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 18 package org.apache.commons.pool; 19 20 import java.util.NoSuchElementException; 21 22 /** 23 * A "keyed" pooling interface. 24 * <p> 25 * A keyed pool pools instances of multiple types. Each 26 * type may be accessed using an arbitrary key. 27 * </p> 28 * <p> 29 * Example of use: 30 * <pre style="border:solid thin; padding: 1ex;" 31 * > Object obj = <code style="color:#00C">null</code>; 32 * Object key = <code style="color:#C00">"Key"</code>; 33 * 34 * <code style="color:#00C">try</code> { 35 * obj = pool.borrowObject(key); 36 * <code style="color:#0C0">//...use the object...</code> 37 * } <code style="color:#00C">catch</code>(Exception e) { 38 * <code style="color:#0C0">// invalidate the object</code> 39 * pool.invalidateObject(key, obj); 40 * <code style="color:#0C0">// do not return the object to the pool twice</code> 41 * obj = <code style="color:#00C">null</code>; 42 * } <code style="color:#00C">finally</code> { 43 * <code style="color:#0C0">// make sure the object is returned to the pool</code> 44 * <code style="color:#00C">if</code>(<code style="color:#00C">null</code> != obj) { 45 * pool.returnObject(key, obj); 46 * } 47 * }</pre> 48 * </p> 49 * <p> 50 * {@link KeyedObjectPool} implementations <i>may</i> choose to store at most 51 * one instance per key value, or may choose to maintain a pool of instances 52 * for each key (essentially creating a {@link java.util.Map Map} of 53 * {@link ObjectPool pools}). 54 * </p> 55 * 56 * <p>See {@link BaseKeyedObjectPool} for a simple base implementation.</p> 57 * 58 * @author Rodney Waldhoff 59 * @author Sandy McArthur 60 * @version $Revision: 962893 $ $Date: 2010-07-10 10:37:27 -0700 (Sat, 10 Jul 2010) $ 61 * @see KeyedPoolableObjectFactory 62 * @see KeyedObjectPoolFactory 63 * @see ObjectPool 64 * @see BaseKeyedObjectPool 65 * @since Pool 1.0 66 */ 67 public interface KeyedObjectPool { 68 /** 69 * Obtains an instance from this pool for the specified <code>key</code>. 70 * <p> 71 * Instances returned from this method will have been either newly created with 72 * {@link KeyedPoolableObjectFactory#makeObject makeObject} or will be a previously idle object and 73 * have been activated with {@link KeyedPoolableObjectFactory#activateObject activateObject} and 74 * then validated with {@link KeyedPoolableObjectFactory#validateObject validateObject}. 75 * <p> 76 * By contract, clients <strong>must</strong> return the borrowed object using 77 * {@link #returnObject returnObject}, {@link #invalidateObject invalidateObject}, or a related method 78 * as defined in an implementation or sub-interface, 79 * using a <code>key</code> that is {@link Object#equals equivalent} to the one used to 80 * borrow the instance in the first place. 81 * <p> 82 * The behaviour of this method when the pool has been exhausted 83 * is not strictly specified (although it may be specified by implementations). 84 * Older versions of this method would return <code>null</code> to indicate exhaustion, 85 * newer versions are encouraged to throw a {@link NoSuchElementException}. 86 * 87 * @param key the key used to obtain the object 88 * @return an instance from this pool. 89 * @throws IllegalStateException after {@link #close close} has been called on this pool 90 * @throws Exception when {@link KeyedPoolableObjectFactory#makeObject makeObject} throws an exception 91 * @throws NoSuchElementException when the pool is exhausted and cannot or will not return another instance 92 */ 93 Object borrowObject(Object key) throws Exception, NoSuchElementException, IllegalStateException; 94 95 /** 96 * Return an instance to the pool. 97 * By contract, <code>obj</code> <strong>must</strong> have been obtained 98 * using {@link #borrowObject borrowObject} 99 * or a related method as defined in an implementation 100 * or sub-interface 101 * using a <code>key</code> that is equivalent to the one used to 102 * borrow the instance in the first place. 103 * 104 * @param key the key used to obtain the object 105 * @param obj a {@link #borrowObject borrowed} instance to be returned. 106 * @throws Exception 107 */ 108 void returnObject(Object key, Object obj) throws Exception; 109 110 /** 111 * <p>Invalidates an object from the pool.</p> 112 * 113 * <p>By contract, <code>obj</code> <strong>must</strong> have been obtained 114 * using {@link #borrowObject borrowObject} or a related method as defined 115 * in an implementation or sub-interface using a <code>key</code> that is 116 * equivalent to the one used to borrow the <code>Object</code> in the first place.</p> 117 * 118 * <p>This method should be used when an object that has been borrowed 119 * is determined (due to an exception or other problem) to be invalid.</p> 120 * 121 * @param key the key used to obtain the object 122 * @param obj a {@link #borrowObject borrowed} instance to be returned. 123 * @throws Exception 124 */ 125 void invalidateObject(Object key, Object obj) throws Exception; 126 127 /** 128 * Create an object using the {@link KeyedPoolableObjectFactory factory} or other 129 * implementation dependent mechanism, passivate it, and then place it in the idle object pool. 130 * <code>addObject</code> is useful for "pre-loading" a pool with idle objects 131 * (Optional operation). 132 * 133 * @param key the key a new instance should be added to 134 * @throws Exception when {@link KeyedPoolableObjectFactory#makeObject} fails. 135 * @throws IllegalStateException after {@link #close} has been called on this pool. 136 * @throws UnsupportedOperationException when this pool cannot add new idle objects. 137 */ 138 void addObject(Object key) throws Exception, IllegalStateException, UnsupportedOperationException; 139 140 /** 141 * Returns the number of instances 142 * corresponding to the given <code>key</code> 143 * currently idle in this pool (optional operation). 144 * Returns a negative value if this information is not available. 145 * 146 * @param key the key to query 147 * @return the number of instances corresponding to the given <code>key</code> currently idle in this pool or a negative value if unsupported 148 * @throws UnsupportedOperationException <strong>deprecated</strong>: when this implementation doesn't support the operation 149 */ 150 int getNumIdle(Object key) throws UnsupportedOperationException; 151 152 /** 153 * Returns the number of instances 154 * currently borrowed from but not yet returned 155 * to the pool corresponding to the 156 * given <code>key</code> (optional operation). 157 * Returns a negative value if this information is not available. 158 * 159 * @param key the key to query 160 * @return the number of instances corresponding to the given <code>key</code> currently borrowed in this pool or a negative value if unsupported 161 * @throws UnsupportedOperationException <strong>deprecated</strong>: when this implementation doesn't support the operation 162 */ 163 int getNumActive(Object key) throws UnsupportedOperationException; 164 165 /** 166 * Returns the total number of instances 167 * currently idle in this pool (optional operation). 168 * Returns a negative value if this information is not available. 169 * 170 * @return the total number of instances currently idle in this pool or a negative value if unsupported 171 * @throws UnsupportedOperationException <strong>deprecated</strong>: when this implementation doesn't support the operation 172 */ 173 int getNumIdle() throws UnsupportedOperationException; 174 175 /** 176 * Returns the total number of instances 177 * current borrowed from this pool but not 178 * yet returned (optional operation). 179 * Returns a negative value if this information is not available. 180 * 181 * @return the total number of instances currently borrowed from this pool or a negative value if unsupported 182 * @throws UnsupportedOperationException <strong>deprecated</strong>: when this implementation doesn't support the operation 183 */ 184 int getNumActive() throws UnsupportedOperationException; 185 186 /** 187 * Clears the pool, removing all pooled instances (optional operation). 188 * Throws {@link UnsupportedOperationException} if the pool cannot be cleared. 189 * 190 * @throws UnsupportedOperationException when this implementation doesn't support the operation 191 */ 192 void clear() throws Exception, UnsupportedOperationException; 193 194 /** 195 * Clears the specified pool, removing all 196 * pooled instances corresponding to 197 * the given <code>key</code> (optional operation). 198 * Throws {@link UnsupportedOperationException} if the pool cannot be cleared. 199 * 200 * @param key the key to clear 201 * @throws UnsupportedOperationException when this implementation doesn't support the operation 202 */ 203 void clear(Object key) throws Exception, UnsupportedOperationException; 204 205 /** 206 * Close this pool, and free any resources associated with it. 207 * <p> 208 * Calling {@link #addObject addObject} or {@link #borrowObject borrowObject} after invoking 209 * this method on a pool will cause them to throw an {@link IllegalStateException}. 210 * </p> 211 * 212 * @throws Exception 213 */ 214 void close() throws Exception; 215 216 /** 217 * Sets the {@link KeyedPoolableObjectFactory factory} the pool uses 218 * to create new instances (optional operation). 219 * Trying to change the <code>factory</code> after a pool has been used will frequently 220 * throw an {@link UnsupportedOperationException}. It is up to the pool 221 * implementation to determine when it is acceptable to call this method. 222 * 223 * @param factory the {@link KeyedPoolableObjectFactory} used to create new instances. 224 * @throws IllegalStateException when the factory cannot be set at this time 225 * @throws UnsupportedOperationException when this implementation doesn't support the operation 226 * @deprecated to be removed in pool 2.0 227 */ 228 void setFactory(KeyedPoolableObjectFactory factory) throws IllegalStateException, UnsupportedOperationException; 229 }