at.molindo.utils.concurrent
Class KeyLock<K,V>

java.lang.Object
  at.molindo.utils.concurrent.KeyLock<K,V>

public class KeyLock<K,V>
extends Object

Constructor Summary

KeyLock()

Method Summary

int	activeCount()
List<K>	activeKeys()
static <K,V> KeyLock<K,V>	newKeyLock()
protected void	onExisting(K key) hook that's called if key is already known.
protected V	replace(V result, Exception ex) how to replace already computed results.
V	withLock(K key, Callable<V> callable)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

KeyLock

public KeyLock()

Method Detail

newKeyLock

public static <K,V> KeyLock<K,V> newKeyLock()

withLock

public V withLock(K key,
                  Callable<V> callable)
           throws Exception

Throws:

Exception

onExisting

protected void onExisting(K key)
                   throws Exception

hook that's called if key is already known. does nothing by default

Throws:

Exception - throw an exception to prevent waiting

replace

protected V replace(V result,
                    Exception ex)
             throws Exception

how to replace already computed results. by default it's null, as users might not want to get concurrency issues on shared results. As a replacement, one could perform a DB lookup if the task is to create/update a DB entity or do a deep clone of the object.

Parameters:

result -

ex -

Returns:

Throws:

Exception

activeCount

public int activeCount()

Returns:

number of active keys

activeKeys

public List<K> activeKeys()

Returns:

a newly created List of all active keys. Changes to this list don't have any effect to this KeyLock (changes to the values will have an undefined effect though).