Using @Id for multiple fields in same class

Question

I am a newbie to Hibernate and have to support an existing application that uses Hibernate It is a pure reporting application - no insert / update / delete - only select

Answer 1

According to the Hibernate docs, Hibernate seems to allow this but it is not however JPA compliant.

5.1.2.1.2. Multiple id properties without identifier type

Another, arguably more natural, approach is to place @Id on multiple properties of your entity. This approach is only supported by Hibernate (not JPA compliant) but does not require an extra embeddable component.

http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html_single/#d0e4819

For a JPA compliant solution you would have to specify an additional @IDClass for this set-up (or use an EmbeddedId):

http://www.objectdb.com/java/jpa/entity/id