Hi there,

I'm facing a little problem when trying to map a singleton using Hibernate.
In fact, there's no way to specify a static method (like "GetInstance") to use, as Hibernate always tries to call the default entity class constructor.
Is there any solution to get this working ?

Thanks.

mmm, you can not map a singleton (why should you?)

a persisted object must be associated with just a single session, and think how you can do this using a singleton?

and do you want to have just a single record in your table?

mmm, you can not map a singleton (why should you?)

a persisted object must be associated with just a single session, and think how you can do this using a singleton?

and do you want to have just a single record in your table?

mmm, you can not map a singleton (why should you?)

a persisted object must be associated with just a single session, and think how you can do this using a singleton?

and do you want to have just a single record in your table?

mmm, you can not map a singleton (why should you?)

a persisted object must be associated with just a single session, and think how you can do this using a singleton?

and do you want to have just a single record in your table?

It's not possible to ask Hibernate to use getInstance(). I guess what you have is a special one-line table containing your "singleton" object data, isn't it ?

If so, I think you should have a look at second-level cache. In fact, having a persistent instance never or very rarely modified (is it your case ?) is typically a use case where to use second-level cache.

If your singleton is going to be often modified, then second-level cache is not the solution. But before going further, please precise what you do so that we can help more usefully :-).

I've written a generic UserType, together with some helpers it can solve this problem.
http://www.codeproject.com/useritems/SingletonUtil.asp

hello,

Thank you very much for these replies.

Yeah that could be a part of the solution. In fact, this singleton represents a parameter table in the database. This means I just need one instance of this class. But then I would have to design a table with only one line and only one colum (ID)... Not really meaningful...

I will look at this, it seems to be very interesting.

By the way I have a question which seems to relate to the same topic :
If I have a class which doesn't contain any attribute, it justs contains one or many persistant lists to other classes. Then I will have a table with only one ID column in the database, which is not really meaningful too...
Is it possible to avoid this ?

Thanks

You mean you've got a class that would have a one-to-many relationship with some others ? If so, yes, you'd have only one id. But if many-to-one, then you would be forced to have some foreign keys in this table.

Well, about avoiding this, it's not really possible to answer without having more infos on why you'd want to create this "central" object knowing some others.