BeginTrans, CommitTrans, and RollbackTrans Methods Example (VJ++)

BeginTrans, CommitTrans, and RollbackTrans Methods Example (VJ++)

This example changes the book type of all psychology books in the Titles table of the database. After the BeginTrans method starts a transaction that isolates all the changes made to the Titles table, the CommitTrans method saves the changes. You can use the Rollback method to undo changes that you saved using the Update method.

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

public class BeginTransX
{
    // The main entry point for the application.

    public static void main (String[] args)
    {
        BeginTransX();
        System.exit(0);
    }

    // BeginTransX function
    static void BeginTransX()
    {
        // Define ADO Objects.
        Connection cnConn1 = null;
        Recordset rstTitles = null;

        //Declarations.
        String strCnn = "Provider=sqloledb;Data Source=srv;"
            + "Initial Catalog=pubs;User Id=sa;Password=;";
        String strTitle;
        String strType;
        BufferedReader in = 
            new BufferedReader (new InputStreamReader (System.in));
        String line = null;
        String strMessage="";
        int intChoice = 0;
        int recordDisplaySize = 15;
        int recordCount = 0;

        try
        {
            // Open a connection.

            cnConn1 = new Connection();
            cnConn1.open(strCnn,"","",AdoEnums.CommandType.UNSPECIFIED);

            // Open the Titles table.
            rstTitles = new Recordset ();
            rstTitles.setCursorType(AdoEnums.CursorType.DYNAMIC);
            rstTitles.setLockType(AdoEnums.LockType.PESSIMISTIC);
            rstTitles.open("titles",cnConn1,AdoEnums.CursorType.DYNAMIC ,
                AdoEnums.LockType.PESSIMISTIC ,AdoEnums.CommandType.TABLE );

            rstTitles.moveFirst();
            cnConn1.beginTrans();

            // Loop through recordset and ask user if he/she wants
            // to change the type for a specified title.

            while (!rstTitles.getEOF())
            {
                strType = rstTitles.getField("type").getString().trim();
                if ((rstTitles.getField("type").getString().
                    trim()).compareTo("psychology")== 0)
                {
                    strTitle = rstTitles.getField("title").getString().trim();
                    System.out.println("\nTitle : " + strTitle + "\n\n" 
                        +  "Change type to self help (1 -> Yes / 2 -> No) ?");
                    // Change the title for the specified book.
                    line = in.readLine().trim();
                    intChoice = Integer.parseInt(line);
                    if ( intChoice == 1)
                    {
                        rstTitles.getField("type").setString("self_help");
                        rstTitles.update();
                    }
                }
                rstTitles.moveNext();
            }

            // Ask if the user wants to commit to all the 
            // changes made above.
            System.out.println
                ("\n\nSave all changes (1 -> Yes / 2 -> No) ?");
            line = in.readLine().trim();
            intChoice = Integer.parseInt(line);
            if ( intChoice == 1)
                cnConn1.commitTrans();
            else
                cnConn1.rollbackTrans();

            // Print current data in recordset.
            rstTitles.requery();
            rstTitles.moveFirst();

            while(true)
            {
                strMessage = strMessage +"\n " + 
                    rstTitles.getField("title").getString()+" - "
                    + rstTitles.getField("type").getString() ;

                if ( recordCount == recordDisplaySize)
                {
                    System.out.println(strMessage);
                    System.out.println("\n\nPress <Enter> key to continue..");
                    line = in.readLine();
                    strMessage = "";
                    recordCount = 0;
                }
                recordCount++;
                rstTitles.moveNext();
                if(rstTitles.getEOF())
                {
                    System.out.println(strMessage);
                    break;
                }
            }
            System.out.println("\n\nPress <Enter> key to continue..");
            line = in.readLine();

            // Restore original data because this 
            // is a demonstration.
            rstTitles.moveFirst();
            while (!rstTitles.getEOF())
            {
                if ((rstTitles.getField("type").getString().
                    trim().compareTo("self_help"))== 0)
                {
                    rstTitles.getField("type").setString("psychology");
                    rstTitles.update();
                }
                rstTitles.moveNext();
            }
            //Cleanup objects before exit.
            rstTitles.close();
            cnConn1.close();
        }
        catch( AdoException ae )
        {
            // Notify user of any errors that result from ADO.

            // Check for null pointer for connection object.
            if(rstTitles.getActiveConnection()==null)
                System.out.println("Exception: " + ae.getMessage());

            // As passing a Recordset, check for null pointer first.
            if (rstTitles != null)
            {
                PrintProviderError(rstTitles.getActiveConnection());
            }
            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");
    }
}