Advanced Oracle PL/SQL Programming with Packages

22.1. The Challenge of Exception Handling

Do you test your own programs? If you do, I am willing to wager large sums of money that your users feel as if they are the ones doing the testing. Authors of a program cannot find all the bugs in their software. They have, in fact, an uncanny ability to unconsciously follow a path through their code that avoids all bugs and logical holes.Programmers cannot be responsible for testing their own code.

Tightly linked to proper testing is proper error handling. Even if a program does not have actual bugs, it does need to handle abnormal conditions gracefully. Yet exception handling is the last thing any of us wants to worry about when we build our PL/SQL programs. To recognize the need to write exception handlers is to acknowledge that things might go wrong. Who can afford the time and resources to focus on the negative? It is all we can do to get our programs to work properly under normal circumstances—to conform, in other words, to the specifications. How many times do you hear others (never yourself, right?) say things like this: "After I get my program to work, I'll go back and put in the exception handlers." Of course, no one ever has the time to "go back."

Anticipating and handling the problems in one's program is crucial to writing a robust application. PL/SQL offers a very powerful architecture for dealing with abnormal conditions: the exception section and exception handlers. Yet this architecture can also be difficult to use, particularly ...