Gson deserialization

package com.zybnet.so;

import java.math.BigDecimal;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonSyntaxException;


public class GsonDeserialization {

    public static void main(String[] args) throws JsonSyntaxException, ClassNotFoundException {
        // Create the order
        Order order = new Order(new Customer("John", City.NEW_YORK), new BigDecimal("9.99"));

        // Create the envelope
        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        Envelope<Order> envelope = new Envelope<Order>(order);
        String serialized = gson.toJson(envelope);
        System.out.println(serialized);

        // Read the envelope
        Envelope<?> receivedEnvelope = gson.fromJson(serialized, Envelope.class);
        Object result = gson.fromJson(receivedEnvelope.contents, Class.forName(receivedEnvelope.clazz));
        System.out.println("Result: " + result);

        assert result.getClass().equals(Order.class);
    }

    public static class Envelope<T> {
        public String clazz;
        public JsonElement contents;
        public Envelope (T contents) {
            this.clazz = contents.getClass().getName();
            this.contents = new Gson().toJsonTree(contents, contents.getClass());
        }
    }

    public static enum City {
        NEW_YORK("New York City", "00100"),
        SAN_FRANCISCO("San Francisco", "00200");

        public String name, zip;

        City(String name, String zip) {
            this.name = name;
            this.zip = zip;
        }

        public String toString() {
            return String.format("%s, zip code: %s", name, zip);
        }
    }

    public static class Customer {
        public Customer(String name, City city) {
            this.name = name;
            this.city = city;
        }

        String name;
        City city;

        public String toString() {
            return String.format("%s from %s", name, city);
        }
    }

    public static class Order {
        public Order(Customer customer, BigDecimal total) {
            this.customer = customer;
            this.total = total;
            id = 123456789L;
        }

        Long id;
        Customer customer;
        BigDecimal total;

        public String toString(){
            return String.format("Order by %s, total $%s", customer, total);
        }
    }
}