title: '400 Bad Request' when post json in Flask
body: <p>My application is very simple,</p>
  
  <pre><code>#@csrt.exempt
  @app.route('/preorders/json', methods=['POST'])
  def json_create_preorders():
      #print request
      print 'test'
      #print request.json
      print request.mimetype
      print request.json
      print 'aaa',request.get_json(force=True)
      print request.json['product_id']
      if not request.json or not 'product_id' in request.json or not 'customer_name' in request.json or not 'customer_phone' in request.json:
          abort(400)
      preorder=Preorder(request.json['customer_name'],request.json['customer_phone'],request.json['product_id'])
      db.session.add(preorder)
      db.session.commit()
      return jsonify({'status':'success'}), 201
  </code></pre>
  
  <p>POST json with curl,</p>
  
  <pre><code>curl -i -H "Content-Type: application/json" -X POST -d '{"product_id":"111", "customer_name"="xiaokun", "customer_phone"="1231"}' http://xxxx/preorders/json
  </code></pre>
  
  <p>Check from server, 'test' and 'request.mimetype' are printed. Then is a 400 response.
  Anyone can help to have a look?</p>