Generics and Spring Data JPARepository

Question

This is a follow-up question based on Oliver Gierke's suggestion.

We have two tables (almost same information) but for some external reasons, cannot use a common single table. I am getting an error that the base class is not a mapped entity. Oliver Gierke has mentioned in his response that it would work only for Single Table. I am assuming that is the reason. if so, could someone explain why such limitation and how can I make the following work.

Base entity:

   @MappedSuperclass
   public abstract class DecisionEntity {

Inherited classes:

   @Entity
   @Table(name="DM_INSP_TASKING_RULES_RSLT")
   public class DmInspTaskingRulesRslt extends DecisionEntity implements Serializable {

   @Entity
   @Table(name="DM_UW_REF_RULES_RSLT")
   public class DmUwRefRulesRslt extends DecisionEntity implements Serializable {

The Repository

   @Repository
   public interface DecisionManagementRepository<T extends DecisionEntity> extends    JpaRepository<DecisionEntity, Long> { 

Have defined 'packagesToScan' and also listed all the 3 classes in persistence.xml. I am getting the 'Non an Managed Entity' for 'DecisionEntity' class. I tried Inheritence Type - 'TABLE_PER_CLASS

Answer 1

This is not supported by Spring Data JPA and Java Persistance API Specification.

• Spring Data JPA Issue DATAJPA-264

  Repositories: throw exception at startup if entity is a not an @Entity (e.g. for @MappedSuperclass)

  Status: Investigating
  Resolution: Unresolved
  

• The JPA specifications says:

  A mapped superclass, unlike an entity, is not queryable and must not be passed as an argument to EntityManager or Query operations. Persistent relationships defined by a mapped superclass must be unidirectional.