You don't believe in asking easy questions, do you? People write books about this sort of thing. So rather than trying to answer your question directly, here's a list of references.
- Redbook: XML Powered by Domino How to use XML with Lotus Domino is a comprehensive guide to the whole area of using XML with Notes/Domino. The example in section 5.5 is pretty close to what you're trying to do.
- LDD Today article: Domino development with servlets This article discusses how to write Java servlets (and Domino Java agents) that access Domino data. It's a couple of years old, but it's still a very good article. These days you don't have to write all the code manually since there are better tools for producing the servlets and tying them into Domino; most notably, Websphere Studio family of products. But it's still the same kind of code. So all you need is a servlet of the kind shown here, plus you add the ability to load and parse the XML information you were sent.
- Another good example of this kind of coding is Integrating Amazon Web services with your Notes databases.