Login Form with Flask, MongoDB, and Docker

Sharon Rajendra Manmothe
Sep 8, 2025
2 min read

Updated: Sep 9, 2025

Step 1: Install Docker

Go to Docker Desktop.
Download Docker Desktop for Windows (since you’re on Windows).
Install it → follow setup wizard.
After install, open PowerShell/Command Prompt and run:
docker --version
If you see version info → Docker is installed successfully.

Step 2: Setup Project Folder

Create a new folder for your app:

mkdir flask-login-app
cd flask-login-app

Inside this folder, create files like this:

flask-login-app/
 ├── app.py
 ├── requirements.txt
 ├── templates/
 │    └── login.html
 ├── Dockerfile

Step 3: Create HTML Login Form

Create templates/login.html:

<!DOCTYPE html>
<html>
<head>
    <title>Login Form</title>
</head>
<body>
    <h2>Login Page</h2>
    <form action="/login" method="POST">
        <label>Username:</label>
        <input type="text" name="username" required><br><br>

        <label>Password:</label>
        <input type="password" name="password" required><br><br>

        <button type="submit">Login</button>
    </form>
</body>
</html>

Step 4: Python Flask App

Create app.py:

from flask import Flask, render_template, request, redirect
from pymongo import MongoClient

app = Flask(__name__)

# Connect to MongoDB (running locally in Compass)
client = MongoClient("mongodb://host.docker.internal:27017/")  # Docker → local MongoDB
db = client["loginDB"]
users = db["users"]

@app.route("/")
def home():
    return render_template("login.html")

@app.route("/login", methods=["POST"])
def login():
    username = request.form["username"]
    password = request.form["password"]

    # Check if user exists in DB
    user = users.find_one({"username": username, "password": password})

    if user:
        return "Welcome {username}, you are logged in!"
    else:
        return "Invalid username or password"

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=5000, debug=True)

Step 5: Requirements File

Create requirements.txt:

flask
pymongo

Step 6: Dockerfile

Create Dockerfile:

# Use official Python image
FROM python:3.9

# Set working directory
WORKDIR /app

# Copy requirements and install
COPY requirements.txt .
RUN pip install -r requirements.txt

# Copy project
COPY . .

# Run Flask app
CMD ["python", "app.py"]

Step 7: Build Docker Image

In project folder, run:

docker build -t flask-login-app .

Step 8: Run Flask Container

docker run -d -p 5000:5000 flask-login-app

Now open browser → http://localhost:5000 → you’ll see the login form.

$50

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