/*
* 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.pool2;
An interface defining life-cycle methods for instances to be served by an ObjectPool. By contract, when an ObjectPool delegates to a PooledObjectFactory,
-
makeObject is called whenever a new instance is needed.
-
activateObject is invoked on every instance that has been passivated before it is borrowed from the pool.
-
validateObject may be invoked on activated instances to make sure they can be borrowed from the pool. validateObject may also be used to test an instance being returned to the pool before it is passivated. It will only be invoked on an activated instance.
-
passivateObject is invoked on every instance when it is returned to the pool.
-
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.
PooledObjectFactory must be thread-safe. The only promise an 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.
While clients of a KeyedObjectPool borrow and return instances of the underlying value type V, the factory methods act on instances of PooledObject<V>. These are the object wrappers that pools use to track and maintain state information about the objects that they manage.
Type parameters: - <T> – Type of element managed in this factory.
See Also: Since: 2.0
/**
* An interface defining life-cycle methods for instances to be served by an
* {@link ObjectPool}.
* <p>
* By contract, when an {@link ObjectPool} delegates to a
* {@link PooledObjectFactory},
* </p>
* <ol>
* <li>
* {@link #makeObject} is called whenever a new instance is needed.
* </li>
* <li>
* {@link #activateObject} is invoked on every instance that has been
* {@link #passivateObject passivated} before it is
* {@link ObjectPool#borrowObject borrowed} from the pool.
* </li>
* <li>
* {@link #validateObject} may be invoked on {@link #activateObject activated}
* instances to make sure they can be {@link ObjectPool#borrowObject borrowed}
* from the pool. {@link #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.
* </li>
* <li>
* {@link #passivateObject} is invoked on every instance when it is returned
* to the pool.
* </li>
* <li>
* {@link #destroyObject} is invoked on every instance when it is being
* "dropped" from the pool (whether due to the response from
* {@link #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.
* </li>
* </ol>
* {@link PooledObjectFactory} 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 <code>PoolableObjectFactory</code>
* at a time.
* <p>
* While clients of a {@link KeyedObjectPool} borrow and return instances of
* the underlying value type {@code V}, the factory methods act on instances of
* {@link PooledObject PooledObject<V>}. These are the object wrappers that
* pools use to track and maintain state information about the objects that
* they manage.
* </p>
*
* @param <T> Type of element managed in this factory.
*
* @see ObjectPool
*
* @since 2.0
*/
public interface PooledObjectFactory<T> {
Creates an instance that can be served by the pool and wrap it in a PooledObject to be managed by the pool. Throws: - Exception – if there is a problem creating a new instance,
this will be propagated to the code requesting an object.
Returns: a PooledObject wrapping an instance that can be served by the pool
/**
* Creates an instance that can be served by the pool and wrap it in a
* {@link PooledObject} to be managed by the pool.
*
* @return a {@code PooledObject} wrapping 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.
*/
PooledObject<T> 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.
Params: - p – a
PooledObject wrapping the instance to be destroyed
Throws: - Exception – should be avoided as it may be swallowed by
the pool implementation.
See Also:
/**
* Destroys an instance no longer needed by the pool.
* <p>
* It is important for implementations of this method to be aware that there
* is no guarantee about what state <code>obj</code> will be in and the
* implementation should be prepared to handle unexpected errors.
* </p>
* <p>
* Also, an implementation must take in to consideration that instances lost
* to the garbage collector may never be destroyed.
* </p>
*
* @param p a {@code PooledObject} wrapping 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(PooledObject<T> p) throws Exception;
Ensures that the instance is safe to be returned by the pool.
Params: - p – a
PooledObject wrapping the instance to be validated
Returns: false if obj is not valid and should
be dropped from the pool, true otherwise.
/**
* Ensures that the instance is safe to be returned by the pool.
*
* @param p a {@code PooledObject} wrapping the instance to be validated
*
* @return <code>false</code> if <code>obj</code> is not valid and should
* be dropped from the pool, <code>true</code> otherwise.
*/
boolean validateObject(PooledObject<T> p);
Reinitializes an instance to be returned by the pool.
Params: - p – a
PooledObject wrapping the instance to be activated
Throws: - Exception – if there is a problem activating
obj,
this exception may be swallowed by the pool.
See Also:
/**
* Reinitializes an instance to be returned by the pool.
*
* @param p a {@code PooledObject} wrapping the instance to be activated
*
* @throws Exception if there is a problem activating <code>obj</code>,
* this exception may be swallowed by the pool.
*
* @see #destroyObject
*/
void activateObject(PooledObject<T> p) throws Exception;
Uninitializes an instance to be returned to the idle object pool.
Params: - p – a
PooledObject wrapping the instance to be passivated
Throws: - Exception – if there is a problem passivating
obj,
this exception may be swallowed by the pool.
See Also:
/**
* Uninitializes an instance to be returned to the idle object pool.
*
* @param p a {@code PooledObject} wrapping the instance to be passivated
*
* @throws Exception if there is a problem passivating <code>obj</code>,
* this exception may be swallowed by the pool.
*
* @see #destroyObject
*/
void passivateObject(PooledObject<T> p) throws Exception;
}