Java – persistent error message: an instance of an empty PK was incorrectly provided for the lookup operation

I'm trying to use NetBeans 7.01 to learn JSF 2.0 and JPA tutorials I am using Oracle Xe and JDBC_ 6. I used the JSF page from the entity wizard to generate my JSF page Everything is normal because I can retrieve data from the database and display them However, when I try to create or update records in the database, I receive this error:

How did this happen and how should I solve it?

Solution

This basically means that you did the following:

Entity entity = em.find(Entity.class,null);

Please note that PK is empty here To fix your problem, make sure it is not null