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JPA2: how to persist data using @MapKeyColumn

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Posts: 115
Eclipse IDE Tomcat Server Java
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In my example I have two entities to persist. But when I try to using @MapKeyColumn annotation , I am confused on how to use this annotation and how to persist the data. This is the example that is explained in the "PRO JPA2 book". When I try to run this code it will generate the exception

two entities:-

and :

my service class function

when i try to insert the data using setEmpCabin(...) function , it wil generate the exception

Posts: 14
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If you haven't sorted this out already, it is highly likely that this section below is the culprit. I would assume that the cabin_id is being persisted before you reach line 3. The reason lies with how you are propagating your transactions.

When you create the employee, you are passing in a department object which, for this to work, should have empCabin already. You are using container-managed transaction in you beans so once the method finishes the transaction will commit. For this to work before line 2, make sure you set the empCabin. Try that and see how it works..

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