Ejemplo del método GetRows (VJ++)

Se aplica a: Access 2013, Office 2013

En este ejemplo se usa el método GetRows para recuperar un número especificado de filas de un objeto Recordset y rellenar una matriz con los datos resultantes. El método GetRows devolverá un número de filas menor que el deseado en los dos siguientes casos: si se alcanza EOF o si GetRows ha tratado de recuperar un registro anteriormente eliminado por otro usuario. La función devuelve False sólo si se produce el segundo caso. Se requiere la función GetRowsOK para que se ejecute este procedimiento.

 
// 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