You should look at JAXB. It is part of Java since JRE 6. It is pretty easy to use and allows you to drive the XML schema from your Java object model. The best part is that you don't need any extra jar files or libraries as it is part of Java. Check out the javax.xml.bin package.
Info on the JAXB Project itself:
https://jaxb.dev.java.net
Link to the JavaDocs in the JRE:
http://java.sun.com/javase/6/docs/api/javax/xml/bind/package-frame.html
