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


Application logging is one of the most fundamental aids when it comes to diagnosing issues in running code. In a lot of code bases, logging tends to be an after-thought where developers add log statements only after they encounter problems. This results in log statements being strewn almost randomly throughout the code base. Here is a simple example of code within a command handler to log its execution time among other things:

There is no doubt that this logging code can be invaluable when troubleshooting issues. However, when we look at the preceding code, the logging code seems to dominate the entire method obscuring the domain logic. This might feel innocuous, but when this is done in multiple places, it can get quite repetitive, cumbersome, and error-prone – compromising readability. In fact, we have seen cases where seemingly innocent log statements have introduced performance issues (for example, within a loop with an expensive argument...