How should we integrate PayPal adaptive (and IPN) API in a Java webserver environment?

As I'm currently integrating a paypal layer in my spring based server (that should be usable by multiple clients asking me to implement their webstore):

And as there's surprisingly very few info to find on t开发者_如何学Pythonhe Spring/Paypal topic, I could only find this article: http://blog.mushiengine.com/2010/08/25/paypal-adaptive-api-and-spring-3-rest-template-%E2%80%94-part-2/

I was wondering if there are perhaps some guidelines or best practices concerning the topic?

Any comments on the topic more than welcome!

Jochen

Since you are having problems finding information that's Java-specific you can look into Grail's PayPal plugin (http://www.grails.org/plugin/paypal-pro) for some reference.