How to handle exceptions

 Domain Driven Challenges: How to handle exceptions

Welcome to my series Domain Driven Challenges, where we dive into Domain Driven Design topics that often are not focused on enough and I have seen implemented wrong while being a Tech Lead. The examples are written in Java but can be applied in most languages.

One of the core concepts of Domain Driven Design (DDD from now on) is the Ubiquitous Language. We understand what the function or class is doing based on the naming, and even the business domain users should be able to follow along.

Many times we read a lot of great examples on how to implement a lot of different things:

Service Layer pattern

Repository pattern

Using interfaces and infrastructure

Dependency inversion

However, a lot of these topics are mostly covered in the positive or happy flow, but what if we also want to properly handle edge cases or scenario’s that should trigger an error?

Enter Exceptions

Exceptions allow us to abort functions and code when certain conditions are met and let higher level code know that something went wrong (by catching the exception). To explain this concept, let’s setup an example:

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