001package org.eclipse.aether.spi.connector.checksum;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 *
012 *  http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022import java.util.List;
023import java.util.Map;
024
025import org.eclipse.aether.RepositorySystemSession;
026import org.eclipse.aether.spi.connector.ArtifactDownload;
027
028/**
029 * Component able to provide (expected) checksums to connector beforehand the download happens. Checksum provided by
030 * this component are of kind {@link org.eclipse.aether.spi.connector.checksum.ChecksumPolicy.ChecksumKind#PROVIDED}.
031 *
032 * @since 1.8.0
033 */
034public interface ProvidedChecksumsSource
035{
036    /**
037     * May return the provided checksums (for given artifact transfer) from source other than remote repository, or
038     * {@code null} if it have no checksums available for given transfer. Provided checksums are "opt-in" for
039     * transfer, in a way IF they are available upfront, they will be enforced according to checksum policy
040     * in effect. Otherwise, provided checksum verification is completely left out.
041     * <p>
042     * For enabled provided checksum source is completely acceptable to return {@code null} values, as that carries
043     * the meaning "nothing to add here", as there are no checksums to be provided upfront transfer. Semantically, this
044     * is equivalent to returning empty map, but signals the intent better.
045     *
046     * @param transfer                   The transfer that is about to be executed.
047     * @param checksumAlgorithmFactories The checksum algorithms that are expected.
048     * @return Map of expected checksums, or {@code null}.
049     */
050    Map<String, String> getProvidedArtifactChecksums( RepositorySystemSession session,
051                                                      ArtifactDownload transfer,
052                                                      List<ChecksumAlgorithmFactory> checksumAlgorithmFactories );
053}