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.UnknownHostException; 31 32 /** 33 * DNS resolver that uses the default OS implementation for resolving host names. 34 * 35 * @since 4.2 36 */ 37 public class SystemDefaultDnsResolver implements DnsResolver { 38 39 public static final SystemDefaultDnsResolversolver.html#SystemDefaultDnsResolver">SystemDefaultDnsResolver INSTANCE = new SystemDefaultDnsResolver(); 40 41 @Override 42 public InetAddress[] resolve(final String host) throws UnknownHostException { 43 return InetAddress.getAllByName(host); 44 } 45 46 @Override 47 public String resolveCanonicalHostname(final String host) throws UnknownHostException { 48 if (host == null) { 49 return null; 50 } 51 final InetAddress in = InetAddress.getByName(host); 52 final String canonicalServer = in.getCanonicalHostName(); 53 if (in.getHostAddress().contentEquals(canonicalServer)) { 54 return host; 55 } 56 return canonicalServer; 57 } 58 }