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 */
017
018 package org.apache.commons.pool;
019
020 /**
021 * A simple base implementation of {@link ObjectPool}.
022 * Optional operations are implemented to either do nothing, return a value
023 * indicating it is unsupported or throw {@link UnsupportedOperationException}.
024 *
025 * @author Rodney Waldhoff
026 * @author Sandy McArthur
027 * @version $Revision: 1084645 $ $Date: 2011-03-23 10:11:19 -0700 (Wed, 23 Mar 2011) $
028 * @since Pool 1.0
029 */
030 public abstract class BaseObjectPool implements ObjectPool {
031 /**
032 * Obtains an instance from the pool.
033 *
034 * @return an instance from the pool
035 * @throws Exception if an instance cannot be obtained from the pool
036 */
037 public abstract Object borrowObject() throws Exception;
038
039 /**
040 * Returns an instance to the pool.
041 *
042 * @param obj instance to return to the pool
043 */
044 public abstract void returnObject(Object obj) throws Exception;
045
046 /**
047 * <p>Invalidates an object from the pool.</p>
048 *
049 * <p>By contract, <code>obj</code> <strong>must</strong> have been obtained
050 * using {@link #borrowObject borrowObject}.<p>
051 *
052 * <p>This method should be used when an object that has been borrowed
053 * is determined (due to an exception or other problem) to be invalid.</p>
054 *
055 * @param obj a {@link #borrowObject borrowed} instance to be disposed.
056 * @throws Exception
057 */
058 public abstract void invalidateObject(Object obj) throws Exception;
059
060 /**
061 * Not supported in this base implementation.
062 * @return a negative value.
063 *
064 * @throws UnsupportedOperationException
065 */
066 public int getNumIdle() throws UnsupportedOperationException {
067 return -1;
068 }
069
070 /**
071 * Not supported in this base implementation.
072 * @return a negative value.
073 *
074 * @throws UnsupportedOperationException
075 */
076 public int getNumActive() throws UnsupportedOperationException {
077 return -1;
078 }
079
080 /**
081 * Not supported in this base implementation.
082 *
083 * @throws UnsupportedOperationException
084 */
085 public void clear() throws Exception, UnsupportedOperationException {
086 throw new UnsupportedOperationException();
087 }
088
089 /**
090 * Not supported in this base implementation.
091 * Always throws an {@link UnsupportedOperationException},
092 * subclasses should override this behavior.
093 *
094 * @throws UnsupportedOperationException
095 */
096 public void addObject() throws Exception, UnsupportedOperationException {
097 throw new UnsupportedOperationException();
098 }
099
100 /**
101 * Close this pool.
102 * This affects the behavior of <code>isClosed</code> and <code>assertOpen</code>.
103 */
104 public void close() throws Exception {
105 closed = true;
106 }
107
108 /**
109 * Not supported in this base implementation.
110 * Always throws an {@link UnsupportedOperationException},
111 * subclasses should override this behavior.
112 *
113 * @param factory the PoolableObjectFactory
114 * @throws UnsupportedOperationException
115 * @throws IllegalStateException
116 * @deprecated to be removed in pool 2.0
117 */
118 public void setFactory(PoolableObjectFactory factory) throws IllegalStateException, UnsupportedOperationException {
119 throw new UnsupportedOperationException();
120 }
121
122 /**
123 * Has this pool instance been closed.
124 * @return <code>true</code> when this pool has been closed.
125 */
126 public final boolean isClosed() {
127 return closed;
128 }
129
130 /**
131 * Throws an <code>IllegalStateException</code> when this pool has been closed.
132 * @throws IllegalStateException when this pool has been closed.
133 * @see #isClosed()
134 */
135 protected final void assertOpen() throws IllegalStateException {
136 if (isClosed()) {
137 throw new IllegalStateException("Pool not open");
138 }
139 }
140
141 /** Whether or not the pool is closed */
142 private volatile boolean closed = false;
143 }