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 import org.apache.commons.text.StringSubstitutor;
23
24 /**
25 * Looks up keys related to DNS entries like host name, canonical host name, host address.
26 * <p>
27 * The lookup keys are:
28 * </p>
29 * <ul>
30 * <li><b>name|<em>address</em></b>: for the host name, for example {@code "name|93.184.216.34"} ->
31 * {@code "example.com"}.</li>
32 * <li><b>canonical-name|<em>address</em></b>: for the canonical host name, for example {@code "name|93.184.216.34"} ->
33 * {@code "example.com"}.</li>
34 * <li><b>address|<em>hostname</em></b>: for the host address, for example {@code "address|example.com"} ->
35 * {@code "93.184.216.34"}.</li>
36 * <li><b><em>address</em></b>: same as {@code address|hostname}.</li>
37 * </ul>
38 *
39 * <p>
40 * Using a {@link StringLookup} from the {@link StringLookupFactory}:
41 * </p>
42 *
43 * <pre>
44 * StringLookupFactory.INSTANCE.dnsStringLookup().lookup("address|apache.org");
45 * </pre>
46 * <p>
47 * Using a {@link StringSubstitutor}:
48 * </p>
49 *
50 * <pre>
51 * StringSubstitutor.createInterpolator().replace("... ${dns:address|apache.org} ..."));
52 * </pre>
53 * <p>
54 * The above examples convert {@code "address|apache.org"} to {@code "95.216.24.32} (or {@code "40.79.78.1"}).
55 * </p>
56 *
57 * @since 1.8
58 */
59 final class DnsStringLookup extends AbstractStringLookup {
60
61 /**
62 * Defines the singleton for this class.
63 */
64 static final DnsStringLookup INSTANCE = new DnsStringLookup();
65
66 /**
67 * No need to build instances for now.
68 */
69 private DnsStringLookup() {
70 // empty
71 }
72
73 /**
74 * Looks up the DNS value of the key.
75 *
76 * @param key the key to be looked up, may be null
77 * @return The DNS value.
78 */
79 @Override
80 public String lookup(final String key) {
81 if (key == null) {
82 return null;
83 }
84 final String[] keys = key.trim().split("\\|");
85 final int keyLen = keys.length;
86 final String subKey = keys[0].trim();
87 final String subValue = keyLen < 2 ? key : keys[1].trim();
88 try {
89 final InetAddress inetAddress = InetAddress.getByName(subValue);
90 switch (subKey) {
91 case InetAddressKeys.KEY_NAME:
92 return inetAddress.getHostName();
93 case InetAddressKeys.KEY_CANONICAL_NAME:
94 return inetAddress.getCanonicalHostName();
95 case InetAddressKeys.KEY_ADDRESS:
96 return inetAddress.getHostAddress();
97 default:
98 return inetAddress.getHostAddress();
99 }
100 } catch (final UnknownHostException e) {
101 return null;
102 }
103 }
104
105 }