Nest JS User registration with Sendgrid email Integration Part-6

Nest JS User registration with Sendgrid email Integration Part-6

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Blog Name Link
Part-1 Nest JS Building REST APIs using Mongo DB Part-1
Part-2 Nest JS APIs with mongoose Mongo DB Database Part-2
Part-3 Nest JS Building Auth Service with JWT Tokens Part-3
Part-4 Nest JS with Mongo DB Managing Relationships Part-4
Part-5 How to manage environment variables in Nest JS Part-5

In this post, I will demonstrate how to kickstart a simple RESTful APIs with NestJS from a newbie's viewpoint.

Github Link

What is NestJS?

As described in the Nestjs website, Nestjs is a progressive Node.js framework for building efficient, reliable and scalable server-side applications.

Nestjs combines the best programming practice and the cutting-edge techniques from the NodeJS communities.

  • A lot of NestJS concepts are heavily inspired by the effort of the popular frameworks in the world, esp. Angular .
  • Nestjs hides the complexities of web programming in NodeJS, it provides a common abstraction of the web request handling, you are free to choose Expressjs or Fastify as the background engine.
  • Nestjs provides a lot of third party project integrations, from database operations, such as Mongoose, TypeORM, etc. to Message Brokers, such as Redis, RabbitMQ, etc.

If you are new to Nestjs like me but has some experience of Angular , TypeDI or Spring WebMVC, bootstraping a Nestjs project is really a piece of cake.

Make sure you have installed the latest Nodejs.

npm i -g @nestjs/cli

When it is finished, there is a nest command available in the Path. The usage of nest is similar with ng (Angular CLI), type nest --help in the terminal to list help for all commands.

❯ nest --help
Usage: nest <command> [options]

  -v, --version                                   Output the current version.
  -h, --help                                      Output usage information.

  new|n [options] [name]                          Generate Nest application.
  build [options] [app]                           Build Nest application.
  start [options] [app]                           Run Nest application.
  info|i                                          Display Nest project details.
  update|u [options]                              Update Nest dependencies.
  add [options] <library>                         Adds support for an external library to your project.
  generate|g [options] <schematic> [name] [path]  Generate a Nest element.
    Available schematics:
      │ name          │ alias       │
      │ application   │ application │
      │ class         │ cl          │
      │ configuration │ config      │
      │ controller    │ co          │
      │ decorator     │ d           │
      │ filter        │ f           │
      │ gateway       │ ga          │
      │ guard         │ gu          │
      │ interceptor   │ in          │
      │ interface     │ interface   │
      │ middleware    │ mi          │
      │ module        │ mo          │
      │ pipe          │ pi          │
      │ provider      │ pr          │
      │ resolver      │ r           │
      │ service       │ s           │
      │ library       │ lib         │
      │ sub-app       │ app         │

Now generate a Nestjs project via:

nest new nestjs-sample

Open it in your favorite IDEs, such as Intellij WebStorm or VSCode.

Exploring the project files

Expand the project root, you will see the following like tree nodes.

├── nest-cli.json
├── package.json
├── package-lock.json
├── src
│   ├── app.controller.spec.ts
│   ├── app.controller.ts
│   ├── app.module.ts
│   ├── app.service.ts
│   └── main.ts
├── test
│   ├── app.e2e-spec.ts
│   └── jest-e2e.json
└── tsconfig.json

The default structure of this project is very similar with the one generated by Angular CLI.

  • src/main.ts is the entry file of this application.
  • *src/app** is the top level component in a nest application.
    • There is an app.module.ts is a Nestjs Module which is similar with Angular NgModule, and used to organize codes in the logic view.
    • The app.service.ts is an @Injectable component, similar with the service in Angular or Spring's Service, it is used for handling business logic. A service is annotated with @Injectable.
    • The app.controller.ts is the controller of MVC, to handle incoming request, and responds the handled result back to client. The annotatoin @Controller() is similar with Spring MVC's @Controller.
    • The app.controller.spec.ts is test file for app.controller.ts. Nestjs uses Jest as testing framework.
  • test folder is for storing e2e test files.

Handling user registration

In the previous posts, the user sample data is initialized in a service which is observing an OnMoudleInit event.

In this post we will add an endpoint to handle user registration request, including:

  • Add an endpoint /register to handling user registration progress
  • Hashing password with bcrypt
  • Sending notifications via SendGrid mail service

Registering a new user

Generate a register controller.

nest g controller user/register --flat

Fill the following content into the RegisterController.

// user/register.controller.ts

export class RegisterController {
  constructor(private userService: UserService) {}

  register(@Body() registerDto: RegisterDto, @Res() res: Response): Observable<Response> {
    const username = registerDto.username;

    return this.userService.existsByUsername(username).pipe(
      flatMap((exists) => {
        if (exists) {
          throw new ConflictException(`username:${username} is existed`);
        } else {
          const email =;
          return this.userService.existsByEmail(email).pipe(
            flatMap((exists) => {
              if (exists) {
                throw new ConflictException(`email:${email} is existed`);
              } else {
                return this.userService.register(registerDto).pipe(
                  map((user) =>
                      .location('/users/' +

In the above codes, we will check user existence by username and email respectively, then save the user data into the MongoDB database.

In the UserService, add the missing methods.

export class UserService {
  existsByUsername(username: string): Observable<boolean> {
    return from(this.userModel.exists({ username }));

  existsByEmail(email: string): Observable<boolean> {
    return from(this.userModel.exists({ email }));

  register(data: RegisterDto): Observable<User> {
    const created = this.userModel.create({,
      roles: [RoleType.USER],

    return from(created);

Create a DTO class to represent the user registration request data. Generate the DTO skeleton firstly.

nest g class user/register.dto --flat

And fill the following content.

import { IsEmail, IsNotEmpty, MaxLength, MinLength } from 'class-validator';

export class RegisterDto {
  readonly username: string;

  readonly email: string;

  @MinLength(8, { message: ' The min length of password is 8 ' })
  @MaxLength(20, { message: " The password can't accept more than 20 characters " })
  // @Matches(/^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])[0-9a-zA-Z]{8,20}$/,
  //     { message: " A password at least contains one numeric digit, one supercase char and one lowercase char" }
  // )
  readonly password: string;

  readonly firstName?: string;

  readonly lastName?: string;

In the above codes, the @IsNotEmpty(),@IsEmail, @MinLength(), @MaxLength(), @Matches() are from class-validator. If you have some experience of Java EE/Jakarta EE Bean Validation or Hibernate Validators, these annotations are easy to understand.

  • @IsNotEmpty() to check if the given value is empty
  • @IsEmail to validate if the input string is an valid email format
  • @MinLength() and @MaxLength()are to limit the length range of the input value
  • @Matches() is flexible for custom RegExp matches.

More info about the usage of class-validator, check the details of project typestack/class-validator.

In the previous posts, we have applied a global ValidationPipe in bootstrap function in the main.ts entry file. When registering with invalid data,it will return a 404 error.

 $ curl http://localhost:3000/register -d "{}" {"statusCode":400,"message":["username should not be empty","email must be an em ail","email should not be empty"," The password can't accept more than 20 charac ters "," The min length of password is 8 ","password should not be empty","first Name should not be empty","lastName should not be empty"],"error":"Bad Request"}

Add a test for the RegisterController.

describe('Register Controller', () => {
  let controller: RegisterController;
  let service: UserService;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      controllers: [RegisterController],
      providers: [
          provide: UserService,
          useValue: {
            register: jest.fn(),
            existsByUsername: jest.fn(),
            existsByEmail: jest.fn(),

    controller = module.get<RegisterController>(RegisterController);
    service = module.get<UserService>(UserService);

  it('should be defined', () => {

  describe('register', () => {
    it('should throw ConflictException when username is existed ', async () => {
      const existsByUsernameSpy = jest.spyOn(service, 'existsByUsername').mockReturnValue(of(true));
      const existsByEmailSpy = jest.spyOn(service, 'existsByEmail').mockReturnValue(of(true));
      const saveSpy = jest.spyOn(service, 'register').mockReturnValue(of({} as User));

      const responseMock = {
        location: jest.fn().mockReturnThis(),
        json: jest.fn().mockReturnThis(),
        send: jest.fn().mockReturnThis(),
      } as any;
      try {
        await controller.register({ username: 'hantsy' } as RegisterDto, responseMock).toPromise();
      } catch (e) {

    it('should throw ConflictException when email is existed ', async () => {
      const existsByUsernameSpy = jest.spyOn(service, 'existsByUsername').mockReturnValue(of(false));
      const existsByEmailSpy = jest.spyOn(service, 'existsByEmail').mockReturnValue(of(true));
      const saveSpy = jest.spyOn(service, 'register').mockReturnValue(of({} as User));

      const responseMock = {
        location: jest.fn().mockReturnThis(),
        json: jest.fn().mockReturnThis(),
        send: jest.fn().mockReturnThis(),
      } as any;
      try {
        await controller
          .register({ username: 'hantsy', email: '' } as RegisterDto, responseMock)
      } catch (e) {

    it('should save when username and email are available ', async () => {
      const existsByUsernameSpy = jest.spyOn(service, 'existsByUsername').mockReturnValue(of(false));
      const existsByEmailSpy = jest.spyOn(service, 'existsByEmail').mockReturnValue(of(false));
      const saveSpy = jest.spyOn(service, 'register').mockReturnValue(of({ _id: '123' } as User));

      const responseMock = {
        location: jest.fn().mockReturnThis(),
        status: jest.fn().mockReturnThis(),
        send: jest.fn().mockReturnThis(),
      } as any;

      const locationSpy = jest.spyOn(responseMock, 'location');
      const statusSpy = jest.spyOn(responseMock, 'status');
      const sendSpy = jest.spyOn(responseMock, 'send');

      await controller
        .register({ username: 'hantsy', email: '' } as RegisterDto, responseMock)


In the above testing codes, we go through all conditions and make sure all code blocks in the RegisterController are hit.

Correspondingly add tests for the newly added methods in UserService . Here I skip the testing codes here, please check the source code yourself.

Hashing password

In the former posts, we used plain text to store the password field in user document. In a real world application, we should choose a hash algorithm to encode the plain password for security consideration.

Bcrypt is very popular for hashing password.

Install bcypt firstly.

npm install --save bcrypt

When saving a new user, hashing the password then save it. Add a pre save hook in the User model.

async function preSaveHook(next) {
  // Only run this function if password was modified
  if (!this.isModified('password')) return next();

  // Hash the password
  const password = await hash(this.password, 12);
  this.set('password', password);


UserSchema.pre<User>('save', preSaveHook);

The preSave hook will be invoked before the new user data is being persisted into the MongoDB.

When a user is trying to login via username and password pair, it should check if password is matched to the one in the database.

Add a method to the User model.

function comparePasswordMethod(password: string): Observable<boolean> {
  return from(compare(password, this.password));

UserSchema.methods.comparePassword = comparePasswordMethod;

Change the validateUser method of the AuthService, check the password if matched there.

flatMap((user) => {
    const { _id, password, username, email, roles } = user;
    return user.comparePassword(pass).pipe(map(m => {
        if (m) {
            return { id: _id, username, email, roles } as UserPrincipal;
        }else {
            throw new UnauthorizedException('username or password is not matched')

It is a little difficult to test the hooks of the User model, to simplify the testing work, here I extract the hooks to standalone functions, and mock the calling context in the tests.

// see:
describe('preSaveHook', () => {
  test('should execute next middleware when password is not modified', async () => {
    const nextMock = jest.fn();
    const contextMock = {
      isModified: jest.fn(),
    await, nextMock);

  test('should set password when password is modified', async () => {
    const nextMock = jest.fn();
    const contextMock = {
      isModified: jest.fn(),
      set: jest.fn(),
      password: '123456',
    await, nextMock);

Explore other tests for comparePasswordMethod etc in the user.mdoel.sepc.ts.

Now run the application, have a look at the log in the console about the user initialization, as you see the password stored in the MongoDB is hashed.

(UserModule) is initialized...
    roles: [ 'USER' ],
    _id: 5f477055fb9a2b3fa4cb1c21,
    username: 'hantsy',
    password: '$2b$12$/spjKM3Vdf5vRJE9u2cHaulIAWzKMbNVSyHjMp9E9PifbSEHTQrJy',
    email: '',
    createdAt: 2020-08-27T08:35:33.800Z,
    updatedAt: 2020-08-27T08:35:33.800Z,
    __v: 0
    roles: [ 'ADMIN' ],
    _id: 5f477055fb9a2b3fa4cb1c22,
    username: 'admin',
    password: '$2b$12$kFhASRJPkb/WD99J4uZrf.ZkkeKghpvf/6pgVGQArGiIgXu5aNMe.',
    email: '',
    createdAt: 2020-08-27T08:35:33.801Z,
    updatedAt: 2020-08-27T08:35:33.801Z,
    __v: 0

Registration Welcome Notification

Generally, in a real world application, a welcome email should be sent to the new registered user when the registration is completed successfully.

There are several modules can be used to send emails in NodeJS applications, for example, nodemailer etc. There are also some cloud service for emails, such as SendGrid. There is an existing Nestjs module to integrate SendGrid to Nestjs, check ntegral/nestjs-sendgrid project.

In this sample, we will not use the existing one, and create a new home-use module for this application.

Install sendgrid npm package firstly.

npm i @sendgrid/mail

Generate a sendgrid module and a sendgrid service.

nest g mo sendgrid
nest g s sendgrid

Add the following content into the SendgridService.

export class SendgridService {
  constructor(@Inject(SENDGRID_MAIL) private mailService: MailService) {}

  send(data: MailDataRequired): Observable<any> {
    return from(this.mailService.send(data, false));

Create a provider to expose the MailService from @sendgrid/mail package.

export const sendgridProviders = [
    provide: SENDGRID_MAIL,
    useFactory: (config: ConfigType<typeof sendgridConfig>): MailService => {
      const mail = new MailService();
      //mail.setTwilioEmailAuth(username, password)
      return mail;
    inject: [sendgridConfig.KEY],

Accordingly, add a config for sendgrid.

export default registerAs('sendgrid', () => ({
  apiKey: process.env.SENDGRID_API_KEY || 'SG.test',

Signup SendGrid and generate an API Key for your applications to send emails.

Declares sendgrid related config, provider and service in SendgridModule.

  imports: [ConfigModule.forFeature(sendgridConfig)],
  providers: [...sendgridProviders, SendgridService],
  exports: [...sendgridProviders, SendgridService],
export class SendgridModule {}

Change the register function in the UserService.

const msg = {
  from: '', // Use the email address or domain you verified above
  subject: 'Welcome to Nestjs Sample',
  templateId: 'd-cc6080999ac04a558d632acf2d5d0b7a',
  personalizations: [
      dynamicTemplateData: { name: data.firstName + ' ' + data.lastName },
return this.sendgridService.send(msg).pipe(
  catchError((err) => of(`sending email failed:${err}`)),
  tap((data) => console.log(data)),
  flatMap((data) => from(created))

The templateId is the id of the templates managed by SendGrid. SendGrid has great web UI for you to compose and manage email templates.

Ideally, a user registration progress should be split into two steps.

  • Validate the user input data from the registration form, and persist it into the MongoDB, then send a verification number to verify the registered phone number, email, etc. In this stage, the user account will be suspended to verify.
  • The registered user receive the verification number or links in emails, provide it in the verification page or click the link in the email directly, and get verified. In this stage, the user account will be activated.

Grab [the source codes from my github] Github Link