Date: Tue, 07 Feb 2012 10:21:42 +0100
From: Short <lamia@mail.com>
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Subject: JPA and composite primary key
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Hi.
Here's the scenario:
An abstract class that defines an Id "generated":
public abstract Class1{
     [...]
     @Column(name = "ID")
     @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = 
"IdSequenceGen")
     @Id
     public Long getId()
     {
         return this.id;
     }
     [...]
}

An entity Class, extending Class1, that has a composite PK: The 'Class1' 
ID and a second field:

@Entity
@IdClass(Class2.class)
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@SequenceGenerator(name = "IdSequenceGen", sequenceName = "SQ_CLASS2")
@Table(name = "CIM_PERSON_DEMOGRAPHIC")
public class Class2 extends Class1{
     private Integer prog = 0;

     @Column(name = "PROG")
     @Id
     public Integer getProg()
     {
         return prog;
     }
     [...]
}

But in this case I've this error at runtime:
javax.persistence.PersistenceException: [PersistenceUnit: datamodel] 
Unable to configure EntityManagerFactory
	at 
org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:375)
	at 
org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:56)
	at 
javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:48)
	at 
javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:32)
	at 
com.noemalife.platform.dm.test.AbstractTest.buildEntityManager(AbstractTest.java:111)
Caused by: org.hibernate.AnnotationException: Unknown Id.generator: 
IdSequenceGen

How can i solve this problem?

Thank you so much