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 instances to be served by an 021 * {@link ObjectPool}. 022 * <p> 023 * By contract, when an {@link ObjectPool} delegates to a 024 * {@link PooledObjectFactory}, 025 * </p> 026 * <ol> 027 * <li> 028 * {@link #makeObject} is called whenever a new instance is needed. 029 * </li> 030 * <li> 031 * {@link #activateObject} is invoked on every instance that has been 032 * {@link #passivateObject passivated} before it is 033 * {@link ObjectPool#borrowObject borrowed} from the pool. 034 * </li> 035 * <li> 036 * {@link #validateObject} may be invoked on {@link #activateObject activated} 037 * instances to make sure they can be {@link ObjectPool#borrowObject borrowed} 038 * from the pool. {@link #validateObject} may also be used to 039 * test an instance being {@link ObjectPool#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} is invoked on every instance when it is returned 045 * to the pool. 046 * </li> 047 * <li> 048 * {@link #destroyObject} is invoked on every instance when it is being 049 * "dropped" from the pool (whether due to the response from 050 * {@link #validateObject}, or for reasons specific to the pool 051 * implementation.) There is no guarantee that the instance being destroyed 052 * will be considered active, passive or in a generally consistent state. 053 * </li> 054 * </ol> 055 * {@link PooledObjectFactory} must be thread-safe. The only promise 056 * an {@link ObjectPool} makes is that the same instance of an object will not 057 * be passed to more than one method of a {@code PoolableObjectFactory} 058 * at a time. 059 * <p> 060 * While clients of a {@link KeyedObjectPool} borrow and return instances of 061 * the underlying value type {@code V}, the factory methods act on instances of 062 * {@link PooledObject PooledObject<V>}. These are the object wrappers that 063 * pools use to track and maintain state information about the objects that 064 * they manage. 065 * </p> 066 * 067 * @param <T> Type of element managed in this factory. 068 * 069 * @see ObjectPool 070 * 071 * @since 2.0 072 */ 073public interface PooledObjectFactory<T> { 074 075 /** 076 * Creates an instance that can be served by the pool and wrap it in a 077 * {@link PooledObject} to be managed by the pool. 078 * 079 * @return a {@code PooledObject} wrapping an instance that can be served by the pool 080 * 081 * @throws Exception if there is a problem creating a new instance, 082 * this will be propagated to the code requesting an object. 083 */ 084 PooledObject<T> makeObject() throws Exception; 085 086 /** 087 * Destroys an instance no longer needed by the pool, using the default (NORMAL) 088 * DestroyMode. 089 * <p> 090 * It is important for implementations of this method to be aware that there 091 * is no guarantee about what state {@code obj} will be in and the 092 * implementation should be prepared to handle unexpected errors. 093 * </p> 094 * <p> 095 * Also, an implementation must take in to consideration that instances lost 096 * to the garbage collector may never be destroyed. 097 * </p> 098 * 099 * @param p a {@code PooledObject} wrapping the instance to be destroyed 100 * 101 * @throws Exception should be avoided as it may be swallowed by 102 * the pool implementation. 103 * 104 * @see #validateObject 105 * @see ObjectPool#invalidateObject 106 */ 107 void destroyObject(PooledObject<T> p) throws Exception; 108 109 /** 110 * Destroys an instance no longer needed by the pool, using the provided 111 * DestroyMode. 112 * 113 * @param p a {@code PooledObject} wrapping the instance to be destroyed 114 * @param mode DestroyMode providing context to the factory 115 * 116 * @throws Exception should be avoided as it may be swallowed by 117 * the pool implementation. 118 * 119 * @see #validateObject 120 * @see ObjectPool#invalidateObject 121 * @see #destroyObject(PooledObject) 122 * @see DestroyMode 123 * @since 2.9.0 124 */ 125 default void destroyObject(final PooledObject<T> p, final DestroyMode mode) throws Exception { 126 destroyObject(p); 127 } 128 129 /** 130 * Ensures that the instance is safe to be returned by the pool. 131 * 132 * @param p a {@code PooledObject} wrapping the instance to be validated 133 * 134 * @return {@code false} if {@code obj} is not valid and should 135 * be dropped from the pool, {@code true} otherwise. 136 */ 137 boolean validateObject(PooledObject<T> p); 138 139 /** 140 * Reinitializes an instance to be returned by the pool. 141 * 142 * @param p a {@code PooledObject} wrapping the instance to be activated 143 * 144 * @throws Exception if there is a problem activating {@code obj}, 145 * this exception may be swallowed by the pool. 146 * 147 * @see #destroyObject 148 */ 149 void activateObject(PooledObject<T> p) throws Exception; 150 151 /** 152 * Uninitializes an instance to be returned to the idle object pool. 153 * 154 * @param p a {@code PooledObject} wrapping the instance to be passivated 155 * 156 * @throws Exception if there is a problem passivating {@code obj}, 157 * this exception may be swallowed by the pool. 158 * 159 * @see #destroyObject 160 */ 161 void passivateObject(PooledObject<T> p) throws Exception; 162}