It seems that http-clustering don't works if I use getAttribute/setAttribute. If I use putValue/getValue it works. I bound some objects to the session but got a "Class Cast Exception". After putting those serializable classes into their own jar and putting this into lib it works so far. But if the object bound to the session was modified by node 1 it was not updated on node 2. Now I use getValue to get the bound object. Call some methods which modify the internal state of that object and use putValue. That worked. I bet the "putValue / setAttribute" is a bug but what's up with the other two problems?