mybatis-config.xml ：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
    
    <!-- 讀取db.properties文件 -->
    <properties resource="db.properties" />
    <!--  全局配置參數，需要時再設置 -->
    <settings>
        <!-- 開啟全局二級緩存 -->
        <!-- <setting name="cacheEnabled" value="true" /> -->
        <!-- 開啟全局延遲加載 -->
        <setting name="lazyLoadingEnabled" value="true"/>
        <setting name="aggressiveLazyLoading" value="false"/>
    </settings>
    
    <typeAliases>
        <typeAlias type="com.Mybaits.pojo.ctAniamlPojo"
            alias
 
="ctAniaml" />
        <typeAlias type="com.Mybaits.pojo.animalPojo"
            alias="Aniaml" />  
        <typeAlias type="com.Mybaits.pojo.thirdExtendsPojo"
            alias="ThirdExtends" />
    </typeAliases>
    
    <!-- 配置數據源 -->
    <environments default="development">
        <environment id="development">
            <!-- 配置事務 -->
            <transactionManager type="JDBC" />
            <!-- 配置連接池 -->
            <dataSource type="POOLED">
                <property name="driver" value="${dataSource.driverClass}" />
                <property name="url" value="${dataSource.jdbcUrl}" />
                <property name="username" value="${dataSource.user}" />
                <property name="password" value="${dataSource.password}" />
            </dataSource>
        </environment>
    </environments>
    <!-- 映射Sql.xml文件 -->
    <mappers>
        <mapper resource="com/Mybaits/mapper/ctAniamlMapper.xml" />
        <mapper resource="com/Mybaits/mapper/animalMapper.xml" />
    </mappers>
</configuration>

SQL語句映射mapper：

<?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="com.Mybaits.mapper.animalmapperInteger">
    <!-- 嵌套查詢 -->
    <resultMap type="Aniaml" id="SelectAnimalResultMap">
        <id column="id" property="id" />
        <result column="animal" property="animal" />
        <association column="Species_id" property="ctAniaml"
            javaType
 
="ctAniaml"
            select="com.Mybaits.mapper.ctAnimalmapperInteger.SelectCtAnimalById" />
    </resultMap>
    <select id="SelectAnimalById" parameterType="int"
        resultMap="SelectAnimalResultMap">
        select *from animal where id=#{id}
    </select>

    <!-- 嵌套結果 -->
    <resultMap type="Aniaml" id="AniamlResultMapNest">
        <id column="an_id" property="id" />
        <result column="animal" property="animal" />
        <!-- <result column="Species_id" property="speciesid" /> -->
        <association column="Species_id" property="ctAniaml"
            javaType="ctAniaml">
            <id column="id" property="id" />
            <result column="species" property="species" />
        </association>
    </resultMap>
    <select id="SelectContent" resultMap="AniamlResultMapNest">
        SELECT
        a.id ,
        a.Species ,
        b.id as an_id,

        b.animal
        FROM cttable a LEFT JOIN animal b ON
        a.id=b.Species_id ORDER BY a.id
    </select>

    <!-- 擴展結果集 -->
    <resultMap type="ThirdExtends" id="SelectAnimalExtendsResultMap">
        <id column="a_id" property="Extend_id" />
        <result column="a_animal" property="animal" />
        <result column="b_species" property="species" />
       
    </resultMap>
    <select id="SelectAnimalByIdExtends" parameterType="int"
        resultMap="SelectAnimalExtendsResultMap">
        SELECT a.id as a_id,
        a.animal as a_animal,
        b.Species as b_species
        FROM animal a LEFT JOIN cttable b ON a.Species_id=b.id
        WHERE a.id=#{id};
    </select>
</mapper>

mybatis-config.xml 和 mapper基本設置