How to throw Attribute Level Validation in AMimpl

In Application Module

import oracle.apps.fnd.framework.OAAttrValException;

if (EndDate == null) // throwing Attribute Level Validation if the endDate is NULL

          {
              throw new OAAttrValException(OAAttrValException.TYP_VIEW_OBJECT,
                "xxIncreaseWorkVO1",
                 rowi.getKey(),
                 "RoleEndDate",
                 rowi.getAttribute("RoleEndDate"),
                 "PA",
                 "XX_ROLE_ED_NOT_BLANK");
          }

Note: Don't forget to create one Primary Key in VO.