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Exception Handler

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  • The Exception Handler element starts an action flow for handling all exceptions or exceptions of a certain type. You can define logic to handle exceptions pre-defined exceptions (like Database Exceptions), or custom exceptions (called User Exceptions) raised by your application logic.

    Set the Exception Handler's Exception property to the exception type you want to handle in the flow of the Exception Handler. To handle all types of exceptions, set the Exception property to All Exceptions.

    For example, the following flow handles the Not Registered exception:

    Exception Handler example

    There's a hierarchy of exception types in OutSystems. If you define an Exception Handler that handles a "parent" exception type, this Exception Handler can also handle any "children" exception type. Check Handle Exceptions for more information.

    In the exception-handling flow started by an Exception Handler element you can perform tasks like displaying a feedback message, logging exception details, and even raising a different type of exception.

    Check Exception Handling Mechanism to learn more about the chain of Exception Handlers that the platform searches for when an exception occurs.

    Logging exceptions

    If you set the Log Error property to Yes, the platform creates a log for the exception type configured in the Exception property, when such an exception occurs. You can check for logged exceptions in Service Center under Monitoring > Errors.

    Aborting database transactions

    When you handle an exception in an action running on server side, you can choose what happens to the database transaction by setting the Abort Transaction property of the Exception Handler:

    • Set the Abort Transaction property to Yes if you want that all the database transactions that weren't committed are aborted and changes rolled back in the database.

    • Set the Abort Transaction property to No if you want that the database transaction to continue as if no exception had occurred. This transaction is committed by the next CommitTransaction Server Action or implicitly by OutSystems, typically at the end of request execution.

    In Reactive Web and Mobile apps, the Abort Transaction property isn't available when you are handling exceptions in client side.


    Name Description Mandatory Default value Observations
    Name Identifies an element in the scope where it is defined, like a screen, action, or module. Yes
    Exception Type of exception to handle. Yes There is a call hierarchy for exceptions that determines the error handler behavior. For more info see Exception Handling Mechanism.
    Abort Transaction Set to Yes to abort the transaction and rollback changes. Yes Yes This property is only available in Traditional Web Apps or in a server-side context (for all apps).
    Log Error Set to Yes to log an error when the exception occurs. Yes Yes

    Runtime Properties

    Name Description Read Only Type Observations
    ExceptionMessage Text that explains the reason for the last error. Yes Text
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