Cancel-Methode (Beispiel) (VJ++)

Gilt für: Access 2013, Office 2013

In diesem Beispiel wird die Cancel-Methode verwendet, um einen für ein Connection-Objekt ausgeführten Befehl abzubrechen, wenn die Verbindung ausgelastet ist.

 
// BeginCancelJ 
import com.ms.wfc.data.*; 
import java.io.* ; 
 
public class CancelX 
{ 
 // The main entry point for the application. 
 
 public static void main (String[] args) 
 { 
 CancelX(); 
 System.exit(0); 
 } 
 
 // CancelX function 
 
 static void CancelX() 
 { 
 // Define command strings. 
 String strCmdChange = "UPDATE titles SET type = 'self_help' " 
 + "WHERE type = 'psychology'"; 
 String strCmdRestore = "UPDATE titles SET type = 'psychology' " 
 + "WHERE type = 'self_help'"; 
 String strCnn = "Provider='sqloledb';Data Source='MySqlServer';" 
 + "Initial Catalog='Pubs';Integrated Security='SSPI';"; 
 
 // Define ADO Objects. 
 Connection cnConn1 = null; 
 
 //Declarations. 
 boolean booChanged = false; 
 BufferedReader in = 
 new BufferedReader (new InputStreamReader(System.in)); 
 String line = null; 
 
 try 
 { 
 // Open a connection. 
 cnConn1 = new Connection(); 
 cnConn1.open(strCnn); 
 
 // Begin a transaction, then execute a command asynchronously. 
 cnConn1.beginTrans(); 
 cnConn1.execute(strCmdChange, 
 AdoEnums.ExecuteOption.ASYNCEXECUTE); 
 
 // do something else for a little while - this could be changed. 
 
 for (int intLoop = 0; intLoop < 10; intLoop++) 
 { 
 System.out.println(intLoop); 
 } 
 
 // If the command has NOT completed, cancel the execute 
 // and roll back the transaction. Otherwise, commit the 
 // transaction. 
 
 if ((cnConn1.getState() & AdoEnums.ObjectState.EXECUTING) > 0) 
 { 
 cnConn1.cancel(); 
 cnConn1.rollbackTrans(); 
 booChanged = false; 
 System.out.println("\nUpdate canceled."); 
 } 
 else 
 { 
 cnConn1.commitTrans(); 
 booChanged = true; 
 System.out.println("\nUpdate complete."); 
 } 
 
 //If the change was made, restore the data 
 // because this is a demonstration. 
 
 if(booChanged ) 
 { 
 cnConn1.execute(strCmdRestore); 
 System.out.println("\nData restored."); 
 } 
 
 System.out.println("\n\nPress <Enter> to continue.."); 
 in.readLine(); 
 } 
 catch( AdoException ae ) 
 { 
 // Notify user of any errors that result from ADO. 
 
 // As passing a connection, check for null pointer first. 
 if (cnConn1 != null) 
 { 
 PrintProviderError(cnConn1); 
 } 
 else 
 { 
 System.out.println("Exception: " + ae.getMessage()); 
 } 
 } 
 
 // System read requires this catch. 
 catch( java.io.IOException je) 
 { 
 PrintIOError(je); 
 } 
 finally 
 { 
 // Cleanup objects before exit. 
 if (cnConn1 != null) 
 if (cnConn1.getState() == 1) 
 cnConn1.close(); 
 } 
 } 
 
 // 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"); 
 } 
} 
 
// EndCancelJ