thermcampos blog

javalin the lightweight java framework

2026-10-01T18:15:11Z

I'd like to introduce you all to Javalin. Java is known for being heavy and bloated, verbose, often flagged as bad choice for cold-start functions, or simple MVPs or POCs. Often because it's slow, or memory-heavy consumer, which I could agree with, on some situations.

This is specially interestring if you're coming from languages such as Go or Typescript and is already familiar with express.js or chi from Golang. The learning curve for a full Java backend app will be pretty smoth.

Let's cut to the chase, no rambling, no time spent. Javalin is simple, lightweight, interoperable, flexible, supports OpenAPI and runs on top of Jetty JVM web-server, that includes SSL and HTTP3.

Here's what a Hello World would look like, if you're curious.

import io.javalin.Javalin;

void main() {
  var app = Javalin.create(config -> {
    config.routes.get("/", ctx -> ctx.result("Hello World"));
  }).start(7070);
}

And that's it! No annotations needed, controllers, or any of the boilerplate that Springs like. As simple as that.

If you're a maven person, you can get started in the maven-setup page, but ify you're a graddle person, use the graddle-setup page.

On their page there's plenty of useful tutorials and code snippets, check it out. And now if you want to go straight to the code, find their GitHub repo at: https://github.com/javalin/javalin

Native build

Javalin also supports GraalVM. GraalVM builds are OS-native binaries, compiled into full executable apps that can run without the JVM. This is super attractive for Serverless and functions that needs cold-start within seconds.

Here's an example from their main page: https://javalin.io/2018/09/27/javalin-graalvm-example.html and if you want something more complete, including tests, Flyway migrations, and more, you can take a look at this personal project: https://github.com/thermcampos/lin-order-java.

That's all for today. If you have any questions, I'll be happy to answer. Reach out by using the comment system below or any of the link in the about page.

Thanks for reading.

minimal initramfs script

2026-09-10T12:59:27Z

After several years having Debian as my main Linux distro, I've decided to go back to Gentoo, the distro who caught my attention since day one. However, my root partition is encrypted. While Debian has an out-of-the-box solution that makes everyone's life easier and almost transparent, Gentoo goes the opposite way. You have to connect the dots and make it work yourself. I had to stop, plan for a moment, and get ready.

In this short post, I'll be sharing the steps I took, the shell scripts, and how I wired up a minimal init script, that I called initramfs, although it's not quite that, this is much smaller and single purposed, decrypt my root partition.

Long story short, I needed to find a way to decrypt, mount and boot my new OS having the root partition encrypted. Using Gentoo's live-cd I was able to try the script partially, and confirm the decryption works. All I needed was having a busybox environment with all crypt libs on it. Using Gentoo itself for that, I compiled some packages with static linked dependencies.

Then build the initial script that's going to do all the heavy-lifting.

TL;DR, here are the scripts:

Create the initramfs directory, embed busybox and the crypt libs and tools on it

#!/bin/sh
set -e
STAGE="${1:-/usr/src/initramfs}"

mkdir -p "$STAGE"/{bin,sbin,lib,dev,proc,sys,mnt/root,run}

cp /sbin/busybox "$STAGE/bin/"
"$STAGE/bin/busybox" --install -s "$STAGE/bin"

cp /sbin/cryptsetup "$STAGE/sbin/"
cp /sbin/lvm "$STAGE/sbin/"

for bin in /sbin/cryptsetup /sbin/lvm; do
    ldd "$bin" | awk '{print $3}' | grep -v '^$'
done | sort -u | while read -r lib; do
    mkdir -p "$STAGE$(dirname "$lib")"
    cp -L "$lib" "$STAGE$lib"
done

cp init "$STAGE/init"
chmod +x "$STAGE/init"

echo "Staged tree ready at $STAGE — cd there and run the cpio|gzip packaging step."

create the init script (it needs to be called only init) at /usr/src/initramfs

#!/bin/sh

rescue_shell() {
    echo "Something went wrong v3. Dropping to a shell."
    exec /bin/sh
}

mount -t proc none /proc
mount -t sysfs none /sys
mount -t devtmpfs none /dev
mkdir -p /run/cryptsetup
export DM_DISABLE_UDEV=1

ROOT=$(sed -n 's/.*\broot=\([^ ]*\).*/\1/p' /proc/cmdline)

cryptsetup luksOpen /dev/nvme0n1p3 gentoo_root || rescue_shell
lvm vgchange -ay || rescue_shell

mount -o ro "$ROOT" /mnt/root || rescue_shell

exec switch_root /mnt/root /sbin/init

Finally generate the image that goes to /boot and grub

#!/bin/bash

KERNEL="7.2.4-gentoo"

cd /usr/src/initramfs

find . | cpio -o -H newc | gzip > /boot/initramfs-$KERNEL.img

grub-mkconfig -o /boot/grub/grub.cfg

Done. With luck, you should have a minimal setup ready to decrypt and boot your OS. Feel free to get in touch and ask for help, if needed. I have these scripts versioned on my personal repo, find then here: https://github.com/thermcampos/gentoo-config-files/tree/main/kernel

That's all. Thanks for reading.

monthly updates

2026-09-08T17:50:18Z

September has just started and is already flying away, going by light-speed fast! Christmas is almost knocking on the door. But I'm here to talk about updates and what's going on recently. Let's dive in!

hybrid work

I decided (not entirely by choice) to go regularly to a coworking space near my apartment. By regularly, I mean at least three times a week. The reasons are noisy constructions at my building, constructions inside our apartment, and giving my wife some space. (our apartment is very small, and she's in a graduate program, needs silence to study).

I gotta admit, I thought I'd hate, but actually I can see its value now. Getting out of the house is doing me so much good. I like the walking commute. The space is on the fourth floor with a nice view, and there's free coffee included!

This is unexpected from me because I've been working from home since 2019, 7 years now, and until recently I was strongly refusing to go back to any office. But here I am, and I'm pretty happy. Anyways, let's see what the recommendations section brought this time.

recommendations

Along with updates, I'd like to share findings that caught my attention. They might be useful, handy, entertaining. you judge.

I'd like to kick off with Cassidy Williams. She's a Senior Director of Developer Advocacy at GitHub and keeps a newsletter that's so well-curated, it'd be a sin not to share it. You can have a glance at it here.
If you are in the AI world, Devthusiast might interest you. This newsletter covers what's happening and the bleeding-edge tech updates.
Now if you're into AI and also into software engineering, take a look at Matt Pocock's skillset to go the opposite way of vibe-coders. Matt shared a YouTube Video with first steps and how to get started.
On the frontend and UI/UX side, there's a great article that went around the internet in the last few weeks about what would be the best dark mode toggle. Very interesting discussion. Read it here

That's all for today! Thanks for reading. If you like this content, you might consider subscribing via RSS to this category: use this URL

hello world

2026-08-24T19:59:46Z

Welcome to the very first post. Long time ago (2011-2013) I use to write to a personal blog like this, then life got busy, and all faded away. I must say I tried writing here and there some of my technical discoveries and helping content, but never actually found a nice place where personal thoughts fit nicely along with tech findings.

In the past few days I decided to go back to Gentoo, after more or less 7 years using Debian Sid (the only truly rolling release Debian flavor), and that brought a lot of memories. And blogging was one of them. So I decided to re-write and bring back to life the old Blohg engine, a lightweight python Flask app that uses git as back-end and Jinja2 to render templates.

I also decided to get back to IRC, where I spent a lot of time in the past chatting with friends about Linux. But the old server is gone, Freenode. Now the common choice seems to be Libera. If you're in there too, ping me anytime, just search for my handler thermcampos.

there's more

Another reason that helped me decide having a personal blog again was a post that I can't find right now (sorry) saying that many people don't write because they think the content will be the same as other people, but there's a gotcha, even though is the same content as the other people, it is your content with your words. Then bum! That was enough. And here I am. Here we are.

Comments will come soon. In the meanwhile, feel free to ping me and chat using any of the options in the /contact page.

Bye for now.