Python Tornado请求JSON

Question

My application accepts data from POST method which I am running through JQuery's AJAX request. I am sending JSON formatted data, but in handler as I accept request and access the data it turns out to be byte string type.

I am using my_body = self.request.body method.

For example, if I am sending {"drzava":"rs","kategorija":"general"} received data looks like b'drzava=rs&kategorija=general'.

Problem is, afterwards I can't use tornado.escape.json_decode(), to make it dictionary. I keep getting the following error:

Traceback (most recent call last):
  File "/home/stefan/.local/lib/python3.6/site-packages/tornado/web.py", line 1697, in _execute
    result = method(*self.path_args, **self.path_kwargs)
  File "main.py", line 164, in post
    telo_json = tornado.escape.json_decode(telo)
  File "/home/stefan/.local/lib/python3.6/site-packages/tornado/escape.py", line 83, in json_decode
    return json.loads(to_basestring(value))
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

I will post the code, if needed.

Answer 1

The data you receive in your Tornado server application depends on how your data is being "packaged" by the client.

You could have application/x-www-form-urlencoded data (seems to be your case above) which you can process in Tornado using get_body_argument:

drzava = self.get_body_argument("drzava", None)
kategorija = self.get_body_argument("kategorija", None)

or you could have application/json (seems to be want you want):

data = tornado.escape.json_decode(self.request.body)

In order to send JSON data from your browser you need to actually send JSON data and specify the content type:

var data = {"drzava":"rs", "kategorija":"general"};
$.ajax({
    url: YOUR_URL,
    type: "POST",
    data: JSON.stringify(data),
    contentType: "application/json",
    ...

EDIT:
In the end the issue was that the HTML page was sending the data using a form and would not actually use the JS code.