sto sviluppando un'applicazione in hibernate e, mandandola in esecuzione mi dà qst errore:

%%%% Error Creating SessionFactory %%%%
org.hibernate.MappingException: could not instantiate id generator [entity-name=de.laliluna.library.Customer]
at org.hibernate.id.IdentifierGeneratorFactory.create (IdentifierGeneratorFactory.java:132)
at org.hibernate.mapping.SimpleValue.createIdentifier Generator(SimpleValue.java:175)
at org.hibernate.impl.SessionFactoryImpl.<init>(Sessi onFactoryImpl.java:224)
at org.hibernate.cfg.Configuration.buildSessionFactor y(Configuration.java:1327)
at de.laliluna.library.HibernateSessionFactory.curren tSession(HibernateSessionFactory.java:73)
at de.laliluna.library.test.LibraryTest.main(LibraryT est.java:235)
Caused by: org.hibernate.MappingException: Dialect does not support sequences
at org.hibernate.dialect.Dialect.getSequenceNextValSt ring(Dialect.java:619)
at org.hibernate.id.SequenceGenerator.configure(Seque nceGenerator.java:88)
at org.hibernate.id.IdentifierGeneratorFactory.create (IdentifierGeneratorFactory.java:127)
... 5 more
Exception in thread "main" java.lang.NullPointerException
at de.laliluna.library.HibernateSessionFactory.curren tSession(HibernateSessionFactory.java:83)
at de.laliluna.library.test.LibraryTest.main(LibraryT est.java:235)

cosa potrebbe essere?