001// Copyright 2006, 2008, 2009, 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;
016
017import org.apache.tapestry5.ioc.Resource;
018import org.apache.tapestry5.services.InvalidationEventHub;
019import org.apache.tapestry5.services.ResourceDigestGenerator;
020
021/**
022 * Caches information about resources on the classpath. In addition, acts as an invalidation hub for any resources for
023 * which information is obtained (when any of the resources are changed, invalidation listeners are notified so they can
024 * clear their caches).
025 * <p/>
026 * Note that the name and role of this class changed (and diminished) quite a bit in Tapestry 5.3. It is now focused on
027 * determining which files require a digest, and which what the digests are for resources.
028 * <p/>
029 * Further, in 5.4, this service has been stripped down to an unused placeholder; it only present to prevent
030 * errors where modules have contributed a String extension to protected (even though the service is internal). As of
031 * 5.4, all assets have a built-in checksum in the URL directly (in 5.3 and earlier, the URL included the application
032 * version number).
033 *
034 * @deprecated Deprecated in 5.4 with no replacement; see release notes about classpath assets moving to /META-INF/assets/.
035 *             To be removed in 5.5.
036 */
037public interface ResourceDigestManager extends InvalidationEventHub
038{
039    /**
040     * Returns true if the path requires that the client URL for the resource include a digest to validate that the
041     * client is authorized to access the resource.
042     *
043     * As of 5.4, simply returns false.
044     *
045     * @param resource
046     * @return true if digest is required for the resource
047     * @see ResourceDigestGenerator#requiresDigest(String)
048     */
049    boolean requiresDigest(Resource resource);
050
051    /**
052     * Returns the digest for the given path.
053     * <p/>
054     * As of 5.4, simple returns null.
055     *
056     * @param resource
057     * @return the digest, or null if the resource does not exist
058     */
059    String getDigest(Resource resource);
060}