EntityManager.refresh() works only on managed entities.

[CatchSandeepVaid]

Why can't EntityManager.refresh() work on detatched entities? Any reason behind this ?

[r035198x]

If the EntityManager is container managed and of type PersistenceContextType.TRANSACTION then a transaction is required. Otherwise how does the implementation know which database to refresh from?

[CatchSandeepVaid]

Agreed.. transaction is required but what it has to do with detatched instance ?
Moreover:
P-331 says : "We use the method to undo changes made by the ItemManager client and return fresh entity data from the database."
but when we call merge() (before refresh()), the changes made by the client will get reflected in the database.