Package org.apache.commons.pool

Interface PoolableObjectFactory<T>

  • Type Parameters:
    T - the type of objects held in this pool
    All Known Implementing Classes:
    BasePoolableObjectFactory
    public interface PoolableObjectFactory<T>
    An interface defining life-cycle methods for instances to be served by an ObjectPool.

    By contract, when an 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 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.

    Since:
    Pool 1.0
    Version:
    $Revision: 1222388 $ $Date: 2011-12-22 13:28:27 -0500 (Thu, 22 Dec 2011) $
    Author:
    Rodney Waldhoff, Sandy McArthur
    See Also:
    ObjectPool

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      void activateObject​(T obj)
      Reinitialize an instance to be returned by the pool.
      void destroyObject​(T obj)
      Destroys an instance no longer needed by the pool.
      T makeObject()
      Creates an instance that can be served by the pool.
      void passivateObject​(T obj)
      Uninitialize an instance to be returned to the idle object pool.
      boolean validateObject​(T obj)
      Ensures that the instance is safe to be returned by the pool.

    • Method Detail

      • makeObject

        T makeObject()
      throws Exception
        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:
        Exception - if there is a problem creating a new instance, this will be propagated to the code requesting an object.

      • destroyObject

        void destroyObject​(T obj)
            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:
        Exception - should be avoided as it may be swallowed by the pool implementation.
        See Also:
        validateObject(T), ObjectPool.invalidateObject(T)

      • validateObject

        boolean validateObject​(T obj)
        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.

      • activateObject

        void activateObject​(T obj)
             throws Exception
        Reinitialize an instance to be returned by the pool.
        Parameters:
        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(T)

      • passivateObject

        void passivateObject​(T obj)
              throws Exception
        Uninitialize an instance to be returned to the idle object pool.
        Parameters:
        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(T)