Hi,

I never used composite primary key before, but now I have a situation, which needs one. I have 3 questions:
1. Which is the best strategy of the following available in Hibernate (EJB3), what are advantages/disadvantages of each?

annotate the component property as @Id and make the component class @Embeddable
annotate the component property as @EmbeddedId
annotate the class as @IdClass and annotate each property of the entity involved in the primary key with @Id

2. Is there a way to create this key class in the same file as the main class? Creating it as inner class is not allowed - it sould be top level class, is there any way around this?

3. Any better strategy than creating a key class for every single class that I have?

Thanks

My personal preference has been to use the @IdClass, but each scenario has specific curcumstances which may effect your choice.




Here's a good tutorial on how to map compound primary keys with Hibernate and JPA:

http://www.hiberbook.com/HiberBookWeb/learn.jsp?tutorial=15usingcompoundprimarykeys

I always make my primary key classes toplevel classes, and not inner classes, or even non-public classes within the same Java class file as the associated instance. I recommend that people using composite primary keys do the same.

Good luck!