Howto for usage of EclipseLink in JavaEE Webapps (I know JPA in Java SE)

Hi!

So far I've used EclipseLink only in Java SE projects. As I do really appreciate it, I've considered using
it in a Apache Wicket web application.

Is there any documentation available which describes the differences between JPA usage in Java SE and
Java EE environments?

I've already tried some things like fetching, adding and deleting objects from the database, but i am quite
unsure how for example the EntityManagers should be handled. In Java SE I requested one EntityManager
for each form and everything worked fine... This is just one example question, but there are many many more...

I'd be glad if anyone of you could supply me a good link!

Best Regards,
  christian