Documentation clarification.

[rosenhauer]

I was transitioning from the basic WebServer to ESPAsyncWebServer and was using js to send (Fetch) Requests

const request = new Request("http://192.168.0.80/sendcommand", {
      method: "POST",
      mode: "cors", // no-cors, cors, *same-origin
      body: JSON.stringify({ command: theCommand , password: '1234'}),
    });
    fetch(request)
    .then((response) => {
      if (response.status === 200) {
        return;
        //return response.json();
      } else {
        throw new Error("Something went wrong on API server!");
      }
    })
    .catch((error) => {
      console.error(error);
    });

This was working fine under the old WebServer but I wanted to add LittleFS support to server files from the SPIFF partition.

After converting I wasn't getting the "sendCommand" message body. Took some searching to find out how to get it.

server.on("/sendcommand", HTTP_POST, [](AsyncWebServerRequest *request){
    //do nothing and don't remove it
  }, NULL, [](AsyncWebServerRequest *request, uint8_t *data, size_t len, size_t index, size_t total){
    JsonDocument body;
    DeserializationError error = deserializeJson(body, (const char*)data);
    
    String theCommand;
    String thePassword;

    if (!error) {
      if (body.containsKey("command")) {
        theCommand = String(body["command"].as<String>());
      }
      if (body.containsKey("password")) {
        thePassword = String(body["password"].as<String>());
      }

      Serial.printfln("Command:%s Password=%s", theCommand.c_str(), thePassword.c_str());
      // Do something with the payload...

      request->send(200, "text/plain", "success");
    } else {
      request->send(404, "text/plain", "");
    }
  });

Again not an issue but rather that it took forever to find that the server.on function has a version with three calls and that the third one is what will process the body. Feel free to close. But I wanted to document it for others.