what's better for JPA/Hibernate composite primary keys, @IdClass or @EmbeddedId implementations and why?
This is an intentionally naive question. I decided to use @EmbeddedId (for whatever reason) and I feel like I made the wrong choice. Dereferencing the embeddedId that contains the column properties is redundant and quite error-prone when coding.
Are there any more reasons for and/or against the other? Is the a recommendation by the JPA (spec)?
First, if possible, avoid composite ids at all costs. But if you really need, I would recommend @EmbeddedId.
@IdClass is basically a leftover from EJB 2.1 times to make it easier from migrating from BMP. In some other rare corner cases it may be better than @EmbeddedId too. However, generally @EmbeddedId is better and more OO since it encapsulates the concept os the key much better in the object.
You may want to use @AttributeOverride(s) if you need in the key field.
I don't see why do you think that dereferencing the embedded id is redundant and error-prone.
I. Remember using idclass to do it. But I'd recommend doing everything you can to avoid multi field keys. They just create extra work.
