The below post explains how to write json data to file using JsonGenerator. JsonGenerator writes the data to a file in streaming way, helping the developer using the api to avoid creating an object representation of the data.
We can get an instance of JsonGenerator with the help of an instance of JsonFactory as shown below.

JsonFactory jsonFactory = new JsonFactory();
JsonGenerator jsonGenerator = jsonFactory.createGenerator(fw);

where fw is a FileWriter

The methods of JsonGenerator that are used are as mentioned below
1) writeStartObject sends the character “{” to the stream marking the start of the object.
2) writeEndObject sends the character “}” to the stream marking the end of the object.
3) writeStartArray sends the character “[” to the stream marking the start of the array.
4) writeEndArray sends the character “]” to the stream marking the end of the array.
5) writeObjectField sends the field name and its value together to the stream.
6) writeFieldName sends only the field name to the stream.

Main Code

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;

public class ProcessingDemo5 {
    public static void main(String[] args) throws IOException {
        JsonFactory jsonFactory = new JsonFactory();
        File file = new File("jsondata5.json");
        try(FileWriter fw = new FileWriter(file);) {
            JsonGenerator jsonGenerator = jsonFactory.createGenerator(fw);
            jsonGenerator.writeStartObject();
                jsonGenerator.writeObjectField("firstName", "Duke");
                jsonGenerator.writeObjectField("lastName", "Java");
                jsonGenerator.writeObjectField("age", 18);
                jsonGenerator.writeObjectField("streetAddress", "100 Internet Dr");
                jsonGenerator.writeObjectField("city", "JavaTown");
                jsonGenerator.writeObjectField("state", "JA");
                jsonGenerator.writeObjectField("postalCode", "12345");
                jsonGenerator.writeFieldName("phoneNumbers");
                jsonGenerator.writeStartArray();
                    jsonGenerator.writeStartObject();
                        jsonGenerator.writeObjectField("Mobile", "111-111-1111");
                    jsonGenerator.writeEndObject();
                    jsonGenerator.writeStartObject();
                    jsonGenerator.writeObjectField("Home", "222-222-2222");
                jsonGenerator.writeEndObject();
                jsonGenerator.writeEndArray();
                jsonGenerator.writeFieldName("numbers");
                jsonGenerator.writeStartArray();
                    jsonGenerator.writeNumber(1);
                    jsonGenerator.writeNumber(2);
                    jsonGenerator.writeNumber(3);
                    jsonGenerator.writeNumber(4);
                jsonGenerator.writeEndArray();
            jsonGenerator.writeEndObject();
            
            jsonGenerator.flush();
            jsonGenerator.close();
        }
    }
}

Output

{“firstName”:”Duke”,”lastName”:”Java”,”age”:18,”streetAddress”:”100 Internet Dr”,”city”:”JavaTown”,”state”:”JA”,”postalCode”:”12345″,”phoneNumbers”:[{“Mobile”:”111-111-1111″},{“Home”:”222-222-2222″}],”numbers”:[1,2,3,4]}