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Easy Redis Java client and Real-Time Data Platform. Valkey compatible. Sync/Async/RxJava3/Reactive API. Client side caching. Over 50 Redis based Java objects and services: JCache API, Apache Tomcat, Hibernate, Spring, Set, Multimap, SortedSet, Map, List, Queue, Deque, Semaphore, Lock, AtomicLong, Map Reduce, Bloom filter, Scheduler, RPC
/*
* Copyright 2024 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:
*
* https://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 java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* Looks up the {@code nameserver}s from the {@code /etc/resolv.conf} file, intended for Linux and macOS.
*/
final class ResolvConf {
private final List nameservers;
/**
* Reads from the given reader and extracts the {@code nameserver}s using the syntax of the
* {@code /etc/resolv.conf} file, see {@code man resolv.conf}.
*
* @param reader contents of {@code resolv.conf} are read from this {@link BufferedReader},
* up to the caller to close it
*/
static ResolvConf fromReader(BufferedReader reader) throws IOException {
return new ResolvConf(reader);
}
/**
* Reads the given file and extracts the {@code nameserver}s using the syntax of the
* {@code /etc/resolv.conf} file, see {@code man resolv.conf}.
*/
static ResolvConf fromFile(String file) throws IOException {
FileReader fileReader = new FileReader(file);
try {
BufferedReader reader = new BufferedReader(new FileReader(file));
return fromReader(reader);
} finally {
fileReader.close();
}
}
/**
* Returns the {@code nameserver}s from the {@code /etc/resolv.conf} file. The file is only read once
* during the lifetime of this class.
*/
static ResolvConf system() {
ResolvConf resolvConv = ResolvConfLazy.machineResolvConf;
if (resolvConv != null) {
return resolvConv;
}
throw new IllegalStateException("/etc/resolv.conf could not be read");
}
private ResolvConf(BufferedReader reader) throws IOException {
List nameservers = new ArrayList();
String ln;
while ((ln = reader.readLine()) != null) {
ln = ln.trim();
if (ln.isEmpty()) {
continue;
}
if (ln.startsWith("nameserver")) {
ln = ln.substring("nameserver".length()).trim();
nameservers.add(new InetSocketAddress(ln, 53));
}
}
this.nameservers = Collections.unmodifiableList(nameservers);
}
List getNameservers() {
return nameservers;
}
private static final class ResolvConfLazy {
static final ResolvConf machineResolvConf;
static {
ResolvConf resolvConf;
try {
resolvConf = ResolvConf.fromFile("/etc/resolv.conf");
} catch (IOException e) {
resolvConf = null;
} catch (SecurityException ignore) {
resolvConf = null;
}
machineResolvConf = resolvConf;
}
}
}
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