Java tutorial
/* * Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved. * Copyright 2004 The Apache Software Foundation * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package javax.servlet.http; import java.util.EventListener; /** * Interface for receiving notification events about HttpSession * attribute changes. * * <p>In order to receive these notification events, the implementation * class must be either declared in the deployment descriptor of the web * application, annotated with {@link javax.servlet.annotation.WebListener}, * or registered via one of the addListener methods defined on * {@link javax.servlet.ServletContext}. * * <p>The order in which implementations of this interface are invoked is * unspecified. * * @since Servlet 2.3 */ public interface HttpSessionAttributeListener extends EventListener { /** * Receives notification that an attribute has been added to a * session. * * @param event the HttpSessionBindingEvent containing the session * and the name and value of the attribute that was added */ default public void attributeAdded(HttpSessionBindingEvent event) { } /** * Receives notification that an attribute has been removed from a * session. * * @param event the HttpSessionBindingEvent containing the session * and the name and value of the attribute that was removed */ default public void attributeRemoved(HttpSessionBindingEvent event) { } /** * Receives notification that an attribute has been replaced in a * session. * * @param event the HttpSessionBindingEvent containing the session * and the name and (old) value of the attribute that was replaced */ default public void attributeReplaced(HttpSessionBindingEvent event) { } }