Reactive Programming

What is Reactive Programming?

• Reactive programming is about asynchronous data streams and non-blocking execution.

• Instead of waiting for operations to complete, you define what should happen when data becomes available

• What we have doing so far was Imperative programming in traditional Spring Boot projects.

// Imperative vs Reactive

// Imperative (Traditional)
List<String> results = new ArrayList<>();
for (String name : names) {
    String result = processName(name); // Blocks thread
    results.add(result);
}

// Reactive (Non-blocking)
Flux.fromIterable(names)
    .flatMap(name -> Mono.fromCallable(() -> processName(name)))
    .collectList()
    .subscribe(results -> System.out.println("Done!"));

Backpressure Concept

graph LR
    A[Publisher] --> B[Subscriber]
    B --> C[Request N Items]
    A --> D[Send N Items]

Key Concepts:

• Asynchronous: Operations don’t block threads
• Event-driven: React to data availability
• Backpressure: Consumer controls data flow rate
• Functional style: Use operators to transform data

Reactive Streams Specification

• Publisher: Produces data
• Subscriber: Consumes data
• Subscription: Controls flow
• Processor: Both Publisher and Subscriber