1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.pool2; 18 19 /** 20 * A simple base implementation of {@link ObjectPool}. 21 * Optional operations are implemented to either do nothing, return a value 22 * indicating it is unsupported or throw {@link UnsupportedOperationException}. 23 * <p> 24 * This class is intended to be thread-safe. 25 * </p> 26 * 27 * @param <T> Type of element pooled in this pool. 28 * 29 * 30 * @since 2.0 31 */ 32 public abstract class BaseObjectPool<T> extends BaseObject implements ObjectPool<T> { 33 34 private volatile boolean closed; 35 36 /** 37 * Not supported in this base implementation. Subclasses should override 38 * this behavior. 39 * 40 * @throws UnsupportedOperationException if the pool does not implement this 41 * method 42 */ 43 @Override 44 public void addObject() throws Exception { 45 throw new UnsupportedOperationException(); 46 } 47 48 /** 49 * Throws an {@code IllegalStateException} when this pool has been 50 * closed. 51 * 52 * @throws IllegalStateException when this pool has been closed. 53 * 54 * @see #isClosed() 55 */ 56 protected final void assertOpen() throws IllegalStateException { 57 if (isClosed()) { 58 throw new IllegalStateException("Pool not open"); 59 } 60 } 61 62 @Override 63 public abstract T borrowObject() throws Exception; 64 65 /** 66 * Not supported in this base implementation. 67 * 68 * @throws UnsupportedOperationException if the pool does not implement this 69 * method 70 */ 71 @Override 72 public void clear() throws Exception { 73 throw new UnsupportedOperationException(); 74 } 75 76 /** 77 * {@inheritDoc} 78 * <p> 79 * This affects the behavior of {@code isClosed} and 80 * {@code assertOpen}. 81 * </p> 82 */ 83 @Override 84 public void close() { 85 closed = true; 86 } 87 88 /** 89 * Not supported in this base implementation. 90 * 91 * @return a negative value. 92 */ 93 @Override 94 public int getNumActive() { 95 return -1; 96 } 97 98 /** 99 * Not supported in this base implementation. 100 * 101 * @return a negative value. 102 */ 103 @Override 104 public int getNumIdle() { 105 return -1; 106 } 107 108 @Override 109 public abstract void invalidateObject(T obj) throws Exception; 110 111 /** 112 * Has this pool instance been closed. 113 * 114 * @return {@code true} when this pool has been closed. 115 */ 116 public final boolean isClosed() { 117 return closed; 118 } 119 120 @Override 121 public abstract void returnObject(T obj) throws Exception; 122 123 @Override 124 protected void toStringAppendFields(final StringBuilder builder) { 125 builder.append("closed="); 126 builder.append(closed); 127 } 128 }