GetRows Method Example (VJ++)

This example uses the GetRows method to retrieve a specified number of rows from a Recordset and to fill an array with the resulting data. The GetRows method will return less than the desired number of rows in two cases: either if EOF has been reached, or if GetRows tried to retrieve a record that was deleted by another user. The function returns False only if the second case occurs. The GetRowsOK function is required for this procedure to run.

// BeginGetRowsJ
// The WFC class includes the ADO objects.

import com.ms.wfc.data.*;
import java.io.* ;
import com.ms.com.*;

public class GetRowsX 
{
    // The main entry point for the application.

   static Variant avarRecords = null;

   public static void main (String[] args)
   {
      GetRowsX();
      System.exit(0);
   }

   // GetRowsX  function

   static void GetRowsX()
   {

      // Define ADO Objects.
      Recordset rstEmployees = null;

      // Declarations.
      BufferedReader in = 
         new BufferedReader (new InputStreamReader(System.in));
      String line = null;
      String strCnn = "Provider='sqloledb';Data Source='MySqlServer';"
            + "Initial Catalog='Pubs';Integrated Security='SSPI';";

      int intRows;
      int intRecord;
      int intUBound;
      int intDisplaysize = 15;

      try
      {
         // Open recordset with names and hire dates from Employees table.
         rstEmployees = new Recordset();
         rstEmployees.open("SELECT fName, lName, hire_date " +
                        "FROM Employee ORDER BY lName", strCnn,
                        AdoEnums.CursorType.FORWARDONLY,
                        AdoEnums.LockType.READONLY,
                        AdoEnums.CommandType.TEXT);

         while(true)
         {
            // Get user input for number of rows.
            System.out.println(
            "\nEnter number of rows to retrieve. (<= 0 to Exit)");
            line = in.readLine().trim();

            // Convert string entry to int.
            intRows = Integer.parseInt(line);

            // Exit the application if intRows is negative or zero.
            if(intRows <= 0)
               break;

            // If GetRowsOK is successful, print the results,
            // noting if the end of the file was reached.
            if(GetRowsOK(rstEmployees,intRows))
            {
               SafeArray sa = avarRecords.toSafeArray();
               intUBound = sa.getUBound(2);
               if ( intRows > (intUBound + 1))
                  System.out.println("\n(Not enough records in " +
                     "Recordset to retrieve " + intRows + " rows.)");
               System.out.println("\n" + (intUBound+ 1) +
                              " records found.\n");

               // Print the retrieved data.

               for ( intRecord = sa.getLBound();
                   intRecord  <= intUBound; intRecord++)
               {

                  System.out.println(
                     " " + sa.getString(0, intRecord) + " " +
                     sa.getString(1, intRecord) + ", " +
                     sa.getString(2, intRecord));
                  if ( ((intRecord +1) % intDisplaysize) == 0)
                  {
                     System.out.println("\nPress <Enter> to continue..");
                     in.readLine();
                  }

               }
            }
            else
            {
               // Assuming the GetRows error was due to data
               // changes by another user, use Requery to
               // refresh the Recordset and start over.
               System.out.println("\nGetRows failed--retry? (Y/N)");
               if(in.readLine().trim().toUpperCase().equals("Y"))
                  rstEmployees.requery();
               else
               {
                  System.out.println("GetRows failed!");
                  break;
               }
            }

            // Because using GetRows leaves the current
            // record pointer at the last record accessed,
            // move the pointer back to the beginning of the
            // Recordset before looping back for another search.
            rstEmployees.moveFirst();
         }

         // Cleanup objects before exit.
         rstEmployees.close();

      }
      catch( AdoException ae )
      {
         // Notify user of any errors that result from ADO.

         // As passing a Recordset, check for null pointer first.
         if (rstEmployees != null)
         {
            PrintProviderError(rstEmployees.getActiveConnection());
         }
         else
         {
            System.out.println("Exception: " + ae.getMessage());
         }
      }

      // System read requires this catch.
      catch( java.io.IOException je)
      {
         PrintIOError(je);
      }

      // Display Error that the application has attempted to convert
      // a string of inappropriate format to one of the numeric types.
      catch(java.lang.NumberFormatException ne)
      {
         System.out.println(
            "Exception: Must specify an Integer value." );
      }   
      
      finally
      {
         // Cleanup objects before exit.   
         if (rstEmployees != null)
            if (rstEmployees.getState() == 1)
               rstEmployees.close();
      }

   }

   // GetRowsOK Function

   static boolean GetRowsOK(Recordset rstTemp,int intNumber)
      {
      // Store results of GetRows method in array.
      avarRecords = rstTemp.getRows(intNumber);

      // Return False only if fewer than the desired
      // number of rows were returned, but not because the
      // end of the Recordset was reached.
      if ( intNumber > (avarRecords.toSafeArray().getUBound(2)+ 1)
               && !(rstTemp.getEOF()))
         return false;
      else
         return true;

   }

   // PrintProviderError Function

   static void PrintProviderError( Connection Cnn1 )
   {
      // Print Provider errors from Connection object.
      // ErrItem is an item object in the Connections Errors collection.
      com.ms.wfc.data.Error  ErrItem = null;
      long nCount = 0;
      int  i      = 0;

      nCount = Cnn1.getErrors().getCount();

      // If there are any errors in the collection, print them.
      if( nCount > 0);
      {
         // Collection ranges from 0 to nCount - 1
         for (i = 0; i< nCount; i++)
         {
            ErrItem = Cnn1.getErrors().getItem(i);
            System.out.println("\t Error number: " + ErrItem.getNumber()
               + "\t" + ErrItem.getDescription() );
         }
      }

   }

   // PrintIOError Function

   static void PrintIOError( java.io.IOException je)
   {
      System.out.println("Error \n");
      System.out.println("\tSource = " + je.getClass() + "\n");
      System.out.println("\tDescription = " + je.getMessage() + "\n");
   }
}
// EndGetRowsJ

See Also

BOF, EOF Properties | GetRows Method | Recordset Object