ObjectMapper mapper = new ObjectMapper();
ObjectNode jsonNode1 = mapper.createObjectNode();
ObjectNode jsonNode2 = mapper.createObjectNode();
jsonNode2.put("id", id);
jsonNode2.set("msg", "hello");
jsonNode1.put("sernum", 123456);
jsonNode1.put("method", "MethodName");
jsonNode1.set("params", jsonNode2);

public static ObjectNode compileJson(ObjectNode objectNode, Object ... args) {
String fieldName = "";
for(int i=0; i<args.length;i++){
    if(i % 2 == 0){
        fieldName = args[i].toString();
    } else {
        switch(args[i].getClass().getCanonicalName()){
            case "com.fasterxml.jackson.databind.node.ObjectNode":
                objectNode.set(fieldName, (ObjectNode) args[i]);
                break;
            case "java.lang.String":
                objectNode.put(fieldName, (String)args[i]);
                break;
            case "java.lang.Long":
                objectNode.put(fieldName, (Long) args[i]);
                break;
            default:
                break;
        }
    }
}
return objectNode;
}    

ObjectMapper mapper = new ObjectMapper();
ObjectNode jsonNode1 = mapper.createObjectNode();
ObjectNode jsonNode2 = mapper.createObjectNode();
authRequestJsonNode = compileJson(jsonNode1, "params", jsonNode2 , "method", "MethodName");