Interfaces with hibernate annotations

Question

i am wondering how i would be able to annotate an interface

@Entity
@Table(name = \"FOLDER_TABLE\")
public class Folder implements Serializable, Hierarchy {
         


        

Answer 1

You can map interfaces in Hibernate, as part of inheritance hierarchies. This is quite surely possible with XML mapping, as it is described in Chapter 9 of the Hibernate reference, among others.

Annotation based mapping is a different story though. I am not so familiar with it, but Java Persistence with Hibernate includes examples for this too. Adapted to your case, it would look like

@MappedSuperclass
public interface Hierarchy {
}

@Entity
@Table(name = "FOLDER_TABLE")
public class Folder implements Serializable, Hierarchy { ... }

@Entity
@Table(name = "FILE_INFORMATION_TABLE")
public class FileInformation implements Serializable, Hierarchy { ... }

This mapping would use a table per concrete class with implicit polymorphism.

However, other sources suggest that annotation support for interfaces may not be working / stable yet:

• there is a related open bug report on using the @Entity annotation with interfaces, which also includes some patches,
• here is a related (fairly old) thread, describing a workaround using XML mapping.

So you may need to experiment, including changing your inheritance mapping strategy, maybe turning the interface into an abstract class (if it's possible - since a class can only extend a single base class)...