Domain-Driven Design - sample to showcase how to work with legacy projects

Project Details

The sample project is a Package Delivery System which keeps track of packages for delivery with the following features:

• create delivery: select customer and address
• edit package: select products
• send package to customer.

The Package Delivery System is a desktop application written in WPF. It uses Dapper to execute SQL queries.

The Anti-Corruption Layer

The anti-corruption layer is an adapter layer which handles the conversation between the legacy code and the bubble context.

Benefits:

• combines the benefits of a full rewrite with gradual refactoring: working on a greenfield domain model while still delivering business value.

Considerations:

• the anti-corruption layer is an additional service that must be managed, maintained and scaled
• it may add latency.

How to refactor

• introduce a bubble context with the new domain model with proper encapsulation
• create the anti-corruption layer to handle the conversation between the legacy code and the bubble context (through repositories in this case)

• promote the anti-corruption layer to the synchronizing anticorruption layer which resides in its own bounded context (create a separate DB for the bubble context)

For the current sample, the following approach has been used:

• created triggers for both databases to monitor changes
• only monitored the data the context own
• added a new table synchronization in order to reduce the pressure on the domain tables
• the synchronization between the bubble context DB and the legacy DB is done asynchronously
• the bubble has been decoupled from ACL.

Branches

• Initial - the initial branch contains the legacy project.
• Master - the master branch will contain the code after refactoring.