Designing Hexagonal Architecture with Java: An architect*s guide to building maintainable and change-tolerant applications with Java and Quarkus

A practical guide for software architects and Java developers to build cloud-native hexagonal applications using Java and Quarkus to create systems that are easier to refactor, scale, and maintain

Key Features

• Learn techniques to decouple business and technology code in an application
• Apply hexagonal architecture principles to produce more organized, coherent, and maintainable software
• Minimize technical debts and tackle complexities derived from multiple teams dealing with the same code base

Book Description

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.

What you will learn

• Find out how to assemble business rules algorithms using the specification design pattern
• Combine domain-driven design techniques with hexagonal principles to create powerful domain models
• Employ adapters to make the system support different protocols such as REST, gRPC, and WebSocket
• Create a module and package structure based on hexagonal principles
• Use Java modules to enforce dependency inversion and ensure isolation between software components
• Implement Quarkus DI to manage the life cycle of input and output ports

Who this book is for

This book is for software architects and Java developers who want to improve code maintainability and enhance productivity with an architecture that allows changes in technology without compromising business logic, which is precisely what hexagonal architecture does. Intermediate knowledge of the Java programming language and familiarity with Jakarta EE will help you to get the most out of this book.

Table of Contents

1. Why Hexagonal Architecture?
2. Wrapping Business Rules inside Domain Hexagon
3. Handling Behavior with Ports and Use Cases
4. Creating Adapters to Interact with the Outside World
5. Exploring the Nature of Driving and Driven Operations
6. Building the Domain Hexagon
7. Building the Application Hexagon
8. Building the Framework Hexagon
9. Applying Dependency Inversion with Java Modules
10. Adding Quarkus to a Modularized Hexagonal Application
11. Leveraging CDI Beans to Manage Ports and Use Cases
12. Using RESTEasy Reactive to Implement Input Adapters
13. Persisting Data with Output Adapters and Hibernate Reactive
14. Setting Up Dockerfile and Kubernetes Objects for Cloud Deployment
15. Good Design Practices for Your Hexagonal Application

Davi Vieira is a software craftsman with a vested interest in the challenges faced by large enterprises in software design, development, and architecture. He has more than 10 years of experience constructing and maintaining complex, long-lasting, and mission-critical systems using object-oriented languages. He values the good lessons and the software development tradition left by others who came before him. Inspired by this software tradition, he develops and evolves his ideas.