How do I get the request params from a ESPAsyncWebServer?

Question

I currently have the following code

server.on("/on", HTTP_POST, [](AsyncWebServerRequest *request) {
 Serial.println("ON hit.");
 String message;
 Serial.println(request->url());
 if (request->hasParam("device"))
 {
 message = request->getParam("device")->value();
 }
 else
 {
 message = " not specified";
 }
 request->send(200, "text/plain", "On, GET: " + message);
 Serial.print("Device ");
 Serial.println(message);
....

When sending in a request I get the out put, "Device not specified".

I take a look at the request-params() which gives me back a count of params that are in there and it's returning 1. I write this out:

server.on("/off", HTTP_POST, [](AsyncWebServerRequest *request) {
 Serial.println("OFF hit.");
 String message;
 int params = request->params();
 Serial.printf("%d params sent in\n", params);
 for (int i = 0; i < params; i++)
 {
 AsyncWebParameter *p = request->getParam(i);
 if (p->isFile())
 {
 Serial.printf("_FILE[%s]: %s, size: %u", p->name().c_str(), p->value().c_str(), p->size());
 }
 else if (p->isPost())
 {
 Serial.printf("_POST[%s]: %s", p->name().c_str(), p->value().c_str());
 }
 else
 {
 Serial.printf("_GET[%s]: %s", p->name().c_str(), p->value().c_str());
 }
 }
 if (request->hasParam("device"))
 {
 message = request->getParam("device")->value();
 }
 else
 {
 message = "not specified";
 }
 request->send(200, "text/plain", "Off, GET: " + message);
 Serial.print("Device ");
 Serial.println(message);

and get the output now of

1 params sent in
_POST[device]: puddle
Device not specified 

If I try to do something like request->getParam(0)->value().c_str() I get a stack dump of a bunch of hex values that I have no idea what it means: but it looks like a big fat error.

• Juraj: try hasParam("device", true)
• dandavis: usually params are for GET while POST has a separate interface
• rball: @Juraj that was it. Want to make an answer? Lol, feel pretty silly.
• Dakkar: just in case, someone finds this snipplet: In addition to @Juraj (correct) answer: If you want to access this param you also have to inform the function, that you want the url parameters: message = request->getParam("device", true)->value();

Answer 1

For POST request the hasParam needs to know if you want to test the url parameters or x-www-form-urlencoded parameters in body of the POST request. The second parameter of the hasParam is boolean post and it has default value false. Use hasParam("device", true).