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

Persisting aggregates

When working with any system of even moderate complexity, we are required to make interactions durable; that is, interactions need to outlast system restarts, crashes, and so on. So the need for persistence is a given. While we should always endeavor to abstract persistence concerns from the rest of the system, our persistence technology choices can have a significant impact on the way we architect our overall solution. We have a couple of choices in terms of how we choose to persist aggregate state that are worth mentioning:

  • State-stored
  • Event-sourced

Let’s examine each of these techniques in more detail in the following sections.

State-stored aggregates

Saving current values of entities is by far the most popular way to persist state – thanks to the immense popularity of relational databases and Object-Relational Mapping (ORM) tools such as Hibernate. And there is good reason for this ubiquity. Until recently, a majority...