Controllers and Routes

Introduction to controllers and routes

In this lesson, we’ll delve into a fundamental aspect of NestJS development: controller routing and request handling. We’ll learn how to define routes, handle various HTTP methods, and manage incoming data using route parameters, query parameters, and request bodies.

Controllers

In NestJS, a controller is a class that handles HTTP requests and generates corresponding responses. Controllers act as essential intermediaries between the client’s requests and the services responsible for processing those requests. They receive incoming requests, invoke the corresponding services, and then return the results to the client.

Controllers are responsible for the following:

• Request handling: Controllers define how incoming HTTP requests are handled within the application. They specify which endpoint or route corresponds to a particular controller method.

• Business logic orchestration: Controllers delegate business operations to service classes, ensuring the separation of concerns and maintainability.

• Data transformation: Controllers facilitate data transformation by handling route parameters, query parameters, and request bodies. They ensure the incoming data is appropriately parsed and validated before passing it to the services.

The controller is defined as a class with the @Controller decorator, as in the example below: