001// Copyright 2005 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.tapestry.asset;
016
017/**
018 * Calculates the digest value, as a string, for a particular classpath resource. This is primarily
019 * used by the {@link org.apache.tapestry.asset.AssetService}to authenticate requests (you are not
020 * allowed access to a resource unless you can provide the correct digest value).
021 * 
022 * @author Howard M. Lewis Ship
023 * @since 4.0
024 */
025public interface ResourceDigestSource
026{
027    /**
028     * Calculates the DIGEST checksum for a classpath resource. Because this is expensive, the value
029     * may be cached.
030     * 
031     * @param resourcePath
032     *            the classpath resource, which should start with a leading slash.
033     * @return A string representation of the digest for the provided resource path.
034     * @throws ApplicationRuntimeException
035     *             if the resource does not exist, or there is an error calculating the checksum.
036     */
037
038    public String getDigestForResource(String resourcePath);
039}