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

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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.