Book Image

Designing Hexagonal Architecture with Java

By : Davi Vieira
Book Image

Designing Hexagonal Architecture with Java

By: Davi Vieira

Overview of this book

Hexagonal architecture enhances developers' productivity by decoupling business code from technology code, making the software more change-tolerant, and allowing it to evolve and incorporate new technologies without the need for significant refactoring. By adhering to hexagonal principles, you can structure your software in a way that reduces the effort required to understand and maintain the code. This book starts with an in-depth analysis of hexagonal architecture's building blocks, such as entities, use cases, ports, and adapters. You'll learn how to assemble business code in the Domain hexagon, create features by using ports and use cases in the Application hexagon, and make your software compatible with different technologies by employing adapters in the Framework hexagon. Moving on, you'll get your hands dirty developing a system based on a real-world scenario applying all the hexagonal architecture's building blocks. By creating a hexagonal system, you'll also understand how you can use Java modules to reinforce dependency inversion and ensure the isolation of each hexagon in the architecture. Finally, you'll get to grips with using Quarkus to turn your hexagonal application into a cloud-native system. By the end of this hexagonal architecture book, you'll be able to bring order and sanity to the development of complex and long-lasting applications.
Table of Contents (21 chapters)
1
Section 1: Architecture Fundamentals
7
Section 2: Using Hexagons to Create a Solid Foundation
12
Section 3: Becoming Cloud-Native

Chapter 2: Wrapping Business Rules inside Domain Hexagon

In the previous chapter, we learned about the Domain as the first hexagon in hexagonal architecture. By being the innermost hexagon, the Domain does not depend on anything above it. Also, we make all the other hexagons depend on the Domain to conduct their operations. This kind of arrangement confers the Domain hexagon a degree of responsibility and relevance far higher than other hexagons. We employ such an arrangement because it is on a domain where we group all the business rules and data that most represent the problem we are trying to solve.

Among the techniques to model a problem domain, Domain Driven Design (DDD) is widely adopted in projects that emphasize software code as a medium to convey knowledge about a business. An always-present concern to separate what constitutes the core problem domain and what is secondary to it makes DDD a suitable approach to support the hexagonal architecture goal to separate technology...