Interface KeyedObjectPool<K,​V>

  • Type Parameters:
    K - The type of keys maintained by this pool.
    V - Type of element pooled in this pool.
    All Superinterfaces:
    AutoCloseable, Closeable
    All Known Implementing Classes:
    GenericKeyedObjectPool

    public interface KeyedObjectPool<K,​V>
    extends Closeable
    A "keyed" pooling interface.

    A keyed pool maintains a pool of instances for each key value.

    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 GenericKeyedObjectPool for an implementation.

    Since:
    2.0
    See Also:
    KeyedPooledObjectFactory, ObjectPool, GenericKeyedObjectPool
    • Method Summary

      All Methods Instance Methods Abstract Methods Default Methods 
      Modifier and Type Method Description
      void addObject​(K key)
      Creates an object using the factory or other implementation dependent mechanism, passivate it, and then place it in the idle object pool.
      default void addObjects​(Collection<K> keys, int count)
      Calls addObject(Object) with each key in keys for count number of times.
      default void addObjects​(K key, int count)
      Calls addObject(Object) key count number of times.
      V borrowObject​(K key)
      Borrows 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()
      Closes this pool, and free any resources associated with it.
      int getNumActive()
      Gets the total number of instances currently borrowed from this pool but not yet returned.
      int getNumActive​(K key)
      Gets the number of instances currently borrowed from but not yet returned to the pool corresponding to the given key.
      int getNumIdle()
      Gets the total number of instances currently idle in this pool.
      int getNumIdle​(K key)
      Gets the number of instances corresponding to the given key currently idle in this pool.
      void invalidateObject​(K key, V obj)
      Invalidates an object from the pool.
      default void invalidateObject​(K key, V obj, DestroyMode destroyMode)
      Invalidates an object from the pool, using the provided DestroyMode.
      void returnObject​(K key, V obj)
      Return an instance to the pool.
    • Method Detail

      • borrowObject

        V borrowObject​(K key)
                throws Exception,
                       NoSuchElementException,
                       IllegalStateException
        Borrows 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 (optionally) 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 behavior of this method when the pool has been exhausted is not strictly specified (although it may be specified by implementations).

        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
      • close

        void close()
        Closes this pool, and free any resources associated with it.

        Calling addObject or borrowObject after invoking this method on a pool will cause them to throw an IllegalStateException.

        Implementations should silently fail if not all resources can be freed.

        Specified by:
        close in interface AutoCloseable
        Specified by:
        close in interface Closeable
      • getNumActive

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

        int getNumActive​(K key)
        Gets the number of instances currently borrowed from but not yet returned to the pool corresponding to the given key. Returns a negative value if this information is not available.
        Parameters:
        key - the key to query
        Returns:
        the number of instances currently borrowed from but not yet returned to the pool corresponding to the given key.
      • getNumIdle

        int getNumIdle()
        Gets the total number of instances currently idle in this pool. Returns a negative value if this information is not available.
        Returns:
        the total number of instances currently idle in this pool.
      • getNumIdle

        int getNumIdle​(K key)
        Gets the number of instances corresponding to the given key currently idle in this pool. 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.
      • 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 - if the instance cannot be invalidated
      • invalidateObject

        default void invalidateObject​(K key,
                                      V obj,
                                      DestroyMode destroyMode)
                               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 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.
        destroyMode - destroy activation context provided to the factory
        Throws:
        Exception - if the instance cannot be invalidated
        Since:
        2.9.0
      • 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:
        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