Transform recursive join into java object

Question

Let's say I have following model

public class ExampleComment {
    private int id;
    private Integer commentOf;
    private List<ExampleComment> comments;
    ...
    getters, setters
    ...
}

And database:

id | commentOf 
1  | null 
2  | 1  
3  | 1  
4  | 2  

If I use some nasty sql procedure (which is probably not correct solution?), I still have no clue how to transfer it into java object in mybatis.

I know that when I was doing the same in .net, it was made by entity framework, so probably it should be possible to make in mybatis, but I cant find any solution on google.

Answer 1

Assuming the comments property will have all comments for which current comment is in COMMENTOF column, following should work.

Main Comment ResultMap:

<resultMap id="commentMap" type="ExampleComment">
    <id property="id" column="id" />
    <result property="commentOf" column="commentOf" />
    <collection property="comments" javaType="ArrayList" column="COMMENTOF" ofType="ExampleComment" select="selectChildComments"
</resultMap>

Select selectChildComments:

<select id="selectChildComments" resultMap="commentMap">
  SELECT ID, COMMENTOF FROM COMMENT_TABLE WHERE COMMENTOF=#{id}
</select>