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.connector.checksum;
020
021import java.util.List;
022import java.util.Map;
023
024import org.eclipse.aether.RepositorySystemSession;
025import org.eclipse.aether.spi.connector.ArtifactDownload;
026
027/**
028 * Component able to provide (expected) checksums to connector beforehand the download happens. Checksum provided by
029 * this component are of kind {@link org.eclipse.aether.spi.connector.checksum.ChecksumPolicy.ChecksumKind#PROVIDED}.
030 *
031 * @since 1.8.0
032 */
033public interface ProvidedChecksumsSource {
034    /**
035     * May return the provided checksums (for given artifact transfer) from source other than remote repository, or
036     * {@code null} if it have no checksums available for given transfer. Provided checksums are "opt-in" for
037     * transfer, in a way IF they are available upfront, they will be enforced according to checksum policy
038     * in effect. Otherwise, provided checksum verification is completely left out.
039     * <p>
040     * For enabled provided checksum source is completely acceptable to return {@code null} values, as that carries
041     * the meaning "nothing to add here", as there are no checksums to be provided upfront transfer. Semantically, this
042     * is equivalent to returning empty map, but signals the intent better.
043     *
044     * @param transfer                   The transfer that is about to be executed.
045     * @param checksumAlgorithmFactories The checksum algorithms that are expected.
046     * @return Map of expected checksums, or {@code null}.
047     */
048    Map<String, String> getProvidedArtifactChecksums(
049            RepositorySystemSession session,
050            ArtifactDownload transfer,
051            List<ChecksumAlgorithmFactory> checksumAlgorithmFactories);
052}