Cancel Method Example (VJ++)

Cancel Method Example (VJ++)

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

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=srv;"
            + "Initial Catalog=Pubs;User Id=sa;Password=;";

        // 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();

            // Cleanup objects before exit.
            cnConn1.close();

        }
        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);
        }
    }

    // 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");
    }
}