In this article I refer to an application I created a couple of months ago.

It’s about a booking system with which players can book ice-hockey trainings in different locations, the coach can confirm participation in a training session and a club manager can organize training sessions and bill the players for booked trainings.

You can see the code on my  GitHub Account and read a detailed application description in the style of a user manual on my blog  Digitaldocblog.

In my booking system I give users different roles in my app and depending on their role, the users have different authorizations. An admin for example is able to access more sensitive data and functionalities than a normal player or a coach. So my app must know the role of a user to assign different authorizations to the particular user.

Clients, usually browsers send requests the app. The app responds to requests and is solely responsible for ensuring that the client only has access to the data that are intended for it. This request and response game is based on the HTTP protocol. HTTP is a stateless network protocol and requests cannot be related to each other. Each request is isolated and unrelated to previous requests and the server has no chance to recognize clients and does therefore not know their role.

This problem can be solved with sessions and cookies and means that session management must be implemented in the application. The application creates a session and stores session data such as the role of a requestor in this session. The session has a unique ID and the app saves only this ID in a cookie. The cookie is transferred to the browser and stored locally there.

From now on, the browser always sends this cookie with the HTTP request and thus identifies itself to the application. The application can check the role of the requestor in the stored session data and control the appropriate access.

Basic setup of the server

First we need a working Server OS. I run Linux Ubuntu in production and have written an article about the  basic setup of a production Linux server on my blog site  Digitaldocblog. Since I am going to store the sessions in a MongoDB, MongoDB must be installed on the Linux server. I use MongoDB Community Edition but you can also install or upgrade to the MongoDB Enterprise Server version. In the lower part of the article you find the instructions how to install and setup your MongoDB Community Edition on your Linux System. In case you want to read the original documentation go on the MongoDB site and read how to install the  MongoDB Community Edition for your OS.

In my express application I use a number of external modules or dependencies that have to be installed for the application in order for the application to run. In the repository of the  bookingsystem on my  GitHub account you find the  package.json file which contains all the necessary dependencies. In principle, it is sufficient if you put this package.json file in your application main directory and install all dependencies with npm install.

Alternatively, of course, all modules can also be installed individually with

npm install <module> --save

#nodejs #expressjs #programming #javascript