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.pool;
028
029import java.util.concurrent.Future;
030
031import org.apache.http.concurrent.FutureCallback;
032
033/**
034 * {@code ConnPool} represents a shared pool connections can be leased from
035 * and released back to.
036 *
037 * @param <T> the route type that represents the opposite endpoint of a pooled
038 *   connection.
039 * @param <E> the type of the pool entry containing a pooled connection.
040 * @since 4.2
041 */
042public interface ConnPool<T, E> {
043
044    /**
045     * Attempts to lease a connection for the given route and with the given
046     * state from the pool.
047     *
048     * @param route route of the connection.
049     * @param state arbitrary object that represents a particular state
050     *  (usually a security principal or a unique token identifying
051     *  the user whose credentials have been used while establishing the connection).
052     *  May be {@code null}.
053     * @param callback operation completion callback.
054     *
055     * @return future for a leased pool entry.
056     */
057    Future<E> lease(final T route, final Object state, final FutureCallback<E> callback);
058
059    /**
060     * Releases the pool entry back to the pool.
061     *
062     * @param entry pool entry leased from the pool
063     * @param reusable flag indicating whether or not the released connection
064     *   is in a consistent state and is safe for further use.
065     */
066    void release(E entry, boolean reusable);
067
068}