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.util.repository;
020
021import org.eclipse.aether.repository.Proxy;
022import org.eclipse.aether.repository.ProxySelector;
023import org.eclipse.aether.repository.RemoteRepository;
024
025import static java.util.Objects.requireNonNull;
026
027/**
028 * A proxy selector that delegates to another selector but only if a repository has no proxy yet. If a proxy has already
029 * been assigned to a repository, that is selected.
030 */
031public final class ConservativeProxySelector implements ProxySelector {
032
033    private final ProxySelector selector;
034
035    /**
036     * Creates a new selector that delegates to the specified selector.
037     *
038     * @param selector The selector to delegate to in case a repository has no proxy yet, must not be {@code null}.
039     */
040    public ConservativeProxySelector(ProxySelector selector) {
041        this.selector = requireNonNull(selector, "proxy selector cannot be null");
042    }
043
044    public Proxy getProxy(RemoteRepository repository) {
045        requireNonNull(repository, "repository cannot be null");
046        Proxy proxy = repository.getProxy();
047        if (proxy != null) {
048            return proxy;
049        }
050        return selector.getProxy(repository);
051    }
052}