ClassNotFoundException: ExchangeFunction when using WebTestClient with Spring MVC #26308
Description
After reading release notes for Spring Framework 5.3 and the Reference Documentation I wanted to use WebTestClient in a Spring MVC application, but it fails with:
Injection of autowired dependencies failed; nested exception is java.lang.NoClassDefFoundError: org/springframework/web/reactive/function/client/ExchangeFunction Caused by: java.lang.NoClassDefFoundError: org/springframework/web/reactive/function/client/ExchangeFunction at org.springframework.test.web.reactive.server.DefaultWebTestClientBuilder.build(DefaultWebTestClientBuilder.java:268) at com.example.mvcwebtestclient.GreetingControllerTest.create(GreetingControllerTest.java:23) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) Reproducing
build.gradle
dependencies { implementation(platform("org.springframework.boot:spring-boot-dependencies:2.4.1")) implementation 'org.springframework.boot:spring-boot-starter-data-mongodb-reactive' implementation 'org.springframework.boot:spring-boot-starter-web' testImplementation 'org.springframework.boot:spring-boot-starter-test' testImplementation 'io.projectreactor:reactor-test' }GreetingController.java
@RestController @RequestMapping("/greetings") public class GreetingController { @GetMapping public Flux<String> findAll() { return Flux.just("Hello", "world!"); } }GreetingControllerTest.java
@SpringBootTest class GreetingControllerTest { private WebTestClient client; @Autowired public void create(WebApplicationContext context) { client = MockMvcWebTestClient.bindToApplicationContext(context) .configureClient() .build(); } @Test public void findsAll() { client.get().uri("/greetings") .exchange() .expectStatus().isOk(); } }Workaround
Add webflux dependency:
implementation 'org.springframework.boot:spring-boot-starter-webflux'I think it's a bug in code or at least a bug in documentation. The documentation does not mention in any place that you need WebFlux to test your MVC applications. This is an idea that looks absurd at first sight, so if it is really the case, it should be explicitly explained that you really need to do it.