JPA - Entity SequenceGenerator

@Entity
@NamedQueries({
@NamedQuery(name = "Departments.findAll", query = "select o from Departments o")
})
public class Departments implements Serializable {
@Id
@Column(name="DEPARTMENT_ID", nullable = false)
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator = "DEPARTMENTS_GEN")
@SequenceGenerator(name="DEPARTMENTS_GEN", sequenceName = "DEPARTMENTS_SEQ")
private Long departmentId;
@Column(name="DEPARTMENT_NAME", nullable = false, length = 30)
private String departmentName;

// setters and getters

}