Project Reactor

Project Reactor is a reactive programming library for building non-blocking applications on the JVM, implementing the Reactive Streams specification. It provides composable asynchronous sequence APIs—Flux for 0..N items and Mono for 0..1 items—enabling efficient, backpressure-aware data streams. It is a core component of the Spring WebFlux stack for reactive web applications.

Also known as: Reactor, Reactor Core, Reactor Project, Spring Reactor, Reactive Streams Java

Why learn Project Reactor?

Developers should learn Project Reactor when building high-throughput, low-latency applications that require non-blocking I/O, such as microservices, real-time data processing, or streaming APIs. It is essential for leveraging reactive programming in Java and Kotlin ecosystems, particularly with Spring Boot's reactive stack, to handle concurrent requests efficiently without thread exhaustion.

Learning Resources

• docs: Project Reactor Reference Guide
• tutorial: Reactive Programming with Reactor 3
• tutorial: Building Reactive Microservices with Spring WebFlux and Project Reactor
• docs: Project Reactor on GitHub