Json Library for ESP8266 and ESP32

A Simple and easy to use Json library to parse and stringify a Json object. No need to allocate buffer, no need additional setup, just create your Json object and you are done!

Example

Using Json is as simple as it should be!

Parse Json from String

Just create Json object and put the String into it's constructor.

Json      json("{\"name\":\"John\", \"age\":30, \"car\":null}");
JsonArray jsonArray("[3.14, false, \"Hello World\"]");

Adding Elements to a Json Object

Create empty Json object and fill it by calling add.

Json json;
json.add("key"     , "value");
json.add("integer" , 2);
json.add("float"   , 3.141592, 6);
json.add("boolean" , true);
json.add("null");
json.add("array"   , JsonArray()
                        .push(2)
                        .push(3.14)
                        .push(false)
                        .push("Hello"));
json.add("object"  , Json()
                        .add("key", "value")
                        .add("number", 12)
                        .add("bool", false));

Retrieving Elements from a Json Object

Retrieving element is very easy, you can cast it or just assign it to an existing variable. If such element doesn't exist, a new element with the provided key will be created. Those newly created elements will contain value null.

//Assign elements to the existing variable
String    value   = json["key"];
int       integer = json["integer"];
float     pi      = json["float"];
bool      isAlive = json["boolean"];
Json      obj     = json["object"];
JsonArray arr     = json["array"];

//Retrieve elements by casting
Serial.println((String)    json["key"]);
Serial.println((int)       json["integer"]);
Serial.println((float)     json["float"]);
Serial.println((bool)      json["boolean"]);
Serial.println((Json)      json["object"]);
Serial.println((JsonArray) json["array"]);

//Retrieve elements using template (generic)
Serial.println(json["key"].as<String>());
Serial.println(json["integer"].as<int>());
Serial.println(json["float"].as<float>());
Serial.println(json["boolean"].as<bool>());
Serial.println(json["object"].as<Json>());
Serial.println(json["array"].as<JsonArray>());

Modifying Elements of a Json Object

Assigning a direct child is very easy and straightforward. Assigning a nested object on the other hand, you need to cast it as a reference to be able to change it's value. The new value doesn't necessarily has the same type as the old value. You can assign the existing element with an arbitrary value and type.

json["key"]      = "new value";
json["integer"]  = "i am not an integer anymore";
json["float"]    = 6.28;
json["boolean"]  = "i am also not a boolean anymore";
json["object"]   = Json().add("key", "value");
json["array"]    = JsonArray().push("value");

//Nested Object
json["object"].as<Json&>()["key"] = "new value"
json["array"].as<JsonArray&>()[0] = "new value"

Miscellaneous

Other methods are described here.

//Stringify a Json object
String payload = json.toString();

//Removing element
json.remove("key");

//Get the type of the element
String type = json.getTypeString("key");

//Get the size of Json object
size_t size = json.size();

//Check whether an element does exist
bool isExist = json.contains("key");

//Attach debugger
JSUtil.attachDebugger(Serial);

//Detach debugger
JSUtil.detachDebugger();

//Iterating element
for (auto& element : json) {
    Serial.print(element.first);
    Serial.print(" ");
    Serial.print(element.second.getValue());
    Serial.print(" ");
    Serial.print(JSUtil.typeToString(element.second.getType()));
}

//Stream Json object into Serial
JSUtil.prettyPrint(Serial, json);