Nest JS Architecture

Client Server Architecture

in client server architecture client send request to the server and server process the request and send back response to the client.

Nest js Architecture

Controllers

Controllers responsible to handle request.it has multiple request handler attached for different requestes.

Services

All the business logic is present here.it's responsible for communicating with database. and after process it sends data to the controller then controller send response to the client.

There are 4 types of scope

1. Global Scope

2. Module Scope

3. Controller Scope

4. Request Handle/Route Scope

Middleware

it's executed before reaching request to the controller.if you want manipulate request object you can do it there. we can add middleware at global scope, controller scope, Request handler scope.

Guard

it's responsible to check is request should be process or not. we use this for validation of user is user authenticated or not.

Pipe

if you want to transform or validate request object you can use pipe in nest js.

Interceptor

it's similar to middleware but executed both request and response time.

Exception Filter

if any error occurs at application it is handled by Exception filter at global level.

Order of excution

1. Middleware

2. Guards

3. Interceptor

4. Pipe