java - 如何在 Hibernate 中为子查询的结果行指定别名？

Question

示例类:

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

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

我想在 PostgreSQL 语法中执行的示例查询:

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

我如何在 Hibernate 中执行此操作？

我问这个问题的原因是，当客户属性为 null 时，Hibernate 似乎会抛出“未知实体:null”错误。

这就是我试图用 Criteria 做的:

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();

我收到一个错误，似乎来自第 2 行。

Answer 1

您可以定义别名并使用它。像这样

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