大部分現實應用中我們并不需要把數據庫中的整行數據都拉出來, 所以要做擴展結果集

筆記: 在實際項目過程中, 先用逆向工程自動生成, 然后再做擴展結果集來滿足大部分的現實需要

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本節內容應該注意擴展結果集的命名方式

創建一個擴展類ShopCustom, (這樣命名可以和Shop在項目樹里面排列在一起)

package io.github.coinsjack.pojo;public class ShopCustom extends Shop {private String shopName;private String shopDesc;public ShopCustom() {}

創建一個mapper接口 ShopMapperCustom?

package io.github.coinsjack.dao;import io.github.coinsjack.pojo.ShopCustom;public interface ShopMapperCustom {ShopCustom getShopById(Integer id);}

創建對應的映射文件

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="io.github.coinsjack.dao.ShopMapperCustom"><cache/> <resultMap id="shopResultMap" type="ShopCustom"><id column="shop_id" property="id" ></id><result column="shop_name" property="shopName"></result><result column="shop_desc" property="shopDesc"/></resultMap><select id="getShopById" parameterType="int" resultMap="shopResultMap" >select `shop_id`, `shop_name`, `shop_desc`from tb_shopwhere `shop_id` = #{id}</select> </mapper>

測試

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

結果

2018-12-29 11:33:32,656 [main] DEBUG [io.github.coinsjack.dao.ShopMapperCustom] - Cache Hit Ratio [io.github.coinsjack.dao.ShopMapperCustom]: 0.0 2018-12-29 11:33:33,128 [main] DEBUG [io.github.coinsjack.dao.ShopMapperCustom.getShopById] - ==> Preparing: select `shop_id`, `shop_name`, `shop_desc` from tb_shop where `shop_id` = ?? 2018-12-29 11:33:33,237 [main] DEBUG [io.github.coinsjack.dao.ShopMapperCustom.getShopById] - ==> Parameters: 29(Integer) 2018-12-29 11:33:33,309 [main] DEBUG [io.github.coinsjack.dao.ShopMapperCustom.getShopById] - <== Total: 1 ShopCustom{shopName='暴漫奶茶店', shopDesc='過來喝喝就知道啦，你是我的奶茶'}

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Java知識點

如果父類實現了某接口,子類也會繼承接口的實現

總結

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