/*****************************************************************
 *   Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 ****************************************************************/
/*
 * Copyright 2010 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.cayenne.util.concurrentlinkedhashmap;

/**
 * A listener registered for notification when an entry is evicted. An instance may be
 * called concurrently by multiple threads to process entries. An implementation should
 * avoid performing blocking calls or synchronizing on shared resources.
 * <p>
 * The listener is invoked by {@link ConcurrentLinkedHashMap} on a caller's thread and
 * will not block other threads from operating on the map. An implementation should be
 * aware that the caller's thread will not expect long execution times or failures as a
 * side effect of the listener being notified. Execution safety and a fast turn around
 * time can be achieved by performing the operation asynchronously, such as by submitting
 * a task to an {@link java.util.concurrent.ExecutorService}.
 */
interface EvictionListener<K, V> {

    /**
     * A call-back notification that the entry was evicted.
     * 
     * @param key the entry's key
     * @param value the entry's value
     */
    void onEviction(K key, V value);
}