/*
 * 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.
In order to receive these notification events, the implementation class must be either declared in the deployment descriptor of the web application, annotated with WebListener, or registered via one of the addListener methods defined on ServletContext. 
The order in which implementations of this interface are invoked is
unspecified.
Since:
Servlet 2.3/**
 * 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.
Params:
event – the HttpSessionBindingEvent containing the session
and the name and value of the attribute that was added/**
     * 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.
Params:
event – the HttpSessionBindingEvent containing the session
and the name and value of the attribute that was removed/**
     * 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.
Params:
event – the HttpSessionBindingEvent containing the session
and the name and (old) value of the attribute that was replaced/**
     * 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) {}

}