What's New in Uniface 10.4.02

Exception handling is a significant enhancement to the Uniface scripting language that makes it easier for you to create maintainable, robust, and readable code. It removes the need for inline error checking on each statement and enables you to encapsulate the error handling into centralized routines.

Currently, when a ProcScript statement or function causes a runtime error, Uniface sets $procerror and $procerorcontext. Typically, you need to add ProcScript after the instruction to check for errors and deal with them. If this does not happen, errors are ignored and code execution continues.

When exception handling is enabled, a ProcScript statement or function that results in a runtime error causes Uniface to stop code execution and throw an exception that contains the ProcScript error. A thrown exception needs to be caught to deal with the error. If it is not caught, Uniface exits with an uncaught exception.

Exceptions provide a fail fast mechanism that makes it easier for you to find programming mistakes and to identify configuration errors and environment failures. It ensures that applications in a non-controlled state do not continue running, with the risk of unnoticed data corruption and security vulnerabilities.

You can enable exceptions on a per module basis using the throws declaration, or using try-catch blocks. This enables you to take advantage of the new exception handling feature without interfering with existing code. You can also throw custom exceptions using the throw and throw/list commands.

For more information, see Runtime Error Handling in ProcScript, Exception Handling, Custom Exception Handling, and Best Practices for using Exceptions in Uniface.

In this release, the new exception handling feature includes:

• New ProcScript commands to control and implement exception handling:
  • throws—declares that any runtime error ($procerror) that occurs in the module will be regarded as an exception. For more information, see throws.
  • try-endtry—block declaration that specifies the code that can throw an exception. For more information, see try.
  • catch—specifies code within the try block that will handle any resulting exceptions. For more information, see catch.
  • throw, throw/list— throw a custom exception value. For more information, see throw and throw/list.
• $procerrorcontext has been enhanced to include the call stack when a module throws an exception, and the return value for selected web request triggers. The call stack describes the stack of commands that were executed until the command that caused the exception, allowing you to quickly trace which module and instructions caused the exception. For more information, see $procerrorcontext and ProcScript Call Stack.
• For the preActivate trigger, $procerrorcontext has been enhanced to indicate whether the exception was caused by a negative return value or an actual exception. For more information, see trigger preActivate.
• Default reporting on uncaught exceptions—when an uncaught exception occurs, Uniface reports the exception details( $procerrorcontext) in a readable format so that you can quickly see what is wrong and fix the problem.
  

  For interactive GUI and CHUI applications, the information is displayed in a dialog, else exception details are written to the log file. This dialog can be suppressed using the $SUPPRESS_UNCAUGHT_EXCEPTION_DIALOG assignment setting. For more information, see $SUPPRESS_UNCAUGHT_EXCEPTION_DIALOG.

  In the Web Application Server, Uniface now includes exceptions as part of the response to the web request. You can customize this reporting with the USYSHTTP component.

• Updated templates which are exception-enabled by default.

  When creating new objects, all triggers and operations include the throws statement, enabling exceptions for new development. These templates are delivered in the utemplates.xml file, located in the uniface\misc directory of your Uniface installation.

You can find an online course on How to Use Exceptions in ProcScript on the Rocket^® Uniface elearning site (learn.uniface.com).