001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  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.apache.activemq.transport.discovery.zeroconf;
018
019import java.io.IOException;
020import java.net.InetAddress;
021import java.util.HashMap;
022import java.util.Map;
023import java.util.concurrent.atomic.AtomicInteger;
024import javax.jmdns.JmDNS;
025
026public final class JmDNSFactory {
027
028    static Map<InetAddress, UsageTracker> registry = new HashMap<InetAddress, UsageTracker>();
029
030    static class UsageTracker {
031        AtomicInteger count = new AtomicInteger(0);
032        JmDNS jmDNS;
033    }
034
035    private JmDNSFactory() {        
036    }
037    
038    static synchronized JmDNS create(final InetAddress address) throws IOException {
039        UsageTracker tracker = registry.get(address);
040        if (tracker == null) {
041            tracker = new UsageTracker();
042            tracker.jmDNS = JmDNS.create(address);
043            registry.put(address, tracker);
044        }
045        tracker.count.incrementAndGet();
046        return tracker.jmDNS;
047    }
048
049    static synchronized boolean onClose(InetAddress address) {
050        UsageTracker tracker = registry.get(address);
051        if (tracker != null) {
052            if (tracker.count.decrementAndGet() == 0) {
053                registry.remove(address);
054                return true;
055            }
056        }
057        return false;
058    }
059}