Building Scalable Server-Side Applications with NestJS
NestJS is a Node.js web framework built with TypeScript that enables developers to build scalable server-side applications. The server side of an application performs crucial logic such as handling requests, sending responses, storing data in a database, and more. In this article, we will explore the fundamental concepts of routes and controllers in NestJS.
Understanding HTTP Requests
Before diving into NestJS routes and controllers, let’s review the basics of HTTP requests. An HTTP request is a user’s request to perform an action related to a resource. These requests are made through a client, such as a browser or application, and are classified by verbs. The most commonly used verbs are:
- GET: Retrieve a resource or a list of resources
- POST: Create a new resource entry
- PUT: Update an existing resource
- DELETE: Delete an existing resource
Defining NestJS Routes and Controllers
In NestJS, a route is a combination of an HTTP method, a path, and the function to handle it defined in an application. A controller is a class defined with methods for handling one or more requests. The controller provides the handler function for a route. In NestJS, routes are defined in the controller alongside the handler method using decorators.
Creating a NestJS Project
To get started with NestJS, we need to create a new project. We can do this using the NestJS CLI. Once installed, we can run the Nest command to create a new project.
Setting up the Database and ORM
For our example application, we will use a MySQL database and TypeORM to handle operations to our DB. We will install the required packages and configure our database connection.
Creating Entities and Services
Next, we will create a Tree entity and a TreeService to handle operations on our Tree entity. We will use the repository design pattern to abstract communication with the data layer.
Defining Routes and Controllers
Now that we have set up our database and entities, we can define our routes and controllers. We will create a TreeController to handle requests related to our Tree entity.
Passing Parameters in Routes
We can pass parameters in routes using the @Param() decorator. This allows us to access the parameter value in our handler function.
Passing a Request with a Payload Body
We can pass a payload body in requests using the @Body() decorator. This allows us to access the payload body in our handler function.
Passing Query Parameters in Routes
We can pass query parameters in routes using the @Query() decorator. This allows us to access the query parameter value in our handler function.
Validating Route Parameters
We can validate route parameters using pipes. This ensures that the data sent via parameters matches what our application expects.
By following these steps, we can build scalable server-side applications with NestJS. We can define routes and controllers to handle requests, pass parameters and payload bodies, and validate route parameters to ensure data consistency.