org.forgerock.openig.tools.authentication.chf

Class AsyncRefreshableSupplier<V,E extends Exception>

java.lang.Object

org.forgerock.openig.tools.authentication.chf.AsyncRefreshableSupplier<V,E>

Type Parameters:

V - input type of the function parameter

E - supported exception type of the function parameter

public final class AsyncRefreshableSupplier<V,E extends Exception>
extends Object

This utility class supports a lock-downgrading strategy to make sure that 2 concurrent calls to compute the "cached" value will result in a single computation. It supports concurrent refreshment.

Constructor Summary

Constructors

Constructor and Description
AsyncRefreshableSupplier(AsyncFunction<Context,V,E> compute) Creates a provider ensuring "only-once" invocation of the given compute function.

Method Summary

Modifier and Type	Method and Description
Promise<V,E>	get(Context context) Computes (or re-computes) the value in a thread-safe manner, making sure that only 1 thread will compute the value, the other being blocked, waiting for the result to be computed.
Promise<V,E>	refresh(Context context) Refresh (and returns) the value, in a thread-safe manner.

Methods inherited from class java.lang.Object

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

Constructor Detail

AsyncRefreshableSupplier

public AsyncRefreshableSupplier(AsyncFunction<Context,V,E> compute)

Creates a provider ensuring "only-once" invocation of the given compute function.

Parameters:

compute - computation function

Method Detail

get

public Promise<V,E> get(Context context)

Computes (or re-computes) the value in a thread-safe manner, making sure that only 1 thread will compute the value, the other being blocked, waiting for the result to be computed.

Parameters:

context - Service context

Returns:

computed promise

refresh

public Promise<V,E> refresh(Context context)

Refresh (and returns) the value, in a thread-safe manner.

It works like this:

• The thread try to take the refresh lock, if it succeed that means that no refresh is in progress, therefore it can safely invalidate the value and returns the newly computed value.
• Other concurrent threads will not have the lock (using the else branch of the condition) and will all be together waiting for the lock to be released.
• When the lock is released, all concurrent threads are notified (one after the other) and returns the refreshed value.

Parameters:

context - Service context

Returns:

refreshed value