When a runtime error occurs in a PowerBuilder application, unless that error is trapped, a single application event (SystemError) fires to handle the error no matter where in the application the error happened. Although some errors can be handled in the system error event, catching the error closer to its source increases the likelihood of recovery from the error condition.
You can use exception-handling classes and syntax to handle context-sensitive errors in PowerBuilder applications. This means that you can deal with errors close to their source by embedding error-handling code anywhere in your application. Well-designed exception-handling code can give application users a better chance to recover from error conditions and run the application without interruption.
Exception handling allows you to design an application that can recover from exceptional conditions and continue execution. Any exceptions that you do not catch are handled by the runtime system and can result in the termination of the application.
PowerBuilder clients can catch exceptions thrown from EAServer components and recover from them. Components developed with PowerBuilder can also define and throw their own exception types, making them more consistent with other EAServer component types like Java.
Exception handling can be found in such object-oriented languages as Java and C++. The implementation for PowerBuilder is similar to the implementation of exception handling in Java. In PowerBuilder, the TRY, CATCH, FINALLY, THROW, and THROWS reserved words are used for exception handling. There are also several PowerBuilder objects that descend from the Throwable object.
