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

Chapter 5: Implementing Domain Logic

To communicate effectively, the code must be based on the same language used to write the requirements – the same language that the developers speak with each other and with domain experts.

– Eric Evans

In the Command Query Responsibility Segregation (CQRS) section of the book, we described how DDD and CQRS complement each other and how the command side (write requests) is the home of business logic. In this chapter, we will implement the command-side API for the Letter of Credit (LC) application using Spring Boot, Axon Framework, JSR-303 bean validations, and persistence options by contrasting between state-stored and event-sourced aggregates. The list of topics to be covered is as follows:

  • Identifying aggregates
  • Handling commands and emitting events
  • Test-driving the application
  • Persisting aggregates
  • Performing validations

By the end of this chapter, you will have learned how to implement the core...