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 * </p> 026 * 027 * @param <T> Type of element pooled in this pool. 028 * @since 2.0 029 */ 030public abstract class BaseObjectPool<T> extends BaseObject implements ObjectPool<T> { 031 032 private volatile boolean closed; 033 034 /** 035 * Not supported in this base implementation. Subclasses should override 036 * this behavior. 037 * 038 * @throws UnsupportedOperationException if the pool does not implement this 039 * method 040 */ 041 @Override 042 public void addObject() throws Exception { 043 throw new UnsupportedOperationException(); 044 } 045 046 /** 047 * Throws an {@code IllegalStateException} when this pool has been 048 * closed. 049 * 050 * @throws IllegalStateException when this pool has been closed. 051 * @see #isClosed() 052 */ 053 protected final void assertOpen() throws IllegalStateException { 054 if (isClosed()) { 055 throw new IllegalStateException("Pool not open"); 056 } 057 } 058 059 @Override 060 public abstract T borrowObject() throws Exception; 061 062 /** 063 * Not supported in this base implementation. 064 * 065 * @throws UnsupportedOperationException if the pool does not implement this 066 * method 067 */ 068 @Override 069 public void clear() throws Exception { 070 throw new UnsupportedOperationException(); 071 } 072 073 /** 074 * {@inheritDoc} 075 * <p> 076 * This affects the behavior of {@code isClosed} and 077 * {@code assertOpen}. 078 * </p> 079 */ 080 @Override 081 public void close() { 082 closed = true; 083 } 084 085 /** 086 * Not supported in this base implementation. 087 * 088 * @return a negative value. 089 */ 090 @Override 091 public int getNumActive() { 092 return -1; 093 } 094 095 /** 096 * Not supported in this base implementation. 097 * 098 * @return a negative value. 099 */ 100 @Override 101 public int getNumIdle() { 102 return -1; 103 } 104 105 @Override 106 public abstract void invalidateObject(T obj) throws Exception; 107 108 /** 109 * Has this pool instance been closed. 110 * 111 * @return {@code true} when this pool has been closed. 112 */ 113 public final boolean isClosed() { 114 return closed; 115 } 116 117 @Override 118 public abstract void returnObject(T obj) throws Exception; 119 120 @Override 121 protected void toStringAppendFields(final StringBuilder builder) { 122 builder.append("closed="); 123 builder.append(closed); 124 } 125}