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Spring Boot 4 Microservices & REST APIs · Lesson

Reactive Controllers

Build non-blocking endpoints with WebFlux.

Reactive Web Endpoints

With WebFlux you write @RestController classes just like in Spring MVC, but methods return reactive types instead of plain objects.

  • Return Mono<T> for a single resource
  • Return Flux<T> for a collection or stream

Returning a Mono

A handler returning Mono resolves to a single JSON object. The framework subscribes for you.

@RestController
@RequestMapping("/users")
public class UserController {
    @GetMapping("/{id}")
    public Mono<User> getUser(@PathVariable String id) {
        return userService.findById(id);
    }
}

All lessons in this course

  1. Mono and Flux Basics
  2. Reactive Controllers
  3. WebClient for Reactive Calls
  4. Backpressure and Operators
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