Spring WebFlux: When to Use It and How to Build With It
Spring WebFlux enables reactive programming in Spring. Here’s when and how to use it. When to Use WebFlux Use WebFlux When: High concurrency requirements Non-blocking I/O needed Streaming data Microservices with reactive backends Use MVC When: Traditional request-response Blocking operations Existing Spring MVC codebase Simpler mental model needed Basic Setup Dependencies <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId> </dependency> Reactive Controller @RestController public class UserController { @GetMapping("/users") public Flux<User> getUsers() { return userService.findAll(); } @GetMapping("/users/{id}") public Mono<User> getUser(@PathVariable Long id) { return userService.findById(id); } @PostMapping("/users") public Mono<User> createUser(@RequestBody Mono<User> user) { return userService.save(user); } } Reactive Types Mono // Single value or empty Mono<String> mono = Mono.just("Hello"); Mono<String> empty = Mono.empty(); Mono<String> error = Mono.error(new RuntimeException()); Flux // Multiple values Flux<String> flux = Flux.just("A", "B", "C"); Flux<Integer> range = Flux.range(1, 10); Reactive Repository public interface UserRepository extends ReactiveCrudRepository<User, Long> { Flux<User> findByStatus(String status); Mono<User> findByEmail(String email); } Error Handling @GetMapping("/users/{id}") public Mono<User> getUser(@PathVariable Long id) { return userService.findById(id) .switchIfEmpty(Mono.error(new UserNotFoundException())) .onErrorResume(error -> { // Handle error return Mono.empty(); }); } Testing @SpringBootTest @AutoConfigureWebTestClient class UserControllerTest { @Autowired private WebTestClient webTestClient; @Test void shouldGetUsers() { webTestClient.get() .uri("/users") .exchange() .expectStatus().isOk() .expectBodyList(User.class); } } Best Practices Use reactive types throughout Avoid blocking operations Handle errors properly Use backpressure Monitor performance Conclusion Spring WebFlux provides: ...