001// Copyright 2006, 2008 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.services;
016
017import org.apache.tapestry5.ioc.annotations.UsesConfiguration;
018
019import java.net.URL;
020
021/**
022 * Responsible for determining which classpath resources require checksums, and for generating checksums for such
023 * resources.
024 * <p/>
025 * The service's configuration identifies which file extensions will be secured using an checksum. The default list
026 * (in Tapestry 5.3) is
027 * "class" and "tml". Note that in 5.4, there are no longer any contributions to this service by Tapestry, and
028 * that the service is not normally instantiated: it is maintained for backwards compatibility, in case
029 * applications or third-party modules make a contribution.
030 *
031 * @see org.apache.tapestry5.ioc.internal.util.ClasspathResource
032 * @see org.apache.tapestry5.internal.services.ClasspathAssetFactory
033 * @deprecated Deprecated in 5.4 with no replacement; see release notes about classpath assets moving
034 *             to /META-INF/assets/, and content checksums inside asset URLs
035 */
036@UsesConfiguration(String.class)
037public interface ResourceDigestGenerator
038{
039    /**
040     * Examines the path (typically, the file name extension at the end of the path) to determine if a checksum is
041     * required for the path. The path is {@link org.apache.tapestry5.ioc.Resource} style, without a leading slash.
042     * <p/>
043     * As of Tapestry 5.4, simply returns false.
044     */
045    boolean requiresDigest(String path);
046
047    /**
048     * Reads the content of a URL (presumably, for a resource on the classpath) and generates a digest of its content.
049     * This digest will be incorporated into the URL provided to the client, to verify that the client has been
050     * "granted" access to this resource. This is only used for resources where {@link #requiresDigest(String)} is
051     * true.
052     * <p/>
053     * As of Tapestry 5.4, simply returns null.
054     *
055     * @param url
056     * @return the digest for the resource
057     */
058    String generateDigest(URL url);
059}