public class Main {

    public static class A {

        public Integer i1;
        public Integer i2;
    }

    public static void main(String[] ignore) {
        Config build = JsoniterSpi.getCurrentConfig().copyBuilder()
                .indentionStep(2)
                .build();

        JsoniterSpi.setDefaultConfig(build);
        JsoniterSpi.setCurrentConfig(build);

        System.out.println(JsonStream.serialize(new A()));
    }
}