Package org.keycloak.utils

Class StreamsUtil

java.lang.Object

org.keycloak.utils.StreamsUtil

public class StreamsUtil
extends Object

Constructor Summary

Constructors

Constructor	Description
StreamsUtil()

Method Summary

Modifier and Type	Method	Description
static <T> Stream<Collection<T>>	chunkedStream(Stream<T> originalStream, int chunkSize)	A Java stream utility that splits a stream into chunks of a fixed size.
static <T> Stream<T>	closing(Stream<T> stream)	Returns the original stream that is closed on terminating operation.
static <T> Predicate<T>	distinctByKey(Function<? super T,?> keyExtractor)	distinctByKey is not supposed to be used with parallel streams To make this method synchronized use ConcurrentHashMap<Object, Boolean> instead of HashSet
static <T> Stream<T>	paginatedStream(Stream<T> originalStream, Integer first, Integer max)	Returns the original stream that is limited with skip and limit functions based on values of first and max parameters.
static <T> Stream<T>	prepareSortedStreamToWorkInsideOfFlatMapWithTerminalOperations(Stream<T> originalStream)	This works around a bug in JDK 21 (but no longer in JDK 24) where a sorted stream has all its elements processed when used inside of a flatmap and a terminal operation like limit() is used outside of it.
static <T> Stream<T>	throwIfEmpty(Stream<T> stream, RuntimeException ex)	Returns the original stream if the stream is not empty.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

StreamsUtil

public StreamsUtil()

Method Details

closing

public static <T> Stream<T> closing(Stream<T> stream)

Returns the original stream that is closed on terminating operation. It is used, for example, for closing hibernate provided streams since it is required by hibernate documentation.

Parameters:

stream - the stream which is expected to be closed on termination

Returns:

stream that will be closed on terminating operation

throwIfEmpty

public static <T> Stream<T> throwIfEmpty(Stream<T> stream,
 RuntimeException ex)

Returns the original stream if the stream is not empty. Otherwise throws the provided exception.

Parameters:

stream - Stream to be examined.

ex - Exception to be thrown if the stream is empty.

Returns:

Stream

paginatedStream

public static <T> Stream<T> paginatedStream(Stream<T> originalStream,
 Integer first,
 Integer max)

Returns the original stream that is limited with skip and limit functions based on values of first and max parameters.

Type Parameters:

T - Type of items in the stream

Parameters:

originalStream - Stream to be limited.

first - Index of first item to be returned by the stream. Ignored if negative, zero null.

max - Maximum number of items to be returned by the stream. Ignored if negative or null.

Returns:

Stream

distinctByKey

public static <T> Predicate<T> distinctByKey(Function<? super T,?> keyExtractor)

distinctByKey is not supposed to be used with parallel streams To make this method synchronized use ConcurrentHashMap<Object, Boolean> instead of HashSet

chunkedStream

public static <T> Stream<Collection<T>> chunkedStream(Stream<T> originalStream,
 int chunkSize)

A Java stream utility that splits a stream into chunks of a fixed size. Last chunk in the stream might be smaller than the desired size. Ordering guarantees depend on underlying stream.

Type Parameters:

T - The type of the stream

Parameters:

originalStream - The original stream

chunkSize - The chunk size

Returns:

The stream in chunks

prepareSortedStreamToWorkInsideOfFlatMapWithTerminalOperations

public static <T> Stream<T> prepareSortedStreamToWorkInsideOfFlatMapWithTerminalOperations(Stream<T> originalStream)

This works around a bug in JDK 21 (but no longer in JDK 24) where a sorted stream has all its elements processed when used inside of a flatmap and a terminal operation like limit() is used outside of it. See StreamUtilTests.testSortedInsideOfFlatMapShouldRespectTerminalOperation for an example. Possible JDK-8196106 as the reference to the bug.

Type Parameters:

T - The type of the stream

Parameters:

originalStream - The original stream

Returns:

The stream that is lazily evaluating