023.ManyToOne对象关联查询

1.在GoodsDetail.java中添加少的一方的实体

private Goods goods;

2.在goods_detail.xml中进行对象关联的描述

<resultMap id="rmGoodsDetail" type="com.imooc.mybatis.entity.GoodsDetail">
        <id column="gd_id" property="gdId"/>
        <result column="goods_id" property="goodsId"/>
        <association property="goods" select="goods.selectById" column="goods_id"></association>
    </resultMap>
    <select id="selectManyToOne" resultMap="rmGoodsDetail">
        select * from t_goods_detail limit 0,20
    </select>

3.测试用例

/**
     * 测试多对一对象关联映射
     */
    @Test
    public void testManyToOne() throws Exception
    {
        SqlSession session = null;
        try
        {
            session = MyBatisUtils.openSession();
            List<GoodsDetail> list = session.selectList("goodsDetail.selectManyToOne");
            for (GoodsDetail gd : list)
            {
                System.out.println(gd.getGdPicUrl() + ":" + gd.getGoods().getTitle());
            }
        }
        catch (Exception e)
        {
            throw e;
        }
        finally
        {
            MyBatisUtils.closeSession(session);
        }
    }