001// Licensed under the Apache License, Version 2.0 (the "License");
002// you may not use this file except in compliance with the License.
003// You may obtain a copy of the License at
004//
005//     http://www.apache.org/licenses/LICENSE-2.0
006//
007// Unless required by applicable law or agreed to in writing, software
008// distributed under the License is distributed on an "AS IS" BASIS,
009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
010// See the License for the specific language governing permissions and
011// limitations under the License.
012
013package org.apache.tapestry5.services;
014
015import org.apache.tapestry5.ioc.annotations.UsesConfiguration;
016
017import java.net.URL;
018
019/**
020 * Responsible for determining which classpath resources require checksums, and for generating checksums for such
021 * resources.
022 *
023 * The service's configuration identifies which file extensions will be secured using an checksum. The default list
024 * (in Tapestry 5.3) is
025 * "class" and "tml". Note that in 5.4, there are no longer any contributions to this service by Tapestry, and
026 * that the service is not normally instantiated: it is maintained for backwards compatibility, in case
027 * applications or third-party modules make a contribution.
028 *
029 * @see org.apache.tapestry5.ioc.internal.util.ClasspathResource
030 * @see org.apache.tapestry5.internal.services.ClasspathAssetFactory
031 * @deprecated Deprecated in 5.4 with no replacement; see release notes about classpath assets moving
032 *             to /META-INF/assets/, and content checksums inside asset URLs
033 */
034@UsesConfiguration(String.class)
035public interface ResourceDigestGenerator
036{
037    /**
038     * Examines the path (typically, the file name extension at the end of the path) to determine if a checksum is
039     * required for the path. The path is {@link org.apache.tapestry5.ioc.Resource} style, without a leading slash.
040     *
041     * As of Tapestry 5.4, simply returns false.
042     */
043    boolean requiresDigest(String path);
044
045    /**
046     * Reads the content of a URL (presumably, for a resource on the classpath) and generates a digest of its content.
047     * This digest will be incorporated into the URL provided to the client, to verify that the client has been
048     * "granted" access to this resource. This is only used for resources where {@link #requiresDigest(String)} is
049     * true.
050     *
051     * As of Tapestry 5.4, simply returns null.
052     *
053     * @param url
054     * @return the digest for the resource
055     */
056    String generateDigest(URL url);
057}