Mybatis nested collection doesn't work correctly with column prefix

Question

I need to set collection for object in another collection using mybatis mappings.

It works for me w/o using columnPrefix, but I need it since there are a lot of repeteable columns.

     <resultMap id="ParentMap" type="org.example.mybatis.Parent">
        <id column="Id" jdbcType="VARCHAR" property="id" />
        <result column="Name" jdbcType="VARCHAR" property="name" />
        <result column="SurName" jdbcType="VARCHAR" property="surName" />

        <collection property="childs"
        javaType="ArrayList" ofType="org.example.mybatis.Child"
        resultMap="ChildMap" columnPrefix="c_"/>       
    </resultMap>

<resultMap id="ChildMap" type="org.example.mybatis.Parent">
    <id column="Id" jdbcType="VARCHAR" property="id" />
    <result column="ParentId" jdbcType="VARCHAR" property="parentId" />
    <result column="Name" jdbcType="VARCHAR" property="name" />
    <result column="SurName" jdbcType="VARCHAR" property="surName" />
    <result column="Age" jdbcType="INTEGER" property="age" />

    <collection property="toys"
        javaType="ArrayList" ofType="org.example.mybatis.Toy"
        resultMap="ToyMap" columnPrefix="t_"/>   
</resultMap>

<resultMap id="ToyMap" type="org.example.mybatis.Toy">
    <id column="Id" jdbcType="VARCHAR" property="id" />
    <result column="ChildId" jdbcType="VARCHAR" property="childId" />
    <result column="Name" jdbcType="VARCHAR" property="name" />
    <result column="Color" jdbcType="VARCHAR" property="color" />
</resultMap>

<sql id="Parent_Column_List">
    p.Id, p.Name, p.SurName,
</sql>  

<sql id="Child_Column_List">
    c.Id as c_Id, c.ParentId as c_ParentId, c.Name as c_Name, c.SurName as c_Surname, c.Age as c_Age,
</sql>

<sql id="Toy_Column_List">
    t.Id as t_Id, t.Name as t_Name, t.Color as t_Color
</sql>  

<select id="getParent" parameterType="java.lang.String" resultMap="ParentMap" >
    select 
    <include refid="Parent_Column_List"/>
    <include refid="Child_Column_List" />
    <include refid="Toy_Column_List" />
    from Parent p

    left outer join Child c on p.Id = c.ParentId
    left outer join Toy t on c.Id = t.ChildId
    where p.id = #{id,jdbcType=VARCHAR}

With columnPrefix all works fine, but nested toys collection is empty. Sql query on database works correctly and all toys are joined.

May be i missed something or this is bug with mybatis?

Answer 1

This is my working example

<resultMap id="categoryPreferenceValueMap" type="SyncCategoryPreferenceValueModel">

         <id property="preferenceTypeId" column="preference_type_id" />
         <result property="title" column="title"/>
         <result property="index" column="type_index"/>
          <result property="updatedAt" column="category_updated_at" />


          <collection property="preferences" column="p_preference_id" ofType="SyncPreferenceModel" >
            <id property="preferenceId" column="p_preference_id" />
            <result property="title" column="p_preference_title" />
            <result property="index" column="preference_index" />
            <result property="updatedAt" column="preference_updated_at" />


            <collection property="preferenceValues" column="p_v_preference_value_id"  ofType="SyncPreferenceValueModel"  >
                <id property="preferenceValueId" column="p_v_preference_value_id" />
                <result property="preferenceValue" column="p_v_preference_value" />
                <result property="updatedAt" column="preference_value_updated_at" />

            </collection>  
         </collection>
    </resultMap>

This is my query

<select id="getPrefersenceWithValues" resultMap="categoryPreferenceValueMap">
    SELECT  
        PT.preference_type_id, PT.title, PT.type_index,PT.updated_at as  category_updated_at,
        P.preference_id as p_preference_id , P.title as p_preference_title  ,P.index as preference_index,

        P.updated_at as preference_updated_at,

        PV.preference_value_id as p_v_preference_value_id ,PV.preference_value as p_v_preference_value  

    FROM preference_types PT
    INNER JOIN preferences P ON PT.preference_type_id=P.preference_type_id 
        INNER JOIN preference_values PV ON P.preference_id=PV.preference_id 

    ORDER BY type_index

</select>

ANd OUT put is

 [
    {
      "preferenceTypeId": "1",
      "title": "abc BASICS",
      "index": "1",
      "updatedAt": 1,
      "preferences": [
        {
          "preferenceId": "1",
          "title": "xyz xyz",
          "preferenceTypeId": null,
          "gender": null,
          "index": 1,
          "updatedAt": 1,
          "preferenceValues": [
            {
              "preferenceId": null,
              "preferenceValueId": "2",
              "preferenceValue": "30-60",
              "gender": null,
              "updatedAt": 0
            },
            {
              "preferenceId": null,
              "preferenceValueId": "1",
              "preferenceValue": "0-30",
              "gender": null,
              "updatedAt": 0
            }
          ]
        }
      ]
    }
  ]

Answer 2

I had the same problem as you have. The reason for returning null is that ChildMap have a column prefix 'c_' and ToyMap's prefix is 't_', but ChildMap includes ToyMap by collection attribute. So, Actually in this case, all columns in Toy table must have a prefix 'c_t_'.

<sql id="Toy_Column_List">
    t.Id as c_t_Id, t.Name as c_t_Name, t.Color as c_t_Color
</sql>