The most valuable free resource is the official code repository. Packt Publishing hosts the complete code for the book on GitHub, allowing you to follow along and experiment with working examples.
To build a clean Hexagonal Architecture in Java, organize your package structure to strictly enforce these boundaries. Below is a practical guide based on a simple banking application handling money transfers. 1. Package Structure
This contains your pure Java classes, entities, and business logic. It has zero external dependencies—meaning no javax.persistence annotations, no Spring Framework imports, and no third-party HTTP clients. Pillar 2: Ports (Interfaces) The most valuable free resource is the official
Enforce strict boundary lines using your project package structure. A common setup looks like this: com.company.project.domain (Entities/Value Objects) com.company.project.ports.in (Driving Interfaces) com.company.project.ports.out (Driven Interfaces)
Tracking data flows through ports and adapters requires a shift in mindset compared to traditional 3-tier models. Best Practices for Java Projects Below is a practical guide based on a
Traditional layered architecture couples business logic with databases or user interfaces. Hexagonal Architecture solves this by placing domain logic at the center of the application. The Core Philosophy
To prevent developers from accidentally importing adapter or framework classes into the domain layer, add the ArchUnit library to your test suite. ArchUnit validates your package dependencies automatically during your CI/CD builds. It has zero external dependencies—meaning no javax
// Inbound Port public interface CreateUserUseCase User createUser(User user); Use code with caution. 2. Outbound Ports (Repository Interfaces)
Let us look at a practical example of a user registration system built with standard Java structures. Step 1: The Domain Entity
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