This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
There's no direct way to use Java data types with web services, as that would undermine the cross-platform compatibility. You could transform the list into an array (which is supported), or -alternatively- embed a serialized representation (either binary of XML) if compatibility isn't important to you, although I would advise against that.