DART & GAE : Why a POST method send from dart can't be evaluate in GAE? - google-app-engine

Question

I have a Dart code used to send an HttpRequest with a POST method to my GAE WepApp2 application. The dart code is executed in chromium and serve by Chrome dev editor. I add in my GAE code some headers to avoid the XHR error in the client side.
The dart code send the datas to my GAE app but I can't read the data with self.request.POST.get("language")) and the app never enter in def post(self): section but with self.request.body I can read the data.
Could you explain that and provide some correction to have a full POST compliant code?
dart:
void _saveData() {
HttpRequest request = new HttpRequest(); // create a new XHR
// add an event handler that is called when the request finishes
request.onReadyStateChange.listen((_) {
if (request.readyState == HttpRequest.DONE &&
(request.status == 200 || request.status == 0)) {
// data saved OK.
print(request.responseText);
}
});
// POST the data to the server
var url = "http://127.0.0.1:8080/savedata";
request.open("POST", url, async: false);
String jsonData = JSON.encode({"language":"dart"});
request.send(jsonData);
}
GAE code in my handler:
def savedata(self):
logging.info("test")
logging.info(self.request.body)
logging.info(self.request.POST.get("language"))
def post(self):
logging.info("test 2")
logging.info(self.request.POST.get("language"))
self.response.headers["Access-Control-Allow-Origin"] = "http://127.0.0.1:49981"
self.response.headers["Access-Control-Allow-Methods"] = "POST, GET, OPTIONS"

Answer 1

In Dart, if you don't specify request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded") in your HttpRequest, the data is considered by GAE like a bite stream and you can only read them with self.request.body
If you add the Content-Type header in Dart you need also to change the data formating. In my case I mimic a form sending with POST method so I change String jsonData = JSON.encode({"language":"dart"}); by String jsonData = "language=dart2";
IN GAE python I can now read the data with self.request.POST.get("language")
If you need to send a JSON from DART to GAE, you can encode the string like this:
String jsonData = JSON.encode({"test":"valuetest1"});
String datas = "datas=$jsonData";
request.send(datas);
In GAE you can read the datas like this:
my_json = json.loads(self.request.POST.get("datas"))
logging.info(my_json["test"])
The complete code:
Dart
void _saveData2() {
String url = "http://127.0.0.1:8080/savedata";
HttpRequest request = new HttpRequest()
..open("POST", url, async: true)
..setRequestHeader("Content-Type", "application/x-www-form-urlencoded")
..responseType = "arraybuffer";
String jsonData = JSON.encode({"test":"valuetest1"});
String datas = "datas=$jsonData";
request.send(datas);
}
GAE
class PageHandler(webapp2.RequestHandler):
def savedata(self):
self.response.headers.add_header('Access-Control-Allow-Origin', '*')
self.response.headers['Content-Type'] = 'application/json'
#logging.info(self.request)
my_json = json.loads(self.request.POST.get("datas"))
logging.info(my_json["test"])