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     */
017    package org.apache.activemq.util;
018    
019    import java.net.InetAddress;
020    import java.net.UnknownHostException;
021    
022    public class InetAddressUtil {
023    
024            /**
025             * When using the {@link java.net.InetAddress#getHostName()} method in an 
026             * environment where neither a proper DNS lookup nor an <tt>/etc/hosts</tt> 
027             * entry exists for a given host, the following exception will be thrown: 
028             * <code>
029             * java.net.UnknownHostException: &lt;hostname&gt;: &lt;hostname&gt;
030         *  at java.net.InetAddress.getLocalHost(InetAddress.java:1425)
031         *   ...
032             * </code>
033             * Instead of just throwing an UnknownHostException and giving up, this 
034             * method grabs a suitable hostname from the exception and prevents the 
035             * exception from being thrown. If a suitable hostname cannot be acquired
036             * from the exception, only then is the <tt>UnknownHostException</tt> thrown. 
037             * 
038             * @return The hostname 
039             * @throws UnknownHostException
040             * @see {@link java.net.InetAddress#getLocalHost()}
041             * @see {@link java.net.InetAddress#getHostName()}
042             */
043            public static String getLocalHostName() throws UnknownHostException {
044                    try {
045                            return (InetAddress.getLocalHost()).getHostName();
046                    } catch (UnknownHostException uhe) {
047                            String host = uhe.getMessage(); // host = "hostname: hostname"
048                            if (host != null) {
049                                    int colon = host.indexOf(':');
050                                    if (colon > 0) {
051                                            return host.substring(0, colon);
052                                    }
053                            }
054                            throw uhe;
055                    }
056            }
057    }