You might consider Digest Access Authentication. Essentially the protocol is as follows:
All of this communication is made through headers, which, as jmort253 points out, is generally more secure than communicating sensitive material in the url parameters.
Digest Access Authentication is supported by Spring Security. Notice that, although the docs say that you must have access to your client's plain-text password, you can successfully authenticate if you have the HA1 hash for your client.