2018-07-12 Mybatis的一对一关联查询

//一对一关联查询，以订单为中心 关联用户查询

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<?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">
<!-- 写Sql语句   -->
<mapper namespace="com.ryan.mybatis.pojo.OrderDao">
    

    
    <!-- public List<Order> selectOrder();
     -->
     <resultMap type="Order" id="order">
        <id column="user_id"  property="userId"/>
         <result column="id"  property="id"/>
          <result column="number"  property="number"/>
        <association property="user" javaType="User">
           <id column="user_id" property="id"/>
           <result column="username" property="username"/>
        </association>
     </resultMap>
    <select id="selectOrder" resultMap="order">
    SELECT
    o.id,
    o.user_id,
    o.number,
    o.createtime,
    u.id,
    u.username 
    FROM
    `order` o
    LEFT JOIN `USER` u ON o.user_id = u.id
    </select>
    

</mapper>

package com.ryan.mybatis.pojo;

import java.util.List;

public interface OrderDao {

    //一对一关联查询，以订单为中心 关联用户查询


public List<Order> selectOrder();

}

package com.ryan.mybatis.pojo;


import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
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.Test;



public class Test1 {
    

    @Test
    public void demo1() throws IOException {
        String resource="sqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(in);
        SqlSession sqlSession = sqlSessionFactory.openSession();                
        
        OrderDao user2=sqlSession.getMapper(OrderDao.class);
        List<Order> selectList = user2.selectOrder();
                for (Order user4 : selectList) {
            System.out.println(user4);
        }       
    }
}

package com.ryan.mybatis.pojo;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private Integer id;
    private String username;// 用户姓名
    private String sex;// 性别
    private Date birthday;// 生日
    private String address;// 地址


    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 + "]";
    }

    
    

}