Swing-Applet to Spring communication protocol

We have a Swing Applet client that needs to communicate with a Spring/hibernate application running on tomcat, the requirements are pretty standard , passing data objects through and forth, considering firewalls and performance.
the current implementation is soap with axis 1 (that has some limitations on transmitting hibernate objects and proxies,have to set null on proxies before sending them with axis).

what would you consider as a replacement to soap/axis? Rest? RMI? Spring remoting?