public Object removeSessionData(String key) {
        synchronized (sessionData) {
            return sessionData.remove(key);
        }
    }
Removes session data. Please see {@link #setSessionData(String, Object)} description
for more details.

@param key a <code>String</code> value of stored data ID.
@return the previous value associated with {@code key}, or
        {@code null} if there was no mapping for {@code key}.
@see #setSessionData(String, Object)
xmppserver/src/main/java/org/jivesoftware/openfire/session/LocalSession.java