="cn.my.mybatis.entity.Orders" id="DetialAll" extends="oneOnone">
           <!-- 这里就是映射list集合 -->
           <collection property="detailList" ofType="cn.my.mybatis.entity.Ordersdetail">
               <id column="ordersdetail_id" property="id"/>
               <result column="items_id" property="items_id"/>
               <result column="items_num" property="items_num"/>
               <result column="orders_id" property="orders_id"/>
           </collection>
       </resultMap>
    <!-- 一对多的映射，一个订单对应一个用户，一个订单对应多个详细 -->
       <select id="findDetialAll" resultMap="DetialAll">
           SELECT a.*,b.username,b.birthday,b.sex,b.address,c.id ordersdetail_id,c.items_id,items_num
        FROM `orders` a,`user` b,`orderdetail` c 
        WHERE a.user_id=b.id AND a.id=c.orders_id
       </select>

 

2.3在OrdersDaoMapper.java添加接口方法

 

public List<Orders> findDetialAll();

 

2.4TestOrdersMapper.java中添加测试方法

 @Test  
    public void testfindDetialAll(){  
        SqlSession session = factory.openSession();
        OrdersDaoMapper dao = session.getMapper(OrdersDaoMapper.class);//获取mybatis的动态代码实现接口对象
        List<Orders> list = dao.findDetialAll();
        session.close();  
        for (Orders orders : list) {
            System.out.println(orders);  
        }
    }  

 

测试结果：

Orders [

　　　　id=3, user_id=1, number=1000010, createtime=Wed Feb 04 13:22:35 CST 2015, note=null,

　　　　　　user=User [

　　　　　　　　　　　　id=1, username=王五, sex=2, birthday=null, address=null

　　　　　　　　　　　],

　　　　　　detailList=[

　　　　　　　　　　　　Ordersdetail [id=1, items_id=1, items_num=1, orders_id=0],

　　　　　　　　　　　　Ordersdetail [id=2, items_id=2, items_num=3, orders_id=0]

　　　　　　　　　　]

　　]
Orders [id=4, user_id=1, number=1000011, createtime=Tue Feb 03 13:22:41 CST 2015, note=null, user=User [id=1, username=王五, sex=2, birthday=null, address=null], detailList=[Ordersdetail [id=3, items_id=3, items_num=4, orders_id=0], Ordersdetail [id=4, items_id=2, items_num=3, orders_id=0]]]

 

这个mybatis高级映射就写完了，有时间我会继续往下写的，如果需要加群一起研究的可以q我，939705214，也可以添加群号581591235