11.3. Detach and Attach Callbacks
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## 11.3. Detach and Attach Callbacks

Persistent instances can be notified when they are being detached or attached by implementing the `kodo.runtime.PreDetachCallback` `kodo.runtime.PostDetachCallback` `kodo.runtime.PreAttachCallback` and `kodo.runtime.PostAttachCallback` interfaces. These interfaces are analogous to the notification mechanisms provided by the `javax.jdo.InstanceCallbacks` interface (see Section 4.4, “InstanceCallbacks”).

- `PreDetachCallback.jdoPreDetach` is called on the managed persistent instance before it be to be detached.

- `PostDetachCallback.jdoPostDetach` is called on the detached copy of the persistent instance after the entire detach process is complete. The method takes a single `java.lang.Object` argument, which is the managed instance that the detached copy is the clone of. It can be used to transfer transient or unmanaged state between the managed instance and the detached instance.

- `PreAttachCallback.jdoPreAttach` is called on a detached instance before it is to be attached.

- `PostAttachCallback.jdoPostAttach` is called on the managed instance after it has been attached. It is only invoked after the entire attach process is complete. The method takes a single `java.lang.Object` argument, which is the detach instance that has been attached. It can be used to transfer transient or unmanaged state between the detached instance and the attached instance.

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