Request.Post Method to Web Server using CherryPy - request

Question

I am following the blog: Build your own Python RESTful Web Service to mock a web server using cherrypy.
The server code is
import cherrypy
class MyWebService(object):
#cherrypy.expose
#cherrypy.tools.json_out()
#cherrypy.tools.json_in()
def process(self):
return "hello world!"
if __name__ == '__main__':
config = {'server.socket_host': '0.0.0.0'}
cherrypy.config.update(config)
cherrypy.quickstart(MyWebService())
running above script by python server.py will start a service at http://localhost:8080.
Successful Call
Then we can call the service using post method:
import requests
headers = {'Content-Type': 'application/json'}
response = requests.post('http://localhost:8080/process', headers=headers, json={})
It successfully returns "hello world!" with status= 200.
Failed Call
However, if changing "Content-Type": application/json -> text/plain in headers and json -> data:
headers = {'Content-Type': 'text/plain'}
response = requests.post('http://localhost:8080/process', headers=headers, data={})
It responds the error code 415, and the error message
Traceback (most recent call last):
File "/Users/hshung/opt/anaconda3/lib/python3.9/site-packages/requests/models.py", line 910, in json
return complexjson.loads(self.text, **kwargs)
File "/Users/hshung/opt/anaconda3/lib/python3.9/json/__init__.py", line 346, in loads
return _default_decoder.decode(s)
File "/Users/hshung/opt/anaconda3/lib/python3.9/json/decoder.py", line 337, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/Users/hshung/opt/anaconda3/lib/python3.9/json/decoder.py", line 355, in raw_decode
raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
.....
I did try the following server code
#cherrypy.tools.json_in(content_type=['application/json', 'text/plain'])
The API call still fails, and the status code is 400.
Can anyone who is familiar with cherryPy and API request help me figure out how to fix it?

Answer 1

The problem is that with:
headers = {'Content-Type': 'text/plain'}
response = requests.post('http://localhost:8080/process', headers=headers, data={})
You're sending a POST request with an empty body, it should work if you specify the data param as a string containing any valid json:
headers = {'Content-Type': 'text/plain'}
response = requests.post('http://localhost:8080/process', headers=headers, data='{}')
For reference take a look a the values that are sent:
>>> requests.post('http://localhost:8080/process', headers=headers, json={})
DEBUG:urllib3.connectionpool:Starting new HTTP connection (1): localhost:8080
send: b'POST /process HTTP/1.1\r\nHost: localhost:8080\r\nUser-Agent: python-requests/2.27.1\r\nAccept-Encoding: gzip, deflate, br\r\nAccept: */*\r\nConnection: keep-alive\r\nContent-Type: text/plain\r\nContent-Length: 2\r\n\r\n'
send: b'{}'
reply: 'HTTP/1.1 200 OK\r\n'
header: Content-Type: application/json
header: Server: CherryPy/18.6.1
header: Date: Fri, 22 Jul 2022 23:16:49 GMT
header: Content-Length: 14
DEBUG:urllib3.connectionpool:http://localhost:8080 "POST /process HTTP/1.1" 200 14
<Response [200]>
>>> requests.post('http://localhost:8080/process', headers=headers, data={})
DEBUG:urllib3.connectionpool:Starting new HTTP connection (1): localhost:8080
send: b'POST /process HTTP/1.1\r\nHost: localhost:8080\r\nUser-Agent: python-requests/2.27.1\r\nAccept-Encoding: gzip, deflate, br\r\nAccept: */*\r\nConnection: keep-alive\r\nContent-Type: text/plain\r\nContent-Length: 0\r\n\r\n'
reply: 'HTTP/1.1 400 Bad Request\r\n'
header: Content-Type: text/html;charset=utf-8
header: Server: CherryPy/18.6.1
header: Date: Fri, 22 Jul 2022 23:16:55 GMT
header: Content-Length: 3023
DEBUG:urllib3.connectionpool:http://localhost:8080 "POST /process HTTP/1.1" 400 3023
<Response [400]>
>>> requests.post('http://localhost:8080/process', headers=headers, data='{}')
DEBUG:urllib3.connectionpool:Starting new HTTP connection (1): localhost:8080
send: b'POST /process HTTP/1.1\r\nHost: localhost:8080\r\nUser-Agent: python-requests/2.27.1\r\nAccept-Encoding: gzip, deflate, br\r\nAccept: */*\r\nConnection: keep-alive\r\nContent-Type: text/plain\r\nContent-Length: 2\r\n\r\n'
send: b'{}'
reply: 'HTTP/1.1 200 OK\r\n'
header: Content-Type: application/json
header: Server: CherryPy/18.6.1
header: Date: Fri, 22 Jul 2022 23:17:00 GMT
header: Content-Length: 14
DEBUG:urllib3.connectionpool:http://localhost:8080 "POST /process HTTP/1.1" 200 14
<Response [200]>
>>>
And you're correct with:
#cherrypy.tools.json_in(content_type=['application/json', 'text/plain'])
That is also required.