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Smack/source/org/jivesoftware/smack/util/dns/JavaxResolver.java

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/**
* Copyright 2013 Florian Schmaus
*
* All rights reserved. Licensed 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 org.jivesoftware.smack.util.dns;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
import javax.naming.NamingEnumeration;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
import org.jivesoftware.smack.util.DNSUtil;
/**
* A DNS resolver (mostly for SRV records), which makes use of the API provided in the javax.* namepsace.
*
* @author Florian Schmaus
*
*/
public class JavaxResolver extends DNSResolver {
private static JavaxResolver instance;
private static DirContext dirContext;
static {
try {
Hashtable<String, String> env = new Hashtable<String, String>();
env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
dirContext = new InitialDirContext(env);
} catch (Exception e) {
// Ignore.
}
// Try to set this DNS resolver as primary one
DNSUtil.setDNSResolver(maybeGetInstance());
}
private JavaxResolver() {
}
public static DNSResolver maybeGetInstance() {
if (instance == null && isSupported()) {
instance = new JavaxResolver();
}
return instance;
}
public static boolean isSupported() {
return dirContext != null;
}
@Override
public List<SRVRecord> lookupSRVRecords(String name) {
List<SRVRecord> res = new ArrayList<SRVRecord>();
try {
Attributes dnsLookup = dirContext.getAttributes(name, new String[]{"SRV"});
Attribute srvAttribute = dnsLookup.get("SRV");
@SuppressWarnings("unchecked")
NamingEnumeration<String> srvRecords = (NamingEnumeration<String>) srvAttribute.getAll();
while (srvRecords.hasMore()) {
String srvRecordString = srvRecords.next();
String[] srvRecordEntries = srvRecordString.split(" ");
int priority = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 4]);
int port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 2]);
int weight = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 3]);
String host = srvRecordEntries[srvRecordEntries.length - 1];
SRVRecord srvRecord;
try {
srvRecord = new SRVRecord(host, port, priority, weight);
} catch (Exception e) {
continue;
}
res.add(srvRecord);
}
} catch (Exception e) {
}
return res;
}
}