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 before it is returned from the pool.
3. passivateObject is invoked on every instance when it is returned to the pool.
4. 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.)
5. validateObject is invoked in an implementation-specific fashion to determine if an instance is still valid to be returned by the pool. It will only be invoked on an "activated" instance.