SPA + API: Angular 2 Implementation for the SPA

This document is part of the SPA + API Architecture Scenario and it explains how to implement the SPA in Angular 2. Please refer to the scenario for information on the implemented solution.

The full source code for the Angular 2 implementation of the SPA can be found in this GitHub repository.

1. Configuration

Your application will require certain configuration information. Before carrying on with the rest of the implementation, create an AuthConfig interface which will contain various configuration values. Place this interface in a file called auth0-variables.ts.

2. Authorize the User

Create an Authorization Service

The best way to manage and coordinate the tasks necessary for user authentication is to create a reusable service. With the service in place, you'll be able to call its methods throughout your application. An instance of the WebAuth object from auth0.js can be created in the service.

The service includes several methods for handling authentication.

  • login: calls authorize from auth0.js which initiates Universal Login
  • handleAuthentication: looks for an authentication result in the URL hash and processes it with the parseHash method from auth0.js
  • setSession: sets the user's Access Token, ID Token, and a time at which the Access Token will expire
  • logout: removes the user's tokens from browser storage
  • isAuthenticated: checks whether the expiry time for the Access Token has passed

Process the Authentication Result

When a user authenticates via Universal Login and is then redirected back to your application, their authentication information will be contained in a URL hash fragment. The handleAuthentication method in the AuthService is responsibile for processing the hash.

Call handleAuthentication in your app's root component so that the authentication hash fragment can be processed when the app first loads after the user is redirected back to it.

Add the Callback Component

Using Universal Login means that users are taken away from your application to a page hosted by Auth0. After they successfully authenticate, they are returned to your application where a client-side session is set for them.

You can choose to have users return to any URL in your application that you like; however, it is recommended that you create a dedicated callback route to serve as a central location that the user will be returned to upon successful authentication. Having a single callback route is beneficial for two main reasons:

  • It prevents the need to whitelist multiple (and sometimes unknown) callback URLs
  • It serves as a place to show a loading indicator while your application sets the user's client-side session

Create a component named CallbackComponent and populate it with a loading indicator.

This example assumes some kind of loading spinner is available in an assets directory. See the downloadable sample for a demonstration.

After authentication, users will be taken to the /callback route for a brief time where they will be shown a loading indicator. During this time, their client-side session will be set, after which they will be redirected to the /home route.

3. Get the User Profile

Extract info from the token

This section shows how to retrieve the user info using the Access Token and the /userinfo endpoint. Alternatively, you can just decode the ID Token using a library (make sure you validate it first). The output will be the same. If you need additional user information consider using the our Management API.

To obtain the user's profile, update the existing AuthService class. Add a getProfile function which will extract the user's Access Token from local storage, and then pass that call the userInfo function to retrieve the user's information.

You can now simply call this function from any service where you want to retrieve and display information about the user.

For example you may choose to create a new component to display the user's profile information:

The template for this component looks as follows:

4. Display UI Elements Conditionally Based on Scope

During the authorization process we already stored the actual scopes which a user was granted in the local storage. If the scope returned in the authResult is not empty, it means that a user was issued a different set of scopes than what was initially requested, and we should therefore use authResult.scope to determine the scopes granted to the user.

If the scope returned in authResult is issued is empty, it means the user was granted all the scopes that were requested, and we can therefore use the requested scopes to determine the scopes granted to the user.

Here is the code we wrote earlier for the setSession function that does that check:

Next we need to add a function to the AuthService class which we can call to determine if a user was granted a specific scope:

You can call this method to determine whether we should display a specific UI element, or not. As an example we only want to display the Approve Timesheets link if the user has the approve:timesheets scope. Note in the code below that we added a call to the userHasScopes function to determine whether that link should be displayed or not.

Protect a route

We should also protect a route to not allow a route to be navigated to if a user has not been granted the correct scopes. For this we can add a new ScopeGuardService service class:

And then use that when we configure the routes to determine whether a route can be activated. Notice the use of the new ScopeGuardService in the definition for the approval route below:

5. Call the API

The angular2-jwt module can be used to automatically attach JSON Web Tokens to requests made to your API. It does this by providing an AuthHttp class which is a wrapper over Angular's Http class.

Install angular2-jwt:

Create a factory function with some configuration values for angular2-jwt and add it to the providers array in your application's @NgModule. The factory function should have a tokenGetter function which fetches the access_token from local storage.

After angular2-jwt is configured, you can use the AuthHttp class to make secure calls to your API from anywhere in the application. To do so, inject AuthHttp in any component or service where it is needed and use it just as you would use Angular's regular Http class.

6. Renew the Access Token

Renewing the user's Access Token requires to update the Angular SPA. Add a method to the AuthService which calls the checkSession method from auth0.js. If the renewal is successful, use the existing setSession method to set the new tokens in local storage.

In the AuthService class, add a method called scheduleRenewal to set up a time at which authentication should be silently renewed. In the sample below this is set up to happen 30 seconds before the actual token expires. Also add a method called unscheduleRenewal which will unsubscribe from the Observable.

Finally you need to initiate the schedule renewal. This can be done by calling scheduleRenewal inside your AppComponent which will happen when the page is loaded. This will occur after every authentication flow, either when the user explicitly logs in, or when the silent authentication happens.