How to Build Web APIs with NestJS, Postgres, and Sequelize A Beginner’s Guide

Basically, the contracts are the function signatures of the desired services. For example, the CRM service needs to provide a “notify” function that gets a Book object as a parameter and returns a promise with a boolean value. Node.js is an open-source and cross-platform runtime environment that runs JavaScript outside of the browser. On real applications we would usually be interested on handling more properties besides the company name. To do this, we will create a class that represents a company, add more properties to it, and refactor our controller to use with this class.

Before proceeding, ensure that you have Apache Kafka installed and running on your local machine. NestJS may feel like the Laravel or Rails of the Node.js world as it favors convention over configuration. So, instead of worrying about naming or organizing files and folders, you can focus on building features for your product.

Building a reactive web app in Go with Fir

The first one is the Service role, when a component contains some business logic. The second one is the Repository role, when a component abstracts away the interaction with databases. Through modules we encapsulate related code that composes our application, like components and controllers. To start Nest.js, we need to inform the root module of our application. Although not needed, breaking an app into multiple modules is advised, as it helps keeping different matters encapsulated.

In the main.ts file of the auth-microservice app, remove the boilerplate code of the bootstrap() function and replace it with the NestFactory.createMicroservice() method. Since you’ll be creating multiple backend services, it’s best to have a monorepo to enable code sharing. A monorepo is a single version-controlled code repository that includes various applications and libraries. However, this file uses a hard-coded port number to listen for incoming requests, 3000, making your application less adaptable to different development and production environments. A controller is a class where we will house a bundle of functions.

Add Book Use Case

This type of communication between microservices is known as the request-response pattern. In the AppService, inject the Kafka client for publishing events to the auth-microservice app. When you emit the get_user event, you’ll need to listen for the response from the auth microservice; this is different from what you did for the create_user event. “@nestframework is an architecture framework for @nodejs. Learn how to create scalable and maintainable server-side apps with it.” Nest is a framework for building efficient, scalable Node.js server-side applications. Services in Nest.js handle any complex business logic data manipulations for a specific purpose and return the appropriate response to the controller.

The create route will be a post request to “/posts”, we will use the data in the request body to create a new post. To test this out you’ll need a tool like Postman or Insomnia. The Index route allows us to get all items of our model with a get request. So in our case a get request to “/posts” should get us all the posts.

Why you should learn NestJS

We could clone the Nest.js TypeScript Starter project available on GitHub, or we could use the CLI tool for Nest.js applications. Both alternatives are equally good and provide a solid foundation to build apps. Though, as we want to understand how a Nest.js application is built, we are going to create a new one from scratch.

Nest.js gives you a more structured way of building your server-side applications with Node. Run nest g module /modules/posts.This will automatically add this module to our root module AppModule. An interceptor is a specialised set of middleware that lets you peek into the request that goes into the application. You can peek into the request either before it reaches the controller or after the controller is done with the request before it gets to the client-side as a response.

Generate Auth Controller

This repository is then used to retrieve the inventory for a specific product, so the service can check if there are enough items to be sold. Running this code will trigger a Nest.js application and bootstrap all components defined on UsersModule. In this case, we are exporting a module called UsersModule that contains a single component, UsersService. As this component is defined in the exports property of the @Module decorator, other modules that import UsersModule will be able to use it. We call the validateUser() method in the AuthService (we are yet to write this method), which checks if the user exists and if the password is correct.

• Next, the app.module.ts is the root module of the application and app.service.ts is the service/data model logic of the application.
• We will cover the basics of error handling, how to create custom exceptions, and how to handle errors globally.
• Through modules we encapsulate related code that composes our application, like components and controllers.
• They are mostly used for validation and transforming data before they get to the controller.
• We don’t need to install a TypeScript definition of jwks-rsa because this library already ships with one.
• We simply return what we want and the framework serializes the returned object(s) as JSON.

This simple directory structure can be expanded into a complete project by creating folders and arranging them based on their features. The code above shows a basic type definition for our Todo data. Now this interface can be customized to represent the different database schemas and columns that our application will use. The service class uses the Injectable() https://wizardsdev.com/en/vacancy/middle-nestjs-developer/ decorator showing that it is a provider and it can be injected as a dependency into any other class. Specifically, services are part of the code block that includes only the business logic. The @Controllers, and @Get are the decorators used to inform Nest.js that we are creating a Todos controller and the findAll method is a GET request.

Once unpublished, all posts by alexmercedcoder will become hidden and only accessible to themselves. Once unsuspended, alexmercedcoder will be able to comment and publish posts again. Once suspended, alexmercedcoder will not be able to comment or publish posts until their suspension is removed. Also, the Typescript web framework is officially used in Nest.js to make sure writing clean and correct codes are achieved. We will test our newly developed REST API with Postman and ensure we have the right data. You can read more about Postman and install it on your local machine if you don’t already have it.

Edit, which renders a page with a form to edit an existing object, submitting the form triggers the Update route. In Nest.js, modules are used to organize your project into features and allow you to separate different features for easy structuring. Most importantly, every operation is performed inside the service class, which helps us separate business logic from actual data manipulation. This Nest.js tutorial will demonstrate how to use Nest.js to create a simple Todo application. With this, we will explore how to set up Nest.js with TypeScript.