Listener statement doubt

[Leena Diwan]

Hi Friends,

Can anyone tell me what does the following mean?

The HttpSessionListener and HttpSessionAttributeListener are configured
in the deployment descriptor. Therefore, even if a session attribute implements
these interfaces, the sessionDestroyed() and attributeRemoved()
methods will not be called on that attribute.

Regards,
Leena

[Adrian Pang]

I don't know what the context that paragraph comes from, but I think it means it's not enough that the class implements the interfaces, it also needs to be registered in the web.xml in order for the listener to work.