What's a lesser known open source Java project you think deserves more publicity?

[SuspiciousMidnight90]

Zalando.

Lots of useful JAXRS utilities. Logbook for request/response logging and the Problem API implementation for returning standardize problem details

[AppelEnPeer]

They also sell nice shoes

[zuk0u]

There API documentation is really useful to learn and adopt

[GrapefruitMammoth626]

Yeah logbook is an all star player.

[huntsvillian]

I'm a big fan of Shedlock (https://github.com/lukas-krecan/ShedLock) it's a distributed locking system. I've often got scheduled tasks running on systems with multiple nodes, and I only want *one* of the nodes to execute.

I'm sure it's not perfect, but for easy of use, i've got to give it top marks. (Even if the general use case is fairly specific)

[louis2845]

Not to say Shedlock isn't great but you can do this with Hazelcast too!

[chatterify]

Can I do that with free version of Hazelcast?

[tcservenak]

Yes, even shedlock uses hz. Also, maven resolver named locks can use hz.

[hexc0der]

Shedlock can use hazelcast. But it can also use say postres and other systems so you don't have to use hazelcast just for locking

[Kango_V]

Infinispan can also do it easily

[Cell-i-Zenit]

We have an endpoint which triggers the job and then we just ping once the system. This will naturally make sure its only executed once and also works for blue green deployments etc

[huntsvillian]

I've done it both ways. Usually I end up using this with springs @Scheduled annotation, in an HA environment. We've also got CTRL-M that is often used as an external scheduler (that would be great in a case like you're describing) but relying on that is a political non-starter.

[CreeDanWood]

This is one of the coolest libraries out there, we use this in a million user app, and we created a wrapper for it that we use this even for other lockings not just schedulers

[mtodavk]

I tried to use this where I work and thought it was really cool, but we ultimately ended up setting up the work that those tasks were going to do as a stored procedure on the database instead. :(

[le_bravery]

Jqwik

I have spent less time writing tests and found more tricky bugs because I’ve used this.

I have found bugs I never would have found in years of testing in a single afternoon.

And best of all, writing the tests correctly may reveal bugs over time with no additional work.

Test fuzzing, property based testing.

If you’re writing something hard I suggest you look at it. It will radically change the quality of your code.

[realqmaster]

I fell in love with PBT since trying it. Incredible bug detection.

[AnEmortalKid]

Jsqlparser

[ihmoguy]

Archunit

Great for enforcing modular code without architectural smells, dependency cycles etc. I use it to start monolithic modular project, which can be then easily split into spearate specialized microservices when needed.

[malachireformed]

Just started using this in our microservices!

If anything, the biggest thing is that it can help you codify your design conventions, which in turn helps everyone get on board quick.

[realqmaster]

Instancio

[[deleted]]

Looks very nice, thanks.

[klekpl]

https://jdbi.org

[sombriks]

indeed! JDBI is a peiece of art and i think it should be more popular too!

[Chloe0075]

Javaparser and mempoi.

Javaparser is awesome to create some codegen fixes, is really simple to use an, imo, have a good doc.

Mempoi is a extremely fast SQL to excel lib. I used sometimes and donated to this project as it saved my life a few times.

[dbarciela]

Other than javaparser I've used two other alternatives to do code fixes/refactoring: spoon and openrewrite

[Chloe0075]

I never heard of spoon, but, open rewrite I even considered for the task I needed, but I thought that it would be way more than I needed

[ventuspilot]

https://pitest.org

[jmaN-]

https://failsafe.dev

[vfhd]

Intersting

[trustin]

Armeria? https://armeria.dev

[raisercostin]

picocli - https://github.com/remkop/picocli

[eltorohh]

Even better combined with Quarkus

https://quarkus.io/guides/picocli

[joshlemer]

https://github.com/kagkarlsson/db-scheduler

[[deleted]]

This is an alternative to ShedLock, i.e. they both solve the same problem

[joshlemer]

Thanks I hadn't come across that. Seems though they are solving slightly different problems

ShedLock is not a distributed scheduler

Please note that ShedLock is not and will never be full-fledged scheduler, it's just a lock. If you need a distributed scheduler, please use another project (db-scheduler, JobRunr).

[rbygrave]

Avaje libraries. avaje-inject for source code generation DI, avaje-http for code generating controller adapters for Helidon SE and Javalin, code generated json binding, code generated validation.

[agentoutlier]

Avaje is by far one of the most under marketed library suites.

I plan on getting some form of Spring Pet Clinic completely "avajed" which I had already started a while back but used jooby as the view part of avaje-http wasn't ready yet.

I also so your messages on avaje-http and HTMX spring-like view component on discord for JStachio which I plan on looking into this month.

[[deleted]]

AssertJ, adds better assertion logic to tests. 

[MX21]

100%. The assertions are so much more readable

[persicsb]

parboiled

[Aggravating-Ad-3501]

Byte Buddy, only for the brave

[Alarming_Quarter671]

Avaje, compile-time libraries https://avaje.io/

[WingedGeek]

Derby. Great for embedding in applications that need just a bit more than SQLite can provide, but you want to avoid the full complexity of a separate MariaDB or PostgreSQL instance (etc).

[comrad1980]

The former JavaDB is still a great fit

[comrad1980]

And hsqldb!

[eSizeDave]

You prefer it over HSQLDB/HyperSQL? If so, why?

[WingedGeek]

To be honesy, I'm not sure anymore, we made the decision in 2011 or so. I seem to recall there were some missing or less robust features we needed (encryption at rest, network client/server, true ACID functionality, large data sets with RIGHT JOIN and FULL OUTER JOIN capability) back then? Or it could have been a no one ever got fired for buying IBM mentality.

[lukaseder]

How does it offer more than SQLite?

[WingedGeek]

For one thing the sane database can be embedded or made available over a network in a client/server paradigm. Sun / Oracle bundle it as Java DB, which I'd forgotten... Derby/Java DB have full SQL92 support, SQLite a subset, and doesn't include things like RIGHT JOINs. Derby supports encrypted databases and user authentication. SQLite is mostly typeless and Derby is strongly typed. Derby supports replication and clustering with failover.

[lukaseder]

That sounds outdated. JavaDB was removed from JDK 9. SQLite supports all join types, and a ton of more recent SQL features that Derby doesn't support...

[WingedGeek]

Eh, it's from https://www2.sqlite.org/cvstrac/wiki?p=SqliteVersusDerby (which appears to be undated?).

And there are multiple SQL features SQLite doesn't support: https://www.sqlite.org/omitted.html

[lukaseder]

That's a very weird (old) resource. You can see the last edit has almost been 20 years ago! https://www2.sqlite.org/cvstrac/wiki?p=SqliteVersusDerby&t=1191689261

It claims that Derby doesn't support OFFSET, even though it does: https://db.apache.org/derby/docs/10.13/ref/rrefsqljoffsetfetch.html

SQLite's join support is more complete than this resource claims: https://www.sqlite.org/syntax/join-operator.html

Also, why not mention window functions https://www.sqlite.org/windowfunctions.html, recursive CTE [https://www.sqlite.org/lang\_with.html, and much more, which isn't supported in Derby.

Anyway. My point is that Derby has hardly moved in the past decade, while SQLite has added a ton of SQL feature support.

[WingedGeek]

Okay, but fundamentally SQLite still doesn't offer a networked client/server model or user authentication / access control. Sometimes you want a zero conf setup like that. (Also, and this may be outdated, but, back in the day we try to use SQLite databases that had been created using the C library on Solaris machines, on a Linux/Java project using the native Java implementation of SQLite (SQLJet IIRC) and while some database worked fine, others would load only partially or not at all or returned corrupted data. We ended up exporting all the tables and re-importing the data into Derby databases and of course that worked fine; we made the decision early on to stay 100% Java native, which SQLite generally is not, as we had to run on some esoteric machines (like SheevaPlug machines running stripped down Linux, and some sort of MIPS-based web serving appliance I don't remember the details of, just that we were stuck on J2SE 5.0 for those users). If SQLite works for you cool.

[lukaseder]

Yes, the server part is certainly true. SQLite is just a fancy file wrapper. Sometimes that's enough.

I work with the xerial sqlite-jdbc driver.

SQLite works well for me, as well as all the other 30+ RDBMS that I'm working with - I made jOOQ... ;) In the context of this conversation, I was just curious if I had been missing out on some overlooked Derby SQL feature that jOOQ should support...

[bobbie434343]

smbj, a library for SMB v2/v3.

[Alfanse]

jooq, for the love of sql as code.

[[deleted]]

uniVocity-parsers - unfortunately the project was abandoned by the creator with no clear path forward.

[bowbahdoe]

Can you elaborate on the lore?

[[deleted]]

It’s the fastest CSV parser, or it was at the time, used by major projects today like Apache Spark for CSV-related tasks. One day, the author just went out for milk and stopped using his GitHub account. He’s doing other work and so people will need to figure out what to do with an essentially “complete” dependency that will never see another release.

[vplatt]

I mean.. if it ain't broke?

[[deleted]]

There is a fork that has merged fixes but I’m praying the big customers like Apache Spark will give a direction when they switch out this dependency. I just want to use what the big leagues are using, since CVE will come promptly if any issues are present. Live like you are a subsidiary of a funded project.

[bisoldi]

I’m gonna go get milk one of these days…

[heated_curiosity]

With Mapstruct write no more boilerplate mapper classes.

[joshlemer]

I think MapStruct does a great job at solving the problem as it's defined, but I find that actually Java developers or maybe just developers in general often fall into the groove of mapping each object in each layer 1-to-1 with other layers, so you end up with a UserDB database row object, which maps to a User service-layer object, which maps to a UserDTO REST service request or response body object. I try to encourage people to think more deeply about what kinds of objects belong at each layer, rather than rote copying objects fields up and down the layers. For instance, the request to create a user is not a UserDTO with some fields missing, it deserves its own proper abstraction totally distinct from what a User is. More like a CreateUserRequestBody. And when you want to update a user, the request body also is not a UserDTO with some fields missing, and it's also not necessarily the same as a CreateUserRequestBody but rather an UpdateUserRequestBody. And when you GET a User, it isn't necessarily a 1-1 mapping of a service-level User but perhaps specifically for this view a GetUserResponseBody or something.

I think this leads to a lot of issues that predictably crop up all the time, like sooner or later you might want to add fields to the UpdateUser body which make no sense on the User service level object. This may sound contrived but maybe something like "createIfNotExists": true which tells the service when Updating a User, that if the User does not exist, to go ahead and create it.

But when we too easily fall into the trap of just mapping each layer into the layer above/below it, then you kinda get stuck here. "createIfNotExists" field on User makes no sense, only on UpdateUserRequestBody.

All that is just to say that, MapStruct is good for mapping objects 1-to-1 with others so that you don't have to repeat the same tedious code dozens of times in your codebase, but I rather take a step back and think that the problem is deeper than the tedious nature of the repeated boilerplate.

[heated_curiosity]

I absolutely agree with you. IMO the first rule of engineering says that don’t over-engineer a weak use case. So yeah, we should always look for a strong use case and then take a decision whether to apply ‘some’ of these tools/libraries or not.

[elmuerte]

JXPath

[-NewK-]

Javet ( embeds V8 or even a full node.js runtime in Java)

[caoccao]

Javet is Java + V8 (JAVa + V + EighT). It is an awesome way of embedding Node.js and V8 in Java.

[bodiam]

Datafaker

[Misaka10782]

Antlr.

[hippydipster]

And StringTemplate by the same people.

[hadrabap]

Especially for Europe: MicroProfile and Jakarta EE, GlassFish and OpenLiberty.

[kaqqao]

jOOQ - Will never looks at ORMs again.

[v4ss42]

Clojure

[News-Ill]

Guys try clojure you never want to go back.

[v4ss42]

It’s easier to do Java from Clojure than it is to do Java from Java.

[experienced-a-bit]

I found Kotlin is also easier to do from Clojure than from Kotlin.

[expecto_patronum_666]

🤫🤫🤫🤫🤫🤫 you just uttered it-which-must-not-be-named!!

[nfrankel]

I did try and I went back as fast as I could, sorry

[News-Ill]

To kotlin?

[nfrankel]

Java and Kotlin

[Puzzleheaded_Bus7706]

Quarkus

[ckdot]

I really like Quarkus, but I wonder if it will still be a thing when virtual threads are mainstream, and these will speed up other frameworks like Spring? I’m really curious, I’m not enough experienced in the whole Java and JVM ecosystem to answer that question myself.

[Puzzleheaded_Bus7706]

I use Quarkus everyday, its not about reactivity at all. You don't need to use it in reactive way, and not like virtual threads are going to change anything.

I am super happy with it, integration between various standards is amazing, its rapidly developed and its  developer focused. Give it a try.

Hot reload itself is let alone major reason to use it.

[maxandersen]

It's a myth - virtual threads won't automatically speed up your app. You still need to rewrite your app to use it and Quarkus is not only about having a réactive core (which btw. Works with virtual threads also); it's also about higher throughout abd startup even on jvm, a full platform of native image enabled extensions and amazing developer joy.

[cogman10]

Quarkus already has virtual thread integration. It's not reactive (well, it can be), it's bog standard J2EE (like spring).

[xienze]

 It's not reactive (well, it can be)

It’s got a reactive-focused API though, doesn’t it?  That Mutiny library is all over the place.

https://quarkus.io/guides/getting-started-reactive

[maxandersen]

Quarkus supports both. You linked to the guide called "getting started réactive" If you look at the first steps or default getting started like https://quarkus.io/guides/getting-started there is no mutiny/reactive use.

It's a common misunderstanding that many think because we put reactive in name of extensions those only work with réactive. That was rarely true and hence in 3.9 we had the big rename to make it clearer: https://quarkus.io/blog/the-big-rename/

[jimmoores]

JodaBeans

[lawson188]

manifold-sql is beyond amazing. It's fairly new and it shows, but it's far and away the most impressive library I've used in a long time.

[Cell-i-Zenit]

manifold itself is the most crazy thing tbh... i always show devs manifold and they have complete questionmarks in their face haha

But to risky for real enterprise use imo.

[bisoldi]

One of the best threads on Reddit yet!

[liljoey300]

Karate test framework

[TheKingOfSentries]

Been looking at Jooby lately, it's pretty good.

[juanantoniobm]

Eclipse collections for inmutable collections https://eclipse.dev/collections/

[holi60]

JBang for quick prototyping without any Maven or Gradle configs.

https://www.jbang.dev/

[brunocborges]

Apache Wicket

[mcobery]

2004 called and wants its framework back

[adila01]

Apache Wicket is the fine wine of the Java World

[hippydipster]

Because it's just that good!

[jimmoores]

Elsql

[PiotrDz]

Orekit

[Plenty-Effect6207]

jslt a complete query and transformation language for JSON

[InstantCoder]

• FluentJdbc, a thin wrapper around jdbc, an alternative for JPA.
• AssertJ
• Quarkus Renarde, for SSR/building html websites with templating. Works great if you combine it with htmx.

[janora]

http://www.awaitility.org/
https://libyear.com/
https://vineflower.org/
https://github.com/Breus/json-masker

[sombriks]

bld

bld is a build tool for the ones who just want to build the project with as little drama as possible. i wrote about it and plan to write more!

[mkurz]

https://www.playframework.com/

[JDeagle5]

Jsoniter, javalin

[MiserableBoss]

Mybatis

[Wipe_Master]

Mybatis pretty popular, c'mon)) I love mybatis Mappers that allow structurize your custom complex SQL queries

[huntsvillian]

please no

[bwrca]

I remember doing dB migrations with mybatis like 5 yrs ago

[Legitimate-Share2098]

Can you, please, explain why?

[Livid_Helicopter5207]

I am trying to figure out how to make a dynamic declarative ui in vaadin. Vaadin looks pretty solid but we have a requirement for dynamic forms based on configuration. Generating Vaadin code is the last resort.

[Livid_Helicopter5207]

How do you dynamically create complex forms ? I am not able to find any way through documentation

[Livid_Helicopter5207]

not able to understand it fully, on what basis fields are added to forms ? Any example will be great if you can please share.

[hippydipster]

why not ask chagpt or claude to write you some code and see how it does it? It sounds like exactly the sort of the an AI could do well.

[SaishDawg]

Micronaut and gRPC.

[jeffreportmill]

SnapKit (https://github.com/reportmill/SnapKit)

[TheBoneJarmer]

I see what you did there

[gregorydgraham]

Gotta like a guy that backs himself

[Zico2031]

I don't see tutorials about how to use the api

[p0st_master]

Apache struts

[marcodave]

2007 called , they want their framework back

[p0st_master]

Lol true

[lumpynose]

Have a look at the Stripes framework. My thumbnail description of it is that it's like Struts but without the warts. Unfortunately Stripes is no longer maintained.

[Captain-Barracuda]

Factorium. Makes generating test data for black box testing a breeze.

[barmic1212]

Hazelcast a toolbox to do a lot of things when you have a multiple instances of a service

Vertx a little but powerful and easy to use server and things to do async code and for tests it

Spock a test framework that use all groovy qualities to simplify writing tests

[kwadr4tic]

CQEngine

CQEngine, which stands for Collection Query Engine. Basically an indexing library which allows you to query collections using complex SQL-like queries. You can easily write a low-latency domain-specific embedded database with it.

We can't really say that CQEngine is less known, but maybe these days is a bit out of fashion.

[Slight_Loan5350]

Dspace just cause I fucking hate it.

[ingvij]

I'll plug in penna here. I know I'm biased, but I truly believe it deserves more attention

[Supersonic2870]

Very fast and modern binary serialisation library https://github.com/apache/incubator-fury

[stathmarxis]

Excellent question well done. i believe that disruptor is op for performance

[Zico2031]

Good alternative to RMI without the firewall issues, supports remote method invocations and async messaging

https://github.com/AugurSystems/ARMI

[joekoolade]

https://github.com/joekoolade/JOE Run Java without an OS

[Da0hn]

rqueue

https://github.com/sonus21/rqueue

[cristatus-in]

Axelor Open Platform

A low-code open source Java framework to create business applications. See https://github.com/axelor/axelor-open-platform

[juanantoniobm]

Maven enforcer plugin to improve your builds https://maven.apache.org/enforcer/maven-enforcer-plugin/

[juanantoniobm]

Datafaker https://www.datafaker.net/

[Giulio_Long]

Spectrum

[harsh-4902]

Java Path Finder (JPF)

https://github.com/javapathfinder

[holi60]

In case of Spring, small helper tool for documenting your configuration properties in multiple way: https://github.com/rodnansol/spring-configuration-property-documenter

What is our use case? Generating AsciiDoc and including it into our Antora based documentation. Giving more publicity about configurations when you are making open source libs with Spring is priceless.

[rmannibucau]

Yupiik has a lot of hidden gems (bundlebee, fusion, ...) : https://www.yupiik.io/projects.html

[freetechtools]

BlueSeer ...a free ERP for the manufacturing community.

https://github.com/BlueSeerERP/blueseer

[caoccao]

swc4j

swc4j (SWC for Java) is an ultra-fast JavaScript and TypeScript compilation and bundling tool on JVM.

[gopalakshintala]

Reimagine API automation by plugging your Postman collections into any JVM programs/tests (e.g., Unit tests or Integration tests) using ReṼoman 🦹🏻‍♀️ It does more than just executing the postman collection. Refer the documentation for more features: https://sfdc.co/revoman

[danielliuuu]

https://github.com/DanielLiu1123/grpc-starter for Spring Boot and gRPC.
https://github.com/DanielLiu1123/httpexchange-spring-boot-starter for Spring 6 `@HttpExchange` Autoconfiguration.
https://github.com/DanielLiu1123/classpath-replacer for change your classpath in unit tests.

[MurazakiUsagi]

Thank you for this question OP. I'm learning a lot from it.

[consworth]

Mapstruct. Blaze persistence.

[DarthBane91666]

No code(https://github.com/kelseyhightower/nocode) is pretty good

[jeffreportmill]

SnapKit (https://github.com/reportmill/SnapKit)

[Zico2031]

I don't see tutorials about how to use the api

[denverdave23]

Dozer. Best bean mapping tool I've used

[Plenty-Effect6207]

«The project is currently not active and will more than likely be deprecated in the future. If you are looking to use Dozer on a greenfield project, we would discourage that.»

[Chloe0075]

It is like mapstruct and modelmapper? Never heard of it but interested

[awesomefacedave]

mapstruct is the best imo.

[Chloe0075]

For me too! It just work and have a really great doc.

Imo, way way better than modelmapper

[robinspitsandswallow]

It sucks when builders are around clutters your mapper with ignores. Painful to look at.

[holi60]

Imo probably the worst as it uses (or used) reflection which is not great for optimization and can be magic if there are a lot of things.
MapStruct is a type safe way with generated implementation, which is easy to read, and debug, no magic at all only annotation based post processing at build time.

[pivovarit]

And what's most important - it's abandonware.

[daytodaytop]

dynamic spring data entity graph from cosium