001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements. See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache license, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License. You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the license for the specific language governing permissions and
015     * limitations under the license.
016     */
017    package org.apache.log4j.spi;
018    
019    import org.apache.log4j.Appender;
020    import org.apache.log4j.Category;
021    
022    /**
023     Listen to events occurring within a Hierarchy.
024    
025     @since 1.2
026    
027     */
028    public interface HierarchyEventListener {
029    
030        void addAppenderEvent(Category cat, Appender appender);
031    
032        void removeAppenderEvent(Category cat, Appender appender);
033    }