Advanced Oracle PL/SQL Programming with Packages

22.2. Application-Specific Exception Packages

PLVexc is a very generic, low-level package. It can be used in many different applications and under many different circumstances. This flexibility is one of its key strengths. I have found, on the other hand, that for complex application development, I will usually not want to make calls directly to the PLVexc.handle procedure. Instead, I will build another exception-handling package for my application which, in turn, references PLVexc elements.

This application-specific package offers several advantages, including:

• It is aware of the different kinds of data I need to report on when an error occurs. This awareness helps guarantee a consistent format for error logging; this consistency greatly aids in recovery and analysis efforts.

• It can predefine additional, application-specific exceptions that have no place in PLVexc.

Does this extra layer seem like overkill? Let's explore the motivation for this additional layer of code.

22.2.1. In the Trenches with PLVexc

It is the fall of 1995. I have just built my first version of PLVexc and immediately put it to use in an application that manipulates UPC codes for a retail operation. A UPC code is made up of a 14-digit number and a description. Each UPC (product) has many attributes, such as brand, product type, price, and so on. Each attribute has a name and value.

I find that as I build my exception handlers with PLVexc.handle I need to pass the same information repeatedly to my exception ...