1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27 package org.apache.hc.client5.http;
28
29 import java.net.InetAddress;
30 import java.net.InetSocketAddress;
31 import java.net.UnknownHostException;
32 import java.util.Arrays;
33 import java.util.Collections;
34 import java.util.List;
35 import java.util.stream.Collectors;
36
37 import org.apache.hc.core5.annotation.Contract;
38 import org.apache.hc.core5.annotation.ThreadingBehavior;
39
40 /**
41 * Users may implement this interface to override the normal DNS lookup offered
42 * by the OS.
43 *
44 * @since 4.2
45 */
46 @Contract(threading = ThreadingBehavior.STATELESS)
47 public interface DnsResolver {
48
49 /**
50 * Returns the IP address for the specified host name, or null if the given
51 * host is not recognized or the associated IP address cannot be used to
52 * build an InetAddress instance.
53 *
54 * @see InetAddress
55 *
56 * @param host
57 * The host name to be resolved by this resolver.
58 * @return The IP address associated to the given host name, or null if the
59 * host name is not known by the implementation class.
60 */
61 InetAddress[] resolve(String host) throws UnknownHostException;
62
63 /**
64 * Gets the fully qualified domain name for given host name.
65 * @since 5.0
66 */
67 String resolveCanonicalHostname(String host) throws UnknownHostException;
68
69 /**
70 * Returns a list of {@link InetSocketAddress} for the given host with the given port.
71 *
72 * @see InetSocketAddress
73 *
74 * @since 5.5
75 */
76 default List<InetSocketAddress> resolve(String host, int port) throws UnknownHostException {
77 final InetAddress[] inetAddresses = resolve(host);
78 if (inetAddresses == null) {
79 return Collections.singletonList(InetSocketAddress.createUnresolved(host, port));
80 }
81 return Arrays.stream(inetAddresses)
82 .map(e -> new InetSocketAddress(e, port))
83 .collect(Collectors.toList());
84 }
85 }