MultiTenancyRepository.java

public class MultiTenancyRepository<T, I> extends SimpleJpaRepository<T, I> {

  private final JpaEntityInformation<T, I> entityInformation;
  private final EntityManager entityManager;

  public MultiTenancyRepository(
      final JpaEntityInformation<T, I> entityInformation, final EntityManager entityManager) {
    super(entityInformation, entityManager);
    this.entityInformation = entityInformation;
    this.entityManager = entityManager;
  }

  @Override
  public Optional<T> findById(@NonNull final I id) {
    final Class<T> entityType = this.entityInformation.getJavaType();
    Objects.requireNonNull(id, "ID can not be null for Type [" + entityType + "]");

    final CriteriaBuilder criteriaBuilder = this.entityManager.getCriteriaBuilder();
    final CriteriaQuery<T> cq = criteriaBuilder.createQuery(entityType);

    cq.where(
        criteriaBuilder.equal(
            cq.from(entityType).get(this.entityInformation.getRequiredIdAttribute().getName()),
            id));
    final TypedQuery<T> q = this.entityManager.createQuery(cq);

    return q.getResultStream().findFirst();
  }
  
  @Override
  public T getOne(@NonNull final I i) {
    throw new EntityNotFoundException();
  }

  @Override
  public void delete(@NonNull final T entity) {
    Objects.requireNonNull(
        entity, "Entity can not be null for Object [" + this.entityInformation.getJavaType() + "]");

    if (this.entityInformation.isNew(entity)
        || this.findById(this.entityInformation.getRequiredId(entity)).isEmpty()) {
      return;
    }

    this.entityManager.remove(
        this.entityManager.contains(entity) ? entity : this.entityManager.merge(entity));
  }
}