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 015package org.apache.tapestry5.internal.services.assets; 016 017import org.apache.tapestry5.ioc.Resource; 018import org.apache.tapestry5.ioc.internal.util.URLChangeTracker; 019import org.apache.tapestry5.services.InvalidationEventHub; 020import org.apache.tapestry5.services.InvalidationListener; 021import org.apache.tapestry5.services.UpdateListener; 022import 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 */ 030public 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}