001    /*
002     * Copyright 2003-2004 The Apache Software Foundation
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     *     http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    package org.apache.commons.events.observable.standard;
017    
018    import org.apache.commons.events.observable.ModificationListener;
019    
020    /**
021     * A listener for the <code>StandardModificationHandler</code> that is called
022     * when a collection is about to be modified.
023     *
024     * @since Commons Events 1.0
025     * @version $Revision: 155443 $ $Date: 2005-02-26 13:19:51 +0000 (Sat, 26 Feb 2005) $
026     * 
027     * @author Stephen Colebourne
028     */
029    public interface StandardPreModificationListener extends ModificationListener {
030    
031        /**
032         * A collection modification is occurring.
033         * <p>
034         * To veto the change, throw <code>ModicationVetoedException</code>.
035         * <p>
036         * This method should be processed quickly, as with all event handling.
037         * It should also avoid modifying the event source (the collection).
038         * 
039         * @param event  the event detail
040         * @throws ModicationVetoedException to veto
041         */
042        public void modificationOccurring(StandardPreModificationEvent event);
043        
044    }