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Cancel Method Example (VJ++)
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Cancel Method Example (VJ++)

 

This example uses the Cancel method to cancel a command executing on a Connection object if the connection is busy.

// 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 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");
   }
}

// EndCancelJ
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