NHibernate 2 Annotations: only 1st GeneratorAttribute used

rcasha · **Joined:** Wed Oct 25, 2006 8:45 am **Posts:** 9

I tried posting a bug report on jira but jira currently has its own bugs :)

I have a simple program with 2 classes which use annotations. Both have an [Id] property with [Generator] annotation, however, when I called Serialize(Assembly) only the first one gets the <generator> element in the generated xml.

I tried investigating further, and if I call Serialize(Type) for each class in turn, the same happens - whichever class gets serialized serialized first gets the <generator> element, and the second does not.

I tried this with both the beta1 and svn versions. The classes have a simple structure as follows:

Code:

[Class]
public class Department : BaseRow
{
    private int _ID;
    [Id(Column = "dept_pk", Name="ID", UnsavedValue = "0")]
    [Generator(Class = "native")]
    public override int ID
    {
        get { return this._ID; }
        set { this._ID = value; }
    }

    private string _Name;
    [Property(Column="dept_name")]
    public virtual string Name
    {
        get { return this._Name; }
        set { this._Name = value; }
    }

    public override string Label
    {
        get { return Name; }
    }
}

rcasha · **Joined:** Wed Oct 25, 2006 8:45 am **Posts:** 9

It seems that the cause of this error is related to the default constructors of IdAttribute and GeneratorAttribute (and probably others). These both set the _position variable in BaseAttribute to zero. When the HbmWriter class calls GetSortedAttributes(member), the positions are identical so the order could be anything, which means the IdAttribute could come AFTER the GeneratorAttribute, causing it not to be written.

KPixel · **Posted:** Fri Oct 27, 2006 8:59 am

Solution:

Code:

[Id(...)]
[Generator(1, ...)]

Please, read the documentation.

rcasha · **Joined:** Wed Oct 25, 2006 8:45 am **Posts:** 9

KPixel wrote:

Solution:

Code:

[Id(...)]
[Generator(1, ...)]

Please, read the documentation.

Thanks, it worked. But... what documentation? The NHibernate reference doesn't say much about annotations. Is there some other document somewhere which I missed?

KPixel · **Posted:** Sat Oct 28, 2006 5:17 pm

The documentation coming with NHibernate has a section about NHibernate.Mapping.Attributes.

Here is the online version, note that it is for the version 1.0.2. For the v1.2.0.Beta1, read the one coming with NHibernate.

Here is the link to all NHibernate-related documentation (Don't miss the NHibernate Resources). :)

steinard · **Posted:** Thu Jan 04, 2007 10:31 am

First of all I would like to say that I really like the NHibernate project and I enjoy developing with nHibernate (and spring.net). Being able to automate, build and update the database based on my annotations of my domain classes is very cool, and a major time saviour. Although I find the nHibernate documentation to be fairly good, I must say that the documentation of annotations is very poor, if not almost lacking. The examples I have found (and I have searched the last 6th months or so, and also looked at the content provided by the links above) only covers the very basics, not the more difficult many-to-many and one-to-many mappings for a variety of collections.

To be honest, I find this documentation to be extremly incomplete. The nHibernate resouces does not help much either as almost all examples everywhere use hbm.xml files or if they use annotations, the examples are almost always very basic. The hbm.xml syntax is quite different from the annotation's syntax. Currently I am trying to decipher the nhibernate.annotations.test whenever I wonder how to map something. Have a look at the very intuitive classes!

Creating tests and examples this way is not very fruitful. I cannot understand why anyone would cook up something like this anyway. It is extremly difficult to get anything out of the tests. Why not explain the usages of annotations similar to the java documentation found here?

I would gladly write a chapter on how to use annotations if I only knew more about how to use them. Currently I get by using:

This is of course not enough, I would like to use many more, but I haven't been successful in applying lists, maps or collections in my one-to-many or many-to-many mappings so far (and due to time constraints I haven't had time to investigate what I've specified wrong either, using bag solved the problem there and then...). I hope to see the annotations better documented in the future!

KPixel · **Posted:** Thu Jan 04, 2007 11:28 am

I agree that its documentation could be much better. However, I don't have time to work on it now...

I would be grateful if you could write something to improve the current one. And you can use Hibernate Annotations documentation as a source of inspiration :)

Let me know if I can help you in any way.

Note that using NHibernate.Mapping.Attributes is just like using XML mapping. If you can write a mapping using XML, you can easily convert it in attributes (just make sure that you correctly set the positions).

steinard · **Posted:** Fri Jan 05, 2007 5:03 am

Hi!

Sure, I will try to write a few simple pono classes, use as many different kinds of annotations as possible and start writing a corresponding documentation with code excerpt. If you like I can bundle a very simple test-app (that you could put in your EG project), that can be downloaded and played with as well.

Where do you want this documentation to reside? Maybe Here, as you would probably like to modify, supply, extend and update it?

I think it might be smart to use the Hibernate Annotation documentation for inspiration as it might ease and speed up the work of producing the documentation. What do you think, email me at: steinar.dragsnes (at) gmail.com