1 /* 2 * ==================================================================== 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, 14 * software distributed under the License is distributed on an 15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 16 * KIND, either express or implied. See the License for the 17 * specific language governing permissions and limitations 18 * under the License. 19 * ==================================================================== 20 * 21 * This software consists of voluntary contributions made by many 22 * individuals on behalf of the Apache Software Foundation. For more 23 * information on the Apache Software Foundation, please see 24 * <http://www.apache.org/>. 25 * 26 */ 27 package org.apache.hc.client5.http; 28 29 import java.net.InetAddress; 30 import java.net.InetSocketAddress; 31 import java.net.UnknownHostException; 32 import java.util.Arrays; 33 import java.util.Collections; 34 import java.util.List; 35 import java.util.stream.Collectors; 36 37 import org.apache.hc.core5.annotation.Contract; 38 import org.apache.hc.core5.annotation.ThreadingBehavior; 39 40 /** 41 * Users may implement this interface to override the normal DNS lookup offered 42 * by the OS. 43 * 44 * @since 4.2 45 */ 46 @Contract(threading = ThreadingBehavior.STATELESS) 47 public interface DnsResolver { 48 49 /** 50 * Returns the IP address for the specified host name, or null if the given 51 * host is not recognized or the associated IP address cannot be used to 52 * build an InetAddress instance. 53 * 54 * @see InetAddress 55 * 56 * @param host 57 * The host name to be resolved by this resolver. 58 * @return The IP address associated to the given host name, or null if the 59 * host name is not known by the implementation class. 60 */ 61 InetAddress[] resolve(String host) throws UnknownHostException; 62 63 /** 64 * Gets the fully qualified domain name for given host name. 65 * @since 5.0 66 */ 67 String resolveCanonicalHostname(String host) throws UnknownHostException; 68 69 /** 70 * Returns a list of {@link InetSocketAddress} for the given host with the given port. 71 * 72 * @see InetSocketAddress 73 * 74 * @since 5.5 75 */ 76 default List<InetSocketAddress> resolve(String host, int port) throws UnknownHostException { 77 final InetAddress[] inetAddresses = resolve(host); 78 if (inetAddresses == null) { 79 return Collections.singletonList(InetSocketAddress.createUnresolved(host, port)); 80 } 81 return Arrays.stream(inetAddresses) 82 .map(e -> new InetSocketAddress(e, port)) 83 .collect(Collectors.toList()); 84 } 85 }