Arduinojson: How to convert a JSON object to String or Char*

[ghost]

Thank you so much for your nice work.

I am trying to use your lib to send data over internet. My problem is that
i want to convert a JSON object msg to String or Char* before sending it to internet. However, i don't know how it does.
Hope you can help me.

[tarzan115]

#include <ArduinoJson>
StaticJsonBuffer<SERVER_DATA_JSON_SIZE> jsonBuffer;
JsonObject& root = jsonBuffer.parseObject(jsonFromServer);

const char* yourstring = root["your object"];

or

#include <ArduinoJson>
StaticJsonBuffer<SERVER_DATA_JSON_SIZE> jsonBuffer;
JsonObject& root = jsonBuffer.parseObject(jsonFromServer);

struct DataFromServer
{
     const char* yourString;
     // something
}

DataFromServer data;
data.yourString = root["your object"];

I hope this will help you do that 😄

[ghost]

@tarzan115: Thank you, Luong.
Your code is only for parsing a JSON object of the received msg. I know about this.
However, in my case, i want to convert a JSON object msg to String before i send this msg to internet.

[tarzan115]

here you are 😃

#include <ArduinoJson>
StaticJsonBuffer<CLIENT_DATA_JSON_SIZE> jsonBuffer;
JsonObject& root  = jsonBuffer.createObject();
//do something to generate your json

char jsonChar[100];
root.printTo((char*)jsonChar, root.measureLength() + 1);

[ghost]

@tarzan115 : Thank you so much. I can run well :)

[bblanchon]

@tarzan115 There is a risk of a buffer overrun in your last sample.

Here is the correct code:

char jsonChar[100];
root.printTo(jsonChar);
// or root.printTo(jsonChar, sizeof(jsonChar)); if you want to be more explicit

Note that you can also write to a String:

String jsonStr;
root.printTo(jsonStr);

See:

• API Reference: JsonObject::printTo()

[ghost]

@bblanchon : Thank you so much

[rizban114406]

include

int8_t answer;
void setup() {
Serial.begin(9600);
setNetworkGSM();

}

void loop() {
char body[200];
char response[100];
DynamicJsonBuffer jBuffer;
JsonObject& root = jBuffer.createObject();
JsonObject& root2 = jBuffer.createObject();
JsonArray& data = root.createNestedArray("data");
root2["userid"] = 1;
root2["trip_reference"] = 12434243;
root2["latitude"] = "23.7907832";
root2["longitude"] = "90.4090195";
root2["date"] = "20160510";
root2["time"] = "12:10:02";
root2["speed"] = "100";
root2["distance"] = "100";
data.add(root2);
root.printTo(body);
//Serial.println(body);

doHttpRequests(body,response);
Serial.println(response);
}
void setNetworkGSM()
{
delay(10000);
while (sendATcommand("AT+CREG?", "+CREG: 0,1", 2000) == 0);
sendATcommand("AT+SAPBR=3,1,"Contype","GPRS"", "OK", 2000);
sendATcommand("AT+SAPBR=3,1,"APN","internet"", "OK", 2000);
while (sendATcommand("AT+SAPBR=1,1", "OK", 20000) == 0)
{
delay(5000);
}
}
void doHttpRequests(char* body, char* response)
{
answer = sendATcommand("AT+HTTPINIT", "OK", 10000);
//String data = body;
if (answer == 1)
{
answer = sendATcommand("AT+HTTPPARA="CID",1", "OK", 5000);
if (answer == 1)
{
char aux_str[300];
sprintf(aux_str, "AT+HTTPPARA="URL","http://Server_IP_Address/carcopolo_arduino/Json_index.php?tag=%s&data=%s","insertdevicedata",body);
Serial.print(aux_str);
answer = sendATcommand(""", "OK", 10000);
if (answer == 1)
{
answer = sendATcommand("AT+HTTPACTION=0", "+HTTPACTION: 0,200", 15000);
if (answer == 1)
{
answer = sendATcommand("AT+HTTPREAD", "+HTTPREAD:", 35000);

  if(answer == 1)
  {
    readResponse(response,10000);
  }
}

}
}
}
sendATcommand("AT+HTTPTERM", "OK", 5000);
}

Here is my code. I have made a json object and copied it to a character array named body to send it to the server via get request. I have checked the serial monitor and it prints perfectly.
AT+HTTPPARA="URL","
http://Server_IP_Address/carcopolo_arduino/Json_index.php?tag=insertdevicedata&data={
"data":[{"userid":1,"trip_reference":12434243,"latitude":"23.7907832","longitude":"90.4090195","date":"20160510","time":"12:10:02","speed":"100","distance":"100"}]}"

But I am getting an Error response. I have copied the url and tested it in a browser and it worked fine. Can you please tell me what mistake i have done that i am getting this error??? thanks in advance.