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 */ 017package org.apache.commons.pool2; 018 019/** 020 * An interface defining life-cycle methods for 021 * instances to be served by a {@link KeyedObjectPool}. 022 * <p> 023 * By contract, when an {@link KeyedObjectPool} 024 * delegates to a {@link KeyedPooledObjectFactory}, 025 * <ol> 026 * <li> 027 * {@link #makeObject} is called whenever a new instance is needed. 028 * </li> 029 * <li> 030 * {@link #activateObject} is invoked on every instance that has been 031 * {@link #passivateObject passivated} before it is 032 * {@link KeyedObjectPool#borrowObject borrowed} from the pool. 033 * </li> 034 * <li> 035 * {@link #validateObject} may be invoked on {@link #activateObject activated} 036 * instances to make sure they can be 037 * {@link KeyedObjectPool#borrowObject borrowed} from the pool. 038 * <code>validateObject</code> may also be used to test an 039 * instance being {@link KeyedObjectPool#returnObject returned} to the pool 040 * before it is {@link #passivateObject passivated}. It will only be invoked 041 * on an activated instance. 042 * </li> 043 * <li> 044 * {@link #passivateObject passivateObject} 045 * is invoked on every instance when it is returned to the pool. 046 * </li> 047 * <li> 048 * {@link #destroyObject destroyObject} 049 * is invoked on every instance when it is being "dropped" from the 050 * pool (whether due to the response from <code>validateObject</code>, 051 * or for reasons specific to the pool implementation.) There is no 052 * guarantee that the instance being destroyed will 053 * be considered active, passive or in a generally consistent state. 054 * </li> 055 * </ol> 056 * {@link KeyedPooledObjectFactory} must be thread-safe. The only promise 057 * an {@link KeyedObjectPool} makes is that the same instance of an object will 058 * not be passed to more than one method of a 059 * <code>KeyedPoolableObjectFactory</code> at a time. 060 * <p> 061 * While clients of a {@link KeyedObjectPool} borrow and return instances of 062 * the underlying value type V, the factory methods act on instances of 063 * {@link PooledObject PooledObject<V>}. These are the object wrappers that 064 * pools use to track and maintain state informations about the objects that 065 * they manage. 066 * 067 * @see KeyedObjectPool 068 * @see BaseKeyedPooledObjectFactory 069 * 070 * @param <K> The type of keys managed by this factory. 071 * @param <V> Type of element managed by this factory. 072 * 073 * @version $Revision: 1333925 $ 074 * 075 * @since 2.0 076 */ 077public interface KeyedPooledObjectFactory<K,V> { 078 /** 079 * Create an instance that can be served by the pool and 080 * wrap it in a {@link PooledObject} to be managed by the pool. 081 * 082 * @param key the key used when constructing the object 083 * 084 * @return a {@code PooledObject} wrapping an instance that can 085 * be served by the pool. 086 * 087 * @throws Exception if there is a problem creating a new instance, 088 * this will be propagated to the code requesting an object. 089 */ 090 PooledObject<V> makeObject(K key) throws Exception; 091 092 /** 093 * Destroy an instance no longer needed by the pool. 094 * <p> 095 * It is important for implementations of this method to be aware that there 096 * is no guarantee about what state <code>obj</code> will be in and the 097 * implementation should be prepared to handle unexpected errors. 098 * <p> 099 * Also, an implementation must take in to consideration that instances lost 100 * to the garbage collector may never be destroyed. 101 * 102 * @param key the key used when selecting the instance 103 * @param p a {@code PooledObject} wrapping the instance to be destroyed 104 * 105 * @throws Exception should be avoided as it may be swallowed by 106 * the pool implementation. 107 * 108 * @see #validateObject 109 * @see KeyedObjectPool#invalidateObject 110 */ 111 void destroyObject(K key, PooledObject<V> p) throws Exception; 112 113 /** 114 * Ensures that the instance is safe to be returned by the pool. 115 * 116 * @param key the key used when selecting the object 117 * @param p a {@code PooledObject} wrapping the instance to be validated 118 * 119 * @return <code>false</code> if <code>obj</code> is not valid and should 120 * be dropped from the pool, <code>true</code> otherwise. 121 */ 122 boolean validateObject(K key, PooledObject<V> p); 123 124 /** 125 * Reinitialize an instance to be returned by the pool. 126 * 127 * @param key the key used when selecting the object 128 * @param p a {@code PooledObject} wrapping the instance to be activated 129 * 130 * @throws Exception if there is a problem activating <code>obj</code>, 131 * this exception may be swallowed by the pool. 132 * 133 * @see #destroyObject 134 */ 135 void activateObject(K key, PooledObject<V> p) throws Exception; 136 137 /** 138 * Uninitialize an instance to be returned to the idle object pool. 139 * 140 * @param key the key used when selecting the object 141 * @param p a {@code PooledObject} wrapping the instance to be passivated 142 * 143 * @throws Exception if there is a problem passivating <code>obj</code>, 144 * this exception may be swallowed by the pool. 145 * 146 * @see #destroyObject 147 */ 148 void passivateObject(K key, PooledObject<V> p) throws Exception; 149} 150