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     * <p/>
025     * Notice the capacity is <b>per key</b> which means that each key can contain at most
026     * (the capacity) services. The pool can contain an unbounded number of keys.
027     * <p/>
028     * By default the capacity is set to 100.
029     *
030     * @version 
031     */
032    public interface ServicePool<Key, Service> {
033    
034        /**
035         * Sets the capacity, which is capacity <b>per key</b>.
036         *
037         * @param capacity the capacity per key
038         */
039        void setCapacity(int capacity);
040    
041        /**
042         * Gets the capacity per key.
043         *
044         * @return the capacity per key
045         */
046        int getCapacity();
047    
048        /**
049         * Adds the given service to the pool and acquires it.
050         *
051         * @param key     the key
052         * @param service the service
053         * @return the acquired service, is newer <tt>null</tt>
054         * @throws IllegalStateException if the queue is full (capacity has been reached)
055         */
056        Service addAndAcquire(Key key, Service service);
057    
058        /**
059         * Tries to acquire the service with the given key
060         *
061         * @param key the key
062         * @return the acquired service, or <tt>null</tt> if no free in pool
063         */
064        Service acquire(Key key);
065    
066        /**
067         * Releases the service back to the pool
068         *
069         * @param key     the key
070         * @param service the service
071         */
072        void release(Key key, Service service);
073    
074        /**
075         * Returns the current size of the pool
076         *
077         * @return the current size of the pool
078         */
079        int size();
080    
081        /**
082         * Purges the pool.
083         */
084        void purge();
085    
086    }