According to the Java Persistence API (JPA) specification, if an entity defines an attribute with an EmbeddedId annotation, the embeddable class cannot contain an attribute with an Id annotation. If both the EmbeddedId annotation and the Id annotation are defined, OpenJPA ignores the Id annotation, whereas EclipseLink throws an exception.

This rule detects Embeddable classes that contain attributes with an Id annotation, then the rule flags the Id annotations depending on whether it finds an entity that references the embeddable class using an EmbeddedId annotation.

• If an EmbeddedId annotation references an embeddable class that has an Id annotation, the rule flags the Id annotation as a severe issue. The Id annotation will need to be removed.
• If the rule cannot find a reference from an entity using the EmbeddedId annotation, the rule flags the issue as a warning. You can expand the scope of the analysis to include any attributes annotated with EmbeddedId that might reference the embeddable class and rerun the scan, or you can manually verify that no EmbeddedId annotations reference the embeddable class.

In this example, the rule flags the Id annotation in the EmbeddableObject class.

   import javax.persistence.EmbeddedId;
   import javax.persistence.Entity;
   
   @Entity
   public class MainEntity {

      @EmbeddedId
      private EmbeddableObject eo;
   }

   import javax.persistence.Embeddable;
   import javax.persistence.Id;
   
   @Embeddable
   public class EmbeddableObject {

      @Id
      private int field;

      ...
   }

To resolve the issue, remove the @Id annotation and its import.

   import javax.persistence.Embeddable;
   import javax.persistence.Id;

   @Entity
   public class MainEntity {

      @EmbeddedId
      private EmbeddableObject eo;
   }

   import javax.persistence.Embeddable;
   
   @Embeddable
   public class EmbeddableObject {

      private int field;

      ...
   }

For information about this issue and other OpenJPA to EclipseLink migration issues, see the OpenJPA to EclipseLink JPA Migration: Mappings guide.