001    // Copyright 2006, 2007 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry5.services;
016    
017    /**
018     * Interface for objects that may cache information that can be invalidated. Invalidation occurs when external files,
019     * from which in-memory data is cached, is determined to have changed. Granularity is very limited; when any external
020     * file is found to have changed, the event is fired (with the expectation that the cleared cache will be repopulated as
021     * necessary).
022     *
023     * @see org.apache.tapestry5.services.InvalidationEventHub
024     * @since 5.1.0.0
025     */
026    public interface InvalidationListener
027    {
028        /**
029         * Invoked to indicate that some object is invalid. The receiver should clear its cache.
030         */
031        void objectWasInvalidated();
032    }