001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.eclipse.aether.spi.checksums;
020
021import java.util.List;
022import java.util.Map;
023
024import org.eclipse.aether.RepositorySystemSession;
025import org.eclipse.aether.repository.RemoteRepository;
026import org.eclipse.aether.spi.connector.ArtifactDownload;
027import org.eclipse.aether.spi.connector.checksum.ChecksumAlgorithmFactory;
028import org.eclipse.aether.spi.connector.checksum.ChecksumPolicy;
029
030/**
031 * Component able to provide (expected) checksums to connector beforehand the download happens. Checksum provided by
032 * this component are of kind {@link ChecksumPolicy.ChecksumKind#PROVIDED}. Resolver by default provides one
033 * implementation: an adapter, that makes {@link TrustedChecksumsSource} into {@link ProvidedChecksumsSource}. Users
034 * are encouraged to rely on this adapter, and do not create their own implementations.
035 *
036 * @since 1.9.14
037 */
038public interface ProvidedChecksumsSource {
039    /**
040     * May return the provided checksums (for given artifact transfer) from source other than remote repository, or
041     * {@code null} if it have no checksums available for given transfer. Provided checksums are "opt-in" for
042     * transfer, in a way IF they are available upfront, they will be enforced according to checksum policy
043     * in effect. Otherwise, provided checksum verification is completely left out.
044     * <p>
045     * For enabled provided checksum source is completely acceptable to return {@code null} values, as that carries
046     * the meaning "nothing to add here", as there are no checksums to be provided upfront transfer. Semantically, this
047     * is equivalent to returning empty map, but signals the intent better.
048     *
049     * @param session                    The current session.
050     * @param transfer                   The transfer that is about to be executed.
051     * @param remoteRepository           The remote repository connector is about to contact.
052     * @param checksumAlgorithmFactories The checksum algorithms that are expected.
053     * @return Map of expected checksums, or {@code null}.
054     */
055    Map<String, String> getProvidedArtifactChecksums(
056            RepositorySystemSession session,
057            ArtifactDownload transfer,
058            RemoteRepository remoteRepository,
059            List<ChecksumAlgorithmFactory> checksumAlgorithmFactories);
060}