Spring Boot Reactive Programming

Spring Boot with Reactive Programming enables developers to build non-blocking, event-driven applications that scale efficiently. By leveraging Spring WebFlux and Project Reactor, developers can handle large amounts of concurrent requests with minimal resource consumption, making it ideal for microservices and real-time applications.

🌟 Why Use Reactive Programming?

• Asynchronous & Non-Blocking: Handle multiple requests efficiently without blocking threads.
• Better Scalability: Utilize fewer resources while handling more concurrent users.
• Event-Driven Model: Ideal for microservices, real-time applications, and streaming data.
• Built-in Backpressure: Prevents overwhelming the system with too many requests.

🌟 Prerequisites

Ensure you have the following:

• ☕ Java Development Kit (JDK) 17+
• 📦 Maven or Gradle installed
• 🔤 A Java IDE (e.g., IntelliJ IDEA, Eclipse)

🛠️ Step 1: Add Dependencies

Add the necessary dependency for Spring WebFlux in your pom.xml or build.gradle file.

Maven:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

Gradle:

implementation 'org.springframework.boot:spring-boot-starter-webflux'

📋 Step 2: Create a Reactive REST Controller

Define a non-blocking REST endpoint using Mono and Flux to handle asynchronous processing.

• Java
• Kotlin

package com.example.reactive;

import org.springframework.web.bind.annotation.*;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.time.Duration;
import java.util.List;

@RestController
@RequestMapping("/reactive")
public class ReactiveController {

    @GetMapping("/mono")
    public Mono<String> getMono() {
        return Mono.just("Hello from Reactive Mono!");
    }

    @GetMapping("/flux")
    public Flux<String> getFlux() {
        return Flux.fromIterable(List.of("Hello", "from", "Reactive", "Flux"))
                   .delayElements(Duration.ofSeconds(1));
    }
}

package com.example.reactive

import org.springframework.web.bind.annotation.*
import reactor.core.publisher.Flux
import reactor.core.publisher.Mono
import java.time.Duration

@RestController
@RequestMapping("/reactive")
class ReactiveController {

    @GetMapping("/mono")
    fun getMono(): Mono<String> {
        return Mono.just("Hello from Reactive Mono!")
    }

    @GetMapping("/flux")
    fun getFlux(): Flux<String> {
        return Flux.just("Hello", "from", "Reactive", "Flux")
            .delayElements(Duration.ofSeconds(1))
    }
}

▶️ Running the Application

Run the Spring Boot application:

./mvnw spring-boot:run

Or using Gradle:

gradle bootRun

🧪 Testing the API

Test Mono Endpoint:

curl -X GET http://localhost:8080/reactive/mono

Expected output:

Hello from Reactive Mono!

Test Flux Endpoint:

curl -X GET http://localhost:8080/reactive/flux

Expected output (delayed by 1 second per word):

Hello
from
Reactive
Flux

Spring Boot with WebFlux and Project Reactor allows developers to build highly scalable, non-blocking applications. Whether for microservices, streaming data, or real-time event processing, reactive programming is the future of high-performance applications.