One IdentifierGenerator instance by SessionFactory

fgamito · **Joined:** Mon Apr 04, 2005 5:31 am **Posts:** 3

Hibernate version:3.0.5

I need to implement a IdentifierGenerator that must be one Singleton by SessionFactory.
Anyone can explain the better way to do this ?

Thanks on advance
--
fmg

lance2010 · **Joined:** Thu Oct 06, 2005 7:23 pm **Posts:** 7

fgamito wrote:

Hibernate version:3.0.5

I need to implement a IdentifierGenerator that must be one Singleton by SessionFactory.
Anyone can explain the better way to do this ?

fmg

Assuming the goal is that you simply want to generate ids from the same pool and not that you really need a singleton (you don't have control over this since the framework is responsible for creating identifier generators), something like the following should do the trick.
Note that this is overkill for a primitive integer (you can reduce the code to literally 5 lines, but this should work if you've got a fancier generation algorithm requiring objects.

Code:

public class SharedGenerator implements IdentifierGenerator {
   private static SharedGenerator singleton;
   private static long id = 0;
   
   public SharedGenerator() {
      // Generators are created during mapping, so there should be no need for synchronization
      if (singleton == null) {
         singleton = this;
      }
   }

   public Serializable generate(SessionImplementor session, Object object)
         throws HibernateException {
      if (this == singleton) {
         synchronized (singleton) {
            return new Long(++id);
         }
      } else {
         return singleton.generate(session, object);
      }
   }
}

lance2010 · **Joined:** Thu Oct 06, 2005 7:23 pm **Posts:** 7

Oops - that should read:

Code:

synchronized (singleton) {
   id += 1;
   return new Long(id);
}