Using Simple Query statement in ADF

    private static BigDecimal getUserId(String userName, BaseAMImpl am){
       
        PreparedStatement pStatement = null;
          try {
              String sql = "select user_id from fnd_user where UPPER(user_name) like upper(?)";
              pStatement = am.getDBTransaction().createPreparedStatement(sql, 1);
              pStatement.setString(1, userName);
              ResultSet result = pStatement.executeQuery();
              if (result.next()) {
                  BigDecimal userId = result.getBigDecimal("user_id");
                  return userId;
              }
          } catch (Exception e) {
                e.printStackTrace();
          } finally {
              try {
                  pStatement.close();
              } catch (Exception e) {
                  e.printStackTrace();
              }
          }
          return null;
    }