Custom function using repository in sequence

Question

I created a custom function that needs to be executed in every route of my server.

This function needs to retrive a parameter in the header of the request and check this parameter inside the DB. (controlled by a repository)

how can I gain the access of this repository within my function?

I try different possibilities but I cannot be able to achieve a result:

1. create a repository inside the function (the db seems empty :( )
2. try to pass the repository from the controller (would be okay but in the sequence file I cannot have access to the controller nor the repository :(
3. try to include the controller in the function but like 2.

I'm a beginner of loopback and typescript as you can see =)

Answer 1

I think you are looking for the recently introduced Interceptors, see Interceptors and Interceptor generator.

Since you want to invoke your function for every incoming request, you can use a Global interceptor.

how can I gain the access of this repository within my function?

Write an Interceptor Provider, it allows you to leverage @inject-based dependency-injection to receive the repository. For example:

class MyRequestValidator implements Provider<Interceptor> {
  constructor(
    @repository(TokenRepository) protected tokenRepo: TokenRepository,
    @inject(RestBindings.Http.REQUEST) protected request: Request,
  ) {}

  value() {
    return this.intercept.bind(this);
  }

  async intercept<T>(
    invocationCtx: InvocationContext,
    next: () => ValueOrPromise<T>,
  ) {
    // parse the parameter from this.request.headers[name]
    const token = this.request.headers['x-my-token'];

    // call this.tokenRepo methods to query the database
    const found = await this.tokenRepo.findOne({where:{id: token}});
    const isValid = !found.expired;

    if (!isValid) {
      // throw new Error() to abort with error
      throw new HttpErrors.BadRequest('Invalid token.'));
    }

    // call next() to continue with request handling
    return next();
  }
}