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Top 23 Scala Java Projects
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In the meantime, other query engine support is on the roadmap, including Apache Spark, Apache Flink, and others.
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InfluxDB
InfluxDB – Built for High-Performance Time Series Workloads. InfluxDB 3 OSS is now GA. Transform, enrich, and act on time series data directly in the database. Automate critical tasks and eliminate the need to move data externally. Download now.
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~/project$ sbt run [info] welcome to sbt 1.10.6 (Ubuntu Java 17.0.14) [info] loading settings for project scala-api-heroku-build from plugins.sbt... [info] loading project definition from /home/alvin/repositories/devspotlight/heroku/scala/scala-api-heroku/project [info] loading settings for project root from build.sbt... [info] loading settings for project docs from build.sbt... [info] __ __ [info] \ \ ____ / /____ _ __ __ [info] \ \ / __ \ / // __ `// / / / [info] / / / /_/ // // /_/ // /_/ / [info] /_/ / .___//_/ \__,_/ \__, / [info] /_/ /____/ [info] [info] Version 3.0.6 running Java 17.0.14 [info] [info] Play is run entirely by the community. Please consider contributing and/or donating: [info] https://www.playframework.com/sponsors [info] --- (Running the application, auto-reloading is enabled) --- INFO p.c.s.PekkoHttpServer - Listening for HTTP on /[0:0:0:0:0:0:0:0]:9000 (Server started, use Enter to stop and go back to the console...)
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Comprehensive requirement analysis forms the foundation of successful load testing implementation.
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joern
Open-source code analysis platform for C/C++/Java/Binary/Javascript/Python/Kotlin based on code property graphs. Discord https://discord.gg/vv4MH284Hc
I'm surprised that performance wasn't on the list. The main reason I started Brokk on the JVM was for access to https://github.com/joernio/joern, but high performance code that can easily go multicore is a very nice secondary reason.
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Mill
Mill is a build tool for Java, Scala and Kotlin: 3-6x faster than Maven or Gradle, less fiddling with plugins, and more easily explorable in your IDE
Working on my Mill build tool, aiming to bring a modern developer experience to the JVM ecosystem:
- https://mill-build.org
Build tools are generally an un-sexy field, and JVM build tools perhaps doubly so. But Mill demonstrates that with some thought put into the design and architecture, we can speed up JVM development workflows by 3-6x over traditional JVM tools like Maven or Gradle, and make it subjectively much easier to navigate in IDEs and extend with custom logic.
If you're passionate about developer experience and work on the JVM, I encourage you to give Mill a try!
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Sevalla
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Project mention: I got OpenTelemetry to work. But why was it so complicated? | news.ycombinator.com | 2025-01-10
Have you considered Kamon instead? From personal experience it's really the best tracing solution for Akka and other libraries using Scala Futures. I haven't tried it, but it does have built-in Spring support as well.
https://kamon.io
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Reactive-kafka
Alpakka Kafka connector - Alpakka is a Reactive Enterprise Integration library for Java and Scala, based on Reactive Streams and Akka.
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adam
ADAM is a genomics analysis platform with specialized file formats built using Apache Avro, Apache Spark, and Apache Parquet. Apache 2 licensed.
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bloop
Bloop is a build server and CLI tool to compile, test and run Scala fast from any editor or build tool. (by scalacenter)
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java-webauthn-server
Server-side Web Authentication library for Java https://www.w3.org/TR/webauthn/#rp-operations
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build-server-protocol
Protocol for IDEs and build tools to communicate about compile, run, test, debug and more.
Project mention: Show HN: Gradle plugin for up to 20x faster Java compiles | news.ycombinator.com | 2025-06-03I work professionally in Python these days, but I've just spent a bit of time digging into the contemporary situation because the JVM environment is much more interesting to me, and found this spec: https://build-server-protocol.github.io
Seems the Scala guys have doubled down on the "compiler as a service" approach, presumably because their compile time story continues to be painful. But also looks like the same solution is used for the VS Code Java/Gradle integration, so seems like this might be the more conventional way to go for traditional JVM projects.
For processes where the JIT takes a while to kick in, but also you don't want to waste memory keeping JVMs alive while not doing anything (and compilation could be a good example of that), I wondered if there could be a way to snapshot and restore the JVM state and turns out some people are experimenting with that too: https://openjdk.org/projects/crac/
It's all neat stuff!
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AkkaGRPC
A platform to build and run apps that are elastic, agile, and resilient. SDK, libraries, and hosted environments.
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tscfg
Schema-first, boilerplate-free, type-safe access to configuration properties in Java and Scala
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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).
Scala Java discussion
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A note from our sponsor - SaaSHub
www.saashub.com | 1 Sep 2025
Index
What are some of the best open-source Java projects in Scala? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | Apache Spark | 41,789 |
| 2 | Play | 12,584 |
| 3 | Finagle | 8,834 |
| 4 | Gatling | 6,757 |
| 5 | Lagom | 2,630 |
| 6 | joern | 2,589 |
| 7 | Mill | 2,565 |
| 8 | Kamon | 1,424 |
| 9 | Reactive-kafka | 1,418 |
| 10 | adam | 1,033 |
| 11 | bloop | 927 |
| 12 | Scrooge | 797 |
| 13 | guardrail | 534 |
| 14 | java-webauthn-server | 517 |
| 15 | build-server-protocol | 501 |
| 16 | akka-http-session | 439 |
| 17 | AkkaGRPC | 433 |
| 18 | kmq | 337 |
| 19 | SwayDB | 292 |
| 20 | spark-extension | 229 |
| 21 | Play WS | 226 |
| 22 | kukulcan | 116 |
| 23 | tscfg | 109 |
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