Book Image

Domain-Driven Design with Java - A Practitioner’s Guide

By : Premanand Chandrasekaran, Karthik Krishnan
Book Image

Domain-Driven Design with Java - A Practitioner’s Guide

By: Premanand Chandrasekaran, Karthik Krishnan

Overview of this book

Domain-Driven Design (DDD) makes available a set of techniques and patterns that enable domain experts, architects, and developers to work together to decompose complex business problems into a set of well-factored, collaborating, and loosely coupled subsystems. This practical guide will help you as a developer and architect to put your knowledge to work in order to create elegant software designs that are enjoyable to work with and easy to reason about. You'll begin with an introduction to the concepts of domain-driven design and discover various ways to apply them in real-world scenarios. You'll also appreciate how DDD is extremely relevant when creating cloud native solutions that employ modern techniques such as event-driven microservices and fine-grained architectures. As you advance through the chapters, you'll get acquainted with core DDD’s strategic design concepts such as the ubiquitous language, context maps, bounded contexts, and tactical design elements like aggregates and domain models and events. You'll understand how to apply modern, lightweight modeling techniques such as business value canvas, Wardley mapping, domain storytelling, and event storming, while also learning how to test-drive the system to create solutions that exhibit high degrees of internal quality. By the end of this software design book, you'll be able to architect, design, and implement robust, resilient, and performant distributed software solutions.
Table of Contents (17 chapters)
Part 1: Foundations
Part 2: Real-World DDD
Part 3: Evolution Patterns

Historic event replays

The example we have looked at thus far allows us to listen to events as they occur. Consider a scenario where we need to build a new query from historic events to satisfy an unanticipated new requirement. This new requirement may necessitate the need to create a new query model or, in a more extreme case, a completely new bounded context. Another scenario might be when we may need to correct a bug in the way we had built an existing query model and now need to recreate it from scratch. Given that we have a record of all events that have transpired in the event store, we can use replay events to enable us to construct both new and/or correct existing query models with relative ease.

Important Note

We have used the term event replay in the context of reconstituting the state of event-sourced aggregate instances (discussed in the Event-sourced aggregates section in Chapter 5, Implementing Domain Logic). The event replay mentioned here, although similar in...