org.apache.commons.pool.ObjectPool Maven / Gradle / Ivy
/*
* Copyright 1999-2004 The Apache Software Foundation.
*
* Licensed 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.commons.pool;
/**
* A pooling interface.
*
* ObjectPool defines a trivially simple pooling interface. The only
* required methods are {@link #borrowObject borrowObject} and {@link #returnObject returnObject}.
*
* Example of use:
*
* Object obj = null;
*
* try {
* obj = pool.borrowObject();
* //...use the object...
* } catch(Exception e) {
* //...handle any exceptions...
* } finally {
* // make sure the object is returned to the pool
* if(null != obj) {
* pool.returnObject(obj);
* }
* }
* See {@link org.apache.commons.pool.BaseObjectPool BaseObjectPool} for a simple base implementation.
*
* @author Rodney Waldhoff
* @version $Revision: 155430 $ $Date: 2005-02-26 08:13:28 -0500 (Sat, 26 Feb 2005) $
*
*/
public interface ObjectPool {
/**
* Obtain an instance from my pool.
* By contract, clients MUST return
* the borrowed instance using
* {@link #returnObject(java.lang.Object) returnObject}
* or a related method as defined in an implementation
* or sub-interface.
*
* The behaviour of this method when the pool has been exhausted
* is not specified (although it may be specified by implementations).
*
* @return an instance from my pool.
*/
Object borrowObject() throws Exception;
/**
* Return an instance to my pool.
* By contract, obj MUST have been obtained
* using {@link #borrowObject() borrowObject}
* or a related method as defined in an implementation
* or sub-interface.
*
* @param obj a {@link #borrowObject borrowed} instance to be returned.
*/
void returnObject(Object obj) throws Exception;
/**
* Invalidates an object from the pool
* By contract, obj MUST have been obtained
* using {@link #borrowObject() borrowObject}
* or a related method as defined in an implementation
* or sub-interface.
*
* This method should be used when an object that has been borrowed
* is determined (due to an exception or other problem) to be invalid.
* If the connection should be validated before or after borrowing,
* then the {@link PoolableObjectFactory#validateObject} method should be
* used instead.
*
* @param obj a {@link #borrowObject borrowed} instance to be returned.
*/
void invalidateObject(Object obj) throws Exception;
/**
* Create an object using my {@link #setFactory factory} or other
* implementation dependent mechanism, and place it into the pool.
* addObject() is useful for "pre-loading" a pool with idle objects.
* (Optional operation).
*/
void addObject() throws Exception;
/**
* Return the number of instances
* currently idle in my pool (optional operation).
* This may be considered an approximation of the number
* of objects that can be {@link #borrowObject borrowed}
* without creating any new instances.
*
* @return the number of instances currently idle in my pool
* @throws UnsupportedOperationException if this implementation does not support the operation
*/
int getNumIdle() throws UnsupportedOperationException;
/**
* Return the number of instances
* currently borrowed from my pool
* (optional operation).
*
* @return the number of instances currently borrowed in my pool
* @throws UnsupportedOperationException if this implementation does not support the operation
*/
int getNumActive() throws UnsupportedOperationException;
/**
* Clears any objects sitting idle in the pool, releasing any
* associated resources (optional operation).
*
* @throws UnsupportedOperationException if this implementation does not support the operation
*/
void clear() throws Exception, UnsupportedOperationException;
/**
* Close this pool, and free any resources associated with it.
*/
void close() throws Exception;
/**
* Sets the {@link PoolableObjectFactory factory} I use
* to create new instances (optional operation).
* @param factory the {@link PoolableObjectFactory} I use to create new instances.
*
* @throws IllegalStateException when the factory cannot be set at this time
* @throws UnsupportedOperationException if this implementation does not support the operation
*/
void setFactory(PoolableObjectFactory factory) throws IllegalStateException, UnsupportedOperationException;
}