Yes, it does implement serializable. I've also try String. I found out the problem only occur when I remove the child node. Currently, there is no requirement for removing a node in my application, but I am still curious why JBossCache throws an exception for something as simple as that. By the way, I've tried using the tutorial that bundled in jbosscache-core-3.0.3.GA and got the same exception when attempting to remove the child node. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4230600#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...