I have a situation where a set of entities share a similar composite key class; rather than create a new PK class for each entity, I wanted to genericise the PK.

Here's my generic PK class:

@Embeddable
public class LanguagePK<T> implements Serializable {

 private T describes;

 private String code;

 @Column(name = "LANG_CODE")
 public String getCode() {
 return this.code;
 }

 public void setCode(String code) {
 this.code = code;
 }

 public T getDescribes() {
 return this.describes;
 }

 public void setDescribes(T described) {
 this.describes = described;
 }
}

...and here's a sample entity that embeds it (Foo is another entity)

@Entity
@Table(name = "FOO_LANG")
public class FooLanguage implements Serializable{
 LanguagePK<Foo> pk;

 @EmbeddedId()
 @AttributeOverrides( { @AttributeOverride(name = "describes", column = @Column(name = "FOO_ID")) })
 public LanguagePK<Foo> getPk() {

 if (pk == null) {
 pk = new LanguagePK<Foo>();
 }

 return pk;
 }

 public void setPk(LanguagePK<Foo> pk) {
 this.pk = pk;
 }

 @Transient
 public Foo getFoo() {
 return getPk().getDescribes();
 }

 public void setFoo(Foo e) {
 getPk().setDescribes(e);
 }

 @Transient
 public String getCode() {
 return getPk().getCode();
 }

 public void setCode(String code) {
 getPk().setCode(code);
 }
}

I'm getting the "Property X has an unbound type and no explicit target entity" exception when I try to use it.

 [testng] javax.persistence.PersistenceException: java.lang.IllegalStateException: Property describes has an unbound type and no explicit target entity.
 [testng] at org.hibernate.ejb.Ejb3Configuration.createEntityManagerFactory(Ejb3Configuration.java:217)
 [testng] at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:114)
 [testng] at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:37)
 [testng] at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:27)

I've poked around, but I haven't found any example code on how to do something like this. Am I'm trying to do something I shouldn't?