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 * A simple base implementation of {@link ObjectPool}. 021 * Optional operations are implemented to either do nothing, return a value 022 * indicating it is unsupported or throw {@link UnsupportedOperationException}. 023 * <p> 024 * This class is intended to be thread-safe. 025 * 026 * @param <T> Type of element pooled in this pool. 027 * 028 * @version $Revision: 1333925 $ 029 * 030 * @since 2.0 031 */ 032public abstract class BaseObjectPool<T> implements ObjectPool<T> { 033 /** 034 * Obtains an instance from the pool. 035 * 036 * @return an instance from the pool 037 * 038 * @throws Exception if an instance cannot be obtained from the pool 039 */ 040 @Override 041 public abstract T borrowObject() throws Exception; 042 043 /** 044 * Returns an instance to the pool. 045 * 046 * @param obj instance to return to the pool 047 */ 048 @Override 049 public abstract void returnObject(T obj) throws Exception; 050 051 /** 052 * Invalidates an object from the pool. 053 * <p> 054 * By contract, <code>obj</code> <strong>must</strong> have been obtained 055 * using {@link #borrowObject borrowObject}. 056 * <p> 057 * This method should be used when an object that has been borrowed is 058 * determined (due to an exception or other problem) to be invalid. 059 * 060 * @param obj a {@link #borrowObject borrowed} instance to be disposed. 061 * @throws Exception 062 */ 063 @Override 064 public abstract void invalidateObject(T obj) throws Exception; 065 066 /** 067 * Not supported in this base implementation. 068 * 069 * @return a negative value. 070 */ 071 @Override 072 public int getNumIdle() { 073 return -1; 074 } 075 076 /** 077 * Not supported in this base implementation. 078 * 079 * @return a negative value. 080 */ 081 @Override 082 public int getNumActive() { 083 return -1; 084 } 085 086 /** 087 * Not supported in this base implementation. 088 * 089 * @throws UnsupportedOperationException 090 */ 091 @Override 092 public void clear() throws Exception, UnsupportedOperationException { 093 throw new UnsupportedOperationException(); 094 } 095 096 /** 097 * Not supported in this base implementation.Always throws an 098 * {@link UnsupportedOperationException}, subclasses should override this 099 * behavior. 100 * 101 * @throws UnsupportedOperationException 102 */ 103 @Override 104 public void addObject() throws Exception, UnsupportedOperationException { 105 throw new UnsupportedOperationException(); 106 } 107 108 /** 109 * Close this pool. This affects the behavior of <code>isClosed</code> and 110 * <code>assertOpen</code>. 111 */ 112 @Override 113 public void close() { 114 closed = true; 115 } 116 117 /** 118 * Has this pool instance been closed. 119 * 120 * @return <code>true</code> when this pool has been closed. 121 */ 122 public final boolean isClosed() { 123 return closed; 124 } 125 126 /** 127 * Throws an <code>IllegalStateException</code> when this pool has been 128 * closed. 129 * 130 * @throws IllegalStateException when this pool has been closed. 131 * 132 * @see #isClosed() 133 */ 134 protected final void assertOpen() throws IllegalStateException { 135 if (isClosed()) { 136 throw new IllegalStateException("Pool not open"); 137 } 138 } 139 140 private volatile boolean closed = false; 141}