Created attachment 1075834 [details]
hibernate4.01491237.HHH-5764.tar.gz

When the composite primary key references more than 2 levels, it fails with the error "org.hibernate.AssertionFailure: Unexpected nested component on the referenced entity when mapping a @MapsId: xxx".

For example:
@Entity
@IdClass(Level1EntityPK.class)
public class Level1Entity {

    @Id
    @ManyToOne
    private Level2Entity level2Entity;
    ...
}

@Entity
@IdClass(Level2EntityPK.class)
public class Level2Entity {
    @Id
    @ManyToOne
    private Level3Entity level3Entity;
    
    ...
}

@Entity
@IdClass(Level3EntityPK.class)
public class Level3Entity {

    @Id
    @Column(name = "LEVEL3_ENTITY_NO")
    private String level3EntityNo;
   
    ...
}

A jira https://hibernate.atlassian.net/browse/HHH-5764 has already been raised.