DATACMNS-1637 - Add default stream() method to CloseableIterator.

CloseableIterator now allows construction of a Stream that is associated with a close hook to release resources after its use.

CloseableIterator<Person> iterator = …;

try (Stream<Person> stream = iterator.stream()) {
	assertThat(stream.count()).isEqualTo(3);
}

src/main/java/org/springframework/data/util/CloseableIterator.java

@@ -17,13 +17,18 @@ package org.springframework.data.util;
 
 import java.io.Closeable;
 import java.util.Iterator;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 /**
  * A {@link CloseableIterator} serves as a bridging data structure for the underlying data store specific results that
- * can be wrapped in a Java 8 {@link java.util.stream.Stream}. This allows implementations to clean up any resources
- * they need to keep open to iterate over elements.
+ * can be wrapped in a Java 8 {@link #stream() java.util.stream.Stream}. This allows implementations to clean up any
+ * resources they need to keep open to iterate over elements.
  *
  * @author Thomas Darimont
+ * @author Mark Paluch
  * @param <T>
  * @since 1.10
  */
@@ -35,4 +40,35 @@ public interface CloseableIterator<T> extends Iterator<T>, Closeable {
 	 */
 	@Override
 	void close();
+
+	/**
+	 * Create a {@link Spliterator} over the elements provided by this {@link Iterator}. Implementations should document
+	 * characteristic values reported by the spliterator. Such characteristic values are not required to be reported if
+	 * the spliterator reports {@link Spliterator#SIZED} and this collection contains no elements.
+	 * <p>
+	 * The default implementation should be overridden by subclasses that can return a more efficient spliterator. To
+	 * preserve expected laziness behavior for the {@link #stream()} method, spliterators should either have the
+	 * characteristic of {@code IMMUTABLE} or {@code CONCURRENT}, or be late-binding.
+	 *
+	 * @return a {@link Spliterator} over the elements in this {@link Iterator}.
+	 * @since 2.4
+	 */
+	default Spliterator<T> spliterator() {
+		return Spliterators.spliterator(this, 0, 0);
+	}
+
+	/**
+	 * Return a sequential {@code Stream} with this {@link Iterator} as its source. The resulting stream calls
+	 * {@link #clone()} when {@link Stream#close() closed}. The resulting {@link Stream} must be closed after use, it can
+	 * be declared as a resource in a {@code try}-with-resources statement.
+	 * <p>
+	 * This method should be overridden when the {@link #spliterator()} method cannot return a spliterator that is
+	 * {@code IMMUTABLE}, {@code CONCURRENT}, or <em>late-binding</em>. (See {@link #spliterator()} for details.)
+	 *
+	 * @return a sequential {@code Stream} over the elements in this {@link Iterator}.
+	 * @since 2.4
+	 */
+	default Stream<T> stream() {
+		return StreamSupport.stream(spliterator(), false).onClose(this::close);
+	}
 }