001package org.eclipse.aether.util.repository;
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 static java.util.Objects.requireNonNull;
023
024import org.eclipse.aether.repository.Proxy;
025import org.eclipse.aether.repository.ProxySelector;
026import org.eclipse.aether.repository.RemoteRepository;
027
028/**
029 * A proxy selector that delegates to another selector but only if a repository has no proxy yet. If a proxy has already
030 * been assigned to a repository, that is selected.
031 */
032public final class ConservativeProxySelector
033    implements ProxySelector
034{
035
036    private final ProxySelector selector;
037
038    /**
039     * Creates a new selector that delegates to the specified selector.
040     *
041     * @param selector The selector to delegate to in case a repository has no proxy yet, must not be {@code null}.
042     */
043    public ConservativeProxySelector( ProxySelector selector )
044    {
045        this.selector = requireNonNull( selector, "proxy selector cannot be null" );
046    }
047
048    public Proxy getProxy( RemoteRepository repository )
049    {
050        requireNonNull( repository, "repository cannot be null" );
051        Proxy proxy = repository.getProxy();
052        if ( proxy != null )
053        {
054            return proxy;
055        }
056        return selector.getProxy( repository );
057    }
058
059}