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.UnknownHostException;
31
32 import org.apache.hc.core5.annotation.Contract;
33 import org.apache.hc.core5.annotation.ThreadingBehavior;
34
35 /**
36 * Users may implement this interface to override the normal DNS lookup offered
37 * by the OS.
38 *
39 * @since 4.2
40 */
41 @Contract(threading = ThreadingBehavior.STATELESS)
42 public interface DnsResolver {
43
44 /**
45 * Returns the IP address for the specified host name, or null if the given
46 * host is not recognized or the associated IP address cannot be used to
47 * build an InetAddress instance.
48 *
49 * @see InetAddress
50 *
51 * @param host
52 * The host name to be resolved by this resolver.
53 * @return The IP address associated to the given host name, or null if the
54 * host name is not known by the implementation class.
55 */
56 InetAddress[] resolve(String host) throws UnknownHostException;
57
58 /**
59 * Gets the fully qualified domain name for given host name.
60 * @since 5.0
61 */
62 String resolveCanonicalHostname(String host) throws UnknownHostException;
63
64 }