Open Source: A League of Super Devs?

I always thought contributing to open source was a mission for superhero developers—those with powers beyond mortal coding, building legendary tools to save the dev world. It felt unreachable for someone like me.

But that started to change when I began mentoring (a story for another time), and especially when I fell in love with LangChain4j.

My Origin Story with LangChain4j

LangChain4j is an open source project that changed how we build Java applications powered by AI. Before LangChain4j, it felt like all this AI revolution was only for Python developers.

But that changed after I watched an amazing talk by Lize Raes at Devoxx Belgium 2023. My mind was blown. How could it be possible that by just importing a dependency and writing a few lines of code, a Java app could run a chatbot that talks to an LLM and gives you answers right in the console?

Diving into Docs and Discovering My Powers

I remember spending hours reading the LangChain4j documentation. I ran all the examples from the GitHub repo used in Lize’s talk. I was impressed by how simple it was to build an app with generative AI features.

I learned how to use RAG to give the app specific business context. I’ll never forget debugging my first agent with tools and finally understanding function calling—how incredible it was to see the LLM tell my backend that it needed to call a tool, already with the right parameters! LangChain4j made all of that work seamlessly. It was like discovering my own origin story—LangChain4j felt like the radioactive spider bite that turned me from a regular dev into something more.

From Code Fan to Contributor

Soon after, I had the chance to use LangChain4j in a real production chatbot. It was a great challenge: building a complex app with business rules, a full AI agent, guardrails, several tools integrated with different internal microservices, and storing session memory in an external database.

During this process, something unexpected happened: one feature worked fine when calling Anthropic directly but failed when using the same model through Amazon Bedrock. Time to put on the cape—this was my chance to step up and fix a real-world bug in an open source project.

Becoming a Hero (with a Pull Request)

I searched the LangChain4j GitHub issues and found nothing. So, I opened a new issue. To my surprise, the LangChain4j GitHub profile encouraged me to contribute the fix to the project!

The solution was actually simple and already used in the direct Anthropic call, so I applied it to the Amazon Bedrock module. Everything in the project was very well documented: how to contribute, how to open a PR. I had the honor of discussing the fix with the LangChain4j GitHub profile and eventually having my PR approved and merged. A few days later, I saw my contribution in the release notes—it was a dream come true.

Your Turn to Join the Open Source League

Contributing to open source felt impossible – until it wasn’t. And if I could do it, so can you.

I had no idea this could become real, especially in such an important project like LangChain4j. I also achieved another dream: working with incredible international developers. That’s what happens when you contribute to a big open source project.

If there’s a project you admire and use in your daily work, you can become a contributor. Find the project on GitHub, look for issues labeled good first issue, start small, contribute. The feeling of seeing your name in the release notes and your code running in projects all over the world is addictive. Giving back to a project like LangChain4j, one that’s empowering Java developers everywhere, felt like joining the open source Avengers.

What’s Next

Soon, I’ll share more about LangChain4j, the concepts behind it, and how to create agentic applications. Let’s go Java! Let’s go LangChain4j! Let’s contribute to open source!

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Resources

The mind-blowing talk by Lize Raes – Devoxx Belgium 2023 https://youtu.be/BD1MSLbs9KE?si=inEHySOaxYV2R2x_

The most complete talk I’ve seen about LangChain4j with Quarkus – Georgios Andrianakis, Eric Deandrea, Clement Escoffier – Devoxx Belgium 2024 https://youtu.be/jzuP6l54kWA?si=YW9w2cKEkfrDSiBj