Interface ObjectPool<T>

  • Type Parameters:
    T - Type of element pooled in this pool.
    All Superinterfaces:
    AutoCloseable, Closeable
    All Known Implementing Classes:
    BaseObjectPool, GenericObjectPool, SoftReferenceObjectPool

    public interface ObjectPool<T>
    extends Closeable
    A pooling simple interface.

    Example of use:

     Object obj = null;
    
     try {
         obj = pool.borrowObject();
         try {
             //...use the object...
         } catch(Exception e) {
             // invalidate the object
             pool.invalidateObject(obj);
             // do not return the object to the pool twice
             obj = null;
         } finally {
             // make sure the object is returned to the pool
             if(null != obj) {
                 pool.returnObject(obj);
            }
         }
     } catch(Exception e) {
           // failed to borrow an object
     }

    See BaseObjectPool for a simple base implementation.

    Since:
    2.0
    See Also:
    PooledObjectFactory, KeyedObjectPool, BaseObjectPool
    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      void addObject()
      Creates an object using the factory or other implementation dependent mechanism, passivate it, and then place it in the idle object pool.
      void addObjects​(int count)
      Calls addObject() count number of times.
      T borrowObject()
      Obtains an instance from this pool.
      void clear()
      Clears any objects sitting idle in the pool, releasing any associated resources (optional operation).
      void close()
      Closes this pool, and free any resources associated with it.
      int getNumActive()
      Returns the number of instances currently borrowed from this pool.
      int getNumIdle()
      Returns the number of instances currently idle in this pool.
      void invalidateObject​(T obj)
      Invalidates an object from the pool.
      void invalidateObject​(T obj, DestroyMode mode)
      Invalidates an object from the pool, using the provided DestroyMode
      void returnObject​(T obj)
      Returns an instance to the pool.
    • Method Detail

      • addObjects

        void addObjects​(int count)
                 throws Exception
        Calls addObject() count number of times.
        Parameters:
        count - the number of idle objects to add.
        Throws:
        Exception - when addObject() fails.
        Since:
        2.8.0
      • getNumActive

        int getNumActive()
        Returns the number of instances currently borrowed from this pool. Returns a negative value if this information is not available.
        Returns:
        the number of instances currently borrowed from this pool.
      • getNumIdle

        int getNumIdle()
        Returns the number of instances currently idle in this pool. This may be considered an approximation of the number of objects that can be borrowed without creating any new instances. Returns a negative value if this information is not available.
        Returns:
        the number of instances currently idle in this pool.
      • invalidateObject

        void invalidateObject​(T obj)
                       throws Exception
        Invalidates an object from the pool.

        By contract, obj must have been obtained using borrowObject() or a related method as defined in an implementation or sub-interface.

        This method should be used when an object that has been borrowed is determined (due to an exception or other problem) to be invalid.

        Parameters:
        obj - a borrowed instance to be disposed.
        Throws:
        Exception - if the instance cannot be invalidated
      • invalidateObject

        void invalidateObject​(T obj,
                              DestroyMode mode)
                       throws Exception
        Invalidates an object from the pool, using the provided DestroyMode

        By contract, obj must have been obtained using borrowObject() or a related method as defined in an implementation or sub-interface.

        This method should be used when an object that has been borrowed is determined (due to an exception or other problem) to be invalid.

        Parameters:
        obj - a borrowed instance to be disposed.
        mode - destroy activation context provided to the factory
        Throws:
        Exception - if the instance cannot be invalidated
        Since:
        2.9.0
      • returnObject

        void returnObject​(T obj)
                   throws Exception
        Returns an instance to the pool. By contract, obj must have been obtained using borrowObject() or a related method as defined in an implementation or sub-interface.
        Parameters:
        obj - a borrowed instance to be returned.
        Throws:
        IllegalStateException - if an attempt is made to return an object to the pool that is in any state other than allocated (i.e. borrowed). Attempting to return an object more than once or attempting to return an object that was never borrowed from the pool will trigger this exception.
        Exception - if an instance cannot be returned to the pool