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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  package org.apache.http.pool;
28  
29  import java.util.concurrent.Future;
30  
31  import org.apache.http.concurrent.FutureCallback;
32  
33  /**
34   * <tt>ConnPool</tt> represents a shared pool connections can be leased from
35   * and released back to.
36   *
37   * @param <T> the route type that represents the opposite endpoint of a pooled
38   *   connection.
39   * @param <E> the type of the pool entry containing a pooled connection.
40   * @since 4.2
41   */
42  public interface ConnPool<T, E> {
43  
44      /**
45       * Attempts to lease a connection for the given route and with the given
46       * state from the pool.
47       *
48       * @param route route of the connection.
49       * @param state arbitrary object that represents a particular state
50       *  (usually a security principal or a unique token identifying
51       *  the user whose credentials have been used while establishing the connection).
52       *  May be <code>null</code>.
53       * @param callback operation completion callback.
54       *
55       * @return future for a leased pool entry.
56       */
57      Future<E> lease(final T route, final Object state, final FutureCallback<E> callback);
58  
59      /**
60       * Releases the pool entry back to the pool.
61       *
62       * @param entry pool entry leased from the pool
63       * @param reusable flag indicating whether or not the released connection
64       *   is in a consistent state and is safe for further use.
65       */
66      void release(E entry, boolean reusable);
67  
68  }