    001    // Copyright 2011 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.internal.services.assets;
    016
    017    import org.apache.tapestry5.ioc.Resource;
    018    import org.apache.tapestry5.ioc.internal.util.URLChangeTracker;
    019    import org.apache.tapestry5.services.InvalidationEventHub;
    020    import org.apache.tapestry5.services.InvalidationListener;
    021    import org.apache.tapestry5.services.UpdateListener;
    022    import org.apache.tapestry5.services.assets.ResourceDependencies;
    023
    024    /**
    025     * Tracks resources (at least, resources that can change because they are on the file system) and
    026     * acts as an {@link UpdateListener} to check for changes and notify its listeners.
    027     *
    028     * @since 5.3
    029     */
    030    public interface ResourceChangeTracker extends InvalidationEventHub, ResourceDependencies
    031    {
    032        /**
    033         * Start tracking the resource (or return the last modified time of an already tracked resource). Only file system
    034         * resources are tracked. Resources are tracked until <em>any</em> resource changes, at which points
    035         * {@linkplain InvalidationListener listeners} are notified and the internal state
    036         * is cleared.
    037         *
    038         * @param resource to track
    039         * @return last modified time, to nearest second
    040         * @see URLChangeTracker
    041         */
    042        long trackResource(Resource resource);
    043    }