001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.camel.spi;
018    
019    /**
020     * A service pool is like a connection pool but can pool any kind of objects.
021     * <p/>
022     * Services that is capable of being pooled should implement the marker interface
023     * {@link org.apache.camel.ServicePoolAware}.
024     *
025     * @version $Revision: 779038 $
026     */
027    public interface ServicePool<Key, Service> extends org.apache.camel.Service {
028    
029        /**
030         * Adds the given service to the pool and acquires it.
031         *
032         * @param key the key
033         * @param service the service
034         * @return the acquired service, is newer <tt>null</tt>
035         */
036        Service addAndAcquire(Key key, Service service);
037    
038        /**
039         * Tries to acquire the servie with the given key
040         * 
041         * @param key the key
042         * @return the acquired service, or <tt>null</tt> if no free in pool
043         */
044        Service acquire(Key key);
045    
046        /**
047         * Releases the service back to the pool
048         *
049         * @param key  the key
050         * @param service the service
051         */
052        void release(Key key, Service service);
053    
054    }