1.xml映射类属性是其他类，javaType指定其他类 association -- 联系
<resultMap id="userResultMap" type="com.example.User">
    <id column="id" property="userId" />
    <result column="username" property="userName" />
    <result column="email" property="email" />
    
    <association property="address" javaType="com.example.Address">
        <result column="address_id" property="addressId" />
        <result column="street" property="street" />
        <result column="city" property="city" />
        <!-- 更多属性映射 -->
    </association>
    
</resultMap>

2.xml映射类属性是list，ofType指定list的泛型
<resultMap id="userResultMap" type="com.example.User">
    <id column="id" property="userId" />
    <result column="username" property="username" />
    <result column="email" property="email" />

    <collection property="orders" ofType="com.example.Order">
        <id column="order_id" property="orderId" />
        <result column="order_number" property="orderNumber" />
        <result column="order_date" property="orderDate" />
    </collection>
</resultMap>

3.xml映射类属性是map，即可以用association 又可以用collection
<resultMap id="userResultMap" type="com.example.User">
    <id column="id" property="userId" />
    <result column="username" property="username" />
    <result column="email" property="email" />

    <association property="attributes" javaType="java.util.Map">
        <result column="attribute_key" property="key" />
        <result column="attribute_value" property="value" />
    </association>

</resultMap>

<resultMap id="userResultMap" type="com.example.User">
    <id column="id" property="userId" />
    <result column="username" property="username" />
    <result column="email" property="email" />

    <collection property="attributes" ofType="java.util.HashMap">
        <result column="attribute_key" property="key" />
        <result column="attribute_value" property="value" />
    <collection/>
</resultMap>

4.另外resultMap标签还能嵌套使用
<resultMap id="userResultMap" type="com.example.User">
    <id column="id" property="userId" />
    <result column="username" property="username" />
    <result column="email" property="email" />

    <collection property="roles" ofType="com.example.Role" resultMap="roleResultMap" />
</resultMap>

<resultMap id="roleResultMap" type="com.example.Role">
    <id column="role_id" property="roleId" />
    <result column="role_name" property="roleName" />
</resultMap>