Primary key does not have to be exactly "ID" column.
If there is a unique column in your table, such as "empName", you should anotate it with @Id in the class or write mapping file according to manual at http://docs.jboss.org/hibernate/orm/4.3/manual/en-US/html/ch05.html#mapping-declaration-id
If there is a unique combination of columns in your table, you should use a composite key. You can read about it in section 5.1.2.1. Composite identifier on link above. Some hints about it are also on other question (Hibernate/persistence without @Id)
If there is no unique combination, then I am afraid that there is no way how to use hiberante in your case: (Mapped classes must declare the primary key column of the database table.) from the link above.