Understanding Service, Repository and Controller, PT. 1

These are concepts widely used in Software Architecture, as they help to structure and keep the code more organized. Understand now the roles and responsibilities of each person!

Service

The Service is the layer responsible for validating the request that the user sends. In other words, it is responsible for the business rule or application logic.

To make it easier to understand, imagine that you have an application that will carry out a banking transaction. Before the transaction is completed, you need to validate some information, such as whether there is a credit limit on the account, whether there is any duplication of information that causes a conflict in the database, whether the information sent is correct, and other validations that apply to the logic and business rules.

All this logic behind the application is delegated to the Service layer within the software, and it is this that will signal whether the data sent is in accordance with what is expected.

Repository

This layer is responsible for mediating the database and the rest of the application. It is what will save the data provided by the user in its database. In other words, the complexity of CRUD (Create, Read, Update and Delete) is hidden in the Repository layer, where the database will be accessed and the information sent will be manipulated.

By isolating the database access logic, the code becomes cleaner and easier to understand.

Controller

The Controller handles user requests and issues a response to them. Therefore, it receives the inputs (normally in HTTP via WEB), validates and calls the Service to handle the business logic, and then returns a response to the user.

In other words, it validates the data passed by the user (such as mandatory fields, data type or format and ID validation) BEFORE passing this data to the Service, which in turn will validate the business logic. Afterwards, the Controller sends a response to the user informing whether the request was successful or failed.

But how do the components relate?

When the user makes an HTTP request, the Controller receives it and performs prior validation. If everything is correct, send it to Service.

The Service will take the information and validate it according to the logic behind the application. If everything is in order, send the request to the Repository.

The Repository,, in turn, causes this data to be saved, updated or deleted, according to the request sent to the Controller.

The Controller receives the final response and sends it to the user, informing the success or error of the operation.

SUMMARY

We saw that each layer has its own responsibility, and this makes code maintenance easier.

Service: Business logic, process validation

Repository: Responsible for CRUD in the database

Controller: Responsible for receiving the request via API and informing the user of the final message.

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