Michael Olayemi Michaelin007

Project Reactor: From Zero to Hero

In this series of pages, I will discuss project reactor and reactive programming from basic concepts to reactor internal implementation details. This discussion is based on the official reference documentation, the java-doc, talks by maintainers of reactor e.g. at the spring I/O and other distributed material, and should summarise and connect all this information. It should complement the official reference documentation and java-doc. Although the name says "from zero to hero", basic knowledge about the library is advised to fully benefit from it.

As a short disclaimer, I am a professional software engineer with some years of experience in using reactor, but not a maintainer or creator of the library. Information and knowledge in this post are based on the official documentation and talks, but I cannot exclude misconceptions on my side.

[Why and when to use Reactor](https://gist.github.com/Lukas-Krickl/50f1daebebaa72c7e944b7c319e3c073#file-01-why-and-when-to-use

Introductory resources

High level overview https://yogthos.github.io/ClojureDistilled.html
An Animated Introduction to Clojure https://markm208.github.io/cljbook/
Interactive tutorial in a browser https://tryclojure.org/
Interactive exercises http://clojurescriptkoans.com/
Clerk notebooks with introductory examples https://github.clerk.garden/anthonygalea/notes-on-clojure
More interactive exercises https://4clojure.oxal.org/
Lambda Island tutorials https://lambdaisland.com/
Functional Programming with Clojure resources https://practicalli.github.io/

Deploy Rocket using Letsencrypt and nginx

Information

This guide uses the domain your-domain.tld and its www. prefixed version. It starts the rocket application on 127.0.0.1:1337 and as the user www-data. The proxy listens on port 80 and 443 though.
If you need other values, update them accordingly in your nginx and systemd configs.

Prerequisites

You need to have nginx, certbot and rust installed.

	// $ cc -o checker checker.c
	// $ ./checker
	// $ ffmpeg -i output-%02d.ppm -r 60 output.mp4
	#include <stdio.h>

	int main()
	{
	char buf[256];
	for (int i = 0; i < 60; ++i) {
	snprintf(buf, sizeof(buf), "output-%02d.ppm", i);

	// sdk install java 23.0.1-librca && sdk use java 23.0.1-librca
	// java --enable-preview Main.java
	record Point(int x, int y) {}
	sealed interface Shape permits Rectangle, Circle {}
	record Rectangle(int width, int height) implements Shape {}
	record Circle(int radius) implements Shape {}

	void main() {
	var point = new Point(1, 2);
	println(describePoint(point));

	package old.keke;

	import org.openjdk.jol.info.GraphLayout;

	/*
	last optimization - using short mask for booleans
	*/
	public class FootPrint {

	static final short IS_MALE = 0, IS_EXISTENT_USER = 1, IS_KNOWN_CUSTOMER = 2, IS_BANNED_USER = 3,IS_PREMIUM_USER = 4,

Service	Type	Storage	Limitations
Amazon DynamoDB	⚠️ Proprietary NoSQL	25 GB	⚠️ Payment method required
Amazon RDS	⚠️ Proprietary RDBMS		⚠️ Only free for 1 year
Azure SQL Database	MS SQL Server		⚠️ Only free for 1 year
👉 Clever Cloud	PostgreSQL, MySQL, MongoDB, Redis	256 MB (PostgreSQL)	Max 5 connections (PostgreSQL)

Service	Type	RAM	Storage	Limitations
👉 Adaptable	PaaS	256 MB	Non-persistent? (1 GB database storage available)
AWS EC2	IaaS	1 GB		⚠️ Only free for 1 year

	// Enable component-scanning and auto-configuration with @SpringBootApplication Annotation
	// It combines @Configuration + @ComponentScan + @EnableAutoConfiguration
	@SpringBootApplication
	public class FooApplication {
	public static void main(String[] args) {
	// Bootstrap the application
	SpringApplication.run(FooApplication.class, args);
	}
	}

	import javax.swing.*;
	import java.awt.*;
	import java.util.List;
	import java.util.ArrayList;
	import java.awt.geom.*;
	import java.awt.image.BufferedImage;

	public class DemoViewer {

	public static void main(String[] args) {