org.apache.commons.pool
Interface KeyedPoolableObjectFactory

All Known Implementing Classes:
BaseKeyedPoolableObjectFactory

public interface KeyedPoolableObjectFactory

An interface defining life-cycle methods for instances to be served by a KeyedObjectPool.

By contract, when an KeyedObjectPool delegates to a KeyedPoolableObjectFactory,

  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.

KeyedPoolableObjectFactory must be thread-safe. The only promise an KeyedObjectPool makes is that the same instance of an object will not be passed to more than one method of a KeyedPoolableObjectFactory at a time.

Since:
Pool 1.0
Version:
$Revision: 892236 $ $Date: 2013-12-31 04:43:12 +0000 (Tue, 31 Dec 2013) $
Author:
Rodney Waldhoff, Sandy McArthur
See Also:
KeyedObjectPool

Method Summary
 void activateObject(Object key, Object obj)
          Reinitialize an instance to be returned by the pool.
 void destroyObject(Object key, Object obj)
          Destroy an instance no longer needed by the pool.
 Object makeObject(Object key)
          Create an instance that can be served by the pool.
 void passivateObject(Object key, Object obj)
          Uninitialize an instance to be returned to the idle object pool.
 boolean validateObject(Object key, Object obj)
          Ensures that the instance is safe to be returned by the pool.
 

Method Detail

makeObject

Object makeObject(Object key)
                  throws Exception
Create an instance that can be served by the pool.

Parameters:
key - the key used when constructing the object
Returns:
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.

destroyObject

void destroyObject(Object key,
                   Object obj)
                   throws Exception
Destroy 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:
key - the key used when selecting the instance
obj - the instance to be destroyed
Throws:
Exception - should be avoided as it may be swallowed by the pool implementation.
See Also:
validateObject(java.lang.Object, java.lang.Object), KeyedObjectPool.invalidateObject(java.lang.Object, java.lang.Object)

validateObject

boolean validateObject(Object key,
                       Object obj)
Ensures that the instance is safe to be returned by the pool. Returns false if obj should be destroyed.

Parameters:
key - the key used when selecting the object
obj - the instance to be validated
Returns:
false if obj is not valid and should be dropped from the pool, true otherwise.

activateObject

void activateObject(Object key,
                    Object obj)
                    throws Exception
Reinitialize an instance to be returned by the pool.

Parameters:
key - the key used when selecting the object
obj - the instance to be activated
Throws:
Exception - if there is a problem activating obj, this exception may be swallowed by the pool.
See Also:
destroyObject(java.lang.Object, java.lang.Object)

passivateObject

void passivateObject(Object key,
                     Object obj)
                     throws Exception
Uninitialize an instance to be returned to the idle object pool.

Parameters:
key - the key used when selecting the object
obj - the instance to be passivated
Throws:
Exception - if there is a problem passivating obj, this exception may be swallowed by the pool.
See Also:
destroyObject(java.lang.Object, java.lang.Object)


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