This is a demonstration and test sketch for configuring persistent options via the web interface. This strategy is used in a number of my functional ESP32 and ESP8266 sketches. It consists of a settings.json file in the SPIFFS filesystem and a settings.html file with some javascript.
This specific version is for ArduinoJson 6, there are other examples for version 5 and 7.
The settings can be changed in the webbrowser at http://192.168.1.xxx/settings and clicking "Send". This results in Webserver parsing the arguments and placing the variables in the header, but also places the query string in the body.
The following also results in Webserver parsing the arguments and placing the variables in the header.
curl -X POST 'http://192.168.1.xxx/json?var1=11&var2=22&var3=33'
curl -X PUT 'http://192.168.1.xxx/json?var1=11&var2=22&var3=33'
The following is not parsed, but only places the JSON data in the body.
curl -X POST http://192.168.1.xxx/json -d '{"var1":11,"var2":22,"var3":33}'
curl -X PUT http://192.168.1.xxx/json -d '{"var1":11,"var2":22,"var3":33}'
You should not only write the firmware to the ESP32 module, but also the static content for the web interface. The html, css and javascript files located in the data directory should be written to the SPIFS filesystem on the ESP32. See https://github.com/me-no-dev/arduino-esp32fs-plugin.
You will get a "file not found" error if the firmware cannot access the data files.
This Arduino sketch includes a data directory with a number of files that should be uploaded to the ESP32 using the SPIFFS filesystem uploader tool. At the moment (Feb 2024) the Arduino 2.x IDE does not support the SPIFFS filesystem uploader plugin. You have to use the Arduino 1.8.x IDE (recommended), or the command line utilities for uploading the data.