Pasted from Oracle 9ias
ejb doc Defining an Auto-Generated Primary Key
If you specify a java.lang.Object as the primary key class type in <prim-key-class>, but do not specify the primary key name in <primkey-field>, then the primary key is auto-generated by the container.
The employee example defines its primary key as a java.lang.Object. Thus, the container auto-generates the primary key.
Once defined, the container creates a column called autoid in the entity bean table for the primary key of type LONG. The container uses random numbers for the primary key values.