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 * 029 * @since 2.0 030 */ 031public abstract class BaseObjectPool<T> extends BaseObject implements ObjectPool<T> { 032 033 private volatile boolean closed; 034 035 /** 036 * Not supported in this base implementation. Subclasses should override 037 * this behavior. 038 * 039 * @throws UnsupportedOperationException if the pool does not implement this 040 * method 041 */ 042 @Override 043 public void addObject() throws Exception, UnsupportedOperationException { 044 throw new UnsupportedOperationException(); 045 } 046 047 /** 048 * Throws an {@code IllegalStateException} when this pool has been 049 * closed. 050 * 051 * @throws IllegalStateException when this pool has been closed. 052 * 053 * @see #isClosed() 054 */ 055 protected final void assertOpen() throws IllegalStateException { 056 if (isClosed()) { 057 throw new IllegalStateException("Pool not open"); 058 } 059 } 060 061 @Override 062 public abstract T borrowObject() throws Exception; 063 064 /** 065 * Not supported in this base implementation. 066 * 067 * @throws UnsupportedOperationException if the pool does not implement this 068 * method 069 */ 070 @Override 071 public void clear() throws Exception, UnsupportedOperationException { 072 throw new UnsupportedOperationException(); 073 } 074 075 /** 076 * {@inheritDoc} 077 * <p> 078 * This affects the behavior of {@code isClosed} and 079 * {@code assertOpen}. 080 * </p> 081 */ 082 @Override 083 public void close() { 084 closed = true; 085 } 086 087 /** 088 * Not supported in this base implementation. 089 * 090 * @return a negative value. 091 */ 092 @Override 093 public int getNumActive() { 094 return -1; 095 } 096 097 /** 098 * Not supported in this base implementation. 099 * 100 * @return a negative value. 101 */ 102 @Override 103 public int getNumIdle() { 104 return -1; 105 } 106 107 @Override 108 public abstract void invalidateObject(T obj) throws Exception; 109 110 /** 111 * Has this pool instance been closed. 112 * 113 * @return {@code true} when this pool has been closed. 114 */ 115 public final boolean isClosed() { 116 return closed; 117 } 118 119 @Override 120 public abstract void returnObject(T obj) throws Exception; 121 122 @Override 123 protected void toStringAppendFields(final StringBuilder builder) { 124 builder.append("closed="); 125 builder.append(closed); 126 } 127}