Entity life cycle

The life cycle of an entity instance is managed by its entity manager.

An entity manager instance is associated with a persistence context. Within this persistence context, the entity instances and their life cycle are managed and can be accessed though the entity manager standard operations.

Entity instances become unmanaged and detached when a transaction scope or extended persistence context ends. An important consequence of this fact is that detached entities can be serialized and sent across the network to a remote client. The client can make changes remotely to these serialized object instances and send them back to the server to be merged back and synchronized with the database.
Note: This behavior is very different from the EJB 2.1 entity model, where entities are always managed by the container. Because in EJB 3.0 you are working with entities that are POJOs, this can simplify how you design Java™ EE applications, because you are not forced to use patterns, such as data transfer objects (DTO), between the business logic layer (session beans) and the persistence layer.

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