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.
// 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=srv;"
+ "Initial Catalog=Pubs;User Id=sa;Password=;";
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." );
}
}
// 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 Connection’s 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");
}
}