Hibernate: @ManyToOne(fetch = FetchType.LAZY) does

问题:

I have 2 tables: Order [OrderId(PK), OrderShipmentCode, ...] and Shipment[ShipmentId(PK), ShipmentCode, ...].

In Order class, I declared shipment field as follows:

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "OrderShipmentCode", referencedColumnName = "ShipmentCode", insertable = false, updatable = false, nullable = false)
private Shipment shipment;

When I get the list of Order, the Shipment is also loaded (I saw many separate SELECT queries). But I want the Shipment to be lazy loaded, not to be fetched together with Order.

For other tables, if the referenced column is primary key then the results are as expected (Lazy-loading is used). In my case, ShipmentCode is not Primary Key of Shipment table, and lazy-loading is not used by Hibernate.

Could you show me how to accomplish that goal?

EDIT: The Query code is as bellow:

Criteria criteria = HibernateUtil.getSessionFactory().getCurrentSession().createCriteria(Order.class);
List result = criteria.list();

SQL queries are: 1 SELECT statement for Order table and a bunch of SELECT statement for Shipment

回答1:

You need to specify optional = false:

@OneToOne(optional = false, fetch = FetchType.LAZY)

or simply turn it into a @ManyToOne:

@ManyToOne(fetch = FetchType.LAZY)

回答2:

Try this:

Criteria criteria = HibernateUtil.getSessionFactory()
                                 .getCurrentSession()
                                 .createCriteria(Order.class)
                                 .setFetchMode("shipment", FetchMode.LAZY);