    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    }