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  /*
   * 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
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 package org.apache.commons.pool;

An interface defining life-cycle methods for instances to be served by an org.apache.commons.pool.ObjectPool.

By contract, when an org.apache.commons.pool.ObjectPool delegates to a PoolableObjectFactory,

  1. makeObject is called whenever a new instance is needed.
  2. activateObject is invoked on every instance that has been passivated before it is borrowed from the pool.
  3. validateObject is 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.
  4. passivateObject is invoked on every instance when it is returned to the pool.
  5. 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.

PoolableObjectFactory must be thread-safe. The only promise an org.apache.commons.pool.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.

Parameters:
<T> the type of objects held in this pool
Author(s):
Rodney Waldhoff
Sandy McArthur
Version:
$Revision: 1222388 $ $Date: 2011-12-22 13:28:27 -0500 (Thu, 22 Dec 2011) $
Since:
Pool 1.0
See also:
org.apache.commons.pool.ObjectPool
 
 public interface PoolableObjectFactory<T> {
  
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 activated. They will not be activated before being served by the pool.

Returns:
an instance that can be served by the pool.
Throws:
java.lang.Exception if there is a problem creating a new instance, this will be propagated to the code requesting an object.
 
   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.

Parameters:
obj the instance to be destroyed
Throws:
java.lang.Exception should be avoided as it may be swallowed by the pool implementation.
See also:
validateObject(java.lang.Object)
org.apache.commons.pool.ObjectPool.invalidateObject(java.lang.Object)
  void destroyObject(T objthrows Exception;

  
Ensures that the instance is safe to be returned by the pool. Returns false if obj should be destroyed.

Parameters:
obj the instance to be validated
Returns:
false if obj is not valid and should be dropped from the pool, true otherwise.
  boolean validateObject(T obj);

  
Reinitialize an instance to be returned by the pool.

Parameters:
obj the instance to be activated
Throws:
java.lang.Exception if there is a problem activating obj, this exception may be swallowed by the pool.
See also:
destroyObject(java.lang.Object)
  void activateObject(T objthrows Exception;

  
Uninitialize an instance to be returned to the idle object pool.

Parameters:
obj the instance to be passivated
Throws:
java.lang.Exception if there is a problem passivating obj, this exception may be swallowed by the pool.
See also:
destroyObject(java.lang.Object)
  void passivateObject(T objthrows Exception;
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