io.netty.resolver.dns.NameServerComparator Maven / Gradle / Ivy
/*
* Copyright 2018 The Netty Project
*
* The Netty Project 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.
*/
package io.netty.resolver.dns;
import io.netty.util.internal.ObjectUtil;
import java.io.Serializable;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.util.Comparator;
import java.util.List;
/**
* Special {@link Comparator} implementation to sort the nameservers to use when follow redirects.
*
* This implementation follows all the semantics listed in the
* Comparator apidocs
* with the limitation that {@link InetSocketAddress#equals(Object)} will not result in the same return value as
* {@link #compare(InetSocketAddress, InetSocketAddress)}. This is completely fine as this should only be used
* to sort {@link List}s.
*/
public final class NameServerComparator implements Comparator, Serializable {
private static final long serialVersionUID = 8372151874317596185L;
private final Class preferredAddressType;
public NameServerComparator(Class preferredAddressType) {
this.preferredAddressType = ObjectUtil.checkNotNull(preferredAddressType, "preferredAddressType");
}
@Override
public int compare(InetSocketAddress addr1, InetSocketAddress addr2) {
if (addr1.equals(addr2)) {
return 0;
}
if (!addr1.isUnresolved() && !addr2.isUnresolved()) {
if (addr1.getAddress().getClass() == addr2.getAddress().getClass()) {
return 0;
}
return preferredAddressType.isAssignableFrom(addr1.getAddress().getClass()) ? -1 : 1;
}
if (addr1.isUnresolved() && addr2.isUnresolved()) {
return 0;
}
return addr1.isUnresolved() ? 1 : -1;
}
}