Package org.apache.commons.pool

Interface KeyedObjectPool<K,​V>

  • Type Parameters:
    K - the type of keys in this pool
    V - the type of objects held in this pool
    All Known Implementing Classes:
    BaseKeyedObjectPool, GenericKeyedObjectPool, StackKeyedObjectPool
    public interface KeyedObjectPool<K,​V>
    A "keyed" pooling interface.

    A keyed pool pools instances of multiple types. Each type may be accessed using an arbitrary key.

    Example of use: 

     Object obj = null;
 Object key = "Key";

 try {
     obj = pool.borrowObject(key);
     //...use the object...
 } catch(Exception e) {
     // invalidate the object
     pool.invalidateObject(key, 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(key, obj);
     }
 }

    KeyedObjectPool implementations may choose to store at most one instance per key value, or may choose to maintain a pool of instances for each key (essentially creating a Map of pools).

    See BaseKeyedObjectPool for a simple base implementation.

    Since:
    Pool 1.0
    Version:
    $Revision: 1222396 $ $Date: 2011-12-22 14:02:25 -0500 (Thu, 22 Dec 2011) $
    Author:
    Rodney Waldhoff, Sandy McArthur
    See Also:
    KeyedPoolableObjectFactory, KeyedObjectPoolFactory, ObjectPool, BaseKeyedObjectPool

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      void addObject​(K key)
      Create an object using the factory or other implementation dependent mechanism, passivate it, and then place it in the idle object pool.
      V borrowObject​(K key)
      Obtains an instance from this pool for the specified key.
      void clear()
      Clears the pool, removing all pooled instances (optional operation).
      void clear​(K key)
      Clears the specified pool, removing all pooled instances corresponding to the given key (optional operation).
      void close()
      Close this pool, and free any resources associated with it.
      int getNumActive()
      Returns the total number of instances current borrowed from this pool but not yet returned (optional operation).
      int getNumActive​(K key)
      Returns the number of instances currently borrowed from but not yet returned to the pool corresponding to the given key (optional operation).
      int getNumIdle()
      Returns the total number of instances currently idle in this pool (optional operation).
      int getNumIdle​(K key)
      Returns the number of instances corresponding to the given key currently idle in this pool (optional operation).
      void invalidateObject​(K key, V obj)
      Invalidates an object from the pool.
      void returnObject​(K key, V obj)
      Return an instance to the pool.

    • Method Detail

      • borrowObject

        V borrowObject​(K key)
        throws Exception,
               NoSuchElementException,
               IllegalStateException
        Obtains an instance from this pool for the specified key.

        Instances returned from this method will have been either newly created with makeObject or will be a previously idle object and have been activated with activateObject and then validated with validateObject.

        By contract, clients must return the borrowed object using returnObject, invalidateObject, or a related method as defined in an implementation or sub-interface, using a key that is equivalent to the one used to borrow the instance in the first place.

        The behaviour of this method when the pool has been exhausted is not strictly specified (although it may be specified by implementations). Older versions of this method would return null to indicate exhaustion, newer versions are encouraged to throw a NoSuchElementException.

        Parameters:
        key - the key used to obtain the object
        Returns:
        an instance from this pool.
        Throws:
        IllegalStateException - after close has been called on this pool
        Exception - when makeObject throws an exception
        NoSuchElementException - when the pool is exhausted and cannot or will not return another instance

      • returnObject

        void returnObject​(K key,
                  V obj)
           throws Exception
        Return 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 using a key that is equivalent to the one used to borrow the instance in the first place.
        Parameters:
        key - the key used to obtain the object
        obj - a borrowed instance to be returned.
        Throws:
        Exception

      • invalidateObject

        void invalidateObject​(K key,
                      V 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 using a key that is equivalent to the one used to borrow the Object in the first place.

        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:
        key - the key used to obtain the object
        obj - a borrowed instance to be returned.
        Throws:
        Exception

      • getNumIdle

        int getNumIdle​(K key)
        throws UnsupportedOperationException
        Returns the number of instances corresponding to the given key currently idle in this pool (optional operation). Returns a negative value if this information is not available.
        Parameters:
        key - the key to query
        Returns:
        the number of instances corresponding to the given key currently idle in this pool or a negative value if unsupported
        Throws:
        UnsupportedOperationException - deprecated: when this implementation doesn't support the operation

      • getNumActive

        int getNumActive​(K key)
          throws UnsupportedOperationException
        Returns the number of instances currently borrowed from but not yet returned to the pool corresponding to the given key (optional operation). Returns a negative value if this information is not available.
        Parameters:
        key - the key to query
        Returns:
        the number of instances corresponding to the given key currently borrowed in this pool or a negative value if unsupported
        Throws:
        UnsupportedOperationException - deprecated: when this implementation doesn't support the operation

      • getNumIdle

        int getNumIdle()
        throws UnsupportedOperationException
        Returns the total number of instances currently idle in this pool (optional operation). Returns a negative value if this information is not available.
        Returns:
        the total number of instances currently idle in this pool or a negative value if unsupported
        Throws:
        UnsupportedOperationException - deprecated: when this implementation doesn't support the operation

      • getNumActive

        int getNumActive()
          throws UnsupportedOperationException
        Returns the total number of instances current borrowed from this pool but not yet returned (optional operation). Returns a negative value if this information is not available.
        Returns:
        the total number of instances currently borrowed from this pool or a negative value if unsupported
        Throws:
        UnsupportedOperationException - deprecated: when this implementation doesn't support the operation