com.speedment.runtime.core.util.StreamComposition Maven / Gradle / Ivy
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/*
*
* Copyright (c) 2006-2019, Speedment, Inc. 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.speedment.runtime.core.util;
import com.speedment.runtime.core.stream.AutoClosingStream;
import java.util.function.Function;
import java.util.stream.*;
import static com.speedment.common.invariant.NullUtil.requireNonNullElements;
import static com.speedment.runtime.core.stream.ComposeRunnableUtil.composedClose;
/**
* Utility methods for making sure composed streams are closed properly.
*
* @author Per Minborg
*/
public class StreamComposition {
/**
* Creates a lazily concatenated Stream whose elements are are all the
* elements of the streams in sequential order. The resulting Stream is
* ordered if all of the input streams are ordered, and parallel if at least
* one of the input streams are parallel. When a terminating operation is
* called, all the streams are automatically and explicitly closed, whereby
* their close handlers are invoked. AutoClosing is performed in sequential
* order too. If a Stream throws an Exception, it is still guaranteed that
* all Streams' close methods are called.
*
*
* Streams are processed one at at time. When one is exhausted, a new one
* will start. Parallelism is only supported within the individual streams
* provided.
*
* N.B. a stream's close method may be called even through that stream never
* produced any output, if a preceding stream threw an Exception.
*
* N.B. an UnsupportedOperationException will be thrown if the concatenated
* stream's {@link Stream#iterator()
* } or {@link Stream#spliterator() } methods are called, because they could
* potentially violate the resulting Stream's AutoClose property.
*
* N.B. Use caution when constructing streams from repeated concatenation.
* Accessing an element of a deeply concatenated stream can result in deep
* call chains, or even {@code StackOverflowException}.
*
* @param The type of stream elements
* @param streams to concatenate
* @return the concatenation of the input streams
* @throws UnsupportedOperationException if the concatenated stream's {@link Stream#iterator()
* } or {@link Stream#spliterator() } methods are called, because they could
* potentially violate the resulting Stream's AutoClose property.
*/
@SuppressWarnings("varargs")
@SafeVarargs // Creating a Stream of an array is safe.
public static Stream concatAndAutoClose(Stream... streams) {
requireNonNullElements(streams);
return configureAutoCloseStream(AutoClosingStream.of(Stream.of(streams).flatMap(Function.identity())), streams);
}
/* @SuppressWarnings("varargs")
@SafeVarargs // Creating a Stream of an array is safe.
public static IntStream concatAndAutoClose(IntStream... streams) {
requireNonNullElements(streams);
return configureAutoCloseStream(new AutoClosingIntStream(Stream.of(streams).flatMapToInt(Function.identity())), streams);
}
@SuppressWarnings("varargs")
@SafeVarargs // Creating a Stream of an array is safe.
public static LongStream concatAndAutoClose(LongStream... streams) {
requireNonNullElements(streams);
return configureAutoCloseStream(new AutoClosingLongStream(Stream.of(streams).flatMapToLong(Function.identity())), streams);
}
@SuppressWarnings("varargs")
@SafeVarargs // Creating a Stream of an array is safe.
public static DoubleStream concatAndAutoClose(DoubleStream... streams) {
requireNonNullElements(streams);
return configureAutoCloseStream(new AutoClosingDoubleStream(Stream.of(streams).flatMapToDouble(Function.identity())), streams);
}*/
@SuppressWarnings("varargs")
@SafeVarargs // Creating a Stream of an array is safe.
private static > T configureAutoCloseStream(T concatStream, T... streams) {
@SuppressWarnings("rawtypes")
final boolean parallel = Stream.of(streams).anyMatch(BaseStream::isParallel); // T:::isParallel gives IDE warning
if (parallel) {
concatStream.parallel();
}
concatStream.onClose(() -> composedClose(streams));
return concatStream;
}
/**
* Creates a concatenated Stream whose elements are are all the
* elements of the streams in sequential order. The resulting Stream is
* ordered if all of the input streams are ordered, and parallel if at least
* one of the input streams are parallel.
*
*
* Streams are processed one at at time. When one is exhausted, a new one
* will start. Parallelism is only supported within the individual streams
* provided.
*
* N.B. Use caution when constructing streams from repeated concatenation.
* Accessing an element of a deeply concatenated stream can result in deep
* call chains, or even {@code StackOverflowException}.
*
* @param The type of stream elements
* @param streams to concatenate
* @return the concatenation of the input streams
*/
@SuppressWarnings("varargs")
@SafeVarargs // Creating a Stream of an array is safe.
public static Stream concat(Stream... streams) {
requireNonNullElements(streams);
return Stream.of(streams).flatMap(Function.identity());
}
public StreamComposition() {
StaticClassUtil.instanceNotAllowed(getClass());
}
}