Integration test with TestRestTemplate for Multipart POST request returns 400

Question

I know that similar question has been here already couple of times but following suggested fixes did not solve my problem.

I have a simple controller with the following endpoint:

@RequestMapping(method = RequestMethod.POST)
public ResponseEntity<String> singleFileUpload(@RequestParam("file") MultipartFile file) {
    log.debug("Upload controller - POST: {}", file.getOriginalFilename());

    // do something
}

I am trying to write an integration test for it using Spring TestRestTemplate but all of my attemps end with 400 - Bad Request (no logs clarifying what went wrong in console).

The log inside the controller did not get hit so it failed before getting there.

Could you please take a look on my test and suggest what am I doing wrong?

@Test
public void testUpload() {
    // simulate multipartfile upload
    ClassLoader classLoader = getClass().getClassLoader();
    File file = new File(classLoader.getResource("image.jpg").getFile());

    MultiValueMap<String, Object> parameters = new LinkedMultiValueMap<String, Object>();
    parameters.add("file", file);

    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.MULTIPART_FORM_DATA);

    HttpEntity<MultiValueMap<String, Object>> entity = new HttpEntity<MultiValueMap<String, Object>>(parameters, headers);

    ResponseEntity<String> response = testRestTemplate.exchange(UPLOAD, HttpMethod.POST, entity, String.class, "");

    // Expect Ok
    assertThat(response.getStatusCode(), is(HttpStatus.OK));
}

Answer 1

I tried the following:

@Test
public void testUpload() {
    LinkedMultiValueMap<String, Object> parameters = new LinkedMultiValueMap<String, Object>();
    parameters.add("file", new org.springframework.core.io.ClassPathResource("image.jpg"));

    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.MULTIPART_FORM_DATA);

    HttpEntity<LinkedMultiValueMap<String, Object>> entity = new HttpEntity<LinkedMultiValueMap<String, Object>>(parameters, headers);

    ResponseEntity<String> response = testRestTemplate.exchange(UPLOAD, HttpMethod.POST, entity, String.class, "");

    // Expect Ok
    assertThat(response.getStatusCode(), is(HttpStatus.OK));
}

As you can see I used the org.springframework.core.io.ClassPathResource as object for the file and ti worked like a charm

I hope it's useful

Angelo

Answer 2

FileSystemResource also could be used in case if you want to use java.nio.file.Path.

Package: org.springframework.core.io.FileSystemResource

For example, you could do this:

new FileSystemResource(Path.of("src", "test", "resources", "image.jpg"))

Full code example:

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class UploadFilesTest {

    private final TestRestTemplate template;

    @Autowired
    public UploadFilesTest(TestRestTemplate template) {
        this.template = template;
    }

    @Test
    public void uploadFileTest() {
        var multipart = new LinkedMultiValueMap<>();
        multipart.add("file", file());

        final ResponseEntity<String> post = template.postForEntity("/upload", new HttpEntity<>(multipart, headers()), String.class);

        assertEquals(HttpStatus.OK, post.getStatusCode());
    }

    private HttpHeaders headers() {
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        return headers;
    }

    private FileSystemResource file() {
        return new FileSystemResource(Path.of("src", "test", "resources", "image.jpg"));
    }
}

Rest controller:

@RestController
public class UploadEndpoint {
    @PostMapping("/upload")
    public void uploadFile(@RequestParam("file") MultipartFile file) {
        System.out.println(file.getSize());
    }
}