How can a database be created for each user in MongoDB using NestJS?

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To create a database for each user in MongoDB using NestJS, you can follow these steps:

1. Install the @nestjs/mongoose package to setup the connection between the NestJS application and the MongoDB database.

npm install --save @nestjs/mongoose

1. Include the MongooseModule in the AppModule.

import { Module } from '@nestjs/common';
import { MongooseModule } from '@nestjs/mongoose';
import { AppController } from './app.controller';
import { AppService } from './app.service';

@Module({
  imports: [MongooseModule.forRoot('mongodb://localhost:27017/myapp')],
  controllers: [AppController],
  providers: [AppService],
})

export class AppModule {}

1. Create a custom module for handling the user data. In the user.module.ts file, import the MongooseModule and define a UserSchema for creating the user collection.

import { Module } from '@nestjs/common';
import { MongooseModule } from '@nestjs/mongoose';
import { UserController } from './user.controller';
import { UserService } from './user.service';
import { User, UserSchema } from './user.schema';

@Module({
  imports: [MongooseModule.forFeature([{ name: User.name, schema: UserSchema }])],
  controllers: [UserController],
  providers: [UserService],
})
export class UserModule {}

1. Define a user.service.ts file that will interact with the database to handle user data.

import { Injectable } from '@nestjs/common';
import { InjectModel } from '@nestjs/mongoose';
import { Model } from 'mongoose';
import { User, UserDocument } from './user.schema';

@Injectable()
export class UserService {
  constructor(@InjectModel(User.name) private userModel: Model<UserDocument>) {}

  async createUser(user: User): Promise<User> {
    const createdUser = new this.userModel(user);
    return createdUser.save();
  }

  async getUserById(userId: string): Promise<User> {
    const user = await this.userModel.findById(userId).exec();
    return user && user.toObject();
  }

  // Add other CRUD operations as needed...
}

1. Define a user.controller.ts file that will handle the API endpoints for user data.

import { Controller, Post, Body, Get, Param } from '@nestjs/common';
import { UserService } from './user.service';
import { User } from './user.schema';

@Controller('users')
export class UserController {
  constructor(private readonly userService: UserService) {}

  @Post()
  async createUser(@Body() user: User): Promise<User> {
    return await this.userService.createUser(user)
  }

  @Get(':id')
  async getUserById(@Param('id') userId: string): Promise<User> {
    return await this.userService.getUserById(userId)
  }

  // Add other CRUD API endpoints as needed...
}

1. Finally, create a middleware that will intercept the request and use the current user's ID to connect to their own database. This middleware can be created in the main.tsfile or in a separate file.

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { UserMiddleware } from './user.middleware';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.use(UserMiddleware);
  await app.listen(3000);
}
bootstrap();

import { Request, Response } from 'express';
import { connect, Connection } from 'mongoose';
import { database } from './config/database'; // Database configuration file
import { UserService } from './user/user.service';

export async function UserMiddleware(req: Request, res: Response, next: () => void) {
  const userId = req.headers['user-id'] as string;

  // Connect to the user's database
  const conn: Connection = await connect(database(userId), {
    useNewUrlParser: true,
    useUnifiedTopology: true,
  });

  // Set the current user's ID in the request object for later use
  req['userId'] = userId;

  // Provide the UserService with the connection to the user's database
  const userService = new UserService(conn);

  // Save the UserService in the request object for later use
  req['userService'] = userService;

  next();
}

This middleware will intercept every request ... (more)