MDAC 2.5 SDK - ADO

IsolationLevel and Mode Properties Example (VJ++)

See Also

This example uses the Mode property to open an exclusive connection, and the IsolationLevel property to open a transaction that is conducted in isolation of other transactions.

import com.ms.wfc.data.*;
import java.io.*;

public class IsolationLevelX
{
// The main entry point for the application.
public static void main (String[] args)
{
   IsolationLevelX();
   System.exit(0);
}

// IsolationLevelX Function

static void IsolationLevelX()
{
   // Define ADO Objects
   Connection cnn1 = null;
   Recordset rstTitles = null;

   // Assign connection string to variable
   String strCnn = "Provider=sqloledb;Data Source=srv;"+
               "Initial Catalog=Pubs;User Id=sa;Password=;";

   // Declarations
   BufferedReader in = 
      new BufferedReader ( new InputStreamReader(System.in));
   String line = null;

   try
   {
      // Open connection and Titles table
      cnn1 = new Connection();

      cnn1.setMode(AdoEnums.ConnectMode.SHAREEXCLUSIVE);
      cnn1.setIsolationLevel(AdoEnums.IsolationLevel.ISOLATED);
      cnn1.open(strCnn);

      rstTitles = new Recordset();
      rstTitles.setCursorType(AdoEnums.CursorType.DYNAMIC);
      rstTitles.setLockType(AdoEnums.LockType.PESSIMISTIC);
      rstTitles.open("Titles", cnn1, AdoEnums.CursorType.DYNAMIC, 
         AdoEnums.LockType.PESSIMISTIC);

      cnn1.beginTrans();

      // Display the connection mode
      if (cnn1.getMode() == AdoEnums.ConnectMode.SHAREEXCLUSIVE)
         System.out.println("\n\tConnection mode is exclusive");
      else
         System.out.println("\n\tConnection mode is not exclusive");
      System.out.println("\nPress <Enter> to continue..");
      in.readLine();

      // Display the Isolation level
      if ( cnn1.getIsolationLevel() == AdoEnums.IsolationLevel.ISOLATED)
         System.out.println("\tTransaction is Isolated\n");
      else
         System.out.println("\tTransaction is not Isolated\n");
      System.out.println("\nPress <Enter> to continue..");
      in.readLine();

      // Change the type of psychology titles
      while(!rstTitles.getEOF())
      {

         if(rstTitles.getField("Type").getString().trim().
            equals(new String("psychology")))
         {
            rstTitles.getField("Type").setString("self_help");
            rstTitles.update();
         }
         rstTitles.moveNext();

      }

      // Print current data in recordset
      rstTitles.requery();
      while(!rstTitles.getEOF())
      {
         System.out.println(rstTitles.getField("Title").getString() + 
            " - " + rstTitles.getField("Type").getString() );
         rstTitles.moveNext();
      }
      System.out.println("\nPress <Enter> to continue..");
      in.readLine();

      // Restore original data
      cnn1.rollbackTrans();

      // Cleanup objects before exit
      rstTitles.close();
      cnn1.close();
   }
   catch(AdoException ae)
   {
      // Notify the user of any errors that result from ADO

      // As passing a connection, check for null pointer first
      if(cnn1 !=null)
      {
         PrintProviderError(cnn1);
      }
      else
      {
         System.out.println("Exception:" + ae.getLocalizedMessage());
      }
   }

   // 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");
   }
}