@generated value - 获取ID的值

Question

将车辆对象持久保存到数据库时会自动生成ID.如何在不坚持的情况下获得ID的价值？

这是代码:

public class Vehicle{

    @Id
    @GeneratedValue
    int id;
    private int year;
    private String model;
    //getters, setters
}

UPDATE

    public void updateVehicle(Vehicle vehicle) {

        em.getTransaction().begin();
        Vehicle vehicleDB = em.find(Vehicle.class, vehicle.getId());
        vehicleDB.setYear(vehicle.getYear());
        vehicleDB.setModel(vehicle.getModel());
        em.getTransaction().commit();
}

Answer 1

您不能,因为它是在持久性时由数据库生成的.在此之前,id未定义.