How to implement Generic JPA Repository in Spring Boot - Which can be autowired into spring services for any entity/class type

Question

Here is the sample Generic Repository implementation which extends the spring PagingAndSortingRepository,

@NoRepositoryBean
public interface GenericRepository<T, ID extends Serializable> extends PagingAndSortingRepository<T, ID> {

  public List<T> findByNamedQuery( String name );
  public List<T> findByNamedQueryAndParams( String name, Map<String, Object> params );
  public T findOneByNamedQuery( String name );
  public T findOneByNamedQueryAndParams( String name, Map<String, Object> params );

}

Factory Bean class,

public class GenericRepositoryFactoryBean<R extends JpaRepository<T, I>, T, I extends Serializable> extends
    JpaRepositoryFactoryBean<R, T, I> {

   @SuppressWarnings( "rawtypes" )
   protected RepositoryFactorySupport createRepositoryFactory( EntityManager em )
   {
    return new MyRepositoryFactory(em);
   }

   private static class MyRepositoryFactory<T, I extends Serializable> extends JpaRepositoryFactory {

    private final EntityManager em;

    public MyRepositoryFactory( EntityManager em )
    {
        super(em);
        this.em = em;
    }

    @SuppressWarnings( "unchecked" )
    protected Object getTargetRepository( RepositoryMetadata metadata )
    {
        return new GenericRepositoryImpl<T, I>((Class<T>) metadata.getDomainType(), em);
    }

    protected Class<?> getRepositoryBaseClass( RepositoryMetadata metadata )
    {
        return GenericRepositoryImpl.class;
    }
  }
}

Implementation class,

public final class GenericRepositoryImpl<T, ID extends Serializable> extends SimpleJpaRepository<T, ID> implements
    GenericRepository<T, ID> {

  private final EntityManager em;
  private final Class<T> domainClass;

  public GenericRepositoryImpl( Class<T> domainClass, EntityManager entityManager )
  {
      super(domainClass, entityManager);
      this.em = entityManager;
      this.domainClass = domainClass;
  }

  @Override
  public List<T> findByNamedQuery( final String name )
  {
      validate(name);
      return this.em.createNamedQuery(name, domainClass).getResultList();
  }

  @Override
  public T findOneByNamedQuery( String name )
  {
      validate(name);
      return this.em.createNamedQuery(name, domainClass).getSingleResult();
  }

  @Override
  public List<T> findByNamedQueryAndParams( String name, Map<String, Object> params )
   {
      validate(name, params);
      final TypedQuery<T> query = this.em.createQuery(name, domainClass);
      setParams(query, params);
      return query.getResultList();
   }

}

So when i try to Autowire GenericRepository into services for different types like Customer.java, Message.java etc it is throwing requires at least one bean type of interface GenericRepository. This works if when I create individual repositories for both customer and message type. Without creating multiple repositories, i am not able to implement this.

@Service
@Transactional( noRollbackFor = Exception.class )
public class CustomerService {

@Autowired
private GenericRepository<Customer, Serializable> cr; works fine with just one entity type

@Autowired
private GenericRepository<Message, Serializable> cr; throws exception

If have 100 or more entity classes, then i end up creating 100's of repositories and which is bad. Please let me know if there is a better way to do this.

Answer 1

For what I've read it will be easier to tell the new interface methods what to do by @Query annotation and do not bother yourself with BeanFactory or impl...

 @Repository
 public interface GenericRepository<T, ID extends Serializable> extends JpaRepository<T, ID> {
@Query(value = "SELECT c FROM customers c WHERE c.name = :name")
public List<T> findByNamedQuery( String name );
...
}

Using generics in Spring Data JPA repositories

If that's not applicable for you and you are saying that your code works with one repository but fails when you add second my first thought is to try and set the scope of the bean to prototype but that is just a speculation. I am sorry if i didn't really help, don't hate me too much ^^