使用Hibernate选择最常用的值

Question

@Entity
public class car {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id_car;
    @OneToOne
    private repair id_repair;
}

@Entity
public class repair {
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private int id_repair;
   @OneToOne
   @JoinColumn(name="id_car")
   private car id_car;
}

我写了sql查询，这是我想收到的东西

SELECT id_car,
       COUNT(*) AS c
FROM   repair
GROUP  BY id_car
ORDER  BY c DESC
LIMIT  5

如何使用Hibernate实现这一目标？我希望获得'id_car'和出现次数。

Answer 1

List results = session.createCriteria(Car.class)
    .setProjection( Projections.projectionList()
        .add( Projections.rowCount(),"rCount")
        .add( Projections.groupProperty("id_car") )
    )
    .addOrder(Order.desc("rCount") )
    .setMaxResults(5)
    .list();

Answer 2

Criteria cr = session.createCriteria(Repair.class)
.setProjection(Projections.projectionList()
    .add(Projections.groupProperty("id_car"))
    .add(Projections.rowCount(), "rCount"))
.addOrder(Order.asc("rCount"))
.setMaxResults(5);

if(cr.list().size() > 0) {
    for(Object o : cr.list()) {
        Object[] row = (Object[]) o;
        // Here row[0] will have id_car and 
        // row[1] will have the number of entry in the database.
    }
}