Onion Architecture In ASP NET Core 6 Web API

We could create an initialization script, connect to the Docker container while it is running the database server, and execute the script. But this is a lot of onion architecture manual work, and it is error-prone. To make it straightforward to download the application code and be able to run the application locally we are using Docker.

Implementation of Onion Architecture

That’s because the whole application focuses on logic, so any wrong action could break it down. Briefly, onion architecture is a pattern that is designed to be used at the solution or system level. It comes with several principles and layers that will be explained below. The more involved approach is to define compilation modules representing the layers. Its disadvantage is a more
complicated build structure and setup of your build tool of choice. On the other side though, having the compiler on
your side is very helpful, and prevents the above-mentioned issue.

Frameworks, Clients and Drivers

The domain layers often need information or functionality in order to complete business functionality, however they should not directly depend on these. Instead, the application layer needs to depend on the the contracts defined in the Domain Services layer. Application services also referred to as “Use Cases”, are services responsible for just orchestrating steps for requests and should not have any business logic.

  • Having created a domain model and a web API, we needed to seamlessly connect them.
  • The green layer is the layer of implementation or the Infrastructure layer.
  • In this section, we create an interface and service for our error logging and also services for our Students and Teachers entity.
  • So in functional languages, your data em behaviors won’t tightly coupled, and it isn’t a bad thing.
  • Just to make our solution a bit clean, let’s also add API Versioning to the WebAPI.

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? It’s a software that any developer should be able to do improvements and fixes without worrying about breaking something under the hood. Any developer, familiar with the domain, should be able to understand the code, and easily know where to change things.Modifying the view layer should not break any domain logic.

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After adding all the layers our project structure will look like this. In the case of the API Presentation layer that presents us the object data from the database using the HTTP request in the form of JSON Object. Onion architecture comes with very clear rules about priorities, dependence, and layers.

Implementation of Onion Architecture

However, this architecture pattern is not a silver bullet to every problem. As with all software problems, we need to evaluate whether or not we need this additional abstraction as it is more suited for larger applications with many engineers working on them. As engineers we need to apply critical thinking to determine whether or not it will overall benefit the task at hand. Furthermore, the added complexity of defining contracts / interfaces and religiously enforcing them requires a strong understanding of the pattern.

Layer separation

The Importance of Logging errors in applications cannot be over-emphasized. Lastly, StudentTeacher which is our main API project to also get a reference from StudentTeacher.Service project. Writing Minimal Clean Code and Creating reusable components are some of the things that set you apart from other developers. DEV Community — A constructive and inclusive social network for software developers.

Implementation of Onion Architecture

Notice, that the biggest file is the one for the infrastructure layer. The
infrastructure has all the framework — in this case Spring Boot — database driver, and other dependencies, and itself
depends on both domain and application. There’s of course nothing preventing you from declaring extra dependencies,
say Lombok. The most important thing to note here is that with this build setup, it will not be possible to reverse the
order of dependencies between the layers. 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.

Creating Generic Repository for Data Acces

The one that we used in our most recent
project was to use a package naming convention. This is also the layer that “knows” which operations should be performed atomically, thus the transaction-related code
is placed here. Note, however, that in the example above, the transactions field is actually an interface reference. This is the layer where you place classes describing the core of your business. This Architecture style does have some learning curve for developers in the project, but once mastered, pays back many

Implementation of Onion Architecture

It could be basically a function, instead of a method. As this layer is purely logical, it should be pretty easy to test it, as you don’t have to worry about mocking IO operations. Just to make our solution a bit clean, let’s also add API Versioning to the WebAPI. The presentation layer is where you would Ideally want to put the Project that the User can Access.

Hangfire in ASP.NET Core 3.1 – Background Jobs Made Easy

With onion architecture, there is only an object model at the lowest level, which does not depend on the type of database. The actual type of database and the way of storing data is determined at the upper infrastructure level. The idea of the Onion Architecture is based on the inversion of control principle, i.e. placing the domain and services layers at the center of your application, externalizing the infrastructure.

Remember we created an IApplicationDBContext Interface in the Application Layer? Create a new folder named Context and add a new class ApplicationDbContext. With the CRUD logic out of the way, let’s set up EFCore in the Persistence Layer and try to generate a database.

Business 101

We are creating a project called Presentation and giving it a reference to the Microsoft.AspNetCore.Mvc.Core NuGet package so that it has access to the ControllerBase class. Then we can create our controllers inside this project. To learn how to https://www.globalcloudteam.com/ implement the repository pattern with Entity Framework Core you can check out this article ASP.NET Core Web API – Repository Pattern. With this approach, we are being very explicit about what the higher layers of the Onion can and can not do.

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