Refactoring Kata : How the DDD Strategic Patterns help us to be more Autonomous

(This is a Mob Programming session based on Java & TypeScript)

Everyone of us has already worked on a new app connected to a legacy app and encountered challenging ways to preserve the new app autonomy.

The Workshop is a Refactoring Kata that tries to resolve this problem by using some DDD Strategic Pattern and OOP.

We work on a new app (LMBF) which is dependent on an old app (Shared Objects).
The LMBF app is Downstream of the old app.
The LMBF app depends on the Shared Objects app and we can not modify it.
So, The LMBF app is polluted by the Shared Objects app.
The aim of this Kata is to get freedom back to the LMBF app.

We start by isolating the logic of the Shared Objects app (ACL Pattern) and at some point we discover that another team is working on another app (Other App) which depends on the Shared Objects app.
In a second time, we discover that they share some logic in how they call the Shared Objects app and that’s where we introduce the Open Host Service pattern.

We will also talk about other Strategic Patterns on DDD :
- Customer/Supplier
- Separate Way
- ...