java会话。保存更新具有错误ID的实体

Question

我有一个简单的pojo员工：

@Entity
@Table(name = "employee")
public class Employee {

    @Id@GeneratedValue(strategy=GenerationType.SEQUENCE, generator = "id_Sequence")
    @SequenceGenerator(name = "id_Sequence", sequenceName = "emp_sequence")
    @Column(name = "id")
    private Integer id;

    @Column(name = "name")
    private String name;

    @Column(name = "age")
    private Integer age;

    public Employee() {
        /*
            Just a no-arg constructor for an Entity
        */
    }

    public Employee(Integer id, String name, Integer age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public Employee(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Employee: " + this.id + ", " + this.name + ", " + this.age;
    }

}

当我尝试使用会话在数据库中保存员工时。保存（e）； 所有对象都使用错误的ID更新

将员工添加到数据库的代码：

public static void main(String[] args) {

        Employee em1 = new Employee("Mary Smith", 25);
        Employee em2 = new Employee("John Aces", 32);
        Employee em3 = new Employee("Ian Young", 29);

        System.out.println(" =======CREATE =======");
        create(em1);
        create(em2);
        create(em3);
        System.out.println(" =======READ =======");
        List<Employee> ems1 = read();
        for(Employee e: ems1) {
            System.out.println(e.toString());
        }

    public static Integer create(Employee e) {
        Session session = getSessionFactory().openSession();
        session.beginTransaction();
        session.save(e);
        session.getTransaction().commit();
        session.close();
        System.out.println("Successfully created " + e.toString());
        return e.getId();

    }

    public static List<Employee> read() {
        Session session = getSessionFactory().openSession();
        @SuppressWarnings("unchecked")
        List<Employee> employees = session.createQuery("FROM Employee").list();
        session.close();
        System.out.println("Found " + employees.size() + " Employees");
        return employees;

    }
}

SQL日志：

=======CREATE =======
Hibernate: select emp_sequence.nextval from dual
Hibernate: insert into employee (age, name, id) values (?, ?, ?)
Successfully created Employee: 200, Mary Smith, 25
Hibernate: insert into employee (age, name, id) values (?, ?, ?)
Successfully created Employee: 201, John Aces, 32
Hibernate: insert into employee (age, name, id) values (?, ?, ?)
Successfully created Employee: 202, Ian Young, 29
 =======READ =======
Hibernate: select employee0_.id as id1_0_, employee0_.age as age2_0_, employee0_.name as name3_0_ from employee employee0_
Found 3 Employees
Employee: 7, Ian Young, 29
Employee: 5, Mary Smith, 25
Employee: 6, John Aces, 32

从日志中可以看到，持久化实体中更新的员工ID分别为200、201和202 其中，来自DB的实际ID为7、8和9