Hexagonal Architecture Demo Project about Ticketing and Payment

Related tags

Spring Boot Modular-Architecture-Hexagonal-Demo-Project
Overview

Modular Architecture - Hexagonal Demo Project

This project is a sample production-ready implementation for demonstrating the power of Hexagonal Architecture (aka Ports And Adapters Pattern) written in Java.

Build Ticket API Build Payment API

Lines of Code Coverage Technical Debt Code Smells Maintainability Rating

Table of Contents

Wiki

Reports

Hexagonal Architecture Flow Diagram (click to enlarge)

Hexagonal Architecture Flow Diagram

Motivation

We want to write clean, maintainable, well-defined boundary context, well-tested domain code and isolate business logic from outside concern.

What is the Hexagonal Architecture

The hexagonal architecture was invented by Alistair Cockburn in an attempt to avoid known structural pitfalls in object-oriented software design, such as undesired dependencies between layers and contamination of user interface code with business logic, and published in 2005.

A timeless goal of software engineering has been to separate code that changes frequently from code that is stable.

~ James Coplien / Lean Architecture

We recommend Hexagonal Architecture for those who want to write clean, maintainable, well-defined boundary context, well-tested domain, and decoupling business logic from technical code.

Technologies Used

You can use any programming language for implementing Hexagonal Architecture. Here is the list of technologies we used for the demo application;

  • Spring Boot 2
  • Java 11
  • Gradle 7
  • Mono Repo
  • Docker
  • Mysql
  • Redis
  • Kafka
  • Groovy 3
  • Cucumber
  • GitHub Actions

It's so easy to reach 100% code coverage if you design by tests wisely via TDD. There are the types of tests written:

  • Unit tests
  • Dockerized integration tests
  • Consumer-driven contract tests
  • External verifier contract tests
  • Acceptance tests

What You Will Learn

  • Implementing two microservices with spring boot
  • Designing the APIs with hexagonal architecture
  • Packaging by functions and screaming architecture
  • How Ports and adapters separate business from integration points
  • Writing behavior focused unit tests at domain module
  • Writing integration tests isolated from the business at infra module
  • Using Gradle to configure microservices and modules
  • Using mono-repo to handle all APIs in a single git repository
  • Implementing consumer-driven contract tests
  • Creating different testing styles for validating data adapters, event consumers/publishers, controllers

Useful Links From Authors

  • Modular Architecture for Pragmatic Developers - Slides - Youtube
  • Growing Hexagonal Microservices With TDD - Slides, Youtube
  • It's Not Solid Anymore: Rethinking Software Design and Modularity - Slides, Youtube

Useful Links about Hexagonal Architecture

  • ITT 2018 - Jakub Nabrdalik - Hexagonal Architecture in practice - Youtube
  • Ian Cooper on Hexagonal Architectures at Agile Yorkshire - Youtube
  • Ports and Adapters Pattern, by Juan Manuel Garrido de Paz - Blog
  • DDD, Hexagonal, Onion, Clean, CQRS, … How I put it all together, by Herberto Graca - Blog
  • Hexagonal Architecture: three principles and an implementation example, by Erwan Alliaume, Sébastien Roccaserra - Blog

History

This repository is a side project developed while preparing the conference talk "Growing Hexagonal Microservices With TDD" at Java Day Istanbul 2020. As the authors of this repository, we've been using hexagonal architecture in all microservices (i.e. more than 50+ microservices) running in production since 2017. We believe modularity is the key to building maintainable and high-quality software. That's why we shared our demo project with the community to attract their interest in the topic.

Contributing

Please feel free to open tickets to suggest new features and improvement points. Please feel free to contribute.

Code of Conduct

Please take a look at code of conduct before opening issues or creating pull requests.

Authors

License

Distributed under the MIT License. See LICENSE for more information.

Comments
  • Create stand alone common module

    Create stand alone common module

    It's neither bug nor feature but would definitely eliminate code duplication

    In each services there're common sub-modules for both domain and infra. Certain classes, interfaces and enums such as Event, Status, UseCase, UseCaseHandler are repeatedly created. Considering addition of several other microservices to the project, it'll definitely increase the code repetition.

    It'd be a better implementation to separate common module to an individual one. Such as

    
\common
      \ domain 
             \ commandhandler
                    CommandHandler
      \ infra
             \ entity
                    AbstractEntity
\payment-api
\ticket-api
...

    P.s I'm planning to make a PR for this matter if the issue is also okay with you guys.

    wontfix 
    opened by elshanakberov 3
  • some ducks don't wanna fly and some want

    some ducks don't wanna fly and some want

    How can code duplication be prevented when useCase handlers consist of the same business logic? Multiple inheritance is not permitted just because of ObservableUseCasePublisher class. How is a structure made that resembles the template method approach?

    opened by atakanburakgungor 0
  • Remove spring dependency from domain module

    Remove spring dependency from domain module

    hell yeah, why do we need spring dependency at domain module? for transactional and dependency injection purposes, right? All these can be done without spring at all. Let's do that and show the world we need no spring dependency at domain module.

    opened by lemiorhan 0
  • Added No Use Case Handler

    Added No Use Case Handler

    it's been added the no param use case handler to be able to handle without any use case and return a response model

    By the way, Thanks a lot for this great boilerplate project which you have been released with @lemiorhan. We also have got a production-ready project that this project's help us, it will be released in the near future 🙂

    We needed to return static content to our mobile clients without depending on any request model, that's why we added up the NoUseCaseHandler

    opened by yusufcakal 0
  • Use Java9 modules to protect the modules from unnecessary access

    Use Java9 modules to protect the modules from unnecessary access

    From infra point of view, there is no need to access a jpa repository of domain module. So it will be a great refactoring to adapt with java9 modules and handle access.

    opened by lemiorhan 0
  • Write contract tests for event consumer and producers

    Write contract tests for event consumer and producers

    Kafka event consumers and producers need to have contract tests to validate. That requires additional dependencies to add. Embedded kafka could be used.

    opened by lemiorhan 0
  • Auto trigger acceptance tests when both apis build successfully

    Auto trigger acceptance tests when both apis build successfully

    Since acceptance test workflow is triggered after push, it cannot get the latest codebase from the latest docker image. Build workflows for both apis should complete successfully before acceptance test workflow.

    Github started to support dependencies between workflow very lately. However all solutions have some drawbacks. We should check workflow_run and workflow_dispatch commands at GitHub Actions.

    Reference: https://github.com/marketplace/actions/workflow-run-conclusion-dispatch-action

    opened by lemiorhan 0
  • Upgrade Spring Boot to 2.5 to support Groovy 3 and Gradle 7

    Upgrade Spring Boot to 2.5 to support Groovy 3 and Gradle 7

    https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.5-Release-Notes

    We need to upgrade to the latest 2.5 version of Spring boot to officially support Java 16, Groovy 3, and Gradle 7.

    opened by lemiorhan 0
Owner
Alican Akkuş
Passionate engineer, Agile and Lean practitioner, Pair programming lover
Alican Akkuş
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