Full Deno + MongoDB REST API Project Breakdown sing npm:mongodb and Oak (Step-by-Step)

✅ 1. Project Setup

📄 deno.json or deno.jsonc

This config file lets you run your app using deno task dev:

{
  "tasks": {
    "dev": "deno run --allow-net --allow-env --unstable --compat mod.ts"
  },
  "imports": {
    "@std/assert": "jsr:@std/assert@1",
    "oak": "https://deno.land/x/oak@v12.6.0/mod.ts",
    "mongodb": "npm:mongodb@6.3.0"
  }
}

📁 2. Folder Structure

deno-mongo-api/
│
├── mod.ts                    # Main server file
├── deps.ts                   # Central imports
│
├── db/
│   └── connect.ts            # MongoDB connection
│
├── models/
│   └── user.ts               # MongoDB schema/model
│
├── controllers/
│   └── userController.ts     # All logic for user routes
│
└── routes/
    └── userRoutes.ts         # Defines API routes

🔗 3. deps.ts

Why? Centralize imports so you can manage versions in one place.

export { Application, Router, Context } from "oak";
export { MongoClient, ObjectId } from "mongodb";

🌐 4. mod.ts

Starts the server and adds middleware

import { Application } from "./deps.ts";
import router from "./routes/userRoutes.ts";
const app = new Application();

// Use router
app.use(router.routes());
app.use(router.allowedMethods());
console.log("🚀 Server running at http://localhost:8000");
await app.listen({ port: 8000 });

🧵 5. db/connect.ts

Connects to MongoDB

import { MongoClient } from "../deps.ts";

const client = new MongoClient("mongodb://127.0.0.1:27017");
await client.connect();
const db = client.db("deno_api");
console.log("✅ Connected to MongoDB");
export default db;

• client.connect() → connects to MongoDB
• db("deno_api") → selects database

📄 6. models/user.ts

Defines a TypeScript interface + collection

import db from "../db/connect.ts";
import { ObjectId } from "../deps.ts";

export interface UserSchema {
  _id: ObjectId;
  name: string;
  email: string;
}
const users = db.collection<UserSchema>("users");
export default users;

• Declares schema fields: _id, name, email
• Gets the users collection

🧠 7. controllers/userController.ts

Handles API logic (CRUD)

import { Context, ObjectId } from "../deps.ts";
import users from "../models/user.ts";

interface User {
  name: string;
  email: string;
}
function isKnownError(error: unknown): error is Error {
  return error instanceof Error;
}

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➕ createUser

export const createUser = async (ctx: Context) => {
  try {
    const { name, email }: User = await ctx.request.body({ type: "json" }).value;
    if (!name || !email) {
      ctx.response.status = 400;
      ctx.response.body = { message: "Name and email are required" };
      return;
    }
    const newId = await users.insertOne({ name, email });
    ctx.response.status = 201;
    ctx.response.body = { message: "User created", id: newId };
  } catch (error) {
    ctx.response.status = 500;
    ctx.response.body = isKnownError(error)
      ? { message: "Internal Server Error", error: error.message }
      : { message: "Unknown error occurred" };
  }
};

📥 getUsers

export const getUsers = async (ctx: Context) => {
  try {
    const allUsers = await users.find({}).toArray();
    ctx.response.body = allUsers;
  } catch (error) {
    ctx.response.status = 500;
    ctx.response.body = isKnownError(error)
      ? { message: "Internal Server Error", error: error.message }
      : { message: "Unknown error occurred" };
  }
};

📥 getUser

export const getUser = async (ctx: Context) => {
  try {
    const id = ctx.params.id!;
    const user = await users.findOne({ _id: new ObjectId(id) });
    if (user) {
      ctx.response.body = user;
    } else {
      ctx.response.status = 404;
      ctx.response.body = { message: "User not found" };
    }
  } catch (error) {
    ctx.response.status = 500;
    ctx.response.body = isKnownError(error)
      ? { message: "Internal Server Error", error: error.message }
      : { message: "Unknown error occurred" };
  }
};

✏️ updateUser

export const updateUser = async (ctx: Context) => {
  try {
    const id = ctx.params.id!;
    const { name, email }: User = await ctx.request.body({ type: "json" }).value;
    if (!name || !email) {
      ctx.response.status = 400;
      ctx.response.body = { message: "Name and email are required" };
      return;
    }
    const result = await users.updateOne(
      { _id: new ObjectId(id) },
      { $set: { name, email } }
    );
    ctx.response.body = { message: "User updated", modifiedCount: result.modifiedCount };
  } catch (error) {
    ctx.response.status = 500;
    ctx.response.body = isKnownError(error)
      ? { message: "Internal Server Error", error: error.message }
      : { message: "Unknown error occurred" };
  }
};

❌ deleteUser

export const deleteUser = async (ctx: Context) => {
  try {
    const id = ctx.params.id!;
    const result = await users.deleteOne({ _id: new ObjectId(id) });
    ctx.response.body = { message: "User deleted", deletedCount: result.deletedCount };
  } catch (error) {
    ctx.response.status = 500;
    ctx.response.body = isKnownError(error)
      ? { message: "Internal Server Error", error: error.message }
      : { message: "Unknown error occurred" };
  }
};

🌐 8. routes/userRoutes.ts

Maps URLs to controller functions

import { Router } from "../deps.ts";
import {
  getUsers,
  getUser,
  createUser,
  updateUser,
  deleteUser,
} from "../controllers/userController.ts";

const router = new Router();
router
  .get("/users", getUsers)
  .get("/users/:id", getUser)
  .post("/users", createUser)
  .put("/users/:id", updateUser)
  .delete("/users/:id", deleteUser);
export default router;

✅ Test Your API

Use curl or Postman:

• Create User

curl -X POST http://localhost:8000/users \
  -H "Content-Type: application/json" \
  -d '{"name":"John", "email":"john@example.com"}'

• Get All Users

curl http://localhost:8000/users

• Update User

curl -X PUT http://localhost:8000/users/<id> \
  -H "Content-Type: application/json" \
  -d '{"name":"Johnny", "email":"new@example.com"}'

• Delete User

curl -X DELETE http://localhost:8000/users/<id>

🔚 Summary

✅ You now have a full working REST API in Deno using:

• Oak for server & routing
• npm MongoDB driver (modern way to use Mongo)
• Modular structure (clean separation of concerns)