It’s a good fit for microservices, where data access layer not only comprises database, but also for example an http client, to get data from another microservice, or even from an external system. The circles represent different layers of responsibility. In general, the deeper we dive, the closer we get to the domain and business rules. The outer circles represent mechanisms and the inner circles represent core domain logic. The outer layers depend on inner layers and the inner layers are completely unaware of outer circles. Classes, methods, variables, and source code in general belonging to the outer circle depends on the inner circle but not vice versa.
You can see that we are adding the API Versioning data to the route attribute and also creating an IMediator object. In the Startup/ConfigureServices of the API project, add these lines to register the Versioning. Then, run the following commands to add migrations and to generate/update the database.
What is Onion Architecture?
The main issues we faced were related to maintaining the low connectivity of microservices. That’s why it was difficult to immediately divide the functionality into the necessary microservices. Our customer needed a software system compatible with their hardware so that clients could buy equipment, install software and create and manage content. The challenge was to create a cloud software solution for a digital signage hardware manufacturer.
This layer creates an abstraction between the domain entities and business logic of an application. In this layer, we typically add interfaces that provide object saving and retrieving behavior typically by involving a database. This layer consists of the data access pattern, which is a more loosely coupled approach to data access. Shown above is the proposed Onion Architecture, which has layers defined from core to Infrastructure. The fundamental rule is that all code can depend on layers more central, but code cannot depend on layers further out from the core.
Differences between Onion & Hexagonal Architecture
Using this approach, we can encapsulate all of the rich business logic in the Domain and Service layers without ever having to know any implementation details. In the Service layer, we are going to depend only on the interfaces that are defined by the layer below, which is the Domain layer. It is the outermost layer and contains peripheral aspects such as UI and tests.
However, it’s up to the architect community to consider and argue in the discussion on whether or not to apply the architecture. However, all the other structures of the software are bound by its settings. Delve into the world of cloud computing and unravel the differences between cloud native and cloud based solutions, gaining insights into their unique characteristics and capabilities. Exceptional product leaders unite teams, drive innovation, and create outstanding products with visionary thinking and data-driven decisions.
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At deeper layers, we define abstract interfaces, while at the top layer, we give their concrete implementation. By doing this, we can keep our attention on the domain model and lessen our concern about implementation issues. We may also use dependency injection frameworks like Spring to link interfaces with implementation at runtime. For Example, Infrastructure layer implementations include external services used in Application Services and repositories used in the domain. The core of an onion architecture comprises several concentric layers that interface with one another.
The User Interface layer depends on the Application layer and interacts with the user using the services and interfaces provided by the Application layer. In Onion Architecture, dependencies flow from the outer layers toward the innermost core layer. This means the core layer is entirely decoupled from the outside world and can be tested independently of other components. During my Engineering career, I’ve worked on multiple projects using different architectural styles. At first glance, Clean Architecture provides a better understanding of boundaries and provides a clearer separation of concerns compared to Onion Architecture.
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We will build a RESTful API that follows the Onion architecture, with ASP.NET Core and .NET 5. By doing dependency injection in all the code, everything becomes easier to test. So, the only place in your application that actually creates objects that are capable of doing IO is the application’s entrypoint. The Infrastructure Layer uses them, but is does not create them. If you have a repository that expects a PostgreSQL client, the main should instantiate it and pass it to the repository during its initialization.
- The change in paradigm is not so straightforward, so you will need to invest some time in learning the architecture before you can use it effortlessly.
- Any small change in the Business Logics layer or Data access layer may prove dangerous to the integrity of the entire application.
- It allows developers to focus on the value-providing
implementation rather than thinking Hmm where should I put this class?. - You also need to ensure that each layer only depends on the layer beneath it, and use inversion of control and dependency injection to manage dependencies.
- It addresses the issue of separation of concerns by separating UI, business logic, and data access logic.
Domain Layer – At the very core is the Domain 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. Besides the domain objects, you could also have domain interfaces, but just the interfaces and not any kind of implementation. https://www.globalcloudteam.com/ The core of the business logic should be free (in theory at least) from any of the technical, and
framework-related problems, allowing for easy testing and rapid development. The implementation of the interfaces specified by the domain layer is the responsibility of the infrastructure layer. It offers the necessary infrastructure parts, including messaging, logging, and data access.
Advantages of Onion Architecture in ASP.NET Core
It holds all the logic related to the Business requirements. Now, every application ideally has onion architecture its own dedicated Database. In order to access the Database, we introduce a Data Access Layer.
This provides flexibility in the choice of technologies and platforms used in the implementation of the application. Putting business-specific rules in a centralized place is something suggested by both Clean and Onion Architecture. Although they use different names for very similar concepts, they both encourage us to think about business logic in the same way.
Maintainability
Java developers may not be as interested in Onion Architecture as C# developers. However, the decision to use the architecture is left to the community of architects to debate. As our ApplicationDbContext is configured, let’s generate the migrations and ultimately create a Database using Ef Core Tools – Code First Approach.
