The ability to have real-time two-way communication between the client and the server is a key feature in most modern web apps.

A common pattern when deploying applications to a development, staging, and production environment is to build a jar or docker image one time, then supply different configuration values in the deployment for each stage. This configuration could be a Spring profile in separate yaml documents, additional properties files, environment variables, or some other configuration mechanism.

In traditional web applications, it’s only possible to interact with the server via a request and wait for a response. With modern interactive applications, this approach is not ideal for any user interaction when we want to get updates from the server without having to continuously make requests to learn if anything interesting has happened on the server. The solution is to provide a bi-directional, persistent means of communication between the client and the server. This is where WebSocket comes in.

Recently, I’ve had an issue were I want to be able to run multiple spring boot services locally for testing and development purposes. Unfortunately they all run on the same port so they fail to start!

Some backstory… I was working on a Java app with an Angular 1.x frontend. The base project was generated by JHipster and uses PostgreSQL for the DB and Spring Boot.