Book Image

Designing Hexagonal Architecture with Java - Second Edition

By : Davi Vieira
Book Image

Designing Hexagonal Architecture with Java - Second Edition

By: Davi Vieira

Overview of this book

We live in a fast-evolving world with new technologies emerging every day, where enterprises are constantly changing in an unending quest to be more profitable. So, the question arises — how to develop software capable of handling a high level of unpredictability. With this question in mind, this book explores how the hexagonal architecture can help build robust, change-tolerable, maintainable, and cloud-native applications that can meet the needs of enterprises seeking to increase their profits while dealing with uncertainties. This book starts by uncovering the secrets of the 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 with ports and use cases in the application hexagon, and make your software compatible with different technologies by employing adapters in the framework hexagon. In this new edition, you’ll learn about the differences between a hexagonal and layered architecture and how to apply SOLID principles while developing a hexagonal system based on a real-world scenario. Finally, you’ll get to grips with using Quarkus to turn your hexagonal application into a cloud-native system. By the end of this book, you’ll be able to develop robust, flexible, and maintainable systems that will stand the test of time.
Table of Contents (24 chapters)
1
Part 1: Architecture Fundamentals
7
Part 2: Using Hexagons to Create a Solid Foundation
12
Part 3: Becoming Cloud-Native
18
Part 4: Hexagonal Architecture and Beyond

Defining domain services

The topology and inventory system is about the visualization and management of network assets, so we need to enable a user to handle collections of such network assets. One way to do that is through services. With services, we can define behaviors to deal with system entities and value objects.

All the services that we’ll create in this section reside in the service package.

Let’s start by creating a service to deal with collections of routers.

Router service

In the previous section, when implementing the Router, CoreRouter, and EdgeRouter entities, we also created some methods to return predicates to aid us in filtering collections of routers. With a domain service, we can use these predicates to filter such collections, as follows:

package dev.davivieira.topologyinventory.domain.service;
import dev.davivieira.topologyinventory.domain.
  entity.Equipment;
import dev.davivieira.topologyinventory.domain.
  entity...