A user by the name of YajinZheng has posted a full Maximo REST API for Java! This is some great stuff, plus you can also download it from the Maven repo
The Maximo REST client library provides a set of driver API’s which can be consumed by a JAVA based web component that would like to interface with a Maximo instance. The client APIs use the Maximo NextGen REST/JSON APIs which were originally inspired by the Linked Data principles. Using this API you would be able to create, update, delete and fetch Maximo Business Objects (MBOs) based on the Maximo Integration Framework Object Structures.