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Overview

The JwtPrepareService in NestJS is a service designed for generating JSON Web Tokens (JWTs) as part of the authentication process. This service simplifies the creation and management of JWTs.

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prepareJwtResponse Method

The primary method of JwtPrepareService is prepareJwtResponse, which generates JWTs based on user information and additional parameters:

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Parameters

  • userDocument: The user’s document object from the database.
  • withoutRefreshToken: Optional flag to exclude a refresh token in the response.
  • payload: Additional data to include in the JWT.
  • kind: The type of account (e.g., INTERNAL, APPLE, GOOGLE). For UI purposes only.
  • expiresIn: Token expiry duration. Defaults to 20m.

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JWT Response Structure

The jwtResponse object is structured to include essential authentication details: 
const jwtResponse = {
  access_token: authJwtToken,
  refresh_token: authJwtRefreshToken,
  user: args.userDocument,
};

if (args.kind) {
  jwtResponse["kind"] = args.kind;
}
  • access_token: The JWT for user authentication.
  • refresh_token: An optional token for refreshing the access token.
  • user: The user document containing user details.
  • Additional fields like kind can be conditionally included based on the arguments passed.

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Generating and Structuring the Response

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Token Generation

  • The method constructs a JWT payload from userDocument and any additional payload.
  • It generates an access token, and optionally, a refresh token based on the withoutRefreshToken flag.
  • The tokens are signed with a secret key and an optional expiry time.

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Usage Example

Here’s an example of how to use JwtPrepareService in a controller or service: 
const result = await this.jwtPrepareService.prepareJwtResponse({
  userDocument: req["user"],
  withoutRefreshToken: true,
  payload: {
    resource: resource,
    tokenType: TokenType.DEFAULT,
  },
});