reactjs - Can't read Enum from server (Spring) on React

Question

I try to read Enum (as a response), sending from server (Spring) to client (React) during downloading a file to the DB. But no matter how hard I try, I couldn't read it. My max success was when I use typeof - I got "string": Here is how I treat the response on client:

export default function File() {
    const [selectedFile, setSelectedFile] = useState('');
    const [isFileSelected, setIsFileSelected] = useState(false);
    const [answer, setAnswer] = useState('');

    const fileSelectedHandler = event => {
        setSelectedFile(event.target.files[0]);
        setIsFileSelected(true);
        setAnswer("File is ready for downloading");
    };

     function getValue(answer) {
         console.log("the result of typeof is: " + typeof answer);
        switch (answer) {
            case 'SUCCESS':
                return "One result";
            case 'CHECK_FILE_EXTENSION':
                return "Second result";
            case 'FILE_ALREADY_EXISTS':
                return "Third result";
            default:
                return "File not chosen";
        }
    }

    const fileUploadHandler = () => {
        if (isFileSelected === true) {
            const formData = new FormData();
            formData.append("file", selectedFile);
            fetch("/api/upload", {
                method: 'POST',
                body: formData
            })
                .then(response => response.text())
                .then(response => setAnswer(getValue(response)))

        } else {
            setAnswer('File not chosen');
        }
    };

    return (
          <div align="center">
              <table>
                  <tr>
                      <td>Выберите файл:</td>
                      <td><input type="file" onChange={fileSelectedHandler}/></td>
                  </tr>
                  <tr>
                      <td></td>
                      <td>
                          <button onClick={fileUploadHandler}>Загрузить</button>
                      </td>
                  </tr>
              </table>
              <td>
                  <h1>{answer}</h1>
              </td>
          </div>
    );
}

Here is my Enum on server:

public enum DownloadStatus {
    FILE_ALREADY_EXISTS,
    SUCCESS,
    CHECK_FILE_EXTENSION;
}

Here is a method:

public Enum <DownloadStatus> checkFileNameBeforeUploadToDB (File fileName) throws IOException {
    String fileExtension = getExtension(fileName.getPath());
    if ((fileExtension.equals("xlsx")) || (fileExtension.equals("xls"))) {
        if (isFileNameExistInList(getAll(), fileName)) {
            return DownloadStatus.FILE_ALREADY_EXISTS;
        } else {
            addNewFile(fileName);
            return DownloadStatus.SUCCESS;
        }
    } else {
        return DownloadStatus.CHECK_FILE_EXTENSION;
    }
}

Here is a controller:

@RequestMapping(value = "/api/upload", method = RequestMethod.POST)
@ResponseBody
public Enum<DownloadStatus> uploadFile(@RequestParam("file") MultipartFile multiPartFile) throws IOException, JSONException, NullPointerException {
    File file = convertFromMultipartToFile(multiPartFile);
    return fireService.checkFileNameBeforeUploadToDB(file);
}

Where is my mistake? Thanks is advance :-)

question from:https://stackoverflow.com/questions/65903672/cant-read-enum-from-server-spring-on-react

Answer 1

The deal was in response format. It comes to client not just like "CHECK_FILE_EXTENSION" as I thought, but like So you have to write this case in switch block or you can change response.text() in fileUploadHandler to response.json() and print case in switch block as usually "CHECK_FILE_EXTENSION".