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/*
* ====================================================================
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* .
*
*/
package org.apache.hc.client5.http;
import java.net.InetAddress;
import java.net.UnknownHostException;
/**
* DNS resolver that uses the default OS implementation for resolving host names.
*
* @since 4.2
*/
public class SystemDefaultDnsResolver implements DnsResolver {
/**
* Default instance of {@link SystemDefaultDnsResolver}.
*/
public static final SystemDefaultDnsResolver INSTANCE = new SystemDefaultDnsResolver();
@Override
public InetAddress[] resolve(final String host) throws UnknownHostException {
try {
// Try resolving using the default resolver
return InetAddress.getAllByName(host);
} catch (final UnknownHostException e) {
// If default resolver fails, try stripping the IPv6 zone ID and resolving again
String strippedHost = null;
if (host.charAt(0) == '[') {
final int i = host.lastIndexOf('%');
if (i != -1) {
strippedHost = host.substring(0, i) + "]";
}
}
if (strippedHost != null) {
return InetAddress.getAllByName(strippedHost);
}
throw e;
}
}
@Override
public String resolveCanonicalHostname(final String host) throws UnknownHostException {
if (host == null) {
return null;
}
final InetAddress in = InetAddress.getByName(host);
final String canonicalServer = in.getCanonicalHostName();
if (in.getHostAddress().contentEquals(canonicalServer)) {
return host;
}
return canonicalServer;
}
}
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