Preface

Sometimes, solving problems and expressing our ideas through code is challenging. What looks like an obvious solution in our minds may look unnecessarily complex in the minds of others. But that’s alright if we are open to new ideas and perspectives because we set our minds to learning unexpected things when we have a persistent attitude and a willingness to embrace everything that comes.

I was not expecting it when I was first introduced to hexagonal architecture.

I remember working in a company where most of the software was developed by consultants. Those folks would come, deliver their code, and leave. Although my team and I tried to establish specific standards to ensure consistency in the applications we were responsible for, the harsh reality was that we needed more knowledge to maintain our applications properly. Given the number of systems and the different approaches and architectures employed to build them, it took a lot of work to maintain and add new features to such systems. That’s when a teammate told me about the hexagonal architecture and how it could help us tackle hard-to-maintain software problems.

At that time, there weren’t many books covering the hexagonal architecture. Most of the resources were scattered on the internet through video courses and articles explaining how someone implemented hexagonal architecture. The lack of resources was a considerable obstacle, but using an architecture that could improve software maintainability was very attractive to me. So, I kept researching and experimenting in my own job with the ideas, which would ultimately lead to me writing the first edition of this book.

I am fortunate to have had the opportunity to write the first, and now the second, edition of a book dealing with such a fascinating topic as hexagonal architecture. The second edition has allowed me to employ hexagonal architecture ideas with more recent versions of Java and Quarkus. This edition preserves the fundamentals from the previous one while exploring modern Java’s new and cool features. Also, this edition explores how hexagonal architecture can be used with the acclaimed SOLID principles and how it relates to the widely used layered architecture.

Concepts such as ports, adapters, and use cases are combined with Domain-Driven Design (DDD) elements such as entities and value objects to provide an in-depth guide explaining how to assemble those concepts to untangle the exciting puzzle of designing highly change-tolerable applications with hexagonal architecture. Considering the contemporary cloud-native practices that dictate most enterprise development today, we deep dive into Quarkus to learn how to blend hexagonal architecture ideas with cloud-native development, which enables us to create enterprise-grade hexagonal applications ready to be deployed in any major cloud provider.

So, I encourage you to have a persistent attitude and a willingness to embrace everything that comes and embark with me on this fascinating journey to explore hexagonal architecture.