flink-core/src/main/java/org/apache/flink/util/LambdaUtil.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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.apache.flink.util;

import org.apache.flink.util.function.SupplierWithException;
import org.apache.flink.util.function.ThrowingConsumer;
import org.apache.flink.util.function.ThrowingRunnable;

/** This class offers utility functions for Java's lambda features. */
public final class LambdaUtil {

    private LambdaUtil() {
        throw new AssertionError();
    }

    /**
     * This method supplies all elements from the input to the consumer. Exceptions that happen on
     * elements are suppressed until all elements are processed. If exceptions happened for one or
     * more of the inputs, they are reported in a combining suppressed exception.
     *
     * @param inputs iterator for all inputs to the throwingConsumer.
     * @param throwingConsumer this consumer will be called for all elements delivered by the input
     *     iterator.
     * @param <T> the type of input.
     * @throws Exception collected exceptions that happened during the invocation of the consumer on
     *     the input elements.
     */
    public static <T> void applyToAllWhileSuppressingExceptions(
            Iterable<T> inputs, ThrowingConsumer<T, ? extends Exception> throwingConsumer)
            throws Exception {

        if (inputs != null && throwingConsumer != null) {
            Exception exception = null;

            for (T input : inputs) {

                if (input != null) {
                    try {
                        throwingConsumer.accept(input);
                    } catch (Exception ex) {
                        exception = ExceptionUtils.firstOrSuppressed(ex, exception);
                    }
                }
            }

            if (exception != null) {
                throw exception;
            }
        }
    }

    /**
     * Runs the given runnable with the given ClassLoader as the thread's {@link
     * Thread#setContextClassLoader(ClassLoader) context class loader}.
     *
     * <p>The method will make sure to set the context class loader of the calling thread back to
     * what it was before after the runnable completed.
     */
    public static <E extends Throwable> void withContextClassLoader(
            final ClassLoader cl, final ThrowingRunnable<E> r) throws E {

        try (TemporaryClassLoaderContext ignored = TemporaryClassLoaderContext.of(cl)) {
            r.run();
        }
    }

    /**
     * Runs the given runnable with the given ClassLoader as the thread's {@link
     * Thread#setContextClassLoader(ClassLoader) context class loader}.
     *
     * <p>The method will make sure to set the context class loader of the calling thread back to
     * what it was before after the runnable completed.
     */
    public static <R, E extends Throwable> R withContextClassLoader(
            final ClassLoader cl, final SupplierWithException<R, E> s) throws E {

        try (TemporaryClassLoaderContext ignored = TemporaryClassLoaderContext.of(cl)) {
            return s.get();
        }
    }
}