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 */
027
028package org.apache.http.conn.routing;
029
030import org.apache.http.HttpException;
031import org.apache.http.HttpHost;
032import org.apache.http.HttpRequest;
033import org.apache.http.protocol.HttpContext;
034
035/**
036 * Encapsulates logic to compute a {@link HttpRoute} to a target host.
037 * Implementations may for example be based on parameters, or on the
038 * standard Java system properties.
039 * <p>
040 * Implementations of this interface must be thread-safe. Access to shared
041 * data must be synchronized as methods of this interface may be executed
042 * from multiple threads.
043 * </p>
044 *
045 * @since 4.0
046 */
047public interface HttpRoutePlanner {
048
049    /**
050     * Determines the route for a request.
051     *
052     * @param target    the target host for the request.
053     *                  Implementations may accept {@code null}
054     *                  if they can still determine a route, for example
055     *                  to a default target or by inspecting the request.
056     * @param request   the request to execute
057     * @param context   the context to use for the subsequent execution.
058     *                  Implementations may accept {@code null}.
059     *
060     * @return  the route that the request should take
061     *
062     * @throws HttpException    in case of a problem
063     */
064    public HttpRoute determineRoute(HttpHost target,
065                                    HttpRequest request,
066                                    HttpContext context) throws HttpException;
067
068}