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Building Our Order Processing Page (cont'd)

Page 18 of 22 - Chapter 14

If all has gone without error then we can start processing the order items. We create the command object we will use to execute the AddOrderItem stored procedure then we append the parameters.

// check if stored procedure executed ok
   // abort transaction if failed
   if (loCommand.Parameters("RV") != 0)
   {

      // get Stored Procs return VALUE
      iErrorNo = loCommand.Parameters("RV");
      ObjectContext.SetAbort;
   }
   else
   {
      // Retrieve CustId and OrderId from
      // stored procs output variables
      iCustId = loCommand.Parameters("CustId");
      iOrderId = loCommand.Parameters("OrderId");

      // Create new command object
      // to add each order item detail to database
      loCommand = null;
      loCommand = Server.CreateObject("ADODB.Command");


      loCommand.CommandText = "AddOrderItem";
      loCommand.CommandType = adCmdStoredProc;
      loCommand.Name = "AddOrderItem";

      //Append Parameters @OrderId int, @ItemId int, @Qty int
      loParam = loCommand.CreateParameter("RV", adInteger, _
                                          adParamReturnValue);
      loCommand.Parameters.Append(loParam);

      loParam = loCommand.CreateParameter("OrderId", adInteger, _
                                          adParamInput,0,iOrderId);
      loCommand.Parameters.Append(loParam);

      loParam = loCommand.CreateParameter("ItemId", adInteger, _
                                          adParamInput);
      loCommand.Parameters.Append(loParam);

      loParam = loCommand.CreateParameter("Qty", adInteger, _
                                          adParamInput);
      loCommand.Parameters.Append(loParam);
      loCommand.ActiveConnection = loConn;

Having created our Command object we can reuse it as we loop through the form elements containing the ItemIds and quantities making up the order. After each item has been added using the stored procedure we check that the return value is zero indicating no errors. If there were errors then we call ObjectContext.SetAbort and break out of the loop. Calling SetAbort will roll back all the order items already added to the database as well as the customer and order details added to the database. We are therefore assured that the database will not become corrupted by half completed transactions.

Remember that a return value of 547 indicates an error due to insufficient stock and we will write the code to handle that soon. If it's any other error then the OnTransactionAbort event, which fires as a result of calling SetAbort, will redirect the response to transerror.asp – a page we have yet to create.

Assuming that all has gone well, we call SetComplete to indicate the transaction's success and to ensure the data gets committed to the database. The OnTransactionCommit event fires and the customer is directed to a page confirming the transactions success and e-mails both them and the order shipping department.

var sElementKey;
      var iItemId;
      var iQty;
      // Loop through the item form elements
      for (var iElementCounter = iItemElementStart; _
           iElementCounter <= Request.Form.Count; iElementCounter++)
      {
         sElementKey = new String(Request.Form.Key(iElementCounter));
         // if element NAME starts with ID its an item form element
         if (sElementKey.substr(3,2) == "ID")
         {
            // Get ItemId from form VALUE passed
            iItemId = parseInt _
                           (sElementKey.substring(5,sElementKey.length));

            // move to next element which is quantity VALUE for that item
            iElementCounter++;

            // get quantity
            iQty = parseInt(Request.Form(iElementCounter));

            // set command's parameters
            loCommand.Parameters("ItemId") = iItemId;
            loCommand.Parameters("Qty") = iQty;
            // execute stored procedure
            loCommand.Execute();
            // Any errors?
            if (loCommand.Parameters("RV") != 0)
            {
               // set iErrorNo, abort transaction and break out of loop
               iErrorNo = loCommand.Parameters("RV");
               ObjectContext.SetAbort;
               break;
            }
         }
      }
   }
   // only set complete if transaction complete with no errors
   if (iErrorNo == 0)
      ObjectContext.SetComplete;
}

Finally we come to the end of our order processing script and the catch part of the try statement we set at the beginning of the code. If an error occurs in our code, the statements here execute and we are able to store the description in sErrorDescription and abort the transaction which will lead to the page being redirected to transerror.asp by OnTransactionAbort.

catch(e)
{
   sErrorDescription = e;
   ObjectContext.SetAbort;
}

%>

Save the page as ProcessOrder.asp.

Building Our Order Processing Page

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