Hello,
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)?
As Pascal wrote here's part of the answer:
http://stackoverflow.com/questions/212350/which-anotation-should-i-use-idclass-or-embeddedid
In the end, I believe using @IdClass is much easier in practice, because you have to add the embeddedId property name to dereference PK properties, while these aren't written for all non-PK properties.
You always have to remember exactly which properties are part of a PK and those which are not. That complicates writing JPQL queries unneccessarily.
Also, AFAIK the JPA 2.0 spec allows you to put @Id onto @XToX/@JoinColumn/s properties and it introduces the @MapsId annotation, so that mapping identifying relationships (a.k.a. derived identifiers in JPA) are more natural to implement.