org.apache.commons.pool.PoolableObjectFactory Maven / Gradle / Ivy
/*
* 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.commons.pool;
/**
* An interface defining life-cycle methods for
* instances to be served by an {@link ObjectPool}.
*
* By contract, when an {@link ObjectPool}
* delegates to a {@link PoolableObjectFactory},
*
* -
* {@link #makeObject makeObject}
* is called whenever a new instance is needed.
*
* -
* {@link #activateObject activateObject}
* is invoked on every instance that has been
* {@link #passivateObject passivated} before it is
* {@link ObjectPool#borrowObject borrowed} from the pool.
*
* -
* {@link #validateObject validateObject}
* is invoked on {@link #activateObject activated} instances to make sure
* they can be {@link ObjectPool#borrowObject borrowed} from the pool.
*
validateObject may also be used to test an
* instance being {@link ObjectPool#returnObject returned} to the pool
* before it is {@link #passivateObject passivated}. It will only be invoked
* on an activated instance.
*
* -
* {@link #passivateObject passivateObject}
* is invoked on every instance when it is returned to the pool.
*
* -
* {@link #destroyObject destroyObject}
* is invoked on every instance when it is being "dropped" from the
* pool (whether due to the response from
validateObject,
* or for reasons specific to the pool implementation.) There is no
* guarantee that the instance being destroyed will
* be considered active, passive or in a generally consistent state.
*
*
*
*
* {@link PoolableObjectFactory} must be thread-safe. The only promise
* an {@link ObjectPool} makes is that the same instance of an object will not
* be passed to more than one method of a PoolableObjectFactory
* at a time.
*
*
* @see ObjectPool
*
* @author Rodney Waldhoff
* @author Sandy McArthur
* @version $Revision: 777748 $ $Date: 2009-05-22 20:00:44 -0400 (Fri, 22 May 2009) $
* @since Pool 1.0
*/
public interface PoolableObjectFactory {
/**
* Creates an instance that can be served by the pool.
* Instances returned from this method should be in the
* same state as if they had been
* {@link #activateObject activated}. They will not be
* activated before being served by the pool.
*
* @return an instance that can be served by the pool.
* @throws Exception if there is a problem creating a new instance,
* this will be propagated to the code requesting an object.
*/
Object makeObject() throws Exception;
/**
* Destroys an instance no longer needed by the pool.
*
* It is important for implementations of this method to be aware
* that there is no guarantee about what state obj
* will be in and the implementation should be prepared to handle
* unexpected errors.
*
*
* Also, an implementation must take in to consideration that
* instances lost to the garbage collector may never be destroyed.
*
*
* @param obj the instance to be destroyed
* @throws Exception should be avoided as it may be swallowed by
* the pool implementation.
* @see #validateObject
* @see ObjectPool#invalidateObject
*/
void destroyObject(Object obj) throws Exception;
/**
* Ensures that the instance is safe to be returned by the pool.
* Returns false if obj should be destroyed.
*
* @param obj the instance to be validated
* @return false if obj is not valid and should
* be dropped from the pool, true otherwise.
*/
boolean validateObject(Object obj);
/**
* Reinitialize an instance to be returned by the pool.
*
* @param obj the instance to be activated
* @throws Exception if there is a problem activating obj,
* this exception may be swallowed by the pool.
* @see #destroyObject
*/
void activateObject(Object obj) throws Exception;
/**
* Uninitialize an instance to be returned to the idle object pool.
*
* @param obj the instance to be passivated
* @throws Exception if there is a problem passivating obj,
* this exception may be swallowed by the pool.
* @see #destroyObject
*/
void passivateObject(Object obj) throws Exception;
}