This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
For interoperability, you should not use Java collection, but using arrays is fine. If the array elements conform to JavaBean semantics, then JAXB (the XML <---> Java mapping technology used by JAX-WS) should have no problems with them.