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Provides common core classes and the microkernel powering all Sirius applications

There is a newer version: 12.9.1

/*
 * Made with all the love in the world
 * by scireum in Remshalden, Germany
 *
 * Copyright by scireum GmbH
 * http://www.scireum.de - [email protected]
 */

package sirius.kernel.commons;

/**
 * Provides a value for the given key just like a {@link java.util.function.Function}.
 * 
 * However, the return value is wrapped as {@link Value}. This permits to distinguish between a null
 * and no value. Also by declaring Exception in the throws clause, we delegate the exception handling
 * from the callee to the caller.
 *
 * @param  the type of key used as input for the value supplier.
 */
public interface ValueSupplier {

    /**
     * Computes or fetches the value for the given key.
     *
     * @param key the key to fetch the value for
     * @return the value for the given key or null to indicate that no value is available.
     * @throws Exception in case of an error while fetching the value.
     */
    Value apply(K key) throws Exception;
}