| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.tomcat.dbcp.pool2; |
| |
| import java.io.Closeable; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * A "keyed" pooling interface. |
| * <p> |
| * A keyed pool maintains a pool of instances for each key value. |
| * <p> |
| * Example of use: |
| * <pre style="border:solid thin; padding: 1ex;" |
| * > Object obj = <code style="color:#00C">null</code>; |
| * Object key = <code style="color:#C00">"Key"</code>; |
| * |
| * <code style="color:#00C">try</code> { |
| * obj = pool.borrowObject(key); |
| * <code style="color:#0C0">//...use the object...</code> |
| * } <code style="color:#00C">catch</code>(Exception e) { |
| * <code style="color:#0C0">// invalidate the object</code> |
| * pool.invalidateObject(key, obj); |
| * <code style="color:#0C0">// do not return the object to the pool twice</code> |
| * obj = <code style="color:#00C">null</code>; |
| * } <code style="color:#00C">finally</code> { |
| * <code style="color:#0C0">// make sure the object is returned to the pool</code> |
| * <code style="color:#00C">if</code>(<code style="color:#00C">null</code> != obj) { |
| * pool.returnObject(key, obj); |
| * } |
| * }</pre> |
| * <p> |
| * {@link KeyedObjectPool} implementations <i>may</i> choose to store at most |
| * one instance per key value, or may choose to maintain a pool of instances |
| * for each key (essentially creating a {@link java.util.Map Map} of |
| * {@link ObjectPool pools}). |
| * <p> |
| * See {@link org.apache.tomcat.dbcp.pool2.impl.GenericKeyedObjectPool |
| * GenericKeyedObjectPool} for an implementation. |
| * |
| * @param <K> The type of keys maintained by this pool. |
| * @param <V> Type of element pooled in this pool. |
| * |
| * @see KeyedPooledObjectFactory |
| * @see ObjectPool |
| * @see org.apache.tomcat.dbcp.pool2.impl.GenericKeyedObjectPool GenericKeyedObjectPool |
| * |
| * @since 2.0 |
| */ |
| public interface KeyedObjectPool<K,V> extends Closeable { |
| /** |
| * Obtains an instance from this pool for the specified <code>key</code>. |
| * <p> |
| * Instances returned from this method will have been either newly created |
| * with {@link KeyedPooledObjectFactory#makeObject makeObject} or will be |
| * a previously idle object and have been activated with |
| * {@link KeyedPooledObjectFactory#activateObject activateObject} and then |
| * (optionally) validated with |
| * {@link KeyedPooledObjectFactory#validateObject validateObject}. |
| * <p> |
| * By contract, clients <strong>must</strong> return the borrowed object |
| * using {@link #returnObject returnObject}, |
| * {@link #invalidateObject invalidateObject}, or a related method as |
| * defined in an implementation or sub-interface, using a <code>key</code> |
| * that is {@link Object#equals equivalent} to the one used to borrow the |
| * instance in the first place. |
| * <p> |
| * The behaviour of this method when the pool has been exhausted is not |
| * strictly specified (although it may be specified by implementations). |
| * |
| * @param key the key used to obtain the object |
| * |
| * @return an instance from this pool. |
| * |
| * @throws IllegalStateException |
| * after {@link #close close} has been called on this pool |
| * @throws Exception |
| * when {@link KeyedPooledObjectFactory#makeObject |
| * makeObject} throws an exception |
| * @throws NoSuchElementException |
| * when the pool is exhausted and cannot or will not return |
| * another instance |
| */ |
| V borrowObject(K key) throws Exception, NoSuchElementException, IllegalStateException; |
| |
| /** |
| * Return an instance to the pool. By contract, <code>obj</code> |
| * <strong>must</strong> have been obtained using |
| * {@link #borrowObject borrowObject} or a related method as defined in an |
| * implementation or sub-interface using a <code>key</code> that is |
| * equivalent to the one used to borrow the instance in the first place. |
| * |
| * @param key the key used to obtain the object |
| * @param obj a {@link #borrowObject borrowed} instance to be returned. |
| * |
| * @throws IllegalStateException |
| * if an attempt is made to return an object to the pool that |
| * is in any state other than allocated (i.e. borrowed). |
| * Attempting to return an object more than once or attempting |
| * to return an object that was never borrowed from the pool |
| * will trigger this exception. |
| * |
| * @throws Exception if an instance cannot be returned to the pool |
| */ |
| void returnObject(K key, V obj) throws Exception; |
| |
| /** |
| * Invalidates an object from the pool. |
| * <p> |
| * By contract, <code>obj</code> <strong>must</strong> have been obtained |
| * using {@link #borrowObject borrowObject} or a related method as defined |
| * in an implementation or sub-interface using a <code>key</code> that is |
| * equivalent to the one used to borrow the <code>Object</code> in the first |
| * place. |
| * <p> |
| * This method should be used when an object that has been borrowed is |
| * determined (due to an exception or other problem) to be invalid. |
| * |
| * @param key the key used to obtain the object |
| * @param obj a {@link #borrowObject borrowed} instance to be returned. |
| * |
| * @throws Exception if the instance cannot be invalidated |
| */ |
| void invalidateObject(K key, V obj) throws Exception; |
| |
| /** |
| * Create an object using the {@link KeyedPooledObjectFactory factory} or |
| * other implementation dependent mechanism, passivate it, and then place it |
| * in the idle object pool. <code>addObject</code> is useful for |
| * "pre-loading" a pool with idle objects (Optional operation). |
| * |
| * @param key the key a new instance should be added to |
| * |
| * @throws Exception |
| * when {@link KeyedPooledObjectFactory#makeObject} fails. |
| * @throws IllegalStateException |
| * after {@link #close} has been called on this pool. |
| * @throws UnsupportedOperationException |
| * when this pool cannot add new idle objects. |
| */ |
| void addObject(K key) throws Exception, IllegalStateException, |
| UnsupportedOperationException; |
| |
| /** |
| * Returns the number of instances corresponding to the given |
| * <code>key</code> currently idle in this pool. Returns a negative value if |
| * this information is not available. |
| * |
| * @param key the key to query |
| * @return the number of instances corresponding to the given |
| * <code>key</code> currently idle in this pool. |
| */ |
| int getNumIdle(K key); |
| |
| /** |
| * Returns the number of instances currently borrowed from but not yet |
| * returned to the pool corresponding to the given <code>key</code>. |
| * Returns a negative value if this information is not available. |
| * |
| * @param key the key to query |
| * @return the number of instances currently borrowed from but not yet |
| * returned to the pool corresponding to the given <code>key</code>. |
| */ |
| int getNumActive(K key); |
| |
| /** |
| * Returns the total number of instances currently idle in this pool. |
| * Returns a negative value if this information is not available. |
| * @return the total number of instances currently idle in this pool. |
| */ |
| int getNumIdle(); |
| |
| /** |
| * Returns the total number of instances currently borrowed from this pool but |
| * not yet returned. Returns a negative value if this information is not |
| * available. |
| * @return the total number of instances currently borrowed from this pool but |
| * not yet returned. |
| */ |
| int getNumActive(); |
| |
| /** |
| * Clears the pool, removing all pooled instances (optional operation). |
| * |
| * @throws UnsupportedOperationException when this implementation doesn't |
| * support the operation |
| * |
| * @throws Exception if the pool cannot be cleared |
| */ |
| void clear() throws Exception, UnsupportedOperationException; |
| |
| /** |
| * Clears the specified pool, removing all pooled instances corresponding to |
| * the given <code>key</code> (optional operation). |
| * |
| * @param key the key to clear |
| * |
| * @throws UnsupportedOperationException when this implementation doesn't |
| * support the operation |
| * |
| * @throws Exception if the key cannot be cleared |
| */ |
| void clear(K key) throws Exception, UnsupportedOperationException; |
| |
| /** |
| * Close this pool, and free any resources associated with it. |
| * <p> |
| * Calling {@link #addObject addObject} or |
| * {@link #borrowObject borrowObject} after invoking this method on a pool |
| * will cause them to throw an {@link IllegalStateException}. |
| * <p> |
| * Implementations should silently fail if not all resources can be freed. |
| */ |
| @Override |
| void close(); |
| } |
