Error responses

Nest.js has an exception layer, which is responsible for catching unhandled exceptions from request handlers and returning an appropriate response to the client.

A global exception filter handles all exception thrown from request handlers.

HttpException

If an exception thrown from a request handler is a HttpException, the global exception filter will transform it to the a JSON response.

For example, you can throw an HttpException from the create() handler function if the body is not valid as shown.

import { Body, Controller, HttpException, HttpStatus, Post } from '@nestjs/common';

@Controller('entries')
export class EntryController {
    @Post()
    create(@Body() entry: Entry) {
        if (!entry) throw new HttpException('Bad request', HttpStatus.BAD_REQUEST);
        this.entryService.create(entry);
    }
}

If this exception is thrown, the response would look like this:

{
    "statusCode": 400,
    "message": ...