measureJson()
Description
Computes the length of the minified JSON document that serializeJson() produces, excluding the null-terminator.
This function is handy to fill the Content-Length header in an HTTP message.
Signatures
size_t measureJson(const JsonDocument& doc); Arguments
doc: the JsonDocument to serialize (in fact, you can also use a JsonArray, a JsonObject, or a JsonVariant).
Return value
The number of characters that serializeJson() produces, excluding the null-terminator.
Example
// Send headers client.println("Content-Type: application/json"); client.print("Content-Length: "); client.println(measureJson(doc)); // Terminate headers client.println(); // Send body serializeJson(doc, client); 