SSH failed to lazily initialize a collection of role: com.db.tarena.crm.product.entity.Product.order, no session or session was

一对多  customer -->Order 
<set name="set"  inverse="true" cascade="all-delete-orphan"  > 
  <key column="customer_id"/> 
  <one-to-many class="com.db.tarena.crm.order.entity.Order"/> 
</set> <many-to-one name="customer" column="customer_id" 
cascade="save-update" class="com.db.tarena.crm.customer.entity.Customer"/> 多对多 Order-->Product Order 
<set name="product" table="crm_order_product"  cascade="save-update" inverse="true" lazy="false"  > 
      <key column="order_id" /> 
  <many-to-many class="com.db.tarena.crm.product.entity.Product" column="product_id"/> 
      </set> 
Product 
<set name="order" table="crm_order_product" cascade="save-update"  > 
        <key column="product_id" /> 
        <many-to-many class="com.db.tarena.crm.order.entity.Order" 
        column="order_id"  > </many-to-many> 
      </set> 
测试类ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml"); 
OrderService os=(OrderService) ac.getBean("orderService"); 
ProductService ps=(ProductService) ac.getBean("productService"); 
CustomerService cs=(CustomerService) ac.getBean("customerService"); 
try { 
Order order=new Order(); 
order.setOrder_Note("O(∩_∩"); 
Product product=ps.get(1); 
Customer cus=cs.getCustomer(23); 
order.addProduct(product); //这里报错了题目上的错帮帮忙    ..好像这里没又Session
} catch (Exception e) { 
e.printStackTrace(); 
}