This class Contains methods used to serialize objects into JSON content using the standard JSON encoding. There are number of methods available to create a JSON string as per the request we want to generate for API.
The System.JSONGenerator class is provided to enable the generation of standard JSON-encoded content and gives you more control on the structure of the JSON output.
For the following JSON result type.
{
"type": "Email",
"templateName": "Basic Template 1",
"locationID": "346345",
"from": {
"name": "Jane Smith",
"email": "janesmith@gmail.com"
},
"to": {
"name": "John Doe",
"email": "johndoe@gmail.com",
"phone": "6501235678"
},
"sourceIDs": [
"FACEBOOK"
],
"variables": [
{
"name": "recipient-name",
"value": "John"
},
{
"name": "recipient-last",
"value": "Doe"
}
]
}
The following is the code to generate above JSON
JSONGenerator gen = JSON.createGenerator(true);
gen.writeStartObject();
gen.writeStringField('type','Email');
gen.writeStringField('templateName','Basic Template'); gen.writeStringField('locationID',346345);
gen.writeFieldName('from');
gen.writeStartObject();
gen.writeStringField('name', 'Jane Smith');
gen.writeStringField('email','janesmith@gmail.com');
gen.writeEndObject();
gen.writeFieldName('to');
gen.writeStartObject();
gen.writeStringField('name', 'John Doe');
gen.writeStringField('email', 'johndoe@gmail.com');
gen.writeStringField('phone', '6501235678');
gen.writeEndObject();
// for single variable
gen.writeFieldName('variables');
gen.writeStartArray();
gen.writeStartObject();
gen.writeStringField('name', 'recipient-name');
gen.writeStringField('value', 'John');
gen.writeEndObject();
gen.writeEndArray();
gen.writeFieldName('sourceIDs');
gen.writeStartArray();
gen.writeString('Salesforce');
gen.writeEndArray();
gen.writeEndObject();
For precise information about the JSON Click on the link .
Salesforce vines 