Friday, 10 May 2013

How to implement an entity bean which the PrimaryKey is an autonumeric? | EJB Interview Questions

The EJB 2 Spec (10.8.3 - Special case: Unknown primary key class) says that in cases where the Primary Keys are generated automatically by the underlying database, the bean provider must declare the find By PrimaryKey method to return java.lang.Object and specify the Primary Key Class as java.lang.Object in the Deployment Descriptor.
When defining the Primary Key for the Enterprise Bean, the Deployer using the Container Provider's tools will typically add additional container-managed fields to the concrete subclass of the entity bean class.
In this case, the Container must generate the Primary Key value when the entity bean instance is created (and before ejb Post Create is invoked on the instance.)


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