如何在Hibernate中爲子查詢的結果行提供別名？

Question

實例類：

public Class Order{ 
    private Integer id; 
    private Customer customer; 
} 

public Class Customer{ 
    private Integer id; 
    private String name; 
} 

例子查詢，我想在PostgreSQL的語法來執行：

SELECT order_alias.id 
FROM (select * from order where customer is not null) order_alias 
WHERE order_alias.customer < 10; 

我怎樣才能做到這一點的休眠？

我問這個問題的原因是因爲當customer屬性爲null時，Hibernate似乎會拋出一個「Unknown entity：null」錯誤。

這就是我試圖用標準做：

DetachedCriteria dc = DetachedCriteria.forClass(Order.class, "o"); 
dc.add(Restrictions.lt("o.customer.id", 10); 
dc.setProjection(Projections.property("o.id"); 

Criteria query = Session.createCriteria(OtherClass.class, "oc"); 
query.add(Subqueries.propertyIn("oc.id", dc); 
List<OtherClass> listOC = query.list(); 

而且我得到這似乎是從線2

Answer 1

未來可以定義別名並使用它的錯誤。像這樣

DetachedCriteria dc = DetachedCriteria.forClass(Order.class, "o"); 
dc.createAlias("customer", "customer"); 
dc.add(Restrictions.lt("customer.id", 10); 
dc.setProjection(Projections.property("o.id");