Mybatis学习第22节 -- 高级结果映射 构造方法映射

Posted 2021-02-13 积水成渊

知识储备:  对于大部分编程语言的函数来说, 函数的signature是函数名和函数参数,而对于函数参数的名称, 编译器不关心.

 

为ShopCustom创建一个构造函数

public ShopCustom(Integer id, String shopName, String shopDesc) { this.id = id; this.shopName = shopName; this.shopDesc = shopDesc; }

为ShopMapperCustom添加一个新方法

public interface ShopMapperCustom { ShopCustom getShopById(Integer id); ShopCustom getShopByIdConstructor(Integer id); }

在映射文件中编写相应的配置

对于constructor的参数来说, 关心的只是要把什么内容按序填入就好了, 通过javaType来与构造函数的参数列表产生对应

<resultMap id="shopResultMapConstructor" type="ShopCustom"> <constructor> <idArg column="shop_id" javaType="int"/> <arg column="shop_name" javaType="string"/> <arg column="shop_desc" javaType="string"/> </constructor> </resultMap> <select id="getShopByIdConstructor" parameterType="int" resultMap="shopResultMapConstructor" > select `shop_id`, `shop_name`, `shop_desc` from tb_shop where `shop_id` = #{id} </select>

测试

@Test public void testGetShopByIdCustomConstructor() { SqlSession session = MyBatisUtil.getSqlSession(); ShopMapperCustom mapper = session.getMapper(ShopMapperCustom.class); System.out.println(mapper.getShopByIdConstructor(29)); session.close(); }

结果

2018-12-29 11:53:04,097 [main] DEBUG [io.github.coinsjack.dao.ShopMapperCustom] - Cache Hit Ratio [io.github.coinsjack.dao.ShopMapperCustom]: 0.0 2018-12-29 11:53:04,484 [main] DEBUG [io.github.coinsjack.dao.ShopMapperCustom.getShopByIdConstructor] - ==> Preparing: select `shop_id`, `shop_name`, `shop_desc` from tb_shop where `shop_id` = ?  2018-12-29 11:53:04,576 [main] DEBUG [io.github.coinsjack.dao.ShopMapperCustom.getShopByIdConstructor] - ==> Parameters: 29(Integer) 2018-12-29 11:53:04,649 [main] DEBUG [io.github.coinsjack.dao.ShopMapperCustom.getShopByIdConstructor] - <== Total: 1 ShopCustom{shopName=‘暴漫奶茶店‘, shopDesc=‘过来喝喝就知道啦，你是我的奶茶‘}