How to refresh token in Nestjs

Question

import { ExtractJwt, Strategy } from 'passport-jwt';
import { AuthService } from './auth.service';
import { PassportStrategy } from '@nestjs/passport';
import { Injectable, UnauthorizedException } from '@nestjs/common';
import { JwtPayload } from './model/jwt-payload.model';

@Injectable()
export class JwtStrategy extends PassportStrategy(Strategy) {
  constructor(private readonly authService: AuthService) {
    super({
      jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
      secretOrKey: 'secretKey',
    });
  }

  async validate(payload: JwtPayload) {
    const user = await this.authService.validateUser(payload);
    if (!user) {
      throw new UnauthorizedException();
    }
    return true;
  }
}

Token is extracted from the request by PassportStrategy. I don't know how to catch the error when the token expires or gets invalid. My purpose is if there is an error because the token expired, I need to refresh the token. Otherwise do something else.

Answer 1

Instead of using the built-in AuthGuard you can create your own one and overwrite the request handler:

@Injectable()
export class MyAuthGuard extends AuthGuard('jwt') {

  handleRequest(err, user, info: Error) {
    if (info instanceof TokenExpiredError) {
      // do stuff when token is expired
      console.log('token expired');
    }
    return user;
  }

}

Depending on what you want to do, you can also overwrite the canActivate method where you have access to the request object. Have a look at the AuthGuard sourcecode.