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


In this chapter, we examined how to implement the query side of a CQRS-based system. We looked at how domain events can be consumed in real time to construct materialized views that can be used to service query APIs. We looked at the different query types that can be used to efficiently access the underlying query models. We rounded off by looking at persistence options for the query side.

Finally, we looked at historic event replays and how they can be used to correct errors or introduce new functionality in an event-driven system.

This chapter should give you a good idea of how to build and evolve the query side of a CQRS-based system to meet changing business requirements while retaining all the business logic on the command side.

In this chapter, we looked at how to consume events in a stateless manner (where no two event handlers have knowledge of each other’s existence). In the next chapter, we will continue to look at how to consume events, but this time...