 in java.lang"><code>IllegalStateException</code></a> being thrown.
 Developers should retrieve any information from the session during the
 <a href="../../javax/websocket/Endpoint.html#onClose-javax.websocket.Session-javax.websocket.CloseReason-"><code>Endpoint.onClose(javax.websocket.Session, javax.websocket.CloseReason)</code></a> method. Following the convention of <a href="http://docs.oracle.com/javase/8/docs/api/java/io/Closeable.html?is-external=true" title="class or interface in java.io"><code>Close