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Top 23 Jvm Open-Source Projects
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Project mention: Standing on shoulders: the stack that makes Floci start in ~24ms | dev.to | 2026-05-21
Vert.x is the layer where Floci uses things directly. It's Netty with ergonomics: an event loop, a router, protocol-specific APIs for HTTP, DNS, TCP, WebSockets, gRPC, all sharing the same threading model.
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During my career break that I started in 2025, I started exploring the ever-changing Generative AI landscape. In Decemember, I was exploring Spring Boot as I hadn't used it in anger professionally having used other Java frameworks like Jersey, Play and I wanted to build something.
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ysoserial
A proof-of-concept tool for generating payloads that exploit unsafe Java object deserialization.
Project mention: Gadget chains in Java: how unsafe deserialization leads to RCE? | dev.to | 2025-10-10The problem with exploiting native Java serialization weaknesses is not new. Various enthusiasts have compiled a set of "useful payloads" that exploit gadget chains within various popular libraries (in certain versions) and created the ysoserial utility, which generates such objects in a serialized form. It's super handy for getting familiar with a topic and for testing whether an application is vulnerable—of course, with the author's permission; exploiting such things without the creator's consent is illegal and unethical.
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Testcontainers
Testcontainers is a Java library that supports JUnit tests, providing lightweight, throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container.
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Project mention: Everything You Need to Know about asynchronous programming along with Kotlin + Spring WebFlux | dev.to | 2025-07-26
Project Reactor
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Java had its world changing moment when Ron Pressler gave this talk at Curry On: https://github.com/puniverse/quasar.
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koog
Koog is a JVM (Java and Kotlin) framework for building predictable, fault-tolerant and enterprise-ready AI agents across all platforms – from backend services to Android and iOS, JVM, and even in-browser environments. Koog is based on our AI products expertise and provides proven solutions for complex LLM and AI problems
Project mention: Building an AI task generator for Vikunja that doesn't trust itself | dev.to | 2026-05-31The agent workflow runs on Koog, JetBrains' agent framework for Kotlin. The frontend is React + Vite. Everything ships as Docker Compose behind nginx with TLS.
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Project mention: Presentation Slides for RubyConf Austria 2026 Talk "Frontend Ruby on Rails with Glimmer DSL for Web" | dev.to | 2026-06-02
Charles Nutter had me help him with his JRuby workshop afterwards by showcasing my other Glimmer project, Glimmer DSL for SWT, which runs on JRuby. In about 1 minute, I scaffolded a Hello World desktop app from scratch and then packaged it as a native executable on the Mac. Attendees were impressed. So, I’ve participated in presenting 2 events at this conference.
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Apache Log4j 2
Apache Log4j is a versatile, feature-rich, efficient logging API and backend for Java.
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OpenJ9
Eclipse OpenJ9: A Java Virtual Machine for OpenJDK that's optimized for small footprint, fast start-up, and high throughput. Builds on Eclipse OMR (https://github.com/eclipse/omr) and combines with the Extensions for OpenJDK for OpenJ9 repo.
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kotlin-logging
Lightweight Multiplatform logging framework for Kotlin. A convenient and performant logging facade.
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keyguard-app
Alternative client for the Bitwarden® platform & KeePass (KDBX), created to provide the best user experience possible.
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If you want to use algebraic effects today, I highly recommend Unison. If you’re on the JVM, Flix is doing major advances with effects!
https://www.unison-lang.org/
https://flix.dev/
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Flume
Apache Flume is a distributed, reliable, and available service for efficiently collecting, aggregating, and moving large amounts of log-like data
NOTE:
The open source projects on this list are ordered by number of github stars.
The number of mentions indicates repo mentiontions in the last 12 Months or
since we started tracking (Dec 2020).
Jvm discussion
Jvm related posts
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Every Byte Matters
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Valhalla when? "Now"? Java 27?
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JGuard v0.4.0 – Capability-based security for the JVM (post-SecurityManager)
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More than minimal Java 21 JVM writen in Go
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Library for fast mapping of Java records to native memory
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Pull Request: Java language implementation of value classes and objects
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nowhere: an entire website encoded in a URL
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A note from our sponsor - SaaSHub
www.saashub.com | 7 Jun 2026
Index
What are some of the best open-source Jvm projects? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | JavaGuide | 156,089 |
| 2 | Arthas | 37,337 |
| 3 | JDK | 22,950 |
| 4 | Vert.x | 14,671 |
| 5 | LearningNotes | 13,157 |
| 6 | Play | 12,621 |
| 7 | ysoserial | 8,908 |
| 8 | Testcontainers | 8,655 |
| 9 | reactor-core | 5,223 |
| 10 | FXGL | 4,818 |
| 11 | Quasar | 4,560 |
| 12 | koog | 4,315 |
| 13 | JRuby | 3,903 |
| 14 | Apache Log4j 2 | 3,603 |
| 15 | OpenJ9 | 3,522 |
| 16 | kotlin-logging | 3,078 |
| 17 | teavm | 3,056 |
| 18 | KorGE | 3,015 |
| 19 | keyguard-app | 2,972 |
| 20 | mongo-java-driver | 2,657 |
| 21 | flix | 2,658 |
| 22 | eta | 2,627 |
| 23 | Flume | 2,560 |
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