Reapplied changes from me-no-dev/ESPAsyncWebServer#1384

Author: Niklas Lönn

src/AsyncJson.h

@@ -197,10 +197,10 @@ class AsyncCallbackJsonWebHandler : public AsyncWebHandler {
   public:
 #if ARDUINOJSON_VERSION_MAJOR == 6
     AsyncCallbackJsonWebHandler(const String& uri, ArJsonRequestHandlerFunction onRequest, size_t maxJsonBufferSize = DYNAMIC_JSON_DOCUMENT_SIZE)
-        : _uri(uri), _method(HTTP_POST | HTTP_PUT | HTTP_PATCH), _onRequest(onRequest), maxJsonBufferSize(maxJsonBufferSize), _maxContentLength(16384) {}
+        : _uri(uri), _method(HTTP_GET | HTTP_POST | HTTP_PUT | HTTP_PATCH), _onRequest(onRequest), maxJsonBufferSize(maxJsonBufferSize), _maxContentLength(16384) {}
 #else
     AsyncCallbackJsonWebHandler(const String& uri, ArJsonRequestHandlerFunction onRequest)
-        : _uri(uri), _method(HTTP_POST | HTTP_PUT | HTTP_PATCH), _onRequest(onRequest), _maxContentLength(16384) {}
+        : _uri(uri), _method(HTTP_GET | HTTP_POST | HTTP_PUT | HTTP_PATCH), _onRequest(onRequest), _maxContentLength(16384) {}
 #endif
 
     void setMethod(WebRequestMethodComposite method) { _method = method; }
@@ -211,22 +211,29 @@ class AsyncCallbackJsonWebHandler : public AsyncWebHandler {
       if (!_onRequest)
         return false;
 
-      if (!(_method & request->method()))
+      WebRequestMethodComposite request_method = request->method();
+      if (!(_method & request_method))
         return false;
 
       if (_uri.length() && (_uri != request->url() && !request->url().startsWith(_uri + "/")))
         return false;
 
-      if (!request->contentType().equalsIgnoreCase(JSON_MIMETYPE))
+      if (request_method != HTTP_GET && !request->contentType().equalsIgnoreCase(JSON_MIMETYPE))
         return false;
 
       request->addInterestingHeader("ANY");
       return true;
     }
 
     virtual void handleRequest(AsyncWebServerRequest* request) override final {
+      if((_username != "" && _password != "") && !request->authenticate(_username.c_str(), _password.c_str()))
+        return request->requestAuthentication();
       if (_onRequest) {
-        if (request->_tempObject != NULL) {
+        if (request->method() == HTTP_GET) {
+          JsonVariant json;
+          _onRequest(request, json);
+          return;
+        } else if (request->_tempObject != NULL) {
 
 #if ARDUINOJSON_VERSION_MAJOR == 5
           DynamicJsonBuffer jsonBuffer;