HowTo map <many-to-one> with 2 element primary key?

alexfiftyfour · **Joined:** Mon Dec 22, 2008 6:32 pm **Posts:** 5

Hello!

Again I came across something strange.

I have a Class with two elements as primary key and

Code:

public class Class1
    {
        private int _ID1;
        private int _ID2;
        private Class1 _NextClass1Object;
        private Class1 _PrevClass1Object;

        public virtual int ID1
        {
            get { return _ID1; }
            set { _ID1 = value; }
        }
        
        public virtual int ID2
        {
            get { return _ID2; }
            set { _ID2 = value; }
        }

        public virtual Class1 NextClass1Object
        {
            get { return _NextClass1Object; }
            set { _NextClass1Object = value; }
        }

        public virtual Class1 PrevClass1Object
        {
            get { return _PrevClass1Object; }
            set { _PrevClass1Object = value; }
        }

        public override bool Equals(object obj)
        {
            return base.Equals(obj);
        }
        public override int GetHashCode()
        {
            return base.GetHashCode();
        }
    }

I mapped this class in this way:

Code:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-lazy="true" namespace="HiberTest" assembly="HiberTest">
  <class name="HiberTest.Class1,HiberTest" table="class1" lazy="false">

    <composite-id>
      <key-property name="ID1"/>
      <key-property name="ID2"/>
    </composite-id>

    <many-to-one name="NextClass1Object" class="Class1" column="NextClass1Object"/>
    <many-to-one name="PrevClass1Object" class="Class1" column="PrevClass1Object"/>
  </class>

</hibernate-mapping>

With this mapping I get an error:

Quote:

Foreign key (FK1521A76764F2E76E:class1 [NextClass1Object])) must have same number of columns as the referenced primary key (class1 [ID1, ID2])

Does someone of you know how I can fix this error?

I think I have to put somehow a two element key in one column (obviously not possible).

wolli · **Posted:** Tue Dec 30, 2008 3:10 am

You can specify more columns:

Code:

<many-to-one name="NextClass1Object" class="Class1">
    <column name="NextClass1ObjectID1"/>
    <column name="NextClass1ObjectID2"/>
</many-to-one>

alexfiftyfour · **Joined:** Mon Dec 22, 2008 6:32 pm **Posts:** 5

Hi Wolli,

thanks! This was the solution. Realy Great. :-D

Now in combination with my other post here: http://forum.hibernate.org/viewtopic.php?t=993312 it is possible to inherit from a List and give every member of this list a link to it predecessor and successor.

wolli · **Posted:** Tue Dec 30, 2008 12:35 pm

Quote:

Now in combination with my other post here: http://forum.hibernate.org/viewtopic.php?t=993312 it is possible to inherit from a List and give every member of this list a link to it predecessor and successor.

Is this a question ? As mentioned in the other post, you can't directly inherit from a list. You have to wrap it !