You can't deploy a jar that contains only entities as the deployment can deploy only Java EE components, and entities are not considered to be components.
Now about your first solution.
a) What kind of exception/error message do you get?
b)Which GlassFish build did you use?
c) How do you create an EntityManager and/or EntityManagerFactory in your applications?
d) Do you plan to have that set of entities be mapped to the same set of tables? Will all of the applications be able to update the entities? If the answer is yes to both questions, you can face stale data as updates are not shared between various applications.
Regards,
-marina
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