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));
}

Attribution

It looks like you are setting the ContentType = MULTIPART_FORM_DATA on the test. But your controller is not set to receive this type of request. Try using consumes = {MediaType.MULTIPART_FORM_DATA_VALUE} Please post the rest of the Test class as there are some missing pieces that I couldn't reproduce here – Fukuoka

@BrunoLeite Thank you for the suggestion. I tried it but that is not the case. – Attribution

do you actually return a string with your response entity? have you verified what's at the body of your 400 response in case it provides more details? have you considered running it with a debugger or implementing an exception handler? – Furtado

Yes, String is being returned. It works fine outside of the integration test. In this test I posted. I don't even get the debug line so something is happening before it gets to the body of the controller. – Attribution

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

Triste

It is not clear to me what was causing the problem in the first place. Is the multipart controller not compatible with java.io.File? Anyway, it does work like a charm, thank you. This saved me a lot of work! – Attribution

@Attribution I guess that the rest template is able in managing the org.springframework.core.it.Resource implementation better than passing a simple java.io.File – Triste

I know this is quite old, but can I ask you, where is your "image.jpg" file located in your project? – Hardin

@bot_bot In my code the image is under the classpath (that is in src/main/resources if you are using maven) – Triste

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());
    }
}

Affray

Answer 3

Since MockMultipartFile inherits from MultipartFile, we have access to getResource() method. My implementation as below:

I constructed an array of MockMultipartFiles

@NotNull
    private static MockMultipartFile[] mockMultipartFiles() {
        Path path = Paths.get("src/test/resources/uploads/");

        assertTrue(Files.exists(path));

        File dir = new File(path.toUri());
        assertNotNull(dir);

        File[] files = dir.listFiles();
        assertNotNull(files);

        return Arrays.stream(files).map(file -> {
                    try {
                        return new MockMultipartFile(
                                file.getName(),
                                file.getName(),
                                Files.probeContentType(file.toPath()),
                                Files.readAllBytes(file.toPath())
                        );
                    } catch (IOException ignored) {
                        throw new CustomServerError("unable to convert files in %s to a file".formatted(path.toString()));
                    }
                })
                .toArray(MockMultipartFile[]::new);
    }

Add MockMultipartFiles into LinkedMultiValueMap as Resource

@NotNull
    public static MultiValueMap<String, Object> mockMultiPart(String dto) {
        MultiValueMap<String, Object> multipart = new LinkedMultiValueMap<>();

        // add image files to request
        for (var resource : mockMultipartFiles()) {
            multipart.add("files", resource.getResource());
        }

        // create dto
        HttpHeaders metadataHeaders = new HttpHeaders();
        metadataHeaders.add(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
        multipart.add("dto", new HttpEntity<>(dto, metadataHeaders));

        return multipart;
    }

Waddington