software.amazon.smithy.model.node.IdentityClassCache Maven / Gradle / Ivy

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/*
 * Copyright 2022 Amazon.com, Inc. or its affiliates. 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.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 software.amazon.smithy.model.node;

import java.lang.reflect.Type;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.function.Supplier;
import software.amazon.smithy.utils.Pair;

/**
 * Caches instances of type V, associating them with a given key and Type.
 *
 * Cached values are invalidated if the requested type is not referentially
 * equal to the cached type. This ensures that the most recently loaded versions
 * of classes are being used.
 *
 * @param  The type of the cache key.
 * @param  The type of the cached value.
 */
final class IdentityClassCache {

    private final ConcurrentMap> cache = new ConcurrentHashMap<>();

    /**
     * Retrieves cached value for the key associated with the given Type,
     * computing the value to store if the key isn't present, or if the cache is
     * invalidated.
     *
     * @param forKey The key of the cached value to retrieve.
     * @param forClass The Type that should be associated with the cached value.
     * @param supplierIfNotPresent Function to compute cached value.
     * @return Cached value.
     */
    V getForClass(K forKey, Type forClass, Supplier supplierIfNotPresent) {
        return cache.compute(forKey, (key, current) -> {
            if (current == null || current.getLeft() != forClass) {
                // The key was not present, or the cache was invalidated.
                return Pair.of(forClass, supplierIfNotPresent.get());
            } else {
                return current;
            }
        }).getRight();
    }
}