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# Descriptor Event Manager

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In relational and EIS projects, TopLink raises various instances of `DescriptorEvent` (see Table: Descriptor Events and Table: Descriptor Events) during the persistence life cycle. Each descriptor owns an instance of `DescriptorEventManager` that is responsible for receiving these events and dispatching them to the descriptor event handlers registered with it.

Using a descriptor event handler, you can execute your own application specific logic whenever descriptor events occur, allowing you to take customized action at various points in the persistence life-cycle. For example, using a descriptor event handler, you can do the following:

- Synchronize persistent objects with other systems, services, and frameworks.Maintain nonpersistent attributes of which TopLink is not aware.

- Notify other objects in the application when the persistent state of an object changes.

- Implement complex mappings or optimizations not directly supported by TopLink mappings.

For more information, see the following:

- "Configuring a Domain Object Method as an Event Handler"

- "Configuring a Descriptor Event Listener as an Event Handler"