Working with Collections

smithbstl · **Joined:** Fri Jul 28, 2006 12:01 pm **Posts:** 21

I have an entity (InvalidAddress) with a many to one relationship with another entity (ServiceRequest). I am trying to add an InvalidAddress entity to the InvalidAddressCollection owned by ServiceRequest

Code:

    InvalidAddress invalidAddress = new InvalidAddress();
     
    //perform setters on invalidAddress
     
    invalidAddress.setServiceRequest(serviceRequest);
    serviceRequest.getInvalidAddressCollection().add(invalidAddress);
    entityManager.persist(invalidAddress);

I am getting a NPE because serviceRequest.getInvalidAddressCollection() is returning null when there are no related InvalidAddress entities. I know this makes sense but it seems like a waste to have to do this before I add any related entity to any collection

Code:

    if (serviceRequest.getInvalidAddressCollection() == null) {
       serviceRequest.setInvalidAddressCollection(new java.util.ArrayList();
    }
    serviceRequest.getInvalidAddressCollection().add(invalidAddress);

Is this very repetitive boiler-plate required when working with collections?

It would seem like the EntityManager should initialize the Collection and just return an empty list instead of a null list. Or is that up to me when I implement the getter on ServiceRequest?

Thanks for any advice.

emmanuel · **Posted:** Wed Jul 25, 2007 2:46 pm

No the EntityManager should not change the semantic.
But what people do is

Code:

public class ServiceRequest {
   private Set<InvalidAddress> invalidAddressCollection = new HashSet<InvalidAddress>();
   ...
}

smithbstl · **Joined:** Fri Jul 28, 2006 12:01 pm **Posts:** 21

So is this common practice?

I am just learning JPA and it is not shown like that in any of the examples I can find. Is that going to cause excess memory consumption since a new Set/List/Collection is created when the entity is created?

Thanks again.

christian · **Posted:** Wed Jul 25, 2007 4:13 pm

Just do it...

smithbstl · **Joined:** Fri Jul 28, 2006 12:01 pm **Posts:** 21

Nike.... :-)

Thanks