To initialize a lazy collection with Hibernate core one can use


I have been trying to find an "equivalent" method using only JPA/EntityManager but I can't seem to find any.

What is the "best" method to initialize a proxy set without explicitly using the Hibernate class?

Hi,

I am not aware of an equivalent. You could try to load the entity and its associated collection using the Criteria API. There you can specify the fetch mode (FetchMode.JOIN) which will eagerly fill the collections even if they are mapped as lazy. If you need the collection loaded eagerly all the time why not map it eager? Or why not just rely on transparent lazy loading?
What is your actual use case?

--Hardy

Thankyou for your reply.

I have been working on a Hibernate-Core-only project for some time now and have just started looking into JPA, trying to see where it's the same and where it's different.

In the Hibernate core project we are using the Hibernate.initialize() method in the following situations

- the Collection is rarely needed so mapping it eager is not a desired option
- transparent lazy loading is not an option as the entity is detached
- the method used to load the entity is using HQL for the query and using "left join fetch" on a One-To-Many relation will duplicate rows in the SQL ResultSet.

Our standard approach is as follows

- map almost everything "lazy"
- use explicit HQL for queries, using "left join fetch" for X-To-One relations
- depend on transparent lazy loading while the session is open
- use Hibernate.initialize() for X-To-Many relations, in case the Collections are used after detaching the objects

With this approach using "Hibernate.initialize()" seems logical and I thought something similar would be available in JPA.

Of course we can just access the Collection elements while the session is still open (e.g. getSetOfChildren().size()) for transparent lazy loading, but I think that a dedicated method like "Hibernate.initialize()" is the "cleaner" solution, as it clearly shows the intention.

Sure, you can just call size() to initialize the collection. Why do you not create a project internal helper class/method with an appropriate name. this way your intentions become clear whereas internally you still can just call size().

--Hardy

Sounds like a great idea.

Thanks.

Great info, swillfah!

I tend to use Hibernate.initialize(obj.getSet()) call very often to load association objects that are to be presented on a page.
The one problem i have is that i am not able to initialize set and its dependent associations using single Hibernate.initialize() call.

So if set element class has X-2-one association i would like hibernate to load the set elements along with each associated object with 1 query.