Package org.forgerock.util

Class PerItemEvictionStrategyCache<K,V>

java.lang.Object

org.forgerock.util.PerItemEvictionStrategyCache<K,V>

Type Parameters:

K - Type of the key

V - Type of the value

public class PerItemEvictionStrategyCache<K,V>
extends Object

PerItemEvictionStrategyCache is a thread-safe write-through cache.

Instead of storing directly the value in the backing Map, it requires the consumer to provide a value factory (a Callable). A new FutureTask encapsulates the callable, is executed and is placed inside a ConcurrentHashMap if absent.

The final behavior is that, even if two concurrent Threads are borrowing an object from the cache, given that they provide an equivalent value factory, the first one will compute the value while the other will get the result from the Future (and will wait until the result is computed or a timeout occurs).

Constructor Summary

Constructors

Constructor	Description
PerItemEvictionStrategyCache(ScheduledExecutorService executorService, AsyncFunction<V,Duration,Exception> defaultTimeoutFunction)	Build a new PerItemEvictionStrategyCache using the given scheduled executor.
PerItemEvictionStrategyCache(ScheduledExecutorService executorService, Duration defaultTimeout)	Build a new PerItemEvictionStrategyCache using the given scheduled executor.

Method Summary

Modifier and Type	Method	Description
void	clear()	Clean-up the cache entries.
void	evict(K key)	Evict a cached value from the cache.
Duration	getMaxTimeout()	Gets the maximum timeout (can be null).
V	getValue(K key, Callable<V> callable)	Borrow (and create before hand if absent) a cache entry.
<E extends Exception> V	getValue(K key, Callable<V> callable, AsyncFunction<V,Duration,E> expire)	Borrow (and create before hand if absent) a cache entry.
boolean	isEmpty()	Returns whether this cache is empty or not.
void	setMaxTimeout(Duration maxTimeout)	Sets the maximum timeout.
int	size()	Returns the number of cached values.

Methods inherited from class java.lang.Object

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

Constructor Detail

PerItemEvictionStrategyCache

public PerItemEvictionStrategyCache(ScheduledExecutorService executorService,
                                    Duration defaultTimeout)

Build a new PerItemEvictionStrategyCache using the given scheduled executor.

Parameters:

executorService - scheduled executor for registering expiration callbacks.

defaultTimeout - the default cache entry timeout

PerItemEvictionStrategyCache

public PerItemEvictionStrategyCache(ScheduledExecutorService executorService,
                                    AsyncFunction<V,Duration,Exception> defaultTimeoutFunction)

Build a new PerItemEvictionStrategyCache using the given scheduled executor.

Parameters:

executorService - scheduled executor for registering expiration callbacks.

defaultTimeoutFunction - the function that will compute the cache entry timeout (must not be null) the default timeout to cache the entries

Method Detail

getValue

public V getValue(K key,
                  Callable<V> callable)
           throws InterruptedException,
                  ExecutionException

Borrow (and create before hand if absent) a cache entry. If another Thread has created (or the creation is undergoing) the value, this method waits indefinitely for the value to be available.

Parameters:

key - entry key

callable - cached value factory

Returns:

the cached value

Throws:

InterruptedException - if the current thread was interrupted while waiting

ExecutionException - if the cached value computation threw an exception

getValue

public <E extends Exception> V getValue(K key,
                                        Callable<V> callable,
                                        AsyncFunction<V,Duration,E> expire)
                                 throws InterruptedException,
                                        ExecutionException

Borrow (and create before hand if absent) a cache entry. If another Thread has created (or the creation is undergoing) the value, this method waits indefinitely for the value to be available.

Type Parameters:

E - type of exception

Parameters:

key - entry key

callable - cached value factory

expire - function to override the global cache's timeout

Returns:

the cached value

Throws:

InterruptedException - if the current thread was interrupted while waiting

ExecutionException - if the cached value computation threw an exception

clear

public void clear()

Clean-up the cache entries.

size

public int size()

Returns the number of cached values.

Returns:

the number of cached values

isEmpty

public boolean isEmpty()

Returns whether this cache is empty or not.

Returns:

true if the cache does not contain any values, false otherwise.

evict

public void evict(K key)

Evict a cached value from the cache.

Parameters:

key - the entry key

getMaxTimeout

public Duration getMaxTimeout()

Gets the maximum timeout (can be null).

Returns:

the maximum timeout

setMaxTimeout

public void setMaxTimeout(Duration maxTimeout)

Sets the maximum timeout. If the timeout returned by the timeoutFunction is greater than this specified maximum timeout, then the maximum timeout is used instead of the returned one to cache the entry.

Parameters:

maxTimeout - the maximum timeout to use.