Hibernate取延迟关联对象

背景：
Customer和Order是一对多双向关联关系

当我们取到Customer对象后，把Session关闭，当要使用和该Customer对象关联的Order时，直接调用getOrders()方法导航到Order对象会得到异常。如下：
public static void main(String[] args) {
Customer customer = (Customer)getObject(Customer.class, new Long(26));

System.out.println("customer is detached");

for (Iterator it = customer.getOrders().iterator(); it.hasNext();) {
Order o = (Order)it.next();
System.out.println("Order Id=" + o.getId() + " orderNo=" + o.getOrderNo());
}
}

public static Object getObject(Class clazz, Long id) {
Session session = HibernateUtil.getSession();
Object obj = session.get(clazz, id);
session.close();
return obj;
}
运行以上代码，会得到以下异常。在Session关闭之后，无法取得延迟关联对象。
Exception in thread "main" org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.Customer.orders, no session

or session was closed


解决以上问题，写一个通用方法取延迟关联对象（我写在HibernateUtil类中）
public static void findLazyObjects(Object main, Object proxy) {
if (!Hibernate.isInitialized(proxy)) {
Session session = getSession();

session.update(main);

Hibernate.initialize(proxy);

session.close();
}
}

修改main方法如下
public static void main(String[] args) {
Customer customer = (Customer)getObject(Customer.class, new Long(26));

System.out.println("customer is detached");

//初始化关联对象
HibernateUtil.initLazyObjects(customer, customer.getOrders());

for (Iterator it = customer.getOrders().iterator(); it.hasNext();) {
Order o = (Order)it.next();
System.out.println("Order Id=" + o.getId() + " orderNo=" + o.getOrderNo());
}
}
/**Output：
Hibernate: select customer0_.ID as ID1_0_, customer0_.NAME as NAME1_0_ from CUSTOMERS customer0_ where customer0_.ID=?
customer is detached
Hibernate: select orders0_.CUSTOMER_ID as CUSTOMER3_1_1_, orders0_.ID as ID1_, orders0_.ID as ID2_0_, orders0_.ORDER_NO as ORDER2_2_0_,

orders0_.CUSTOMER_ID as CUSTOMER3_2_0_, orders0_.PRICE as PRICE2_0_ from ORDERS orders0_ where orders0_.CUSTOMER_ID=?
Order Id=25 orderNo=no_002
Order Id=26 orderNo=no_003
Order Id=24 orderNo=no_001
*/