Book Image

Get Your Hands Dirty on Clean Architecture

By : Tom Hombergs
Book Image

Get Your Hands Dirty on Clean Architecture

By: Tom Hombergs

Overview of this book

Building for maintainability is key to keeping development costs low and processes easy. The second edition of Get Your Hands Dirty on Clean Architecture is here to equip you with the essential skills and knowledge to build maintainable software. With this comprehensive guide, you’ll explore the drawbacks of conventional layered architecture and the advantages of domain-centric styles such as Robert C. Martin's Clean Architecture and Alistair Cockburn's Hexagonal Architecture. Then, you’ll dive into hands-on explanations on how to convert hexagonal architecture into actual code. You'll learn in detail about different mapping strategies between the layers of hexagonal architecture and discover how to assemble the architectural elements into an application. Additionally, you’ll understand how to enforce architecture boundaries, which shortcuts produce what types of technical debt, and how, sometimes, it is a good idea to willingly take on those debts. By the end of this second edition, you'll be armed with a deep understanding of the hexagonal architecture style and be ready to create maintainable web applications that save money and time.
Table of Contents (13 chapters)

Visibility Modifiers

Let's start with the most basic tool that Java provides us for enforcing boundaries: visibility modifiers.

Visibility modifiers have been a topic in almost every entry-level job interview I have conducted in the last couple of years. I would ask the interviewee what visibility modifiers Java provides and what their differences are.

Most of the interviewees only list the public, protected, and private modifiers. Almost none know the package-private (or "default") modifier. This is always a welcome opportunity for me to ask some questions about why such a visibility modifier would make sense in order to find out whether the interviewee could abstract the answer from their previous knowledge.

So, why is the package-private modifier such an important modifier? Because it allows us to use Java packages to group classes into cohesive "modules." Classes within such a module can access each other but cannot be accessed from outside of the package. We can...