Entitymanager merge not updating record

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It interprets the O/R mapping specified for an entity and saves the entity in the database.Besides providing these explicit SQL-like CRUD operations, the Entity Manager also quietly tries to keep entities synched with the database automatically as long as they are within the Entity Managers reach (this behind-the-scenes synchronization is what we mean when we talk about "managed" entities in the next section).

When switching from Hibernate to JPA a lot of peopleare dismayed to findthat method missing.The object passed is attached to the persistence context.That means that after invoking Entity Manager.merge, we have to use the entity reference returned from that method in place of the original object passed in.From the other side of the translation bridge, when you request that an entity be "saved" in the database, the Entity-Manager creates the Entity object, populates it with relational data, and "returns" the Entity back to the OO world.Figure 9.1 The Entity Manager acts as a bridge between the OO and relational worlds.

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