001/**
002 *
003 * Copyright 2013-2014 Florian Schmaus
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.jivesoftware.smack.util.dns.javax;
018
019import java.util.ArrayList;
020import java.util.Collections;
021import java.util.Hashtable;
022import java.util.List;
023
024import javax.naming.NamingEnumeration;
025import javax.naming.NamingException;
026import javax.naming.directory.Attribute;
027import javax.naming.directory.Attributes;
028import javax.naming.directory.DirContext;
029import javax.naming.directory.InitialDirContext;
030
031import org.jivesoftware.smack.initializer.SmackAndOsgiInitializer;
032import org.jivesoftware.smack.util.DNSUtil;
033import org.jivesoftware.smack.util.dns.DNSResolver;
034import org.jivesoftware.smack.util.dns.SRVRecord;
035
036/**
037 * A DNS resolver (mostly for SRV records), which makes use of the API provided in the javax.* namespace.
038 * 
039 * @author Florian Schmaus
040 *
041 */
042public class JavaxResolver extends SmackAndOsgiInitializer implements DNSResolver {
043    
044    private static JavaxResolver instance;
045    private static DirContext dirContext;
046    
047    static {
048        try {
049            Hashtable<String, String> env = new Hashtable<String, String>();
050            env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
051            dirContext = new InitialDirContext(env);
052        } catch (Exception e) {
053            // Ignore.
054        }
055
056        // Try to set this DNS resolver as primary one
057        setup();
058    }
059    
060    public JavaxResolver() {
061        
062    }
063
064    public static synchronized DNSResolver getInstance() {
065        if (instance == null && isSupported()) {
066            instance = new JavaxResolver();
067        }
068        return instance;
069    }
070
071    public static boolean isSupported() {
072        return dirContext != null;
073    }
074
075    public static void setup() {
076        DNSUtil.setDNSResolver(getInstance());
077    }
078
079    @Override
080    public List<SRVRecord> lookupSRVRecords(String name) throws NamingException {
081        List<SRVRecord> res = new ArrayList<SRVRecord>();
082
083        Attributes dnsLookup = dirContext.getAttributes(name, new String[] { "SRV" });
084        Attribute srvAttribute = dnsLookup.get("SRV");
085        if (srvAttribute == null)
086            return res;
087        @SuppressWarnings("unchecked")
088        NamingEnumeration<String> srvRecords = (NamingEnumeration<String>) srvAttribute.getAll();
089        while (srvRecords.hasMore()) {
090            String srvRecordString = srvRecords.next();
091            String[] srvRecordEntries = srvRecordString.split(" ");
092            int priority = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 4]);
093            int port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 2]);
094            int weight = Integer.parseInt(srvRecordEntries[srvRecordEntries.length - 3]);
095            String host = srvRecordEntries[srvRecordEntries.length - 1];
096
097            SRVRecord srvRecord = new SRVRecord(host, port, priority, weight);
098            res.add(srvRecord);
099        }
100        return res;
101    }
102
103    @Override
104    public List<Exception> initialize() {
105        return initialize(null);
106    }
107
108    @Override
109    public List<Exception> initialize(ClassLoader classLoader) {
110        setup();
111        return Collections.emptyList();
112    }
113}