Angular 9 - JWT Authentication with Refresh Tokens

Tutorial built with Angular 9.1.9

Other versions available:

• Angular: Angular 14, 10
• Vue: Vue 3

In this post we'll go through an example of how to implement JWT authentication with refresh tokens in Angular 9.

The example angular app has just two routes - a login page (/login) and a home page (/). To login the app sends a POST request to the api to authenticate the username and password, on successful login the app receives a JWT token to make authenticated requests to secure api routes, and a refresh token (in a cookie) to get a new JWT token from the api when the old one expires (a.k.a. to refresh the token).

On startup the app attempts to automatically authenticate by sending the refresh token to the api to get a new JWT token, which enables users to stay logged in between page refreshes and browser sessions until they logout. It works by sending the refresh token cookie stored in the browser to the api, if the cookie doesn't exist or is not valid it will fail silently and the login page will be displayed.

After the user logs in the app starts a countdown to automatically refresh the token one minute before it expires, this is also referred to as "silent refresh" since it happens in the background. The countdown starts again after each silent refresh to keep the user logged in.

The angular app runs with a fake backend by default to enable it to run completely in the browser without a real backend api (backend-less), to switch to a real api you just have to remove or comment out the line below the comment // provider used to create fake backend located in the app module (/src/app/app.module.ts). You can build your own api or hook it up with the ASP.NET Core api or Node.js + MongoDB api available (instructions below).

The example project is available on GitHub at https://github.com/cornflourblue/angular-9-jwt-refresh-tokens.

Here it is in action: (See on StackBlitz at https://stackblitz.com/edit/angular-9-jwt-refresh-tokens)

Update History:

• 17 Jun 2020 - Added instructions on how to run the Angular app with a Node.js + MongoDB api
• 22 May 2020 - Built with Angular 9.1.9

Running the Angular JWT with Refresh Tokens Example Locally

1. Install NodeJS and NPM from https://nodejs.org.
2. Download or clone the Angular project source code from https://github.com/cornflourblue/angular-9-jwt-refresh-tokens
3. Install all required npm packages by running npm install or npm i from the command line in the project root folder (where the package.json is located).
4. Start the app by running npm start from the command line in the project root folder, this will compile the Angular app and automatically launch it in the browser on the URL http://localhost:4200.

NOTE: You can also start the app with the Angular CLI command ng serve --open. To do this first install the Angular CLI globally on your system with the command npm install -g @angular/cli.

For more info on setting up an Angular development environment see Angular - Setup Development Environment.

Running the Angular App with an ASP.NET Core 3.1 API

For full details about the ASP.NET Core api see ASP.NET Core 3.1 API - JWT Authentication with Refresh Tokens. But to get up and running quickly just follow the below steps.

1. Install the .NET Core SDK from https://www.microsoft.com/net/download/core.
2. Download or clone the project source code from https://github.com/cornflourblue/aspnet-core-3-jwt-refresh-tokens-api
3. Start the api by running dotnet run from the command line in the project root folder (where the WebApi.csproj file is located), you should see the message Now listening on: http://localhost:4000.
4. Back in the Angular app, remove or comment out the line below the comment // provider used to create fake backend located in the /src/app/app.module.ts file, then start the Angular app and it should now be hooked up with the ASP.NET Core API.

Running the Angular App with a Node.js + MongoDB API

For full details about the ASP.NET Core api see Node.js + MongoDB API - JWT Authentication with Refresh Tokens. But to get up and running quickly just follow the below steps.

1. Install MongoDB Community Server from  https://www.mongodb.com/download-center/community.
2. Run MongoDB, instructions are available on the install page for each OS at https://docs.mongodb.com/manual/administration/install-community/
3. Download or clone the project source code from https://github.com/cornflourblue/node-mongo-jwt-refresh-tokens-api
4. Install all required npm packages by running npm install or npm i from the command line in the project root folder (where the package.json is located).
5. Start the api by running npm start (or npm run start:dev to start with nodemon) from the command line in the project root folder, you should see the message Server listening on port 4000, and you can view the Swagger API documentation at http://localhost:4000/api-docs.
6. Back in the Angular app, remove or comment out the line below the comment // provider used to create fake backend located in the /src/app/app.module.ts file, then start the Angular app and it should now be hooked up with the Node.js + MongoDB API.

Angular 9 Project Structure

The Angular CLI was used to generate the base project structure with the ng new <project name> command, the CLI is also used to build and serve the application. For more info about the Angular CLI see https://angular.io/cli.

The app and code structure of the tutorial mostly follow the best practice recommendations in the official Angular Style Guide, with a few of my own tweaks here and there.

Each feature has it's own folder (home & login), other shared/common code such as services, models, helpers etc are placed in folders prefixed with an underscore _ to easily differentiate them from features and group them together at the top of the folder structure.

The index.ts files in each folder are barrel files that group the exported modules from each folder together so they can be imported using only the folder path instead of the full module path, and to enable importing multiple modules in a single import (e.g. import { AuthenticationService, UserService } from '../_services').

Path aliases @app and @environments have been configured in tsconfig.json that map to the /src/app and /src/environments directories. This allows imports to be relative to the app and environments folders by prefixing import paths with aliases instead of having to use long relative paths (e.g. import MyComponent from '../../../MyComponent').

Here are the main project files that contain the application logic, I didn't include files that were generated by the Angular CLI ng new command that I left unchanged.

• src
  • app
    • _helpers
      • app.initializer.ts
      • auth.guard.ts
      • error.interceptor.ts
      • fake-backend.ts
      • jwt.interceptor.ts
      • index.ts
    • _models
      • user.ts
      • index.ts
    • _services
      • authentication.service.ts
      • user.service.ts
      • index.ts
    • home
      • home.component.html
      • home.component.ts
      • index.ts
    • login
      • login.component.html
      • login.component.ts
      • index.ts
    • app-routing.module.ts
    • app.component.html
    • app.component.ts
    • app.module.ts
  • environments
    • environment.prod.ts
    • environment.ts
  • index.html
  • main.ts
  • polyfills.ts
  • styles.less
• package.json
• tsconfig.json

App Initializer

The app initializer runs before the app starts up, and it attempts to automatically authenticate the user by calling authenticationService.refreshToken() to get a new JWT token from the api. If the user has logged in previously (without logging out) and the browser still contains a valid refresh token cookie, they will be automatically logged in when the app loads.

The call to the .subscribe() method triggers the request to the api, and the .add() method is used for executing additional logic after the request completes (success or failure), so it works like a promise finally() method.

The app initializer is added to angular app in the providers section of the app module using the APP_INITIALIZER injection token. For more info see https://angular.io/api/core/APP_INITIALIZER.

import { AuthenticationService } from '@app/_services';

export function appInitializer(authenticationService: AuthenticationService) {
    return () => new Promise(resolve => {
        // attempt to refresh token on app start up to auto authenticate
        authenticationService.refreshToken()
            .subscribe()
            .add(resolve);
    });
}

Auth Guard

The auth guard is an angular route guard that prevents unauthenticated users from accessing restricted routes, it does this by implementing the CanActivate interface which allows the guard to decide if a route can be activated with the canActivate() method. If the method returns true the route is activated (allowed to proceed), otherwise if the method returns false the route is blocked.

The auth guard uses the authentication service to check if the user is logged in, if they are logged in it returns true from the canActivate() method, otherwise it returns false and redirects the user to the login page.

Angular route guards are attached to routes in the router config, this auth guard is used in app-routing.module.ts to protect the home page route.

import { Injectable } from '@angular/core';
import { Router, CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot } from '@angular/router';

import { AuthenticationService } from '@app/_services';

@Injectable({ providedIn: 'root' })
export class AuthGuard implements CanActivate {
    constructor(
        private router: Router,
        private authenticationService: AuthenticationService
    ) { }

    canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot) {
        const user = this.authenticationService.userValue;
        if (user) {
            // logged in so return true
            return true;
        } else {
            // not logged in so redirect to login page with the return url
            this.router.navigate(['/login'], { queryParams: { returnUrl: state.url } });
            return false;
        }
    }
}

Http Error Interceptor

The Error Interceptor intercepts http responses from the api to check if there were any errors. If the response is 401 Unauthorized or 403 Forbidden the user is automatically logged out of the application, all other errors are logged to the console and re-thrown up to the calling service so an alert with the error can be displayed in the UI.

It is implemented using the HttpInterceptor interface included in the HttpClientModule, by implementing the HttpInterceptor interface you can create a custom interceptor to catch all error responses from the server in a single location.

Http interceptors are added to the request pipeline in the providers section of the app.module.ts file.

import { Injectable } from '@angular/core';
import { HttpRequest, HttpHandler, HttpEvent, HttpInterceptor } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';

import { AuthenticationService } from '@app/_services';

@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
    constructor(private authenticationService: AuthenticationService) { }

    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        return next.handle(request).pipe(catchError(err => {
            if ([401, 403].includes(err.status) && this.authenticationService.userValue) {
                // auto logout if 401 or 403 response returned from api
                this.authenticationService.logout();
            }

            const error = (err && err.error && err.error.message) || err.statusText;
            console.error(err);
            return throwError(error);
        }))
    }
}

Fake Backend Provider

In order to run and test the Angular application without a real backend API, the example uses a fake backend that intercepts the HTTP requests from the Angular app and sends back "fake" responses. This is done by a class that implements the Angular HttpInterceptor interface, for more information on Angular HTTP Interceptors see https://angular.io/api/common/http/HttpInterceptor or this article.

The fake backend contains a handleRoute function that checks if the request matches one of the faked routes in the switch statement, at the moment this includes requests for handling authentication, refreshing tokens, revoking tokens, and getting all users. Matching requests are intercepted and handled by one of the below // route functions, non-matching requests are sent through to the real backend by calling next.handle(request);. Below the route functions there are // helper functions for returning different response types and performing other tasks such as generating and validating jwt and refresh tokens.

For more info on angular fake backends see this post.

import { Injectable } from '@angular/core';
import { HttpRequest, HttpResponse, HttpHandler, HttpEvent, HttpInterceptor, HTTP_INTERCEPTORS, HttpHeaders } from '@angular/common/http';
import { Observable, of, throwError } from 'rxjs';
import { delay, mergeMap, materialize, dematerialize } from 'rxjs/operators';

// array in local storage for users
const usersKey = 'angular-9-jwt-refresh-token-users';
const users = JSON.parse(localStorage.getItem(usersKey)) || [];

// add test user and save if users array is empty
if (!users.length) {
    users.push({ id: 1,  firstName: 'Test', lastName: 'User', username: 'test', password: 'test', refreshTokens: [] });
    localStorage.setItem(usersKey, JSON.stringify(users));
}

@Injectable()
export class FakeBackendInterceptor implements HttpInterceptor {
    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        const { url, method, headers, body } = request;

        // wrap in delayed observable to simulate server api call
        return of(null)
            .pipe(mergeMap(handleRoute))
            .pipe(materialize()) // call materialize and dematerialize to ensure delay even if an error is thrown (https://github.com/Reactive-Extensions/RxJS/issues/648)
            .pipe(delay(500))
            .pipe(dematerialize());

        function handleRoute() {
            switch (true) {
                case url.endsWith('/users/authenticate') && method === 'POST':
                    return authenticate();
                case url.endsWith('/users/refresh-token') && method === 'POST':
                    return refreshToken();
                case url.endsWith('/users/revoke-token') && method === 'POST':
                    return revokeToken();
                case url.endsWith('/users') && method === 'GET':
                    return getUsers();
                default:
                    // pass through any requests not handled above
                    return next.handle(request);
            }    
        }

        // route functions

        function authenticate() {
            const { username, password } = body;
            const user = users.find(x => x.username === username && x.password === password);
            
            if (!user) return error('Username or password is incorrect');

            // add refresh token to user
            user.refreshTokens.push(generateRefreshToken());
            localStorage.setItem(usersKey, JSON.stringify(users));

            return ok({
                id: user.id,
                username: user.username,
                firstName: user.firstName,
                lastName: user.lastName,
                jwtToken: generateJwtToken()
            })
        }

        function refreshToken() {
            const refreshToken = getRefreshToken();
            
            if (!refreshToken) return unauthorized();

            const user = users.find(x => x.refreshTokens.includes(refreshToken));
            
            if (!user) return unauthorized();

            // replace old refresh token with a new one and save
            user.refreshTokens = user.refreshTokens.filter(x => x !== refreshToken);
            user.refreshTokens.push(generateRefreshToken());
            localStorage.setItem(usersKey, JSON.stringify(users));

            return ok({
                id: user.id,
                username: user.username,
                firstName: user.firstName,
                lastName: user.lastName,
                jwtToken: generateJwtToken()
            })
        }

        function revokeToken() {
            if (!isLoggedIn()) return unauthorized();
            
            const refreshToken = getRefreshToken();
            const user = users.find(x => x.refreshTokens.includes(refreshToken));
            
            // revoke token and save
            user.refreshTokens = user.refreshTokens.filter(x => x !== refreshToken);
            localStorage.setItem(usersKey, JSON.stringify(users));

            return ok();
        }

        function getUsers() {
            if (!isLoggedIn()) return unauthorized();
            return ok(users);
        }

        // helper functions

        function ok(body?) {
            return of(new HttpResponse({ status: 200, body }))
        }

        function error(message) {
            return throwError({ error: { message } });
        }

        function unauthorized() {
            return throwError({ status: 401, error: { message: 'Unauthorized' } });
        }

        function isLoggedIn() {
            // check if jwt token is in auth header
            const authHeader = headers.get('Authorization');
            if (!authHeader.startsWith('Bearer fake-jwt-token')) return false;

            // check if token is expired
            const jwtToken = JSON.parse(atob(authHeader.split('.')[1]));
            const tokenExpired = Date.now() > (jwtToken.exp * 1000);
            if (tokenExpired) return false;

            return true;
        }

        function generateJwtToken() {
            // create token that expires in 15 minutes
            const tokenPayload = { exp: Math.round(new Date(Date.now() + 15*60*1000).getTime() / 1000) }
            return `fake-jwt-token.${btoa(JSON.stringify(tokenPayload))}`;
        }

        function generateRefreshToken() {
            const token = new Date().getTime().toString();

            // add token cookie that expires in 7 days
            const expires = new Date(Date.now() + 7*24*60*60*1000).toUTCString();
            document.cookie = `fakeRefreshToken=${token}; expires=${expires}; path=/`;

            return token;
        }

        function getRefreshToken() {
            // get refresh token from cookie
            return (document.cookie.split(';').find(x => x.includes('fakeRefreshToken')) || '=').split('=')[1];
        }
    }
}

export let fakeBackendProvider = {
    // use fake backend in place of Http service for backend-less development
    provide: HTTP_INTERCEPTORS,
    useClass: FakeBackendInterceptor,
    multi: true
};

JWT Interceptor

The JWT Interceptor intercepts http requests from the application to add a JWT auth token to the Authorization header if the user is logged in and the request is to the application api url (environment.apiUrl).

It is implemented using the HttpInterceptor interface included in the HttpClientModule, by implementing the HttpInterceptor interface you can create a custom interceptor to catch all error responses from the server in a single location.

Http interceptors are added to the request pipeline in the providers section of the app.module.ts file.

import { Injectable } from '@angular/core';
import { HttpRequest, HttpHandler, HttpEvent, HttpInterceptor } from '@angular/common/http';
import { Observable } from 'rxjs';

import { environment } from '@environments/environment';
import { AuthenticationService } from '@app/_services';

@Injectable()
export class JwtInterceptor implements HttpInterceptor {
    constructor(private authenticationService: AuthenticationService) { }

    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        // add auth header with jwt if user is logged in and request is to the api url
        const user = this.authenticationService.userValue;
        const isLoggedIn = user && user.jwtToken;
        const isApiUrl = request.url.startsWith(environment.apiUrl);
        if (isLoggedIn && isApiUrl) {
            request = request.clone({
                setHeaders: { Authorization: `Bearer ${user.jwtToken}` }
            });
        }

        return next.handle(request);
    }
}

User Model

The user model is a small class that defines the properties of a user.

export class User {
    id: number;
    username: string;
    password: string;
    firstName: string;
    lastName: string;
    jwtToken?: string;
}

Authentication Service

The authentication service handles communication between the angular app and the backend api for everything related to authentication. It contains methods for login, logout and refresh token, and contains properties for accessing the current user.

The user property exposes an RxJS observable (Observable<User>) so any component can subscribe to be notified when a user logs in, logs out or has their token refreshed, the notification is triggered by the call to this.userSubject.next() from each method in the service. For more info on communicating between components with RxJS Observables see Angular 9 - Communicating Between Components with Observable & Subject.

The userValue getter allows other components to quickly get the value of the current user without having to subscribe to the user observable.

The login() method POSTs the username and password to the API for authentication, on success the api returns the user details and a JWT token which are published to all subscribers with the call to this.userSubject.next(user), the api also returns a refresh token cookie which is stored by the browser. The method then starts a countdown timer by calling this.startRefreshTokenTimer() to auto refresh the JWT token in the background (silent refresh) one minute before it expires so the user stays logged in.

The logout() method makes a POST request to the API to revoke the refresh token that is stored in a browser cookie, then cancels the silent refresh running in the background by calling this.stopRefreshTokenTimer(), then logs the user out by publishing a null value to all subscriber components (this.userSubject.next(null)), and finally redirects the user to the login page.

The refreshToken() method is similar to the login() method, they both perform authentication, but this method does it by making a POST request to the API that includes a refresh token cookie. On success the api returns the user details and a JWT token which are published to all subscribers with the call to this.userSubject.next(user), the api also returns a new refresh token cookie which replaces the old one in the browser. The method then starts a countdown timer by calling this.startRefreshTokenTimer() to auto refresh the JWT token in the background (silent refresh) one minute before it expires so the user stays logged in.

import { Injectable } from '@angular/core';
import { Router } from '@angular/router';
import { HttpClient } from '@angular/common/http';
import { BehaviorSubject, Observable } from 'rxjs';
import { map } from 'rxjs/operators';

import { environment } from '@environments/environment';
import { User } from '@app/_models';

@Injectable({ providedIn: 'root' })
export class AuthenticationService {
    private userSubject: BehaviorSubject<User>;
    public user: Observable<User>;

    constructor(
        private router: Router,
        private http: HttpClient
    ) {
        this.userSubject = new BehaviorSubject<User>(null);
        this.user = this.userSubject.asObservable();
    }

    public get userValue(): User {
        return this.userSubject.value;
    }

    login(username: string, password: string) {
        return this.http.post<any>(`${environment.apiUrl}/users/authenticate`, { username, password }, { withCredentials: true })
            .pipe(map(user => {
                this.userSubject.next(user);
                this.startRefreshTokenTimer();
                return user;
            }));
    }

    logout() {
        this.http.post<any>(`${environment.apiUrl}/users/revoke-token`, {}, { withCredentials: true }).subscribe();
        this.stopRefreshTokenTimer();
        this.userSubject.next(null);
        this.router.navigate(['/login']);
    }

    refreshToken() {
        return this.http.post<any>(`${environment.apiUrl}/users/refresh-token`, {}, { withCredentials: true })
            .pipe(map((user) => {
                this.userSubject.next(user);
                this.startRefreshTokenTimer();
                return user;
            }));
    }

    // helper methods

    private refreshTokenTimeout;

    private startRefreshTokenTimer() {
        // parse json object from base64 encoded jwt token
        const jwtToken = JSON.parse(atob(this.userValue.jwtToken.split('.')[1]));

        // set a timeout to refresh the token a minute before it expires
        const expires = new Date(jwtToken.exp * 1000);
        const timeout = expires.getTime() - Date.now() - (60 * 1000);
        this.refreshTokenTimeout = setTimeout(() => this.refreshToken().subscribe(), timeout);
    }

    private stopRefreshTokenTimer() {
        clearTimeout(this.refreshTokenTimeout);
    }
}

User Service

The user service contains a single method for getting all users from the api, I included it to demonstrate accessing a secure api endpoint using a JWT token after logging in to the application, the token is added to the authorization header of the http request in the JWT Interceptor above.

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

import { environment } from '@environments/environment';
import { User } from '@app/_models';

@Injectable({ providedIn: 'root' })
export class UserService {
    constructor(private http: HttpClient) { }

    getAll() {
        return this.http.get<User[]>(`${environment.apiUrl}/users`);
    }
}

Home Component Template

The home component template contains html and angular 9 template syntax for displaying a simple welcome message and a list of users from a secure api endpoint.

<div class="card mt-4">
    <h4 class="card-header">You're logged in with Angular 9 + JWT & Refresh Tokens!!</h4>
    <div class="card-body">
        <h6>Users from secure api end point</h6>
        <div *ngIf="loading" class="spinner-border spinner-border-sm"></div>
        <ul *ngIf="users">
            <li *ngFor="let user of users">{{user.firstName}} {{user.lastName}}</li>
        </ul>
    </div>
</div>

Home Component

The home component defines an angular 9 component that gets all users from the user service and makes them available to the template via a users array property.

import { Component } from '@angular/core';
import { first } from 'rxjs/operators';

import { User } from '@app/_models';
import { UserService } from '@app/_services';

@Component({ templateUrl: 'home.component.html' })
export class HomeComponent {
    loading = false;
    users: User[];

    constructor(private userService: UserService) { }

    ngOnInit() {
        this.loading = true;
        this.userService.getAll().pipe(first()).subscribe(users => {
            this.loading = false;
            this.users = users;
        });
    }
}

Login Component Template

The login component template contains a login form with username and password fields. It displays validation messages for invalid fields when the submit button is clicked. The form submit event is bound to the onSubmit() method of the login component.

The component uses reactive form validation to validate the input fields, for more information about angular reactive form validation see Angular 9 - Reactive Forms Validation Example.

<div class="col-md-6 offset-md-3 mt-5">
    <div class="alert alert-info">
        Username: test<br />
        Password: test
    </div>
    <div class="card">
        <h4 class="card-header">Angular 9 JWT Auth with Refresh Tokens</h4>
        <div class="card-body">
            <form [formGroup]="loginForm" (ngSubmit)="onSubmit()">
                <div class="form-group">
                    <label for="username">Username</label>
                    <input type="text" formControlName="username" class="form-control" [ngClass]="{ 'is-invalid': submitted && f.username.errors }" />
                    <div *ngIf="submitted && f.username.errors" class="invalid-feedback">
                        <div *ngIf="f.username.errors.required">Username is required</div>
                    </div>
                </div>
                <div class="form-group">
                    <label for="password">Password</label>
                    <input type="password" formControlName="password" class="form-control" [ngClass]="{ 'is-invalid': submitted && f.password.errors }" />
                    <div *ngIf="submitted && f.password.errors" class="invalid-feedback">
                        <div *ngIf="f.password.errors.required">Password is required</div>
                    </div>
                </div>
                <button [disabled]="loading" class="btn btn-primary">
                    <span *ngIf="loading" class="spinner-border spinner-border-sm mr-1"></span>
                    Login
                </button>
                <div *ngIf="error" class="alert alert-danger mt-3 mb-0">{{error}}</div>
            </form>
        </div>
    </div>
</div>

Login Component

The login component uses the authentication service to login to the application. If the user is already logged in they are automatically redirected to the home page.

The loginForm: FormGroup object defines the form controls and validators, and is used to access data entered into the form. The FormGroup class is part of the Angular Reactive Forms module and is bound to the login template above with the [formGroup]="loginForm" directive.

import { Component, OnInit } from '@angular/core';
import { Router, ActivatedRoute } from '@angular/router';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { first } from 'rxjs/operators';

import { AuthenticationService } from '@app/_services';

@Component({ templateUrl: 'login.component.html' })
export class LoginComponent implements OnInit {
    loginForm: FormGroup;
    loading = false;
    submitted = false;
    returnUrl: string;
    error = '';

    constructor(
        private formBuilder: FormBuilder,
        private route: ActivatedRoute,
        private router: Router,
        private authenticationService: AuthenticationService
    ) { 
        // redirect to home if already logged in
        if (this.authenticationService.userValue) { 
            this.router.navigate(['/']);
        }
    }

    ngOnInit() {
        this.loginForm = this.formBuilder.group({
            username: ['', Validators.required],
            password: ['', Validators.required]
        });

        // get return url from route parameters or default to '/'
        this.returnUrl = this.route.snapshot.queryParams['returnUrl'] || '/';
    }

    // convenience getter for easy access to form fields
    get f() { return this.loginForm.controls; }

    onSubmit() {
        this.submitted = true;

        // stop here if form is invalid
        if (this.loginForm.invalid) {
            return;
        }

        this.loading = true;
        this.authenticationService.login(this.f.username.value, this.f.password.value)
            .pipe(first())
            .subscribe({
                next: () => {
                    this.router.navigate([this.returnUrl]);
                },
                error: error => {
                    this.error = error;
                    this.loading = false;
                }
            });
    }
}

App Routing Module

Routing for the Angular app is configured as an array of Routes, each component is mapped to a path so the Angular Router knows which component to display based on the URL in the browser address bar. The home route is secured by passing the AuthGuard to the canActivate property of the route.

The routes array is passed to the RouterModule.forRoot() method which creates a routing module with all of the app routes configured, and also includes all of the Angular Router providers and directives such as the <router-outlet></router-outlet> directive. For more information on Angular Routing and Navigation see https://angular.io/guide/router.

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';

import { HomeComponent } from './home';
import { LoginComponent } from './login';
import { AuthGuard } from './_helpers';

const routes: Routes = [
    { path: '', component: HomeComponent, canActivate: [AuthGuard] },
    { path: 'login', component: LoginComponent },

    // otherwise redirect to home
    { path: '**', redirectTo: '' }
];

@NgModule({
    imports: [RouterModule.forRoot(routes)],
    exports: [RouterModule]
})
export class AppRoutingModule { }

App Component Template

The app component template is the root component template of the application, it contains the main nav bar which is only displayed for authenticated users, and a <router-outlet> directive for displaying the contents of each view based on the current route / path.

<!-- nav -->
<nav class="navbar navbar-expand navbar-dark bg-dark" *ngIf="user">
    <div class="navbar-nav">
        <a class="nav-item nav-link" routerLink="/">Home</a>
        <a class="nav-item nav-link" (click)="logout()">Logout</a>
    </div>
</nav>

<!-- main app container -->
<div class="container">
    <router-outlet></router-outlet>
</div>

App Component

The app component is the root component of the application, it defines the root tag of the app as <app></app> with the selector property of the @Component() decorator.

The component subscribes to the authenticationService.user observable so it can reactively show & hide the main navigation bar when the user logs in & out of the application. I didn't worry about unsubscribing from the observable here because it's the root component of the application, the only time the app component will be destroyed is when the application is closed which will destroy any subscriptions as well, so there isn't any risk of orphaned subscriptions.

The logout() method is called from the logout link in the main nav bar above to log the user out and redirect them to the login page.

import { Component } from '@angular/core';

import { AuthenticationService } from './_services';
import { User } from './_models';

@Component({ selector: 'app', templateUrl: 'app.component.html' })
export class AppComponent {
    user: User;

    constructor(private authenticationService: AuthenticationService) {
        this.authenticationService.user.subscribe(x => this.user = x);
    }

    logout() {
        this.authenticationService.logout();
    }
}

App Module

The app module defines the root module of the application along with metadata about the module. For more info about angular 9 modules see https://angular.io/docs/ts/latest/guide/ngmodule.html.

This is where the fake backend provider is added to the application, to switch to a real backend simply remove the fakeBackendProvider located below the comment // provider used to create fake backend.

import { NgModule, APP_INITIALIZER } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { ReactiveFormsModule } from '@angular/forms';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';

// used to create fake backend
import { fakeBackendProvider } from './_helpers';

import { AppComponent } from './app.component';
import { AppRoutingModule } from './app-routing.module';

import { JwtInterceptor, ErrorInterceptor, appInitializer } from './_helpers';
import { AuthenticationService } from './_services';
import { HomeComponent } from './home';
import { LoginComponent } from './login';

@NgModule({
    imports: [
        BrowserModule,
        ReactiveFormsModule,
        HttpClientModule,
        AppRoutingModule
    ],
    declarations: [
        AppComponent,
        HomeComponent,
        LoginComponent
    ],
    providers: [
        { provide: APP_INITIALIZER, useFactory: appInitializer, multi: true, deps: [AuthenticationService] },
        { provide: HTTP_INTERCEPTORS, useClass: JwtInterceptor, multi: true },
        { provide: HTTP_INTERCEPTORS, useClass: ErrorInterceptor, multi: true },

        // provider used to create fake backend
        fakeBackendProvider
    ],
    bootstrap: [AppComponent]
})
export class AppModule { }

Production Environment Config

The production environment config contains variables required to run the application in production. This enables you to build the application with a different configuration for each different environment (e.g. production & development) without updating the app code.

When you build the application for production with the command ng build --prod, the output environment.ts is replaced with environment.prod.ts.

export const environment = {
    production: true,
    apiUrl: 'http://localhost:4000'
};

Development Environment Config

The development environment config contains variables required to run the application in development.

Environment config is accessed by importing the environment object into any Angular service or component with the line import { environment } from '@environments/environment' and accessing properties on the environment object, see the user service for an example.

export const environment = {
    production: false,
    apiUrl: 'http://localhost:4000'
};

Main Index Html File

The main index.html file is the initial page loaded by the browser that kicks everything off. The Angular CLI (with Webpack under the hood) bundles all of the compiled javascript files together and injects them into the body of the index.html page so the scripts can be loaded and executed by the browser.

<!DOCTYPE html>
<html>
<head>
    <base href="/" />
    <title>Angular 9 - JWT Authentication with Refresh Tokens</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <!-- bootstrap css -->
    <link href="//netdna.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" rel="stylesheet" />
</head>
<body>
    <app>Loading...</app>
</body>
</html>

Main (Bootstrap) File

The main file is the entry point used by angular to launch and bootstrap the application.

import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app/app.module';
import { environment } from './environments/environment';

if (environment.production) {
    enableProdMode();
}

platformBrowserDynamic().bootstrapModule(AppModule)
    .catch(err => console.error(err));

Polyfills

Some features used by Angular 9 are not yet supported natively by all major browsers, polyfills are used to add support for features where necessary so your Angular 9 application works across all major browsers.

This file is generated by the Angular CLI when creating a new project with the ng new command, I've excluded the comments in the file for brevity.

import 'zone.js/dist/zone';

Global LESS/CSS Styles

The global styles file contains LESS/CSS styles that are applied globally throughout the application.

/* You can add global styles to this file, and also import other style files */
a { cursor: pointer }

Package.json

The package.json file contains project configuration information including package dependencies that get installed when you run npm install and scripts that are executed when you run npm start or npm run build etc. Full documentation is available at https://docs.npmjs.com/files/package.json.

{
    "name": "angular-9-jwt-refresh-tokens",
    "version": "0.0.0",
    "scripts": {
        "ng": "ng",
        "start": "ng serve --open",
        "build": "ng build",
        "test": "ng test",
        "lint": "ng lint",
        "e2e": "ng e2e"
    },
    "private": true,
    "dependencies": {
        "@angular/animations": "^9.1.1",
        "@angular/common": "^9.1.1",
        "@angular/compiler": "^9.1.1",
        "@angular/core": "^9.1.1",
        "@angular/forms": "^9.1.1",
        "@angular/platform-browser": "^9.1.1",
        "@angular/platform-browser-dynamic": "^9.1.1",
        "@angular/router": "^9.1.1",
        "rxjs": "^6.5.4",
        "tslib": "^1.10.0",
        "zone.js": "^0.10.2"
    },
    "devDependencies": {
        "@angular-devkit/build-angular": "^0.901.1",
        "@angular/cli": "^9.1.1",
        "@angular/compiler-cli": "^9.1.1",
        "@angular/language-service": "^9.1.1",
        "@types/node": "^12.11.1",
        "@types/jasmine": "^3.5.0",
        "@types/jasminewd2": "^2.0.3",
        "codelyzer": "^5.1.2",
        "jasmine-core": "^3.5.0",
        "jasmine-spec-reporter": "^4.2.1",
        "karma": "^4.4.1",
        "karma-chrome-launcher": "^3.1.0",
        "karma-coverage-istanbul-reporter": "^2.1.0",
        "karma-jasmine": "^3.0.1",
        "karma-jasmine-html-reporter": "^1.4.2",
        "protractor": "^5.4.3",
        "ts-node": "^8.3.0",
        "tslint": "^6.1.0",
        "typescript": "~3.8.3"
    }
}

TypeScript tsconfig.json

The tsconfig.json file configures how the TypeScript compiler will convert TypeScript into JavaScript that is understood by the browser. For more info see https://www.typescriptlang.org/docs/handbook/tsconfig-json.html.

Most of the file is unchanged from when it was generated by the Angular CLI, only the paths property has been added to map @app and @environments to the /src/app and /src/environments directories. This allows imports to be relative to the app and environments folders by prefixing import paths with aliases instead of having to use long relative paths (e.g. import MyComponent from '../../../MyComponent').

{
    "compileOnSave": false,
    "compilerOptions": {
        "baseUrl": "./",
        "outDir": "./dist/out-tsc",
        "sourceMap": true,
        "declaration": false,
        "downlevelIteration": true,
        "experimentalDecorators": true,
        "module": "esnext",
        "moduleResolution": "node",
        "importHelpers": true,
        "target": "es2015",
        "lib": [
            "es2018",
            "dom"
        ],
        "paths": {
            "@app/*": ["src/app/*"],
            "@environments/*": ["src/environments/*"]
        }
    },
    "angularCompilerOptions": {
        "fullTemplateTypeCheck": true,
        "strictInjectionParameters": true
    }
}