[jboss-user] [EJB 3.0] - How to retrieve foreign key instead of the object (want no l
lpmon
do-not-reply at jboss.com
Tue Dec 4 18:26:26 EST 2007
Goal: ability to retrieve the foreign key without loading the related object/table row.
Scenario:
Entity bean contains a related entity bean.
@Entity
class Unit{ // Unit table
// what kind of unit
Model model; // related object in Model table, related column is modelId
In the Unit table there is a column called modelId to point to the row in the Model table. If I want this key value I can use
Unit u = .... somehow get it with EntityManager or whatever;
int modelId = u.getModel().getId(); // causes read of Model table!
Issue - this will cause a read of the model row from the DB (won't it, as in lazy loading will perform a JIT read)
I only need the modelId which is in the Unit table. It seems there should be a way to do this and not load the related object.
One can do this with EJBQL by using the reserved Class.id syntax. How can I take advantage of that in the ORM classes?
I used a simple example. In my app if I can accomplish this I can easily avoid a lot of unwanted DB fetches.
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