![]() The pom.xml configuration will prevent us over accidentally coupling modules. Therefore, how will the Domain be able to use infra-api if doesn’t depend on them? No one has knowledge of the existence of the others. That’s way, there is no direct dependency between two infra modules. You do not use an infra module directly, you have to pass only through Domain module.The first rule of Hexagonal Architecture is clear : It requires some configuration and a main method or other technical details to run. Since the Domain only contains classes with business rules, it cannot run alone. Each infra represent a detail about infrastructure like database access and external APIcall. ![]() We’ll create a Maven project with movies as the root and 3 submodules like below.Įnter fullscreen mode Exit fullscreen modeĪs you can see, we have one main module named movies-app, one Domain module named movies-domain and one infra module named movies-infra-api. It’s an application retrieving movies information from an external public API. You’ll find the source in the Github repository We will create a new Spring boot application with a very simple case to illustrate this architecture. The module that wants to be used by the Domain, will have to implement this interface (adapter) and map data between him and the Domain. Domain implement this exposed interfaces with these services and if this need to use external concerns, like database access, it will use others interfaces, named port (outbound). The purpose of DDD is keep the focus on the Domain implementation and not worry about technical detail too soon.Īs illustrated in the schema below, we first have an application module (cf: app) who will use the Domain by his interfaces. Like that, you can change any part of the technical details without impacting the Domain. The goal is to have a clear separation between your Domain code (in single project or module) and your supporting code (like database access, APIs call or Framework like Spring in Java). It is also called “ Port and Adapter Architecture “. ![]() It’s a software architecture introduced by Alistair Cockburn in 2005. ![]() So, what is exactly Hexagonal Architecture ? For Microservices, reliability and performance can be a challenge.Īnd even if you choose this way, each microservices needs to have their own internal architecture. Each Architecture decision come with these cons. For this type of architecture, you need to have the ecosystem for managing (for example container management tools like Kubernetes or OpenShift for example) and the need of great scalability. Indeed, microservice are not the only possible implementation. As Mark Richards says about architecture decisions on his book Fundamentals of Software Architecture: “It’s always a trade-off”. It’s what make microservice a good candidate for DDD implementation.īut it is not the only one. Each of them as only one purpose who are translated into Domain bounded context. For example, when you build an e-commerce website or application, you will probably have one microservice for account management, another for payment features and another for stock management. Therefore, each bounded context need to be builded into bounded context. When you translate DDD principels into Architecture Diagram, the most suitable approche is Microservices Architecture. For Example, if we are building an application to track airplane's schedule, we attempt to found in the application Entity like "Airplane" or "Travel" and Value Object like "Destination" or "Arrival".įor more information about DDD I advise you to read this free e-book Each terminology in this Language should be found in the application. We need to create a Ubiquitous Language between all stockholders (Domain team, Technical teams). The whole solution must revolve around the business rules and its terminologies. It is a Software engineering approach that keeps the Domain at the center of our core software set. Like already explained above, The Domain Drive Design was introduced by Eric Evans in 2003. Even though Hexagonal Architecture was first designed for monolithic application, wa can apply to build our microservice as well. Moreover, in a microservice, we need to keep good practices and good architecture. Hexagonal Architecture is also a good candidate for implementing DDD correctly and it is a very good architecture in general described by Robert C. But this is not the only one implementation for DDD concept. When we correlate DDD and Architecture, many of us think of Microservices. In this article we will introduce a software architecture that implements the DDD (Domain Driven Design) introduced by Eric Evan in the “Blue Book” : Domain-Driven Design: Tackling Complexity in the Heart of Software
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