The SoftLayer REST API doesn’t seem to have an XSD, so you can’t use xjc to generate classes. That’s a shame for a strongly-typed language, since you’d now have to manually create classes based on their Data Type Reference.
I didn’t like that and decided to code up a Java class generator (it’s written in Python) based on the Data Type Reference. You can use it to generate a Java class based on the SoftLayer Data Type you pass in. Enjoy!