I have a Python filter to handle a few endpoints to do some configuration and calculation. For that I use the HTTP-GET method. Now, I want to use HTTP-POST to send some data to the Python filter.

Here is my example Request:

curl -H "Content-Type: application/json" -X POST -d '{"username":"xyz","password":"xyz"}' http://localhost:8081/cgi-bin/qgis_mapserv.fcgi?SERVICE=POST_TEST

In the QGIS log file I can clearly see that the request is getting handled somehow:

[1303][12:28:26] REMOTE_ADDR: [1303][12:28:26] CONTENT_TYPE: application/json [1303][12:28:26] HTTP_USER_AGENT: curl/7.47.0 [1303][12:28:26] QgsPostRequestHandler::parseInput [1303][12:28:26] QgsHttpRequestHandler::readPostBody [1303][12:28:26] length is: 35 [1303][12:28:26] {"username":"xyz","password":"xyz"} [1303][12:28:26] inserting pair SERVICE // POST_TEST into the parameter map [1303][12:28:26] Error at line 1, column 1: error occurred while parsing element.

But it is not possible to access the parsed information. I tried it with the same code-snipped which I use to retrieve information from a HTTP-GET Request:

request = self.serverInterface().requestHandler() params = request.parameterMap() service = params.get('SERVICE', '') body = request.body()

Well, I think that there are simple no bindings for Python to handle a HTTP-POST Request?


  • Apache/2.4.10
  • load library /usr/lib/qgispython (2.18.4)
  • Does the service GetCapabilities response say that it can handle HTTP POST? – nmtoken Mar 24 '17 at 18:46
  • Actually not, but i activated for example WFS in the *.qgs file. I can also do geatFeature-Requests. Maybe the problem lies in the log [1303][12:28:26] Error at line 1, column 1: error occurred while parsing element. – Sceada Mar 27 '17 at 7:29
  • But that would mean, that my curl request is not correct. – Sceada Mar 27 '17 at 7:34
  • Well for the WFS i can see the POST section. But i don't want to do a WMS or WFS request, it is completely independent from that. – Sceada Mar 27 '17 at 7:57
  • AFAIK, localhost:8081/cgi-bin/qgis_mapserv.fcgi? defines the service end-point to one or more OGC services, so you should only be able to use the service interfaces supported. – nmtoken Mar 27 '17 at 10:27

Ok, probably I found a workaround which is really bad. I found out, that the best way to get my information is to mix normal text with json. Let me show you what I mean.
curl -i -H "Content-Type: application/text" -X POST -d 'SERVICE=POST_TEST&json={"test":"test", "test2":[1,2,3,4], "test3":{"test4":"test5"}}' 'http://localhost:8081/cgi-bin/qgis_mapserv.fcgi?' -H "Accept: application/text"

What does QGIS do with the request body? It still produce one error message and then a parameter list.
Error at line 1, column 1: error occurred while parsing element. [832][08:53:52] inserting pair SERVICE // POST_TEST into the parameter map [832][08:53:52] inserting pair JSON // {"test":"test", "test2":[1,2,3,4], "test3":{"test4":"test5"}} into the parameter map

The parameter list is now accessible by the parameterMap.
request = self.serverInterface().requestHandler() params = request.parameterMap()

By the way
request = self.serverInterface().requestHandler() body = request.body() is always empty....

Ok back to the workaround. Now I can check first for the SERVICE parameter to pull the rest of the params to the right function and than I can parse the value for the json parameter.
requestBody = json.loads(params.get('JSON', '')) {u'test': u'test', u'test3': {u'test4': u'test5'}, u'test2': [1, 2, 3, 4]}

Well, as I said in the beginning I don't like this kind of workaround!

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