org.elasticsearch.common.lease.Releasables Maven / Gradle / Ivy

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/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.common.lease;

import org.elasticsearch.core.internal.io.IOUtils;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicBoolean;

/** Utility methods to work with {@link Releasable}s. */
public enum Releasables {
    ;

    private static void close(Iterable releasables, boolean ignoreException) {
        try {
            // this does the right thing with respect to add suppressed and not wrapping errors etc.
            IOUtils.close(releasables);
        } catch (IOException e) {
            if (ignoreException == false) {
                throw new UncheckedIOException(e);
            }
        }
    }

    /** Release the provided {@link Releasable}s. */
    public static void close(Iterable releasables) {
        close(releasables, false);
    }

    /** Release the provided {@link Releasable}s. */
    public static void close(Releasable... releasables) {
        close(Arrays.asList(releasables));
    }

    /** Release the provided {@link Releasable}s, ignoring exceptions. */
    public static void closeWhileHandlingException(Iterable releasables) {
        close(releasables, true);
    }

    /** Release the provided {@link Releasable}s, ignoring exceptions. */
    public static void closeWhileHandlingException(Releasable... releasables) {
        closeWhileHandlingException(Arrays.asList(releasables));
    }

    /** Release the provided {@link Releasable}s, ignoring exceptions if success is {@code false}. */
    public static void close(boolean success, Iterable releasables) {
        if (success) {
            close(releasables);
        } else {
            closeWhileHandlingException(releasables);
        }
    }

    /** Release the provided {@link Releasable}s, ignoring exceptions if success is {@code false}. */
    public static void close(boolean success, Releasable... releasables) {
        close(success, Arrays.asList(releasables));
    }

    /** Wrap several releasables into a single one. This is typically useful for use with try-with-resources: for example let's assume
     *  that you store in a list several resources that you would like to see released after execution of the try block:
     *
     *       *  List<Releasable> resources = ...;
     *  try (Releasable releasable = Releasables.wrap(resources)) {
     *      // do something
     *  }
     *  // the resources will be released when reaching here
     *  
     */
    public static Releasable wrap(final Iterable releasables) {
        return () -> close(releasables);
    }

    /** @see #wrap(Iterable) */
    public static Releasable wrap(final Releasable... releasables) {
        return () -> close(releasables);
    }

    /**
     * Equivalent to {@link #wrap(Releasable...)} but can be called multiple times without double releasing.
     */
    public static Releasable releaseOnce(final Releasable... releasables) {
        final AtomicBoolean released = new AtomicBoolean(false);
        return () -> {
            if (released.compareAndSet(false, true)) {
                close(releasables);
            }
        };
    }
}