1/*
2 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package sun.net.dns;
27
28import java.util.List;
29
30/**
31 * The configuration of the client resolver.
32 *
33 * <p>A ResolverConfiguration is a singleton that represents the
34 * configuration of the client resolver. The ResolverConfiguration
35 * is opened by invoking the {@link #open() open} method.
36 *
37 * @since 1.4
38 */
39
40public abstract class ResolverConfiguration {
41
42    private static final Object lock = new Object();
43
44    private static ResolverConfiguration provider;
45
46    protected ResolverConfiguration() { }
47
48    /**
49     * Opens the resolver configuration.
50     *
51     * @return the resolver configuration
52     */
53    public static ResolverConfiguration open() {
54        synchronized (lock) {
55            if (provider == null) {
56                provider = new sun.net.dns.ResolverConfigurationImpl();
57            }
58            return provider;
59        }
60    }
61
62    /**
63     * Returns a list corresponding to the domain search path. The
64     * list is ordered by the search order used for host name lookup.
65     * Each element in the list returns a {@link java.lang.String}
66     * containing a domain name or suffix.
67     *
68     * @return list of domain names
69     */
70    public abstract List<String> searchlist();
71
72    /**
73     * Returns a list of name servers used for host name lookup.
74     * Each element in the list returns a {@link java.lang.String}
75     * containing the textual representation of the IP address of
76     * the name server.
77     *
78     * @return list of the name servers
79     */
80    public abstract List<String> nameservers();
81
82
83    /**
84     * Options representing certain resolver variables of
85     * a {@link ResolverConfiguration}.
86     */
87    public abstract static class Options {
88
89        /**
90         * Returns the maximum number of attempts the resolver
91         * will connect to each name server before giving up
92         * and returning an error.
93         *
94         * @return the resolver attempts value or -1 is unknown
95         */
96        public int attempts() {
97            return -1;
98        }
99
100        /**
101         * Returns the basic retransmit timeout, in milliseconds,
102         * used by the resolver. The resolver will typically use
103         * an exponential backoff algorithm where the timeout is
104         * doubled for every retransmit attempt. The basic
105         * retransmit timeout, returned here, is the initial
106         * timeout for the exponential backoff algorithm.
107         *
108         * @return the basic retransmit timeout value or -1
109         *         if unknown
110         */
111        public int retrans() {
112            return -1;
113        }
114    }
115
116    /**
117     * Returns the {@link #Options} for the resolver.
118     *
119     * @return options for the resolver
120     */
121    public abstract Options options();
122}
123