Reactive Streams Utilities

Reactive Streams Utilities is an exploration of what a standard utilities library for Reactive Streams in the Java Development Kit (JDK) might look like. It aims to fill a gap where developers currently need third-party libraries to perform basic operations on JDK9's java.util.concurrent.Flow interfaces, making reactive programming more accessible within the JDK itself.

Key Features

• Builder Pattern API — Uses a builder pattern to construct Publisher, Subscriber, Processor, or complete graphs, allowing flexible implementation and stage fusion.
• JDK Streams Alignment — API design closely aligns with java.util.stream.Stream for familiarity, using similar naming and scope while providing reactive execution semantics.
• Service Provider Interface (SPI) — Includes an SPI for multiple engine implementations (e.g., Akka Streams, RxJava) via ServiceLoader, enabling customization without locking into a specific implementation.
• Minimal Operator Set — Focuses on essential operations like map, filter, flatMapIterable, and flatMapCompletionStage, avoiding a "kitchen sink" approach for advanced use cases.
• TCK Compliance — Utilizes the Reactive Streams Technology Compatibility Kit to ensure built interfaces conform to the Reactive Streams specification.

Philosophy

The project prioritizes providing a minimal, useful set of operations for everyday streaming use cases within the JDK, ensuring developers can handle basic reactive workflows without external dependencies while allowing third-party libraries for more advanced needs.