Implementing composite keys with JPA and Hibernate

See the original posting on IBM developerWorks – Java

Nowadays, with the widespread use and deployment of Object-Relational Mapping (ORM) tools, you don't generally have to think too hard about such arcane issues as composite keys. Normally, the choice of key design can be a simple integer, and this can be left with confidence to the tooling. Occasionally, you come across a situation where a composite key is required, and you need a strategy for this. This tip shows you how to implement composite keys with JPA and Hibernate.