I have JPA entity (Object A) with a One-Many owning relationship (Object B) in an ArrayList.

I want to be able to query for Object A without having any of the instances of Object B returned (proxies or otherwise) in the One-Many ArrayList.

Is this possible? In rough pseudocode this is what I want:

"from ObjectA where ObjectA.id=5 DO NOT INCLUDE ObjectB"

So, you want an instance of Object A that is not a true representation of its actual state with relation to instances of Object B?

You've mentioned JPA, does this mean that you will not be wanting a native Hibernate solution?

How would expect the caching mechanisms to behave? Are there other areas of your application that are allowed to have proxies representing the list of Object B instances from Object A - normal behaviour?


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Stephen Souness

A hibernate solution is fine.. I am looking for any solution; although I'd prefer a JPA solution, but I am using Hibernate as the JPA implementation.

I'd like to give the option of returning only "ObjectA" without it's relationship or the full ObjectA.

I am not very concerned with the Caching aspect of this (yet).

I would rather not have any ObjectB proxies involved. I want an ObjectA instance returned with the ObjectB arrayList either null or empty.

I'm a little curious about why you want this behaviour. You won't be significantly reducing data traffic between your application and the database, as Hibernate typically finds the count of Object B instances and sets up a single proxy for lazy loading - so memory shouldn't be an issue either.

Are you going to be performing any updates on the retrieved instances of Object A? If so, you will also need to consider how to not effect the relationship with the Object B instances on update, but still effecting them if there is going to be deletion of Object A instances (since you've mentioned that the Object B instances belong to the Object A instances).


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Stephen Souness

(PS: Sorry for having more questions than answers at this point)

Thank you for all of your help. You bring up some good issues.

I will not be performing any updates on the retrieved instances of Object A. The objects will be accessed over RMI (henced Serialized) so the proxies are not necessary.

There will be one process inserting/updating/deleting ObjectA's from the database, and a slew (10+) of other services/processes/computers querying that data over RMI. Some other services only require the ObjectA instance; while some will require attached ObjectB instances. I do not want to include any unnecessary data to the remote services.

Is it feasible to create a Data Transfer Object to represent the Object A instances to the RMI clients?

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Stephen Souness

I'd rather not. Ideally I would just return ObjectA with the ObjectB ArrayList null or empty.