如何在ESP32服务器上处理带有JSON负载的POST请求？

#include <WiFi.h>
#include <ESPAsyncWebServer.h>

const char* ssid = "your_SSID";
const char* password = "your_PASSWORD";
const int serverPort = 80;

AsyncWebServer server(serverPort);

void setup() {
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }
  
  Serial.println("Connected to WiFi");
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());

  server.on("/api", HTTP_POST, [](AsyncWebServerRequest *request){
    String payload = request->arg("plain");
    // 处理JSON负载
    // ...
    request->send(200, "text/plain", "Request received");
  });

  server.begin();
}

void loop() {
  // 处理其他任务
}

#include <ArduinoJson.h>

void handleJsonPayload(const String& payload) {
  StaticJsonDocument<200> doc;
  DeserializationError error = deserializeJson(doc, payload);
  if (error) {
    Serial.print("Deserialization failed: ");
    Serial.println(error.c_str());
    return;
  }

  // 从JSON中提取字段值
  int value = doc["field_name"];
  Serial.print("Field value: ");
  Serial.println(value);

  // 修改字段值
  doc["field_name"] = 123;

  // 将修改后的JSON转换为字符串
  String modifiedPayload;
  serializeJson(doc, modifiedPayload);
  Serial.print("Modified payload: ");
  Serial.println(modifiedPayload);
}