self-referencing classes (unlimited refs, non-tree), ideas?

idfrisbie · **Joined:** Wed Sep 14, 2005 3:38 pm **Posts:** 5

A simple table with columns "id", and "name" are used in conjunction with a mapping table (id_to, id_from) in my application to relate one entity with one or more other entities (call them associations - like marriages). There is only one class - entity.

In SQL, i'd use two inner joins (entity->mapping->entity) to list the entities names associated with a given entity name. With Hibernate, I would like to have a Set defined within the entity class that contains a group of other entities (a references back to records in the same table).

My problem is that I can't figure out how to reflect this kind of table syntax in hibernate. My mapping table is a simple id_to, id_from structure. All examples I have seen using sets always refer to another data table, not a reference back to the originating table.

Can anyone give me a jump start and post a proposed hbm.xml file for my entity class that would persist the relationship mapping discussed above?

Thanks in advance!

Ian

kgignatyev · **Posted:** Mon Sep 19, 2005 5:43 pm

Code:

  <class table="ent" name="Ent">
    <id name="id">
       <generator class="assigned"/>
    </id>
    <property name="name"/>
    <set name="linkedObjects" table="ent_relations" >
      <key column="id1"/>
      <many-to-many class="Ent" column="id2"/>
    </set>
  </class>

Code:

public class Ent {
  private int id;
  String name;
  Set linkedObjects;

  public int getId(){
    return id;
  }

  public void setId( int id ){
    this.id = id;
  }

  public String getName(){
    return name;
  }

  public void setName( String name ){
    this.name = name;
  }

  public Set getLinkedObjects(){
    return linkedObjects;
  }

  public void setLinkedObjects( Set linkedObjects ){
    this.linkedObjects = linkedObjects;
  }
}

Code:

CREATE TABLE ent (
  id int PRIMARY KEY,
  name varchar(50)
);


CREATE TABLE ent_relations (
  id1 int,
  id2 int
);

idfrisbie · **Joined:** Wed Sep 14, 2005 3:38 pm **Posts:** 5

lol, I don't know why I couldn't see that.

thanks kg