HTTP server kata

This project contains the result and notes for Johannes Brodwall's presentation on Building an HTTP Server with Nothing Up My Sleeves.

The presentation builds a (more or less) working HTTP server from scratch in one hour with no real dependencies. It only uses the following:

• The Java 19 programming language
• java.lang, java.util, java.nio and java.io packages
• java.net.Socket and java.net.ServerSocket
• java.net.URL for testing
• JUnit 5 for testing

We use RFC 7230 for reference (it's not the newest, but it's the one I know best)

During the presentation we build a server that can:

• Respond to HTTP requests
• Serve files from disk
• Respond to API requests
• Handle login and user sessions
• Unit tests for all the functionality

During the presentation, we highlight many important developer lessons:

• HTTP is only text sent to and from the server - you can parse and build it just like with files
• How you approach the task of coding is as important as the code you write
• The structure of code is best grown gradually as the code solves more and more functionality
• The process is most engaging then you minimize the time spent with code that doesn't compile or tests that fail
• Refactoring support in your IDE can increase your productivity incredibly

Contents

This repository contains several iterations of building the code bases, each living on a separate branch

Performances

• Performance starting point
• JavaBin Christmas Lecture, 2022
• Sopra Steria DevMeetup, 2023
• Norwegian Police, 2023
• JavaBin Sørlandet in Kristiansand, 2023
• Fredrikstad tech community, 2023

Reference implementations

• A comprehensive server - includes routing and a HttpRequestHandler framework, SSL support, a strong HttpServerRequest class with header parsing, request parsing and cookie parsing, and a fluid HttpServerResponse. This lets you see a fairly comprehensive result
• A stepwise commit log with 50 commits showing a step-by-step approach with each new failing test, each completed test and each refactor as a new commit. This lets you follow the process as I build a fairly functioning server.

Programmer tips

I often get asked how to learn how to work effectively with IntelliJ. Like everything, it's always a matter of practice, but I have a few recommendations as to what to focus on when you practice

IntellJ shortcuts

These are some of the most versatile keyboard shortcuts in IntelliJ. There are many more, but learning these 12 will really speed up your code

Shortcut (Windows)	Shortcut (Mac)	Command
alt-enter	opt-enter	Show content action (quick fix)
ctrl-alt-shift-t	ctrl-t	Refactor this (show refactor menu)
alt-insert	cmd-n	New... (add some content)
ctrl-w	opt-up	Expand selection (add shift to go the other way)
shift-alt-f10	ctrl-opt-r	Run....
shift-alt-f9	ctrl-opt-d	Debug....
shift-f10	ctrl-d	Rerun last....
ctrl-b	cmd-b	Navigate to symbol
alt-ctrl-left	cmd-opt-b	Navigate back
alt-j	ctrl-g	Add next match to selection (multi-cursor)
shift-ctrl-backspace	shift-cmd-backspace	Goto last edit location
shift, shift	shift, shift	Search anywhere

Make yourself familiar with Refactor this (ctrl-alt-shift-t / ctrl-t) and use it to learn the shortcut keys for your favorite refactorings like Extract method, Rename and Inline. Also, make sure you explore what's available on the Content Action (alt-enter).

Also remember basic cursor navigation like ctrl-left and ctrl-right to jump one word at a time, home and end and holding shift to expand selection while you move the cursor.

IntelliJ Live Templates

Less used than the shortcuts, these shorthand ways of writing common bits of Java code can save a bit of time. Write the name of the code template in the right spot and press Tab to have IntelliJ expand it

Template	Result
fori	for (int i=0; i<...; i++) {}
main	public static void main(String[] args) {
sout	System.out.println();