In the world of software development, architecture plays a big role in creating software systems and applications. In fact, the final application outlook depends on the selected architecture solution used during the development and maintenance.

With diverse architectural patterns available, developers have a wide range to choose from. But then, how do you know which architecture suits a specific project? This guide explores all the insights you need to know about hexagonal architecture, including what hexagonal architecture is, the key features, when to use such an architecture, and best practices when using hexagonal architecture, among many other insights.

What is hexagonal architecture? Quick Overview

Also known as adapters or ports architecture, horizontal architecture is a pattern in software design that aims at creating loosely coupled apps for easy connection to their relative softwares through adapters and ports. As a result, it becomes easy to exchange the components at any moment to execute test automation processes.

Components of hexagonal architecture

For a better understanding of hexagonal architecture and how it works, there are three main components that make hexagonal architecture complete. They are adapters, ports, and domains. Below is a detailed description of each:

• Domain – the core

Located in the central layer of the architecture, the domain is the key aspect of the entire architecture as it holds the logic business in relation to the application. It controls data models, app behavior, business restrictions, and general rules. The domain operates as a standalone component from all other layers due to its significant purpose in the hexagonal architecture.

• Ports

These act as entry points, allowing connection and interaction between the adapters and the domain (the core) of an app. So, they majorly operate the adapters and ensure seamless transmission of information. Depending on the nature and functionality of an app, there can be as many ports as needed. It is more like USB ports through which you can connect different devices.

• Adapters

Adapters facilitate communication between the core and users through the ports. Located on the outer layer of the hexagonal architecture, adapters have both output and input elements of an app, which enhances seamless interaction with external services.

Adapters connect the client and app communication through technology such as a REST controller.

Principles of hexagonal architecture

So, what does hexagonal architecture advocate for? The following principles bring out a clear picture of how hexagonal architecture works and operates:

• Effective testing

In hexagonal architecture, the business logic is separated from other components. This means each component can be tested independently without interfering with all other functionalities and performance of the entire unit.

• Business logic isolation

This is a major principle that defines and sets hexagonal architecture apart. The business logic isolation implies separating the unit’s domain models from other database details, set rules, messaging mechanisms, and user interfaces, among many other external components of the app.

• Driven by use cases

The hexagonal architecture focuses solely on use cases and not infrastructure details when formulating the code. This means the whole aspect revolves around coding and how to order files to fulfill specific business dealings and not for technical concerns.

• Directional interchangeability

In hexagonal architecture, directional interchangeability means it is easy to perform reverse flow control where necessary. You can complete this by either using test drivers during the process or simply using a human driver via a graphical interface.

• Ports & adapters

The hexagonal architecture uses ports to define specific functionalities within an app, while adapters redefine the process or ways to access the defined functionalities within the unit.

In this case, several adapters can be used on a single port to offer diverse ways through which the system interacts with other components without impacting the core business logic.

• Embracing change

Finally, hexagonal architecture advocates for change, be it emerging business needs or technological changes. The architecture allows adjustments to accommodate whatever change that comes along.

Benefits of hexagonal architecture

So, why would a development team opt to use hexagonal architecture? What are the advantages of hexagonal architecture? Below is a description of the benefits one gets from hexagonal architecture in software development:

• Ease of adjusting features

You can change the existing features within a hexagonal architecture or even add new ones to enhance the overall functionality and performance of an app.

This is achievable thanks to the business logic isolation, which allows developers to add new features without interfering with other existing components of an app. As a result, there is ultimate flexibility while protecting business details.

In this case, developers can easily scale the app without worrying about negative impacts on other parts of the app.

• Reduced functional risks

In hexagonal architecture, the application will always remain stable throughout, even when some technical changes are implemented. The hexagonal architecture, contrary to some other architectural patterns with tightly coupled logic has its business logic separated from other app’s components. As a result, it is easy to adjust elements in other parts of the app, like the storage facilities database system or any other component of the app, without impacting or risking other functionalities of the unit, thus maintaining its stability always.

• Enhanced scalability

By allowing other parts of the system to function seamlessly even when implementing changes, it becomes easy for businesses to scale appropriately in relation to market trends and changing business dynamics.

• Simplified testing

By isolating the business logic from other components and functionalities of an app, hexagonal architecture enhances better testing. What’s more, it is easy to automate the testing processes by embracing the BDD – behavior-driven development and test-driven development, which make up a hexagonal architecture.

Simplified testing in hexagonal architecture enhances the business logic functionality implementation and improves the overall quality of the code.

• The DDD and BDD approached

Hexagonal architecture embraces DDD – domain-driven design and BDD – behavior-driven development whereby the DDD approach facilitates the designing process of a complex business domain. BDD, on the other hand, facilitates the actual behavior of the system.

All these approaches are possible, thanks to the business logic isolation principle of the hexagonal architecture. This makes it easy for the developers to design the business domain precisely and to have a better view of the expected app behavior, thus enhancing the overall performance & functionality of the app.

These are some of the major hexagonal architecture benefits, making it stand out and be a preferred architectural pattern choice for most software projects.

The development team can easily perform component testing while ensuring the business is adaptable to emerging technical changes and business requirements while ensuring scalability of the business at the same time.

How to design the hexagonal architecture: step-by-step

Once you make a decision to implement or design a hexagonal architecture, there are steps you should follow to ensure you get the most out of the architectural pattern. The steps include the following:

• Define and understand the business domain

Start by having an in-depth understanding of the system’s business logic before you figure out any other step.

Do this by evaluating the business guidelines, use cases, and any other valuable business components. The insights you collect will make up the core of your business domain. Once you are done with this step, you won’t have issues when it comes to the business logic isolation process.

• Design the business model

Next, come up with a business model representing the core elements of your business domain, including rules, values, and entities, among others. The design you create should be independent of other technologies.

Most importantly, the model should not rely on technical concerns, plus it should maintain a high stability rate.

• Establish the adapters and ports

With your business model in place, you can now define the points of interaction within the app, hence the need to establish adapters and ports. The ports are interfaces that establish interaction points. The adapter, on the other hand, plays a role in processing the ports.

• SPI and API interface implementation

Now, divide the interfaces into SPI – service provider interface and API – application provider interface. These two interfaces will complete the business model. The SPI is significant in retrieving infrastructure data, while API makes up components of a business model. In any case, the two interfaces must have clearly defined meanings.

• Design business logic

When designing the business logic within the business model, make sure the code doesn’t rely on data sources and technical aspects. Using the inversion of control will enhance the isolation of the model swiftly.

• Create adapters

Next, you will need to create adapters for the corresponding infrastructure and interface parts. These adapters facilitate interaction within the business model and external components. Besides, they accommodate technologies to align with specific environments for streamlined business logic and the overall stability of the system.

• Test business logic

In hexagonal architecture, it is crucial to perform independent component testing due to business logic isolation. You can use mocks to foster interactions with the adapters.

• Continuous maintenance

Domain advancements keep changing from time to time. Therefore, choose a non-static business model so that you can keep adjusting in response to developmental and technical changes.

What are the challenges or limitations of hexagonal architecture?

While hexagonal architecture has many benefits it offers in software development, there are some inevitable challenges one encounters along the way. Below are some of these challenges in hexagonal architectural patterns:

• Dispersion – In hexagonal architecture, the software pattern can become fragmented and extremely scattered, thus impacting some aspects of the software solution negatively.
• Complexity – when compared to other architectural patterns, hexagonal architecture can be quite complex since it has a lot of elements that require skilled expertise.
• High-cost risk –the fact that hexagonal architecture can be quite complex, and when not applied accurately, it can turn out to be resource and cost-intensive. What’s more, it can take a lot of time to implement in case of such complexities.
• Understanding the code – the complex nature of the hexagonal architecture may need more code compared to other architectural patterns, especially with poor documentation or when the code grows.
• Initial design – a developer must have adequate knowledge and experience in business logic and the entire infrastructure. This is because the initial design continues to become complex from time to time.

When to use hexagonal architecture

In relation to the principles and benefits of hexagonal architecture, this software development approach suits some projects, especially the ones that require decoupling and a high level of flexibility. Similarly, its nature of business logic isolation might not suit some other project. For these reasons, hexagonal architecture is suitable for the following projects:

• Scalable & Flexible systems – these include apps that accommodate frequent change of dependencies or apps that needs a higher level of scalability.
• Long-term corporate apps – these include projects that require sustainable maintenance as they grow from time to time.
• Projects with complex integration – hexagonal architectural pattern suits best projects that require connection to external services or different sources of data to enhance their functionality.

Note: hexagonal architecture might not suit short-term and small projects that are simple with streamlined development procedures.

Hexagonal architecture best practices and expert tips

As you plan to adopt the hexagonal architecture, you are set to receive lots of benefits and some challenges, too. However, with proper planning and following the right steps, you can get the most out of hexagonal architecture. Below are some of the hexagonal architecture best practices that will help you get the most out of it:

• Know your app type

Before you think of adopting hexagonal architecture, make sure you have a clear overview of what you want to create. For instance, a simple app may not fit the hexagonal architecture. A complex app with defined business logic, on the other hand, fits perfectly with the hexagonal architecture.

Therefore, don’t make the mistake of choosing hexagonal architecture when you aren’t sure of the nature of your app.

• State of business rules

Hexagonal architecture suits a project with well-defined and stable business rules since the technical changes, when applied won’t have an adverse effect on the app. Therefore, before you settle with hexagonal architecture, make sure you figure out if your business rules will keep changing or if they are in a stable state.

• Business logic isolation

Apparently, the business logic isolation concept is what defines hexagonal architecture well. In case your project requires business logic isolation, then you can comfortably implement the hexagonal architecture and get the most out of it.

• Have a better understanding of the business domain

Make sure you can comprehend the business domain concept to successfully adopt a hexagonal architectural pattern. Master the business rules, use cases, and essential actors. If you fail to understand the business domain, you are likely to encounter a lot of errors that will, in turn, be costly.

• Prepare a streamlined business model

Formulate a well-defined business model that is independent of technologies. The model you create should align with the business domain concepts. Do not include technical concepts in the model for the effectiveness of the hexagonal architecture.

• Test business logic

Allocate enough time to test the isolated business logic independently. The process ensures no errors and that the business logic is fully functional.

• Documentation is key

Have detailed documentation of your hexagonal architecture, including the business logic, adapters, and interface descriptions. This fosters better understanding and maintenance.

• Maintain a flexible approach

Hexagonal architecture advocates for change and adaptability in different aspects. Therefore, design the model to embrace change when necessary. Of course, hexagonal architecture accommodates these changes without interfering with the stability of the system.

• Version Management

As your app grows and scales to new levels where new versions are updated, make sure you have a streamlined process to manage SPI and API interface versions. This guarantees compatibility between the different versions of the whole unit.

• Stay updated

Finally, you need to always be updated on software development best practices under hexagonal architecture, know how to control the DDD and BDD approaches in hexagonal architecture, master how to automate tests, and, most importantly, embrace hexagonal architecture principles.

With all these in place, you can be sure of a seamless experience with hexagonal architecture.

Hexagonal architecture future trends

Wondering what to expect with hexagonal architecture in the future? Well, as the general software architecture continues to be more innovative, so is the hexagonal architecture.

Besides, the experts within the tech industry continue to explore diverse software design methodologies, hence the need to reevaluate the future trends that are set to transform the software development field in relation to hexagonal architecture.

Below are the common future trends within the hexagonal architecture:

• DevOps on the rise

Hexagonal architecture aligns just perfectly with DevOps patterns. DevOps is a software development trend that keeps gaining traction from time to time.

Just like in hexagonal architecture, DevOps operations advocate for continuous testing, rapid deployment, and streamlined app management.

• Growing dependency on microservices

Another inevitable trend that is set to grow steadily is the microservices integration with hexagonal architecture.

Many organizations are opting for software development solutions that advocate for agility and enhanced scalability, which are common in the case of hexagonal architecture and microservices.

By including single units with ports and adapters, as in the case of hexagonal architectural patterns, it becomes seamless to manage the system even with all the complexities.

• Cloud-native app compliance

With many users opting for cloud-based solutions, most businesses are set to adopt architectural patterns that are compatible with such platforms, just like in the case of hexagonal architecture.

• AI inclusion

Of course, AI has brought about innovative approaches in diverse sectors. It’s automated patterns and algorithms can suit perfectly when integrated with hexagonal architecture. What’s more, it will become easy to build AI components under hexagonal architecture while ensuring the stability of other app functionalities.

Conclusion

Many diverse architectural patterns are available; developers have many options to select from. It all depends on the project dynamics and the team’s expertise. Hexagonal architecture, for instance, is one solid software design approach for apps that require enhanced maintenance, are easy to test, modular, and adaptable to changes.

It offers ultimate flexibility during the development process, thanks to its principle of business logic isolation from other dependencies.

While there are a set of challenges when using hexagonal architecture, the benefits are worth implementation. The long-term benefits will guarantee value out of hexagonal architecture.

Back to You!

If you want to try your next project with hexagonal architecture but don’t know how, reach out to Aalpha Information Systems, and we will be glad to streamline all the processes to ensure seamless project completion.