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Introducing AsyncCache, split from AsyncLoadingCache (fixes #246)
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caffeine/src/main/java/com/github/benmanes/caffeine/cache/AsyncCache.java
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| /* | ||
| * Copyright 2018 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; | ||
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| import java.util.concurrent.CompletableFuture; | ||
| import java.util.concurrent.Executor; | ||
| import java.util.function.BiFunction; | ||
| import java.util.function.Function; | ||
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| import javax.annotation.Nonnull; | ||
| import javax.annotation.Nullable; | ||
| import javax.annotation.concurrent.ThreadSafe; | ||
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| /** | ||
| * A semi-persistent mapping from keys to values. Cache entries are manually added using | ||
| * {@link #get(Object, Function)} or {@link #put(Object, CompletableFuture)}, and are stored in the | ||
| * cache until either evicted or manually invalidated. | ||
| * <p> | ||
| * Implementations of this interface are expected to be thread-safe, and can be safely accessed by | ||
| * multiple concurrent threads. | ||
| * | ||
| * @author ben.manes@gmail.com (Ben Manes) | ||
| * @param <K> the type of keys maintained by this cache | ||
| * @param <V> the type of mapped values | ||
| */ | ||
| @ThreadSafe | ||
| public interface AsyncCache<K, V> { | ||
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| /** | ||
| * Returns the future associated with {@code key} in this cache, or {@code null} if there is no | ||
| * cached future for {@code key}. | ||
| * | ||
| * @param key key whose associated value is to be returned | ||
| * @return the current (existing or computed) future value to which the specified key is mapped, | ||
| * or {@code null} if this map contains no mapping for the key | ||
| * @throws NullPointerException if the specified key is null | ||
| */ | ||
| @Nullable | ||
| CompletableFuture<V> getIfPresent(@Nonnull Object key); | ||
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| /** | ||
| * Returns the future associated with {@code key} in this cache, obtaining that value from | ||
| * {@code mappingFunction} if necessary. This method provides a simple substitute for the | ||
| * conventional "if cached, return; otherwise create, cache and return" pattern. | ||
| * <p> | ||
| * If the specified key is not already associated with a value, attempts to compute its value | ||
| * asynchronously and enters it into this cache unless {@code null}. The entire method invocation | ||
| * is performed atomically, so the function is applied at most once per key. If the asynchronous | ||
| * computation fails, the entry will be automatically removed from this cache. | ||
| * <p> | ||
| * <b>Warning:</b> as with {@link CacheLoader#load}, {@code mappingFunction} <b>must not</b> | ||
| * attempt to update any other mappings of this cache. | ||
| * | ||
| * @param key key with which the specified value is to be associated | ||
| * @param mappingFunction the function to asynchronously compute a value | ||
| * @return the current (existing or computed) future value associated with the specified key | ||
| * @throws NullPointerException if the specified key or mappingFunction is null | ||
| */ | ||
| @Nonnull | ||
| CompletableFuture<V> get(@Nonnull K key, | ||
| @Nonnull Function<? super K, ? extends V> mappingFunction); | ||
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| /** | ||
| * Returns the future associated with {@code key} in this cache, obtaining that value from | ||
| * {@code mappingFunction} if necessary. This method provides a simple substitute for the | ||
| * conventional "if cached, return; otherwise create, cache and return" pattern. | ||
| * <p> | ||
| * If the specified key is not already associated with a value, attempts to compute its value | ||
| * asynchronously and enters it into this cache unless {@code null}. The entire method invocation | ||
| * is performed atomically, so the function is applied at most once per key. If the asynchronous | ||
| * computation fails, the entry will be automatically removed from this cache. | ||
| * <p> | ||
| * <b>Warning:</b> as with {@link CacheLoader#load}, {@code mappingFunction} <b>must not</b> | ||
| * attempt to update any other mappings of this cache. | ||
| * | ||
| * @param key key with which the specified value is to be associated | ||
| * @param mappingFunction the function to asynchronously compute a value | ||
| * @return the current (existing or computed) future value associated with the specified key | ||
| * @throws NullPointerException if the specified key or mappingFunction is null, or if the | ||
| * future returned by the mappingFunction is null | ||
| * @throws RuntimeException or Error if the mappingFunction does when constructing the future, | ||
| * in which case the mapping is left unestablished | ||
| */ | ||
| @Nonnull | ||
| CompletableFuture<V> get(@Nonnull K key, | ||
| @Nonnull BiFunction<? super K, Executor, CompletableFuture<V>> mappingFunction); | ||
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| /** | ||
| * Associates {@code value} with {@code key} in this cache. If the cache previously contained a | ||
| * value associated with {@code key}, the old value is replaced by {@code value}. If the | ||
| * asynchronous computation fails, the entry will be automatically removed. | ||
| * <p> | ||
| * Prefer {@link #get(Object, Function)} when using the conventional "if cached, return; otherwise | ||
| * create, cache and return" pattern. | ||
| * | ||
| * @param key key with which the specified value is to be associated | ||
| * @param valueFuture value to be associated with the specified key | ||
| * @throws NullPointerException if the specified key or value is null | ||
| */ | ||
| void put(@Nonnull K key, @Nonnull CompletableFuture<V> valueFuture); | ||
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| /** | ||
| * Returns a view of the entries stored in this cache as a synchronous {@link Cache}. A mapping is | ||
| * not present if the value is currently being loaded. Modifications made to the synchronous cache | ||
| * directly affect the asynchronous cache. If a modification is made to a mapping that is | ||
| * currently loading, the operation blocks until the computation completes. | ||
| * | ||
| * @return a thread-safe synchronous view of this cache | ||
| */ | ||
| @Nonnull | ||
| Cache<K, V> synchronous(); | ||
| } |
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