We do not yet offer an official asynchronous Java SDK. However, there is an experimental Scala plugin and Play sample application that demonstrate how you can use our Java SDK (which is blocking) for non-blocking operations by wrapping the interaction in a future.
Scala Plugin: https://github.com/stormpath/stormpath-scala/tree/dev
Sample Play app: https://github.com/stormpath/stormpath-play-sample/tree/dev
The plugin provides an asynchronous authentication mechanism, returning a future to collect the authentication result in a non-blocking way. The sample application shows how to use the plugin and how to update an Account’s customData resource, also in a non-blocking fashion.
We hope they provide a solid starting point! However, it is important to note that neither project is complete, or ready for production.