/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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;

import java.util.EventListener;

/**
 * Implementations of this interface receive notifications of changes to the attribute list on the servlet context of a
 * web application. To receive notification events, the implementation class must be configured in the deployment
 * descriptor for the web application.
 *
 * @see ServletContextAttributeEvent
 *
 * @since Servlet 2.3
 */
public interface ServletContextAttributeListener extends EventListener {

    /**
     * Notification that a new attribute was added to the servlet context. Called after the attribute is added. The
     * default implementation is a NO-OP.
     *
     * @param scae Information about the new attribute
     */
    default void attributeAdded(ServletContextAttributeEvent scae) {
    }

    /**
     * Notification that an existing attribute has been removed from the servlet context. Called after the attribute is
     * removed. The default implementation is a NO-OP.
     *
     * @param scae Information about the removed attribute
     */
    default void attributeRemoved(ServletContextAttributeEvent scae) {
    }

    /**
     * Notification that an attribute on the servlet context has been replaced. Called after the attribute is replaced.
     * The default implementation is a NO-OP.
     *
     * @param scae Information about the replaced attribute
     */
    default void attributeReplaced(ServletContextAttributeEvent scae) {
    }
}
