1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.commons.text.lookup;
18
19 import java.net.InetAddress;
20 import java.net.UnknownHostException;
21
22 /**
23 * Looks up keys related to the local host: host name, canonical host name, host address.
24 * <p>
25 * The lookup keys are:
26 * </p>
27 * <ul>
28 * <li><b>name</b>: for the local host name, for example {@code EXAMPLE}.</li>
29 * <li><b>canonical-name</b>: for the local canonical host name, for example {@code EXAMPLE.apache.org}.</li>
30 * <li><b>address</b>: for the local host address, for example {@code 192.168.56.1}.</li>
31 * </ul>
32 *
33 * @since 1.3
34 */
35 final class LocalHostStringLookup extends AbstractStringLookup {
36
37 /**
38 * Defines the singleton for this class.
39 */
40 static final LocalHostStringLookup INSTANCE = new LocalHostStringLookup();
41
42 /**
43 * No need to build instances for now.
44 */
45 private LocalHostStringLookup() {
46 // empty
47 }
48
49 /**
50 * Looks up the value of a local host key.
51 *
52 * @param key the key to be looked up, may be null.
53 * @return The value of the environment variable.
54 */
55 @Override
56 public String lookup(final String key) {
57 if (key == null) {
58 return null;
59 }
60 try {
61 switch (key) {
62 case InetAddressKeys.KEY_NAME:
63 return InetAddress.getLocalHost().getHostName();
64 case InetAddressKeys.KEY_CANONICAL_NAME:
65 return InetAddress.getLocalHost().getCanonicalHostName();
66 case InetAddressKeys.KEY_ADDRESS:
67 return InetAddress.getLocalHost().getHostAddress();
68 default:
69 throw new IllegalArgumentException(key);
70 }
71 } catch (final UnknownHostException e) {
72 return null;
73 }
74 }
75 }