001/*
002 * ====================================================================
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *   http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing,
014 * software distributed under the License is distributed on an
015 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
016 * KIND, either express or implied.  See the License for the
017 * specific language governing permissions and limitations
018 * under the License.
019 * ====================================================================
020 *
021 * This software consists of voluntary contributions made by many
022 * individuals on behalf of the Apache Software Foundation.  For more
023 * information on the Apache Software Foundation, please see
024 * <http://www.apache.org/>.
025 *
026 */
027package org.apache.http.impl.conn;
028
029import java.net.InetAddress;
030import java.net.UnknownHostException;
031import java.util.Arrays;
032import java.util.Map;
033import java.util.concurrent.ConcurrentHashMap;
034
035import org.apache.commons.logging.Log;
036import org.apache.commons.logging.LogFactory;
037import org.apache.http.conn.DnsResolver;
038import org.apache.http.util.Args;
039
040/**
041 * In-memory {@link DnsResolver} implementation.
042 *
043 * @since 4.2
044 */
045public class InMemoryDnsResolver implements DnsResolver {
046
047    /** Logger associated to this class. */
048    private final Log log = LogFactory.getLog(InMemoryDnsResolver.class);
049
050    /**
051     * In-memory collection that will hold the associations between a host name
052     * and an array of InetAddress instances.
053     */
054    private final Map<String, InetAddress[]> dnsMap;
055
056    /**
057     * Builds a DNS resolver that will resolve the host names against a
058     * collection held in-memory.
059     */
060    public InMemoryDnsResolver() {
061        dnsMap = new ConcurrentHashMap<String, InetAddress[]>();
062    }
063
064    /**
065     * Associates the given array of IP addresses to the given host in this DNS overrider.
066     * The IP addresses are assumed to be already resolved.
067     *
068     * @param host
069     *            The host name to be associated with the given IP.
070     * @param ips
071     *            array of IP addresses to be resolved by this DNS overrider to the given
072     *            host name.
073     */
074    public void add(final String host, final InetAddress... ips) {
075        Args.notNull(host, "Host name");
076        Args.notNull(ips, "Array of IP addresses");
077        dnsMap.put(host, ips);
078    }
079
080    /**
081     * {@inheritDoc}
082     */
083    @Override
084    public InetAddress[] resolve(final String host) throws UnknownHostException {
085        final InetAddress[] resolvedAddresses = dnsMap.get(host);
086        if (log.isInfoEnabled()) {
087            log.info("Resolving " + host + " to " + Arrays.deepToString(resolvedAddresses));
088        }
089        if(resolvedAddresses == null){
090            throw new UnknownHostException(host + " cannot be resolved");
091        }
092        return resolvedAddresses;
093    }
094
095}