Inheritance joined-subclass foreign-key/identity column same

xposure · **Joined:** Thu May 15, 2008 10:51 pm **Posts:** 8

I've tried playing with this extensively. I've tried searching google and can't seem to find anything pointing how to do this.

Scenario is i have a class A with a ID, class B extends class A... simple inheritance. In the database class A is a seperate table as class B... A has a auto generated ID... B has a foreign key value ID pointing to A

If i remove the joined-subclass and make Character a property of Player instead of it being inherited i have no problems at all and i can get it to work just fine. I decided i didn't want that design and i want player to inherit character... but character will be inherited from other things as well like NPC class etc...

EDIT: I wanted to point out that if i added another field to the Player table and call it say ID2 and marked it as a identity column, then change the xml to reflect it, i still get the same dupe/key error. So it doesn't have anything to do with both xml files containing a ID field...

heres the code illustrating it.

Hibernate version: 2.0.0.Alpha1

Mapping documents:

Character.hbm.xml

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                  assembly="Convergence.Libraries.Core"
                  namespace="Convergence.Libraries.Core.Entities">

  <class name="Character" table="Character">
    <id name="ID" column="ID" type="Int64">      
      <generator class="identity"/>
    </id>
    
    <property name="Name" type="String" length="50" column="Name"/>
    <property name="Health" type="Int32" column="Health"/>
  </class>
  
</hibernate-mapping>

Player.hbm.xml

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                  assembly="Convergence.Libraries.Core"
                  namespace="Convergence.Libraries.Core.Entities">

  <class name="Player" table="Player" lazy="false">
    <id name="ID" column="ID" type="Int64">
      <generator class="assigned"/>
    </id>

    <property  name="Password" type="String" length="50" column="Password" not-null="true" />

    <joined-subclass name="Character" table="Character">
      <key column="ID"/>
    </joined-subclass>
  </class>
</hibernate-mapping>

Character.cs

Code:

namespace Convergence.Libraries.Core.Entities
{
    public class Character
    {
        public Character() { }
        public Character(string name) 
        {
            Name = name;
        }

        public virtual long ID { get; private set; }
        public virtual string Name { get; private set; }
        public virtual string Health { get; private set; }

    }
}

Player.cs

Code:

using NHibernate;

namespace Convergence.Libraries.Core.Entities
{
    public class Player : Character
    {
        public virtual string Password { get; set; }

        public static Player GetById(long id)
        {
            using (ISession session = Database.GetSession())
                return session.Load<Player>(id);
        }

        public static void Save(Player p)
        {
            using (ISession session = Database.GetSession())
                Save(p, session);
        }

        public static void Save(Player p, ISession session)
        {
            session.Save(p);
        }
    }
}

Full stack trace of any exception that occurs:
Failure line

Code:

cfg.AddAssembly("Convergence.Libraries.Core"); //Could not compile the mapping document: Convergence.Libraries.Core.Entities.Character.hbm.xml

Error (Inner Exception)

Code:

NHibernate.DuplicateMappingException: Duplicate class/entity mapping Convergence.Libraries.Core.Entities.Character
   at NHibernate.Cfg.Mappings.AddClass(PersistentClass persistentClass)
   at NHibernate.Cfg.XmlHbmBinding.RootClassBinder.Bind(XmlNode node, HbmClass classSchema)
   at NHibernate.Cfg.XmlHbmBinding.MappingRootBinder.AddRootClasses(XmlNode parentNode)
   at NHibernate.Cfg.XmlHbmBinding.MappingRootBinder.Bind(XmlNode node)
   at NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc)

Stack Trace

Code:

   at NHibernate.Cfg.Configuration.LogAndThrow(Exception exception)
   at NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc)
   at NHibernate.Cfg.Configuration.ProcessMappingsQueue()
   at NHibernate.Cfg.Configuration.AddDocumentThroughQueue(NamedXmlDocument document)
   at NHibernate.Cfg.Configuration.AddXmlReader(XmlReader hbmReader, String name)
   at NHibernate.Cfg.Configuration.AddInputStream(Stream xmlInputStream, String name)
   at NHibernate.Cfg.Configuration.AddResource(String path, Assembly assembly)
   at NHibernate.Cfg.Configuration.AddAssembly(Assembly assembly)
   at NHibernate.Cfg.Configuration.AddAssembly(String assemblyName)
   at Convergence.Libraries.Core.Database.Initialize() in D:\\source\\.NET\\Convergence\\Libraries\\Convergence.Libraries.Framework\\Database.cs:line 30

Name and version of the database you are using: MSSQL 2005

wolli · **Posted:** Fri May 16, 2008 2:54 am

I didn't use this strategy before, but as far as I understood the documentation and the samples, the subclass mapping is not specified as its own mapping and another id mapping makes no sense, since the class already has an inherited id. Try the following:

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                  assembly="Convergence.Libraries.Core"
                  namespace="Convergence.Libraries.Core.Entities">

  <class name="Player" table="Player" lazy="false">
    <id name="ID" column="ID" type="Int64">
      <generator class="assigned"/>
    </id>

    <property  name="Password" type="String" length="50" column="Password" not-null="true" />

    <joined-subclass name="Character" table="Character">
      <key column="ID"/>

      <property name="Name" type="String" length="50" column="Name"/>
      <property name="Health" type="Int32" column="Health"/> 

    </joined-subclass>

  </class>
</hibernate-mapping>

xposure · **Joined:** Thu May 15, 2008 10:51 pm **Posts:** 8

Well trying your xml i now get a weird error...

Could not find a getter for property 'Password' in class 'Convergence.Libraries.Core.Entities.Character'

Why is it looking for a getter on the character class rather then the Player class where it is defined..

Also if i didn't remove the character xml from being an embedded resource then i would still get the dupe/key error. So my guess is that its nothing to do with the IDs but it trying to make another "Character" class and insert it into a dictionary of some sort (presume a cache of the proxy or reflected schema?)

This is what i'm trying to accomplish...

Code:

public interface IEntity
{
    long ID{get;set;}
}

public class Entity1 : IEntity
{
    public long ID {get;set;}
    public string Name {get;set;}
}

public class Entity2 : IEntity
{
    public long ID {get;set;}
    public string SomeOtherName{get;set;}
}

Table - Entities
bigint - ID - identity - not null

Table - Entity1
bigint - ID - foreign-key (Entities.ID) - not null
string - Name - not null

Table - Entity2
bigint - ID - foreign-key (Entities.ID) - not null
string - SomeOtherName - not null

As you can see that the entity interface has a identity id, but the inherited class 1 and 2 have a foreign-key to that identity column... It only makes sense to describe IEntity in xml, then describe Entity1 and 2 in their own xml file, if not you going to have to change Entity files (1,2) every time the schema changes on IEntity.

heres the xml i used for the new error

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                  assembly="Convergence.Libraries.Core"
                  namespace="Convergence.Libraries.Core.Entities">
  <class name="Player" table="Player" lazy="false">
    <id name="ID" column="ID" type="Int64">
      <generator class="assigned"/>
    </id>

    <property  name="Password" type="String" length="50" column="Password" not-null="true" />

    <joined-subclass name="Character" table="Character">
      <key column="ID"/>

      <property name="Name" type="String" length="50" column="Name"/>
      <property name="Health" type="Int32" column="Health"/>

    </joined-subclass>

  </class>
</hibernate-mapping>

wolli · **Posted:** Fri May 16, 2008 9:21 am

Quote:

Also if i didn't remove the character xml from being an embedded resource then i would still get the dupe/key error. So my guess is that its nothing to do with the IDs but it trying to make another "Character" class and insert it into a dictionary of some sort (presume a cache of the proxy or reflected schema

Yes, you have to remove the Character.hbm.xml, because you already defined that class in the other mapping file.

Quote:

As you can see that the entity interface has a identity id, but the inherited class 1 and 2 have a foreign-key to that identity column... It only makes sense to describe IEntity in xml, then describe Entity1 and 2 in their own xml file, if not you going to have to change Entity files (1,2) every time the schema changes on IEntity.

If your interface only consists of the Id, then I would use a table-per-subclass strategy instead of the joined-subclass strategy. Besides that, you can define the <joined-subclass> in a separate hbm.xml file.

Quote:

Could not find a getter for property 'Password' in class 'Convergence.Libraries.Core.Entities.Character'

Do you still get this exception after removing the Character class mapping ?

xposure · **Joined:** Thu May 15, 2008 10:51 pm **Posts:** 8

Yes, that error is coming without the character xml file.

I guess i'm going to have to go back and look at some more tutorials...

I'm just trying to accomplish the following...

IEntity.hbm.xml

Code:

<xml>
  <identity ID>
</xml>

Entity1.hbm.xml

Code:

<xml>
  <foreign-key Entity_ID=IEntity.ID/>
  <name/>
  <subclass IEntity/>
</xml>

Entity2.hbm.xml

Code:

<xml>
  <foreign-key Entity_ID=IEntity.ID/>
  <SomeOtherName/>
  <subclass IEntity/>
</xml>

Is this possible in the first place? I don't want to have to redefine IEntity in each child entity file, it should be able to pull the information from the IEntity.hbm.xml file. In the end IEntity is going to be rather huge so it would make it a nightmare to managed it any other way.

wolli · **Posted:** Fri May 16, 2008 10:13 am

Yes, you can:

IEntity.hbm.xml

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                  assembly="Convergence.Libraries.Core"
                  namespace="Convergence.Libraries.Core.Entities">
  <class name="Player" table="Player" lazy="false">
    <id name="ID" column="ID" type="Int64">
      <generator class="assigned"/>
    </id>
    <property  name="Password" type="String" length="50" column="Password" not-null="true" />
</hibernate-mapping>

Entity1.hbm.xml

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                  assembly="Convergence.Libraries.Core"
                  namespace="Convergence.Libraries.Core.Entities">
    <joined-subclass name="Character" table="Character">
      <key column="ID"/>

      <property name="Name" type="String" length="50" column="Name"/>
      <property name="Health" type="Int32" column="Health"/>
    </joined-subclass>
  </class>
</hibernate-mapping>

For the exception, post your current mapping file(s).

xposure · **Joined:** Thu May 15, 2008 10:51 pm **Posts:** 8

I did.. its what you originally suggested and i reposted it in my 2nd post.

As for your reply... what about Entity2 and am i seeing that correctly that there is missing opening and closing xml tags?

Code:

<?xml version="1.0" encoding="utf-8" ?> 
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" 
                  assembly="Convergence.Libraries.Core" 
                  namespace="Convergence.Libraries.Core.Entities"> 
  <class name="Player" table="Player" lazy="false"> 
    <id name="ID" column="ID" type="Int64"> 
      <generator class="assigned"/> 
    </id> 

    <property  name="Password" type="String" length="50" column="Password" not-null="true" /> 

    <joined-subclass name="Character" table="Character"> 
      <key column="ID"/> 

      <property name="Name" type="String" length="50" column="Name"/> 
      <property name="Health" type="Int32" column="Health"/> 

    </joined-subclass> 

  </class> 
</hibernate-mapping>

This is causing the getter exception, its looking for the Password getting on the character class rather then the Player class

xposure · **Joined:** Thu May 15, 2008 10:51 pm **Posts:** 8

EDIT: Slow connection

wolli · **Posted:** Fri May 16, 2008 10:25 am

Quote:

As for your reply... what about Entity2 and am i seeing that correctly that there is missing opening and closing xml tags?

Sorry, copy&paste. </class> belongs to IEntity.

Entity2 can be defined the same way as Entity1. You just have <joined-sublass>...</joined-subclass> instead of <class>...</class> in your mapping file.

Can you post the code for Player and Character ? Just the fields and properties ?

xposure · **Joined:** Thu May 15, 2008 10:51 pm **Posts:** 8

Code:

    public class Character
    {
        public virtual long ID { get; private set; }
        public virtual string Name { get; private set; }
        public virtual string Health { get; private set; }
    }


    public class Player : Character
    {
        public virtual string Password { get; set; }
    }

Player xml

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                  assembly="Convergence.Libraries.Core"
                  namespace="Convergence.Libraries.Core.Entities">
<class name="Player" table="Player" lazy="false">
    <id name="ID" column="ID" type="Int64">
      <generator class="assigned"/>
    </id>

    <property  name="Password" type="String" length="50" column="Password" not-null="true" />

    <joined-subclass name="Character" table="Character">
      <key column="ID"/>

      <property name="Name" type="String" length="50" column="Name"/>
      <property name="Health" type="Int32" column="Health"/>

    </joined-subclass>

  </class>
</hibernate-mapping>

xposure · **Joined:** Thu May 15, 2008 10:51 pm **Posts:** 8

EDIT:

wolli · **Posted:** Fri May 16, 2008 10:47 am

Character is mapped as a subclass of Player in opposite to your class hierarchy !

xposure · **Joined:** Thu May 15, 2008 10:51 pm **Posts:** 8

You are absolutely right. I was thinking of it completely backwards for whatever reason lol... Thank you for all your help.

i swapped the xml files around to use the correct <joined-subclass/> elements and i'm on track now. Everything is tested and loading fine.

Thanks again for all your help.

I'm not sure if its documented, but i didn't see creating a seperate file with <joined-subclass> as the start tag anywhere. Just a thought for the docs.

wolli · **Posted:** Fri May 16, 2008 11:43 am

In the source distribution you can find schema definitions for hibernate. If you copy them to C:\Program Files\Microsoft Visual Studio 8\Xml\Schemas (or wherever your VS is installed), you have IntelliSense support in the xml editor. It's not like documentation, but you can easily check what is allowed.