Factory for lifecycle listeners
-------------------------------
Key: CAY-949
URL: https://issues.apache.org/cayenne/browse/CAY-949
Project: Cayenne
Issue Type: New Feature
Components: Cayenne JPA
Affects Versions: 3.0
Reporter: Andrus Adamchik
Assignee: Andrus Adamchik
Fix For: 3.0
So far we've followed the JPA spec in Cayenne classic callbacks/listeners
implementation. I am using listeners extensively and till now I used to install
them in the code. Now that Modeler supports listeners, I discovered that the
default mechanism of listener instantiation
(Class.forName("listenerClass").newInstance()) is inadequate when a listener
has dependencies on its environment. I guess in the J2EE world the dependencies
are obtained via JNDI, but I wanted to use injection as a cleaner approach (and
to avoid setting up JNDI).
So... I wrote an extension point that would allow users to register a factory
object for creating the listeners:
public interface EntityListenerFactory {
<T> T createListener(Class<T> listenerClass, ObjEntity entity);
}
This would support dependency injection (or any other environment specific
customization) of the listener objects, as well as using interfaces for the
listeners - something JPA does not support. So the same listener configuration
may be used with different implementations depending on some app logic.
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