com.github.benmanes.caffeine.cache.Async Maven / Gradle / Ivy
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/*
* Copyright 2015 Ben Manes. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.github.benmanes.caffeine.cache;
import static com.github.benmanes.caffeine.cache.BoundedLocalCache.MAXIMUM_EXPIRY;
import static java.util.Objects.requireNonNull;
import java.io.Serializable;
import java.util.Map;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionException;
import java.util.concurrent.Executor;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Static utility methods and classes pertaining to asynchronous operations.
*
* @author [email protected] (Ben Manes)
*/
final class Async {
static final long ASYNC_EXPIRY = (Long.MAX_VALUE >> 1) + (Long.MAX_VALUE >> 2); // 220 years
private Async() {}
/** Returns if the future has successfully completed. */
static boolean isReady(@Nullable CompletableFuture future) {
return (future != null) && future.isDone()
&& !future.isCompletedExceptionally()
&& (future.join() != null);
}
/** Returns the current value or null if either not done or failed. */
@SuppressWarnings("NullAway")
static @Nullable V getIfReady(@Nullable CompletableFuture future) {
return isReady(future) ? future.join() : null;
}
/** Returns the value when completed successfully or null if failed. */
static @Nullable V getWhenSuccessful(@Nullable CompletableFuture future) {
try {
return (future == null) ? null : future.join();
} catch (CancellationException | CompletionException e) {
return null;
}
}
/**
* A removal listener that asynchronously forwards the value stored in a {@link CompletableFuture}
* if successful to the user-supplied removal listener.
*/
static final class AsyncRemovalListener
implements RemovalListener>, Serializable {
private static final long serialVersionUID = 1L;
final RemovalListener delegate;
final Executor executor;
AsyncRemovalListener(RemovalListener delegate, Executor executor) {
this.delegate = requireNonNull(delegate);
this.executor = requireNonNull(executor);
}
@Override
@SuppressWarnings("FutureReturnValueIgnored")
public void onRemoval(@Nullable K key,
@Nullable CompletableFuture future, RemovalCause cause) {
if (future != null) {
future.thenAcceptAsync(value -> {
if (value != null) {
delegate.onRemoval(key, value, cause);
}
}, executor);
}
}
Object writeReplace() {
return delegate;
}
}
/**
* A weigher for asynchronous computations. When the value is being loaded this weigher returns
* {@code 0} to indicate that the entry should not be evicted due to a size constraint. If the
* value is computed successfully the entry must be reinserted so that the weight is updated and
* the expiration timeouts reflect the value once present. This can be done safely using
* {@link Map#replace(Object, Object, Object)}.
*/
static final class AsyncWeigher implements Weigher>, Serializable {
private static final long serialVersionUID = 1L;
final Weigher delegate;
AsyncWeigher(Weigher delegate) {
this.delegate = requireNonNull(delegate);
}
@Override
public int weigh(K key, CompletableFuture future) {
return isReady(future) ? delegate.weigh(key, future.join()) : 0;
}
Object writeReplace() {
return delegate;
}
}
/**
* An expiry for asynchronous computations. When the value is being loaded this expiry returns
* {@code ASYNC_EXPIRY} to indicate that the entry should not be evicted due to an expiry
* constraint. If the value is computed successfully the entry must be reinserted so that the
* expiration is updated and the expiration timeouts reflect the value once present. The value
* maximum range is reserved to coordinate the asynchronous life cycle.
*/
static final class AsyncExpiry implements Expiry>, Serializable {
private static final long serialVersionUID = 1L;
final Expiry delegate;
AsyncExpiry(Expiry delegate) {
this.delegate = requireNonNull(delegate);
}
@Override
public long expireAfterCreate(K key, CompletableFuture future, long currentTime) {
if (isReady(future)) {
long duration = delegate.expireAfterCreate(key, future.join(), currentTime);
return Math.min(duration, MAXIMUM_EXPIRY);
}
return ASYNC_EXPIRY;
}
@Override
public long expireAfterUpdate(K key, CompletableFuture future,
long currentTime, long currentDuration) {
if (isReady(future)) {
long duration = (currentDuration > MAXIMUM_EXPIRY)
? delegate.expireAfterCreate(key, future.join(), currentTime)
: delegate.expireAfterUpdate(key, future.join(), currentTime, currentDuration);
return Math.min(duration, MAXIMUM_EXPIRY);
}
return ASYNC_EXPIRY;
}
@Override
public long expireAfterRead(K key, CompletableFuture future,
long currentTime, long currentDuration) {
if (isReady(future)) {
long duration = delegate.expireAfterRead(key, future.join(), currentTime, currentDuration);
return Math.min(duration, MAXIMUM_EXPIRY);
}
return ASYNC_EXPIRY;
}
Object writeReplace() {
return delegate;
}
}
}