Develop Reference

Download file functionality for react and python app

I have one button in my react code and when I click it I should be able to download a file. I am using Python for backend(Not any framework). For react part I think this link explains what should be done. On button click, I should do an API call and on its return, I can render this IFrame component. Also, one other answer recommends responseType: 'blob' in axios call. My question is what should the backend do if we want to send a file over.Let's assume it just creates a file and returns it. I am actually using one third-party product which has its own API interface but an example with requests library would do.
def function_called_From_endpoint():
with open(path) as f:
return {'data': f }
Is something like this right?

So, I made it work this way:
def function_called_From_endpoint():
with open(file_path) as f:
data = f.read()
return {"data": data }
and on the front-end:
axios({
url: url, //your url
method: 'GET',
responseType: 'blob', // important
}).then((response) => {
const url = window.URL.createObjectURL(new Blob([response.data]));
const link = document.createElement('a');
link.href = url;
link.setAttribute('download', 'file.txt'); //or any other extension
document.body.appendChild(link);
link.click();
});
As suggested by https://stackoverflow.com/a/53230807/5573241. It worked well.

Uploading an image using the Python Etsy API

I am trying to upload an image to Etsy through the API. However, the example on their website is given in PHP which I don't know how to code. I only know how to work with Python. On their website it says:
Image uploads can be performed using a POST request with the Content-Type: multipart/form-dataheader, following RFC1867.
Their example which is in PHP
// You must define the constants OAUTH_CONSUMER_KEY and OAUTH_CONSUMER_SECRET
// You must also assign values to the variables $access_token, $access_token_secret,
// $listing_id and $filename, and $mimetype.
// Your image file is assumed to be in the same directory as this code.
$oauth = new OAuth(OAUTH_CONSUMER_KEY, OAUTH_CONSUMER_SECRET);
$oauth->enableDebug();
$oauth->setToken($access_token, $access_token_secret);
try {
$source_file = dirname(realpath(__FILE__)) ."/$filename";
$url = "https://openapi.etsy.com/v2/listings/".$listing_id."/images";
$params = array('#image' => '#'.$source_file.';type='.$mimetype);
$oauth->fetch($url, $params, OAUTH_HTTP_METHOD_POST);
$json = $oauth->getLastResponse();
print_r(json_decode($json, true));
} catch (OAuthException $e) {
// You may want to recover gracefully here...
print $oauth->getLastResponse()."\n";
print_r($oauth->debugInfo);
die($e->getMessage());
}
In API doc it says
HTTP Method = POST
URI = /listings/:listing_id/images
This is what I have so far in Python:
client_secret=client_secret,resource_owner_key=resource_owner_key,resource_owner_secret=resource_owner_secret)
url = 'https://openapi.etsy.com/v2/listings'
payload = {'listing_id':'2343432434', 'images': :('test1.jpg', open('test1.jpg', 'rb'), 'image/jpeg')}
result = etsy.post(uri, params=payload)
When I run this code I get an 403 error. How can I fix my code so that it functions correctly? I have looked at other examples and just can't seem to make it work.

Uploading file to Spring REST server using Python Requests

I am trying to upload a file using python requests to my java/scala spring rest server. I am getting the following response:
{"timestamp":1454331913056,"status":400,"error":"Bad Request","exception":"org.springframework.web.bind.MissingServletRequestParameterException","message":"Required MultipartFile parameter 'image' is not present","path":"/parking_api/images"}
my server code:
#RequestMapping(value = Array("/parking_api/images"), method = Array(RequestMethod.POST)) def images(#RequestParam("image") image: MultipartFile) = {
if (image.isEmpty){
// handle empty
new ResponseEntity(response, HttpStatus.BAD_REQUEST
} else {
// process
new ResponseEntity(response, HttpStatus.OK)
}
}
My client code:
requests.post(parking_webservice_address, files={"image": ("image", open(event.pathname, "rb"), "image/jpeg")})
I have tried:
setting files parameter in python code to just {"image":open(...)} instead of tuple
passing image data loaded to memory using open(...).read() to files parameter in python code
setting CommonsMultipartResolver in server like this
#Bean(name="multipartResolver")
public CommonsMultipartResolver multipartResolver(){
return new CommonsMultipartResolver();
}
setting multipart headers manually, but then it server expects boundary which is missing as things get from bad to worse
None of these options have worked for me. What am I missing?

Connecting Python Backend to Android APP

How to use python as a backend for an Android App that is built using C#? The Python Backend is written using the Flask framework. The Android app is built using xamarin.

No matter what type of technology your server or the client use if they can communicate with each other using some sort of standard "protocol".
There are many ways to communicate both sides (client and server) like sockets, xml, json, etc. They just need to understand each other.
In your particular case I suggest to build a REST or RESTful API (https://flask-restful.readthedocs.org/en/0.3.3/) on the server and a REST client library on the client.
There are many ways and libraries to call REST APIs from C#:
The built-in method would be using HttpWebRequest as you can see on this link:
private async Task<JsonValue> FetchWeatherAsync (string url)
{
// Create an HTTP web request using the URL:
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create (new Uri (url));
request.ContentType = "application/json";
request.Method = "GET";
// Send the request to the server and wait for the response:
using (WebResponse response = await request.GetResponseAsync ())
{
// Get a stream representation of the HTTP web response:
using (Stream stream = response.GetResponseStream ())
{
// Use this stream to build a JSON document object:
JsonValue jsonDoc = await Task.Run (() => JsonObject.Load (stream));
Console.Out.WriteLine("Response: {0}", jsonDoc.ToString ());
// Return the JSON document:
return jsonDoc;
}
}
}
But I don´t recommend it if you don´t want your app to be full of crap (boiler plate code) everywhere.
A helper library could be, for example, RESTSharp. It allows you to build REST calls easily and cast the response to your typed objects. Here´s and example:
var client = new RestClient("http://example.com");
// client.Authenticator = new HttpBasicAuthenticator(username, password);
var request = new RestRequest("resource/{id}", Method.POST);
request.AddParameter("name", "value"); // adds to POST or URL querystring based on Method
request.AddUrlSegment("id", "123"); // replaces matching token in request.Resource
// easily add HTTP Headers
request.AddHeader("header", "value");
// add files to upload (works with compatible verbs)
request.AddFile(path);
// execute the request
RestResponse response = client.Execute(request);
var content = response.Content; // raw content as string
// or automatically deserialize result
// return content type is sniffed but can be explicitly set via RestClient.AddHandler();
RestResponse<Person> response2 = client.Execute<Person>(request);
var name = response2.Data.Name;
// easy async support
client.ExecuteAsync(request, response => {
Console.WriteLine(response.Content);
});
// async with deserialization
var asyncHandle = client.ExecuteAsync<Person>(request, response => {
Console.WriteLine(response.Data.Name);
});
// abort the request on demand
asyncHandle.Abort();
You can search "C# REST client" on google and judge by yourself. But IMHO, the easier and nicer to code REST client I´ve ever used is Refit.
Why? you define API calls and responses with just an interface. No coding required at all! Even more, all your API calls will be async by default, something needed for mobile apps to be responsive. From the author´s readme:
public interface IGitHubApi
{
[Get("/users/{user}")]
Task<User> GetUser(string user);
}
var gitHubApi = RestService.For<IGitHubApi>("https://api.github.com");
var octocat = await gitHubApi.GetUser("octocat");
I´ve used this library on Xamarin Android/iOS projects and it works well. No issues at all.
Hope it helps

Upload an image from iphone to GAE blobstore

I spent all this morning looking for a clear example on how to upload a picture taken with an iPhone to the blobstore, but without succeed.
Currently I have my iPhone app developed, which can send pics to the server in PHP, with this code in the server:
// Function to upload a photo in a file and save data in the DB
function upload($photoData, $descr, $phone) {
// Folder to upload data
$path = $_SERVER['DOCUMENT_ROOT']."/program/data/";
// Check if there was no error during the file upload
if ($photoData['error'] == 0) {
$result = query("INSERT INTO pics(descr, phone) VALUES('%s','%s')", $descr, $phone);
if (!$result['error']) {
// Inserted in the database, go on with file storage
// Obtain database link (in lib.php)
global $link;
// Get the last automatically generated ID
$idPhoto = mysqli_insert_id($link);
// Move the temporarily stored file to a convenient location
if (move_uploaded_file($photoData['tmp_name'], $path.$idPhoto.".jpg")) {
// File moved, all good, generate thumbnail
thumb($path.$idPhoto.".jpg", 180);
print json_encode(array('successful' => 1));
} else {
errorJson('Upload on server problem');
}
} else {
errorJson('Save database problem: '.$result['error']);
}
} else {
errorJson('Upload malfunction.');
}
}
The part in Objective-C that makes this works is (I'm using AFNetworking and the object API sharedInstance is an AFJSONRequestOperation class):
// Upload the image and the description to the web service
[[API sharedInstance] commandWithParams:[NSMutableDictionary dictionaryWithObjectsAndKeys:
#"upload", #"command",
UIImageJPEGRepresentation(originalPhoto, 70), #"file",
description, #"descr",
phoneNumber, #"phone",
nil]
onCompletion:^(NSDictionary *json) {
// Finished and response from server
if (![json objectForKey:#"error"]) {
// Success
[[[UIAlertView alloc]initWithTitle:#"Info"
message:#"Thanks"
delegate:nil
cancelButtonTitle:#"Dismiss"
otherButtonTitles: nil] show];
// Send a notification so the main view can reload the data
[[NSNotificationCenter defaultCenter] postNotificationName:#"updateStream" object:nil];
} else {
// Error
NSString* errorMsg = [json objectForKey:#"error"];
[UIAlertView error:errorMsg];
}
}];
This works fine and the images are saved on the server. But I want to make the same with datastore, which you can't save files. So I made a webpage to practice on save images, and I can upload images without any problem in the blobstore from an standard web form. This is the code I'm using to save it in GAE (forget about my own helper classes or functions like PicturePageHandler or render_page):
# Get and post for the create page
class Create(PicturePageHandler, blobstore_handlers.BlobstoreUploadHandler):
def get(self):
if self.user_logged_in():
# The session for upload a file must be new every reload page
uploadUrl = blobstore.create_upload_url('/addPic')
self.render_page("addPicture.htm", form_action=uploadUrl)
def post(self):
if self.user_logged_in():
# Create a dictionary with the values, we will need in case of error
templateValues = self.template_from_request()
# Test if all data form is valid
testErrors = check_fields(self)
if testErrors[0]:
# No errors, save the object
try:
# Get the file and upload it
uploadFiles = self.get_uploads('picture')
# Get the key returned from blobstore, for the first element
blobInfo = uploadFiles[0]
# Add the key and the permanent url to the template
templateValues['blobKey'] = blobInfo.key()
templateValues['servingUrl'] = images.get_serving_url(blobInfo.key(), size=None)
# Save all
pic = Picture.save(self.user.key, **templateValues)
if pic is None:
logging.error('Picture save error.')
self.redirect("/myPics")
except:
self.render_page("customMessage.htm", custom_msg=_("Problems while uploading the picture."))
else:
# Errors, render the page again, with the values, and showing the errors
templateValues = custom.prepare_errors(templateValues, testErrors[1])
# The session for upload a file must be new every reload page
templateValues['form_action'] = blobstore.create_upload_url('/addPic')
self.render_page("addPicture.htm", **templateValues)
My questions are:
Can I still using my Objective-C JSON call to upload a picture to the server or must I completely change the way to upload the picture?
How can I change the Python server code to get the picture from the JSON, if it is possible?

It's not exactly what you're after, but this might help:
http://brunofuster.wordpress.com/2011/03/11/uploading-an-image-from-iphone-to-appengine-blobstore-using-vraptor/