使用Hibernate持久化java.util.Properties？

@Entity
@Table(name = "config")
public class Config {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ElementCollection
    @CollectionTable(name = "properties", joinColumns = @JoinColumn(name = "config_id"))
    @MapKeyColumn(name = "key")
    @Column(name = "value")
    private Map<String, String> properties = new HashMap<>();

    // getters and setters
}

public class ConfigManager {
    private static final SessionFactory sessionFactory;

    static {
        Configuration configuration = new Configuration();
        configuration.configure("hibernate.cfg.xml");
        sessionFactory = configuration.buildSessionFactory();
    }

    public static void saveConfig(Config config) {
        Session session = sessionFactory.openSession();
        session.beginTransaction();
        session.save(config);
        session.getTransaction().commit();
        session.close();
    }

    public static Config getConfig(Long id) {
        Session session = sessionFactory.openSession();
        Config config = session.get(Config.class, id);
        session.close();
        return config;
    }
}

public class Main {
    public static void main(String[] args) {
        Config config = new Config();
        config.getProperties().put("key1", "value1");
        config.getProperties().put("key2", "value2");
        ConfigManager.saveConfig(config);

        Config loadedConfig = ConfigManager.getConfig(config.getId());
        System.out.println(loadedConfig.getProperties());
    }
}