Package org.apache.tomcat.dbcp.pool2

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:

  • Method Summary

    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.
    default List<K>
    getKeys()
    Gets a copy of the pool key list.
    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 Details

    • addObject

      void addObject(K key) throws Exception
      Creates an object using the factory or other implementation dependent mechanism, passivate it, and then place it in the idle object pool. addObject is useful for "pre-loading" a pool with idle objects (Optional operation).
      Parameters:
      key - the key a new instance should be added to
      Throws:
      Exception - when KeyedPooledObjectFactory.makeObject(K) fails.
      IllegalStateException - after close() has been called on this pool.
      UnsupportedOperationException - when this pool cannot add new idle objects.

    • addObjects

      default void addObjects(Collection<K> keys, int count) throws Exception
      Calls addObject(Object) with each key in keys for count number of times. This has the same effect as calling addObjects(Object, int) for each key in the keys collection.
      Parameters:
      keys - Collection of keys to add objects for.
      count - the number of idle objects to add for each key.
      Throws:
      Exception - when addObject(Object) fails.
      IllegalArgumentException - when keyedPool, keys, or any value in keys is null.
      See Also:

    • addObjects

      default void addObjects(K key, int count) throws Exception
      Calls addObject(Object) key count number of times.
      Parameters:
      key - the key to add objects for.
      count - the number of idle objects to add for key.
      Throws:
      Exception - when addObject(Object) fails.
      IllegalArgumentException - when key is null.
      Since:
      2.8.0

    • borrowObject

      V borrowObject(K key) throws Exception
      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

    • clear

      void clear() throws Exception
      Clears the pool, removing all pooled instances (optional operation).
      Throws:
      UnsupportedOperationException - when this implementation doesn't support the operation
      Exception - if the pool cannot be cleared

    • clear

      void clear(K key) throws Exception
      Clears the specified pool, removing all pooled instances corresponding to the given key (optional operation).
      Parameters:
      key - the key to clear
      Throws:
      UnsupportedOperationException - when this implementation doesn't support the operation
      Exception - if the key cannot be cleared

    • 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

    • getKeys

      default List<K> getKeys()
      Gets a copy of the pool key list.

      Note: The default implementation returns an empty list. Implementations should override this method.

      Returns:
      a copy of the pool key list.
      Since:
      2.12.0

    • 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