org.springframework.data.util.StreamUtils Maven / Gradle / Ivy
/*
* Copyright 2015 the original author or authors.
*
* 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 org.springframework.data.util;
import java.util.Iterator;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import org.springframework.util.Assert;
/**
* Spring Data specific Java {@link Stream} utility methods and classes.
*
* @author Thomas Darimont
* @author Oliver Gierke
* @since 1.10
*/
public class StreamUtils {
private StreamUtils() {}
/**
* Returns a {@link Stream} backed by the given {@link Iterator}.
*
* If the given iterator is an {@link CloseableIterator} add a {@link CloseableIteratorDisposingRunnable} wrapping the
* given iterator to propagate {@link Stream#close()} accordingly.
*
* @param iterator must not be {@literal null}
* @return
* @since 1.8
*/
public static Stream createStreamFromIterator(Iterator iterator) {
Assert.notNull(iterator, "Iterator must not be null!");
Spliterator spliterator = Spliterators.spliteratorUnknownSize(iterator, Spliterator.NONNULL);
Stream stream = StreamSupport.stream(spliterator, false);
return iterator instanceof CloseableIterator ? stream.onClose(new CloseableIteratorDisposingRunnable(
(CloseableIterator) iterator)) : stream;
}
/**
* A {@link Runnable} that closes the given {@link CloseableIterator} in its {@link #run()} method. If the given
* {@code closeable} is {@literal null} the {@link #run()} method effectively becomes a noop.
*
* Can be used in conjunction with streams as close action via:
*
*
* CloseableIterator result = ...;
* Spliterator spliterator = ...;
*
* return StreamSupport.stream(spliterator, false).onClose(new CloseableIteratorDisposingRunnable(result));
*
*
* @author Thomas Darimont
* @author Oliver Gierke
* @since 1.10
*/
private static class CloseableIteratorDisposingRunnable implements Runnable {
private CloseableIterator closeable;
/**
* Creates a new {@link CloseableIteratorDisposingRunnable} for the given {@link CloseableIterator}.
*
* @param closeable can be {@literal null}.
*/
public CloseableIteratorDisposingRunnable(CloseableIterator closeable) {
this.closeable = closeable;
}
/*
* (non-Javadoc)
* @see java.lang.Runnable#run()
*/
@Override
public void run() {
if (closeable != null) {
closeable.close();
}
}
}
}