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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.lang;
import java.time.Clock;
import java.time.Duration;
import java.time.Instant;
import java.util.function.Supplier;
/**
* Supplier that caches the value for a given duration with ability to invalidate on demand.
* Is thread safe.
*
* @author freva
*/
public class CachedSupplier<T> implements Supplier<T> {
private final Object monitor = new Object();
private final Supplier<T> delegate;
private final Duration period;
private final Clock clock;
private Instant nextRefresh;
private volatile T value;
public CachedSupplier(Supplier<T> delegate, Duration period) {
this(delegate, period, Clock.systemUTC());
}
CachedSupplier(Supplier<T> delegate, Duration period, Clock clock) {
this.delegate = delegate;
this.period = period;
this.clock = clock;
this.nextRefresh = Instant.MIN;
}
@Override
public T get() {
synchronized (monitor) {
if (clock.instant().isAfter(nextRefresh)) {
this.value = delegate.get();
this.nextRefresh = clock.instant().plus(period);
}
}
return value;
}
public void invalidate() {
synchronized (monitor) {
this.nextRefresh = Instant.MIN;
}
}
}
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