Flask API failing to decode JSON data. Error: "message": "Failed to decode JSON object: Expecting value: line 1 column 1 (char 0)"

Question

I'm setting up a simple rest api using flask and flask-restful. Right now all I'm trying to do is create a post request with some Json data, and then return it just to see if it works. I always get the same error "message": "Failed to decode JSON object: Expecting value: line 1 column 1 (char 0)"

Below is my code

from flask import Flask, jsonify, request
from flask_restful import Resource, Api

app = Flask(__name__)
api = Api(app)


class Tester(Resource):
   def get(self):
       return {'about': 'Hello World'}

   def post(self):
       data_json = request.get_json(force=True)
       return {'you sent': data_json}


api.add_resource(Tester, '/')

if __name__ == '__main__':
    app.run(debug=True)

The curl request I am making to test this is below, I've also tried making request using postman

curl -H "Content-Type: application/json" -X POST -d '{'username':"abc",'password':"abc"}' http://localhost:5000

Answer 1

You need to select raw -> JSON (application/json) in Postman like this:

When it comes to your cURL request, answer explains that windows's command line lacks support of strings with single quotes, so use:

curl -i -H "Content-Type: application/json" -X POST -d "{\"username\":\"abc\", \"password\":\"abc\"}" 127.0.0.1:5000

instead:

curl -H "Content-Type: application/json" -X POST -d '{'username':"abc",'password':"abc"}' http://localhost:5000

\ escapes " character.

Answer 2

You also need to have the Content-Length header enabled.