entity manager

基本解釋

To have persistence actions, you need an entity manager.
要具有持久操作，您需要一個實體管理器。
They should be ready for invocation in any tier, whether within the realm of the entity manager or not.
無論是否在實體管理器中，它們都應該準備好在任何層中調用。
Another restriction arises from the fact that the domain objects can be accessed both in the tier where they are managed by the entity manager and in all the other tiers where they are detached.
另一種限制源自于這樣一個事實：域對象可以通過由實體管理器所管理的域對象所在的層訪問，也可以通過分離它的所有其他層訪問。