🔥 Middleware in NestJS

1️⃣ What is Middleware?

Middleware in NestJS is a function that runs before the request reaches the controller. It can be used for:

✅ Logging requests

✅ Authentication

✅ Modifying request data

✅ Blocking unauthorized requests

🔥 Task 1: Create a Logging Middleware

Step 1: Create a Middleware File

Inside src/, create a new file: logger.middleware.ts

Step 2: Write the Middleware Code

import { Injectable, NestMiddleware } from '@nestjs/common'; import { Request, Response, NextFunction } from 'express'; @Injectable() export class LoggerMiddleware implements NestMiddleware { use(req: Request, res: Response, next: NextFunction) { console.log(`[${new Date().toISOString()}] ${req.method} ${req.url}`); next(); } } 

✔ This middleware logs the method and URL of every request.

✔ next() → Passes control to the next handler (controller or another middleware).

🔥 Task 2: Apply Middleware in app.module.ts

Modify src/app.module.ts to apply the middleware:

import { MiddlewareConsumer, Module, NestModule } from '@nestjs/common'; import { UserModule } from './user/user.module'; import { LoggerMiddleware } from './logger.middleware'; @Module({ imports: [UserModule], }) export class AppModule implements NestModule { configure(consumer: MiddlewareConsumer) { consumer.apply(LoggerMiddleware).forRoutes('*'); // Apply to all routes } } 

✔ This applies the logging middleware to all routes in the app.

🔥 Task 3: Test the Middleware

1️⃣ Start the server

Run the following command:

npm run start 

2️⃣ Send a request

Make a GET request to:

http://localhost:3000/user 

3️⃣ Check the terminal

You should see logs like:

[2025-03-06T10:30:00.123Z] GET /user 

🚀 Bonus: Logging Request Body for POST Requests

Modify the logger.middleware.ts file to log the request body only for POST requests:

import { Injectable, NestMiddleware } from '@nestjs/common'; import { Request, Response, NextFunction } from 'express'; @Injectable() export class LoggerMiddleware implements NestMiddleware { use(req: Request, res: Response, next: NextFunction) { console.log(`[${new Date().toISOString()}] ${req.method} ${req.url}`); // Log request body for POST requests if (req.method === 'POST') { console.log('Request Body:', JSON.stringify(req.body)); } next(); } } 

Now, when you send a POST request, the terminal will display:

[2025-03-06T10:31:00.456Z] POST /user Request Body: {"name":"John","email":"john@example.com"} 

✅ Your Task

🔥 Implement the logging middleware in your NestJS project.

🔥 Modify it to log the request body for POST requests.

🔥 Test it and drop your thoughts in the comments! 🚀

💬 What do you think?

Do you use middleware in your NestJS projects? Share your experience in the comments! 🎯