In this article we'll examine how to handle a Jaguar CORBA_TRANSACTION_ROLLEDBACK exception that is thrown when a Jaguar transaction is aborted. We'll use the BTFBank sample application developed in an article I wrote for PBDJ in October 1999 (Vol. 6, issue10). This example is written in PowerBuilder, but the technique covered here is relevant for any Jaguar client (Java, Web, etc.) or Jaguar component that's involved in a transaction.

When developing a Jaguar component that uses Jaguar transactions, a CORBA_TRANSACTION_ROLLEDBACK exception is generated each time a transaction managed by the Jaguar server is aborted and rolled back. A transaction is marked as requiring a ROLLBACK by a PowerBuilder component's invoking the SetAbort function on the TransactionServer object.

This exception is thrown when the method that's called on a Jaguar component causes the transaction to be rolled back. In a PowerBuilder client this exception is captured by the connection object error event. If the exception isn't handled, the client application will terminate. As a result of throwing the exception, the method return value and any arguments passed by reference (output parameters) are unusable, making it difficult to handle such situations gracefully.

This situation is best illustrated with an example. In our BTFBank example we were able to deposit, withdraw and transfer money from a bank account. In this example a withdrawal of money was canceled if the account didn't have enough funds or wasn't found, or if the SQL to update the database failed. In all cases the SetAbort function was invoked to terminate the transaction. However, in the last article we didn't return a very useful message that would indicate to the client that called the withdrawal why it had failed. The code in Listing 1 modifies the function to accept by reference a string argument in which a message can be returned to be displayed to the user.

On the BTFBank client window we can make the following changes to the call to the withdraw method on the account component so the message returned by the method call is displayed with a MessageBox.

// Withdraw command button
int li_rc
int li_acct, li_tellerid
decimal ld_amount
string ls_msg

li_tellerid = Integer(sle_tellerid.text)
li_acct = Integer(sle_withdraw_account.text)
ld_amount = Real(sle_withdraw_amount.text)

li_rc=in_account.withdraw(li_acct, ld_amount, ls_msg)
IF li_rc <> 1 THEN
MessageBox("BTFBank",ls_msg)
END IF