RdJson (community library)

Summary

Name	Value
Name	RdJson
Version	1.0.12
Installs	3748
License	MIT
Author	Rob Dobson
URL	https://github.com/robdobsn/ParticleRdJson
Repository	https://github.com/robdobsn/ParticleRdJson.git
Download	.tar.gz

Access JSON data on particle

Example Build Testing

Device OS Version:

This table is generated from an automated build. Success only indicates that the code compiled successfully.

Library Read Me

This content is provided by the library maintainer and has not been validated or approved.

RdJson

A library to parse and access JSON data

Usage

Examples of usage

// Example usage for RdJson library
// Rob Dobson 2017

#include "RdJson.h"

SYSTEM_MODE(AUTOMATIC);
SYSTEM_THREAD(ENABLED);

void setup() {

Serial.begin(115200);
delay(5000);
Serial.println("Example usage of RdJson library");

// Test JSON
String jsonStr = "{\"maxSpeed\":12.2, \"message\":\"This is a test\", \"a\":[0,1,2,3], \"b\":{\"c\":42} }";

// Double
Serial.printlnf("Max speed %0.3f", RdJson::getDouble("maxSpeed", 0.0, jsonStr.c_str()));

// String
String messageStr = RdJson::getString("message", "", jsonStr.c_str());
Serial.printlnf("Message %s", messageStr.c_str());

// Array - by extracting string from JSON
bool isValid = false;
jsmnrtype_t objType = JSMNR_UNDEFINED;
int objSize = 0;
String arrayJson = RdJson::getString("a", "", isValid, objType, objSize, jsonStr.c_str());
Serial.printlnf("Array %s valid %d, type %s, size %d", arrayJson.c_str(), isValid, RdJson::getObjTypeStr(objType), objSize);

// Array elements - using a simplified form of XPATH - to get element 2 of the object a use a[2]
long arrayElem = RdJson::getLong("a[2]", 0, jsonStr);
Serial.printlnf("Array element [2] = %ld", arrayElem);

// Extracting an element within a sub-object - use / separator like XPATH - also not that string will get any kind of object
String subObjStr = RdJson::getString("b/c", "", jsonStr.c_str());
Serial.printlnf("Sub-object string %s", subObjStr.c_str());

// A JSON string that is just an array
String jsonStr2 = "[0,1,2,{\"a\":1},4]";

// Entire array
String arrayJson2 = RdJson::getString("", "", isValid, objType, objSize, jsonStr2.c_str());
Serial.printlnf("Array %s valid %d, type %s, size %d", arrayJson2.c_str(), isValid, RdJson::getObjTypeStr(objType), objSize);

// Element of array - that is an object
String arrayJson3 = RdJson::getString("[3]", "", isValid, objType, objSize, jsonStr2.c_str());
Serial.printlnf("Array %s valid %d, type %s, size %d", arrayJson3.c_str(), isValid, RdJson::getObjTypeStr(objType), objSize);
}

void loop() {
}

See the examples folder for more details.

Documentation

Three basic methods are provided to access elements of a JSON string:

getString() getDouble() getLong()

getString() can be used on any kind of element - the parser simply isolates the string in the JSON and returns it.

The method setJsonStr() can be used to set a member variable to avoid passing in the base string repeatedly. Each method is available in static form and, whether or not the static form is used, the JSON is re-parsed for each call to getString, getDouble or getLong. This may be inefficient in some cases but often memory is a more valuable resource than processor cycles.

A very much simplified form of XPATH is available to access members: [] can be used to isolate an element of an array / can be used to specify sub-objects