Question

I have a method that reads data from a comma separated text file and constructs a list of entity objects, let’s say customers.

So it reads for example,

Name
Age
Weight

Then I take these data objects and pass them to a business layer that saves them to a database. Now the data in this file might be invalid, so I’m trying to figure out the best error handling design. For example, the text file might have character data in the Age field.

Now my question is, should I throw an exception such as InvalidAgeException from the method reading the file data? And suppose there is length restriction on the Name field, so if the length is greater than max characters do I throw a NameTooLongException or just an InvalidNameException, or do I just accept it and wait until the business layer gets a hold of it and throw exceptions from there?

(If you can point me to a good resource that would be good too)

Answer 1

I’d say – fail fast and loud. So throw an exception the moment there is an inconsistency (unless you want to get a hold of all the errors in the file and display it to the user… in which case you need a collecting parameter based design vs an exception based one).

• Name custom exception classes to be as ‘intention revealing’ as possible. So a NameTooLongException is better than an InvalidNameException
• Also the exception should be as helpful to the client to fix the problem .. (Ah I need to shorten the name in the file vs digging into the exception/code to know why is the Name invalid.) Shorten the discovery-and-resolution cycle time for your clients.