hibernate如何在类里用注解添加检查约束

@Entity@Table(name="DB_Student")@SequenceGenerator(name="stu_seq",sequenceName="stu_seq",initialValue=1,allocationSize=1)public class Student {    private int id;    private String name;    private Sex sex;    private int age;    private Date birthday;    private boolean statu;        @Id    @Column(name="stu_id")    @GeneratedValue(strategy=GenerationType.SEQUENCE,generator="stu_seq")    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }        @Enumerated(EnumType.STRING)    public Sex getSex() {        return sex;    }    public void setSex(Sex sex) {        this.sex = sex;    }    public Date getBirthday() {        return birthday;    }    public void setBirthday(Date birthday) {        this.birthday = birthday;    }    @Column(nullable=true)    public boolean isStatu() {        return statu;    }    public void setStatu(boolean statu) {        this.statu = statu;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }}