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.camel.util;
018
019import java.net.InetAddress;
020import java.net.UnknownHostException;
021
022/**
023 * Util class for {@link java.net.InetAddress}
024 */
025public final class InetAddressUtil {
026
027    private InetAddressUtil() {
028        // util class
029    }
030
031    /**
032     * When using the {@link java.net.InetAddress#getHostName()} method in an
033     * environment where neither a proper DNS lookup nor an <tt>/etc/hosts</tt>
034     * entry exists for a given host, the following exception will be thrown:
035     * <p/>
036     * <code>
037     * java.net.UnknownHostException: &lt;hostname&gt;: &lt;hostname&gt;
038     * at java.net.InetAddress.getLocalHost(InetAddress.java:1425)
039     * ...
040     * </code>
041     * <p/>
042     * Instead of just throwing an UnknownHostException and giving up, this
043     * method grabs a suitable hostname from the exception and prevents the
044     * exception from being thrown. If a suitable hostname cannot be acquired
045     * from the exception, only then is the <tt>UnknownHostException</tt> thrown.
046     *
047     * @return the hostname
048     * @throws UnknownHostException is thrown if hostname could not be resolved
049     */
050    public static String getLocalHostName() throws UnknownHostException {
051        try {
052            return (InetAddress.getLocalHost()).getHostName();
053        } catch (UnknownHostException uhe) {
054            String host = uhe.getMessage(); // host = "hostname: hostname"
055            if (host != null) {
056                int colon = host.indexOf(':');
057                if (colon > 0) {
058                    return host.substring(0, colon);
059                }
060            }
061            throw uhe;
062        }
063    }
064
065}