How to Inject TypeORM Repositories in NestJS Middleware for Logging HTTP Requests

Learn how to effectively log HTTP requests to a database in NestJS by injecting TypeORM repositories into middleware. This guide explains the setup, addressing common issues along the way.
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How to Inject TypeORM Repositories in NestJS Middleware for Logging HTTP Requests

Logging HTTP requests is an essential feature for web applications, particularly for troubleshooting and monitoring purposes. In a NestJS application, you may want to log each incoming request and, ideally, save this data to a database using TypeORM. However, you might face some challenges, especially when trying to inject a TypeORM repository into middleware. This guide will guide you through the process of configuring your NestJS middleware to achieve this goal.

Understanding the Problem

When you attempt to create a middleware class that uses the TypeORM repository, such as the RequestMiddleware shown below, you may run into the following error:

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This error occurs because the middleware is defined as a standalone TypeScript file and is not part of a module. Therefore, the NestJS dependency injection system cannot resolve the required repository specified in the constructor.

The Middleware Structure

Here's a brief look at the middleware structure in question:

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This code attempts to log details of each HTTP request to a logging service. The end goal is to store these logs in a database, which requires correctly setting up the TypeORM repository within a NestJS module.

The Solution: Integrating the Middleware into a Module

To resolve the dependency injection issue, follow these organized steps:

Step 1: Create a Module for Your Middleware

Make sure your middleware is defined within a NestJS module. If you don't already have a module for your logging functionality, you can create one.

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Step 2: Use the Middleware in Your Application

Next, register the middleware in your main.ts or the appropriate module where your application is set up. This allows NestJS to use the logging middleware while having access to the TypeORM repository.

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Step 3: Save the Requests to the Database

In the use method of the middleware, after logging the message, you would typically want to save the request log to the database. This can be achieved by calling the repository's methods.

For example:

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Conclusion

Integrating TypeORM repositories into NestJS middleware is straightforward once you configure your middleware within the context of a module. By following these organized steps, you can efficiently log HTTP requests and save them to a database. This not only improves the maintainability and functionality of your application but also enhances your logging capabilities, making it easier for you to monitor and troubleshoot as needed.

Now you can catch each request, log the details, and save important information right to your database using TypeORM and NestJS!

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