Call Procedure in OAF (2 input parameters)

Call a custom procedure. Two input parameters of type Varchar:
 OAApplicationModule oam =  pageContext.getApplicationModule(webBean);

 String sql =  "BEGIN xx_custom_pkg.custom_prc (:1,:2); END;";
                    try {
                        OracleCallableStatement cs =
                            (OracleCallableStatement)oam.getOADBTransaction().createCallableStatement(sql,
                                                                                                      2);
                        cs.setString(1, xxAttribute1Value);
                        cs.setString(2, xxAttribute2Value);
                        cs.execute();
                        cs.close();
                      }
                 catch (Exception ex) {
                        pageContext.writeDiagnostics(this,
                                                     "Error:" + ex.toString(),
                                                     OAFwkConstants.PROCEDURE);
                    }