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Asked: 2026-06-10T08:05:42+00:00

I’m trying to do file upload to GAE – serverside code: class UploadHandler(blobstore_handlers.BlobstoreUploadHandler): def

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I’m trying to do file upload to GAE – serverside code: 

 class UploadHandler(blobstore_handlers.BlobstoreUploadHandler):
    def post(self):
            upload_files = self.get_uploads('file')  
            blob_info = upload_files[0] # When using flask, request.files[0] gives correct output.
            self.response.out.write('/serve/%s' % blob_info.key())

With HTML, I can get it to work:

upload_url = blobstore.create_upload_url('/upload')
    self.response.out.write('<html><body>')
    self.response.out.write('<form action="%s" method="POST" enctype="multipart/form-data">' % upload_url)
    self.response.out.write("""Upload File: <input type="file" name="file"><br> <input type="submit"
        name="submit" value="Submit"> </form></body></html>""")

But I must be able to do a multipart post request from Java. I have a flask project hosted on openshift (flask, request.files[0] instead) in which the Java code appears to work: 

HttpParams params = new BasicHttpParams();
params.setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1);
DefaultHttpClient mHttpClient = new DefaultHttpClient(params);
HttpPost httppost = new HttpPost(getString(R.string.url_webservice) + "/upload");
MultipartEntity multipartEntity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
multipartEntity.addPart("file", new FileBody(new File(path)));
httppost.setEntity(multipartEntity);
mHttpClient.execute(httppost, new MyUploadResponseHandler(path));

But when I run it on GAE, im getting an index out of bounds on upload_files[0] when uploading – Where is the error? I cannot seem to find it, the code is so similar to the following which i have confirmed to work (flask, openshift):

def upload_file():
if request.method == 'POST':
    file = request.files['file']
    ...

UPDATE: The complete error log:

list index out of range
Traceback (most recent call last):
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line  1511, in __call__
    rv = self.handle_exception(request, response, e)
  File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1505, in __call__
   rv = self.router.dispatch(request, response)
   File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1253, in default_dispatcher
return route.handler_adapter(request, response)
   File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1077, in __call__
return handler.dispatch()
   File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 547, in dispatch
return self.handle_exception(e, self.app.debug)
   File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 545, in dispatch
return method(*args, **kwargs)
   File "myapp.py", line 22, in post
blob_info = upload_files[0]
 IndexError: list index out of range
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1 Answer

  1. Editorial Team

    blobstore.create_upload_url('/upload') does not produce the url /upload
    yet in the java, /upload is where you are trying to post to
    look at the produced html from that handler and you will see the action url of the form is different.

    You could have a handler respond with an upload url that your java code gets and then uses to post to.

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