@Entity(access = AccessType.PROPERTY)
@Table(name = "Employee")
public class Employee implements Serializable {

    /** identifier field */
    @Id
    @Column(name = "employee_id" ,length = 20)
    private String employeeId = null;

    /** version field */
    @Version
    private int version = 0;
   
    /**
     *
     *
     */
    public Employee() {
    }

    /**
     *
     * @param employeeId
     */
    public Employee(String employeeId) {
        this.employeeId = employeeId;
    }

    /**
     *
     * @return
     */
    public int getVersion() {
       return version;
    }
   
    /**
     *
     * @return
     */
    public String getEmployeeId() {
        return this.employeeId;
    }

    /**
     *
     * @param employeeId
     */
    public void setEmployeeId(String employeeId) {
        this.employeeId = employeeId;
    }

    public String toString() {
        return "EmployeeId (" + getEmployeeId() + ")";
    }

}

...
<mapping class="example.model.Employee"/>
...