unable to read a file from angular and pass it to API built using java

Question

I have application where I am using angular. Input a csv file and add the file to form. below is the code used

var fileInput = document.getElementById('chosenFile');
var fd = new FormData();
fd.append('fileMetadata', JSON.stringify(imgMetadata));
var file = fileInput.files[0];
fd.append('file', file);

now I call http post to send file to my server,

enter code here

$http.post(uploadurl, fd, {
  transformRequest: angular.identity,
  transformResponse: angular.identity,
  headers: {
    "X-XSRF-TOKEN": PluginHelper.getCsrfToken(),
    "Content-Type": undefined
  }
}).then(function successCallback(response) {
  console.log("In success callback");
  var status = response.status;
  if(status == "200")
    {
    var isValid = response.data;
    console.log("FIleupload function in java "+isValid);
    if(isValid == "filecopied")
      {
      $scope.errorText = "filecopied :";
      }
    }
}, function errorCallback(response) {
  console.log("In error callback");
  $scope.errorText = "Error in callback file function";
});

At my server end I have written java code to read the file.

@POST
  @Path("/uploadfile/{csvdata}")
  @Consumes(MediaType.MULTIPART_FORM_DATA)
  @AllowAll
  public Response uploadfile(@PathParam("csvdata") String csvdata, @FormDataParam("fileMetadata") String fileMetadata,
    @FormDataParam("file") InputStream uploadedInputStream,
    @FormDataParam("file") FormDataContentDisposition fileDetail, FormDataMultiPart multiPartData, @FormDataParam("fd") InputStream formdata) throws Exception {
    try {
      if (uploadedInputStream == null) {
        log.error("Error: uploadedInputStream is null");
        //return Response.status(Response.Status.BAD_REQUEST).entity("File input stream is null").build();
      }
      if (formdata == null) {
        log.error("Error: formdata is null");
        //return Response.status(Response.Status.BAD_REQUEST).entity("File input stream is null").build();
      } else {
        log.error("Error: formdata is NOT null");
      }
      // for file field    
      final FormDataBodyPart filePart = multiPartData.getField("<file_field_name>");
      final ContentDisposition fileDetails = filePart.getContentDisposition();
      final InputStream fileInputStream = filePart.getValueAs(InputStream.class);
      log.error(filePart + "-" + fileDetails + "--" + fileInputStream);
      log.error("TRY FILEUPLOAD: " + csvdata);
      log.error("File Metadata: " + fileMetadata);
      // Process the uploaded file
      String uploadedFileLocation = "d://uploaded/" + fileDetail.getFileName();
      log.error("uploadedFileLocation: " + uploadedFileLocation);
      log.error("fileDetail: " + fileDetail.getSize());
      saveToFile(uploadedInputStream, uploadedFileLocation);
      return Response.status(Response.Status.OK).entity("filecopied").build();
  
    } catch (Exception e) {
      log.error("catch uploadfile: " + e.toString() + "-" + e.getMessage());
      return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity("Cannot copy!!").build();
  
    }
  }
  private void saveToFile(InputStream uploadedInputStream, String target) {
    try (OutputStream out = new FileOutputStream(new File(target))) {
      log.error("TRY saveToFile");
      int read;
      byte[] bytes = new byte[1024];
      while ((read = uploadedInputStream.read(bytes)) != -1) {
        out.write(bytes, 0, read);
      }
    } catch (IOException e) {
      log.error("catch saveToFile: " + e.toString() + "-" + e.getMessage());
    }
  }

if you see parameters of the method,

1- @PathParam("csvdata") String csvdata, @FormDataParam("fileMetadata") String fileMetadata,
2- @FormDataParam("file") InputStream uploadedInputStream,
3- @FormDataParam("file") FormDataContentDisposition fileDetail,FormDataMultiPart 
4- multiPartData,@FormDataParam("fd") InputStream formdata

I have tried above options but uploadedInputStream and InputStream comes always null.
i am able to get

csvdata
fileDetail
fileMetadata

but i am unable to get file from xhtml to java API.
Need help in reading file from form .

I have tried passing multiple parameters at java code but no luck.

Sample output i get is

uploadedInputStream is null
formdata is null
catch uploadfile: java.lang.NullPointerException-null

Lars Peterson · Accepted Answer · 2025-03-10 13:27:57Z

0

You need to isolate the problem. Look at the network tab in Chrome/Edge/Firefox, make sure the data is actually being sent by clicking on the relevant request and checking out the request body. You should see the data you need.

If you don't the problem is on the frontend. If you do the problem is on the backend.

Maybe your request headers are the problem:

Change this:

"Content-Type": undefined

To this:

"Content-Type": 'multipart/form-data'

answered Mar 10 at 13:27

Lars Peterson

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