Slicing persistence adapters

In the preceding figures, we saw a single persistence adapter class that implements all persistence ports. There is no rule, however, that forbids us to create more than one persistence adapter, as long as all persistence ports are implemented.

We might choose, for instance, to implement one persistence adapter per group of domain entities for which we need persistence operations (or aggregate in Domain-Driven Design lingo), as shown in Figure 7.4.

Figure 7.4 – We can create multiple persistence adapters, one for each aggregate

This way, our persistence adapters are automatically sliced along the seams of the domain that we support with persistence functionality.

We might split our persistence adapters into even more classes – for instance, when we want to implement a couple of persistence ports using JPA (or another object-relational mapper) and some other ports using plain SQL for better performance. We...