Software development

Introduction To Clean Architecture Medium

A large monolithic application can be difficult for developers to understand and maintain. These services share a domain model consisting of entities such as Product, Order, and Customer. Domain Layer – At the very core is the Domain onion architecture layer which holds all of your domain objects. Please restrict yourself by keeping just the properties or definitions inside your domain objects and not any piece of code which talks to database or has any other business functions.

Benefits and Drawbacks of Onion Architecture

The onion layer solves the problem of tight coupling that we faced with n-tier architecture. This architecture has Domain Layer, Repository Layer, Service Layer and Presentation Layer. The Onion architecture was first introduced by Jeffrey Palermo, to overcome the issues of the traditional N-layered architecture approach which we discussed above. Also, if we will work with Microservice architecture it will get more complex to work with N-Layer architecture, this is one of the major problems with n-tier architecture. It is one of the most popular Architectures in ASP.NET Core Applications.


Developers can take full advantage of the architecture and construction by adhering to best practices. The software components are arranged into concentric layers using the onion architecture, a layered architecture pattern in which each layer is solely dependent upon the layer immediately behind it. Onions are a delicious vegetable and are a core ingredient in cuisines around the world. Perhaps then you are wondering, why are we discussing them in the context of software engineering? Onion architecture is an architectural pattern that promotes a clear separation of concerns, where the core business logic of the application is decoupled from the infrastructure and implementation details. For example, both Onion Architecture and Hexagonal Architecture rely on inversion of control and dependency injection to manage dependencies between layers.

Benefits and Drawbacks of Onion Architecture

Because the layers are separated from one another and can be tested independently, the architecture makes it simpler to develop unit tests. For example, in the next section, which discusses how to solve data management problems that arise in a partitioned architecture, you will see how both HTTP and messaging are used. Many enterprise Java applications consist of a single WAR or EAR file. The same is true of other applications written in other languages such as Ruby and even C++.

Implement a microservice in ASP.NET Core

In the WebApi Project, Properties drill down, you can find a launchsettings.json file. This file holds all the configurations required for the app launch. Thus, the swagger will open up by default every time you run the application. We will have to register Swager within the application service container. Navigate to ../Startup.cs and add these lines to the ConfigureServices method.

Also, it results in shorter development periods since the code is simpler to understand and has fewer defects. These guidelines are crucial because they free developers from the burden of sifting through a maze of disorganized code in order to swiftly add new features and solve errors. After Layered and Hexagonal architectures, the time has come to talk about their close cousin – the Onion Architecture initially introduced in a series of posts by Jeffrey Palermo. The Onion Architecture does not depend on any specific language or framework. You can implement it in basically any language that supports dependency injection.

The Key Differences Between Onion Architecture and Clean Architecture

This is because you end up writing all of your logic in server side code (mainly aspx.cs files). This scenario produces very tight coupling over the period of time and system becomes a nightmare to maintain. It is an ASP.NET Core Web application in this sample but it could be a Unit Test or Web API project.

  • Hope this article helps you in a clear understanding of Onion Architecture.
  • So you can’t just swap out the DAL because you need the one with the abstractions.
  • Onion Architecture is comprised of multiple concentric layers interfacing each other towards the core that represents the domain.
  • That would be insane from the maintainability point of view.
  • I recommend you follow the example application on which I will demonstrate the implementation of the hexagonal architecture in the following parts of this tutorial series.

This way, your DAL would reference/depend on the business layer so that it’s implementations implement the abstractions which exist in the business layer. Now, the business layer can literally exist in complete isolation as far as dependencies are concerned. Building scalable, maintainable, and testable applications can benefit greatly from the Onion architecture. The architecture must be carefully considered before implementation because it might not be appropriate for all projects, especially smaller ones. A potent design paradigm for creating scalable, maintainable, and testable software applications is the onion architecture. Because there is a distinct division of duties, it is simpler to create unit tests, maintain the application, and grow it as necessary.

Briefly about Microservices

Changes to one layer should not have an impact on the others because each layer is responsible for a distinct task. This makes it simpler to update and maintain the application over time. The Onion Architecture encourages a distinct division of responsibilities between the application’s many layers. This increases the application’s modularity and makes it simpler to comprehend and maintain. The Onion Architecture relies heavily on the usage of interfaces. Interfaces specify the agreements between the layers, facilitating the replacement of implementations.

Benefits and Drawbacks of Onion Architecture

We simply move all infrastructure and data access concerns to the external of the application and not into the center. Jeffrey Palermo proposed this approach called Onion Architecture on his blog 2008. However, Jeffrey liked to have an easy to remember name, which allows communicating the architecture pattern more effectively. Overall, onion architecture provides several advantages that make it an ideal choice for building scalable and maintainable software systems. Onion Architecture has great practical value, particularly for creating expansive, intricate software systems.

Essential Principals of Onion architecture

Persistence, Infrastructure and Presentation layers are called Periphery layers. Software should be easily modifiable and remain so throughout its lifetime. To this end, it should be structured into components that are isolated from one another and can be developed and tested independently. The hexagon is also great for drawing in two primary ports on the left and two secondary ports on the right. Cockburn says he’s never encountered a project that required more than four ports for its schematic representation. This is where the dependency inversion principle comes into play.

Benefits and Drawbacks of Onion Architecture

Therefore, our pieces and even the whole project become more easy to maintain, more flexible, easily extendable and more readable. We can be able to make changes even without effecting any other module / class in our project and modify different technologies, tools. We create a loosely coupled structure which we aim in almost every design principle. All source code dependencies point exclusively in the direction of the core.

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The dependency inversion principle is applied when control flows in the opposite direction, i.e., from the core to the infrastructure (e.g., to the database). In the final analysis, therefore, the onion architecture is also almost identical to the hexagonal architecture – it differs only in the explicit “domain model” at the center of the application core. Just as in the hexagonal and clean architecture, all source code dependencies point in the direction of the core. Where the call direction goes opposite to the source code dependency, dependency inversion is applied. Onion Architecture and Clean Architecture both are used to provide a standard architecture to the software.