How to return 404 with Spring WebFlux (#6509)

* feat(response-status): return response http status

* fix(style): improve code style

* BAEL-2716: How to return 404 with Spring WebFlux

* style: apply baeldung intellij formatter

* Delete .gitignore

* config: remove gitignore & remove unused maven plugin

spring-5-webflux/src/main/java/com/baeldung/spring/responsestatus/ResponseStatusController.java

@@ -0,0 +1,64 @@
+package com.baeldung.spring.responsestatus;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.web.bind.annotation.*;
+import org.springframework.web.reactive.function.server.RouterFunction;
+import org.springframework.web.reactive.function.server.RouterFunctions;
+import org.springframework.web.reactive.function.server.ServerResponse;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import static org.springframework.web.reactive.function.server.RequestPredicates.GET;
+
+@RequestMapping("/statuses")
+@RestController
+public class ResponseStatusController {
+
+    @GetMapping(value = "/ok", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
+    public Flux<String> ok() {
+        return Flux.just("ok");
+    }
+
+    @GetMapping(value = "/no-content", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
+    @ResponseStatus(HttpStatus.NO_CONTENT)
+    public Flux<String> noContent() {
+        return Flux.empty();
+    }
+
+    @GetMapping(value = "/accepted", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
+    public Flux<String> accepted(ServerHttpResponse response) {
+        response.setStatusCode(HttpStatus.ACCEPTED);
+        return Flux.just("accepted");
+    }
+
+    @GetMapping(value = "/bad-request")
+    public Mono<String> badRequest() {
+        return Mono.error(new IllegalArgumentException());
+    }
+
+    @ResponseStatus(value = HttpStatus.BAD_REQUEST, reason = "Illegal arguments")
+    @ExceptionHandler(IllegalArgumentException.class)
+    public void illegalArgument() {
+
+    }
+
+    @GetMapping(value = "/unauthorized")
+    public ResponseEntity<Mono<String>> unathorized() {
+        return ResponseEntity
+          .status(HttpStatus.UNAUTHORIZED)
+          .header("X-Reason", "user-invalid")
+          .body(Mono.just("unauthorized"));
+    }
+
+    @Bean
+    public RouterFunction<ServerResponse> notFound() {
+        return RouterFunctions.route(GET("/statuses/not-found"), request -> ServerResponse
+          .notFound()
+          .build());
+    }
+
+}

spring-5-webflux/src/main/java/com/baeldung/spring/responsestatus/SpringResponseStatusApp.java

@@ -0,0 +1,12 @@
+package com.baeldung.spring.responsestatus;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SpringResponseStatusApp {
+
+    public static void main(String[] args) {
+        SpringApplication.run(SpringResponseStatusApp.class, args);
+    }
+}

spring-5-webflux/src/test/java/com/baeldung/spring/responsestatus/ResponseStatusControllerTests.java

@@ -0,0 +1,70 @@
+package com.baeldung.spring.responsestatus;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+public class ResponseStatusControllerTests {
+
+    @Autowired
+    private WebTestClient testClient;
+
+    @Test
+    public void whenCallRest_thenStatusIsOk() {
+        testClient.get()
+                .uri("/statuses/ok")
+                .exchange()
+                .expectStatus()
+                .isOk();
+    }
+
+    @Test
+    public void whenCallRest_thenStatusIsNoContent() {
+        testClient.get()
+                .uri("/statuses/no-content")
+                .exchange()
+                .expectStatus()
+                .isNoContent();
+    }
+
+    @Test
+    public void whenCallRest_thenStatusIsAccepted() {
+        testClient.get()
+                .uri("/statuses/accepted")
+                .exchange()
+                .expectStatus()
+                .isAccepted();
+    }
+
+    @Test
+    public void whenCallRest_thenStatusIsBadRequest() {
+        testClient.get()
+                .uri("/statuses/bad-request")
+                .exchange()
+                .expectStatus()
+                .isBadRequest();
+    }
+
+    @Test
+    public void whenCallRest_thenStatusIsUnauthorized() {
+        testClient.get()
+                .uri("/statuses/unauthorized")
+                .exchange()
+                .expectStatus()
+                .isUnauthorized();
+    }
+
+    @Test
+    public void whenCallRest_thenStatusIsNotFound() {
+        testClient.get()
+                .uri("/statuses/not-found")
+                .exchange()
+                .expectStatus()
+                .isNotFound();
+    }
+}