How to Upload Files to the Server With the File Upload API

   // create a file locally so there is something to upload
   String filename = "myhelloworld-async.txt";
   FileOutputStream fileOutputStream = new FileOutputStream(filename);
   fileOutputStream.write("Hello mbaas!\nUploading files is easy!".getBytes());
   fileOutputStream.close();

   final File file = new File(filename);

   // now upload the file
   Backendless.Files.upload(file, "/myfiles", new AsyncCallback() {
       @Override
       public void handleResponse(BackendlessFile uploadedFile) {
           Log.i(TAG, "File has been uploaded. File URL is - " + uploadedFile.getFileURL());
           file.delete();
       }

       @Override
       public void handleFault(BackendlessFault fault) {
           Log.e(TAG, fault.getMessage());
       }
   });

   // create a file locally so there is something to upload
   val filename = "myhelloworld-async.txt"
   val fileOutputStream = FileOutputStream(filename)
   fileOutputStream.write("Hello mbaas!\nUploading files is easy!".toByteArray())
   fileOutputStream.close()

   val file = File(filename)

   // now upload the file
   Backendless.Files.upload(file, "/myfiles", object : AsyncCallback {
       override fun handleResponse(uploadedFile: BackendlessFile) {
           Log.i(TAG, "File has been uploaded. File URL is - ${uploadedFile.fileURL}")
           file.delete()
       }

       override fun handleFault(fault: BackendlessFault) {
           Log.e(TAG, fault.message)
       }
   })

// create a file data so there is something to upload
NSData *data = [@"Hello mbaas!\nUploading files is easy!" dataUsingEncoding:NSUTF8StringEncoding];
    
// now upload the file
[Backendless.shared.file uploadFileWithFileName:@"myhelloworld.txt" filePath:@"myfiles" content:data overwrite: YES responseHandler:^(BackendlessFile *uploadedFile) {
    NSLog(@"File has been uploaded. File URL is - %@", uploadedFile.fileUrl);
} errorHandler:^(Fault *fault) {
    NSLog(@"Error: %@", fault.message);
}];

// create a file data so there is something to upload
if let data = "Hello mbaas!\nUploading files is easy!".data(using: .utf8) {
            
    // now upload the file
    Backendless.shared.file.uploadFile(fileName: "myhelloworld.txt", filePath: "myfiles", content: data, overwrite: true, responseHandler: { uploadedFile in
        print("File has been uploaded. File URL is - \(uploadedFile.fileUrl ?? "")")
    }, errorHandler: { fault in
        print("Error: \(fault)")
    })            
}

const Backendless = require('backendless')
/*
 Or use `import Backendless from 'backendless'` for client side.
 If you don't use npm or yarn to install modules, you can add the following line
 <script src="//api.backendless.com/sdk/js/latest/backendless.min.js"></script>
 to your index.html file and use the global Backendless variable.
*/

Backendless.initApp('YOUR_APP_ID', 'YOUR_JS_API_KEY')

const handleFileSelect = event => {
  const { files } = event.target // FileList object

  for (let file of files) {
    Backendless.Files.upload(file, '/myFiles')
      .then(onSuccess, onError)
  }
}

const onSuccess = file => {
  console.log('Uploaded file URL - ' + file.fileURL)
}

const onError = error => {
  console.error('Server reported an error: ', error.message)
  console.error('error code: ', error.code)
  console.error('http status: ', error.status)
}

   // create a file locally so there is something to upload
   String filename = "myhelloworld-async.txt";
   File file = await File(filename).writeAsString("Hello mbaas!\nUploading files is easy!");

   Backendless.Files.upload(file, "/myfiles").then((response) {
     print("File has been uploaded. File URL is - " + response);
     file.delete();
   });