Spring MVC multi-part configuration

Trying to write a simple file upload handler using Spring MVC 6.0.6. A file is uploaded using POST, with encoding multipart/form-data. On the server side, the handler is

import jakarta.servlet.annotation.MultipartConfig;import org.springframework.http.HttpStatus;import org.springframework.http.ResponseEntity;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.PostMapping;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.multipart.MultipartFile;@Controller@MultipartConfigpublic class SimpleUpload {    @PostMapping(path = "/upload")    public ResponseEntity<String> uploadFile(@RequestParam("File") MultipartFile file) {        return file.isEmpty() ?                new ResponseEntity<String>(HttpStatus.NOT_FOUND) : new ResponseEntity<String>(HttpStatus.OK);    }}

Getting this error: Unable to process parts as no multi-part configuration has been provided.

I have read other answers about this error, so I have added the multi-part configuration as follows:

@EnableWebMvc@Configuration@Import({ApplicationConfig.class})public class MvcConfig implements WebMvcConfigurer {    @Bean(name = "multipartResolver")    public MultipartResolver getMultipartResolver() {        return new StandardServletMultipartResolver();    }    @Bean(name = "filterMultipartResolver") // alternate name suggested by some people    public MultipartResolver getFilterMultipartResolver() {        return new StandardServletMultipartResolver();    }}

It does not seem to work, because the error is always the same.

The unit test in the application is successful:

@WebAppConfiguration@ContextConfiguration(classes = { MvcConfig.class, SimpleUpload.class })@RunWith(SpringJUnit4ClassRunner.class)public class MultipartPostRequestControllerUnitTest {    @Autowired    private WebApplicationContext webApplicationContext;    @Test    public void whenFileUploaded_thenVerifyStatus() throws Exception {        MockMultipartFile file = new MockMultipartFile("File","hello.txt",                MediaType.TEXT_PLAIN_VALUE,"Hello, World!".getBytes());        MockMvc mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext)                .build();        mockMvc.perform(multipart("/upload")                .file(file))                .andExpect(status().isOk());    }}

But sending a file via Postman to http://127.0.0.1:8080/upload returns an HTTP status 500, with root cause Unable to process parts as no multi-part configuration has been provided.

How can I fix this?

Using Tomcat 10.1.7 to run the app.