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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  
28  package org.apache.http.conn.routing;
29  
30  import org.apache.http.HttpException;
31  import org.apache.http.HttpHost;
32  import org.apache.http.HttpRequest;
33  import org.apache.http.protocol.HttpContext;
34  
35  /**
36   * Encapsulates logic to compute a {@link HttpRoute} to a target host.
37   * Implementations may for example be based on parameters, or on the
38   * standard Java system properties.
39   * <p>
40   * Implementations of this interface must be thread-safe. Access to shared
41   * data must be synchronized as methods of this interface may be executed
42   * from multiple threads.
43   * </p>
44   *
45   * @since 4.0
46   */
47  public interface HttpRoutePlanner {
48  
49      /**
50       * Determines the route for a request.
51       *
52       * @param target    the target host for the request.
53       *                  Implementations may accept {@code null}
54       *                  if they can still determine a route, for example
55       *                  to a default target or by inspecting the request.
56       * @param request   the request to execute
57       * @param context   the context to use for the subsequent execution.
58       *                  Implementations may accept {@code null}.
59       *
60       * @return  the route that the request should take
61       *
62       * @throws HttpException    in case of a problem
63       */
64      public HttpRoute determineRoute(HttpHost target,
65                                      HttpRequest request,
66                                      HttpContext context) throws HttpException;
67  
68  }