Add modulepath support for Java >= 9

[remal]

Ktor application can't be compiled with JDK >=9. I'm getting a lot of such errors:

error: module kotlinx.io.jvm reads package io.ktor.http from both ktor.server.core and ktor.http.jvm
error: module kotlinx.io.jvm reads package io.ktor.http.content from both ktor.server.core and ktor.http.jvm
error: module kotlinx.io.jvm reads package io.ktor.util from both ktor.server.core and ktor.utils.jvm
error: module kotlinx.coroutines.jdk8 reads package io.ktor.http from both ktor.server.core and ktor.http.jvm
error: module kotlinx.coroutines.jdk8 reads package io.ktor.http.content from both ktor.server.core and ktor.http.jvm
error: module kotlinx.coroutines.jdk8 reads package io.ktor.util from both ktor.server.core and ktor.utils.jvm
error: module kotlinx.coroutines.core reads package io.ktor.http from both ktor.server.core and ktor.http.jvm
error: module kotlinx.coroutines.core reads package io.ktor.http.content from both ktor.server.core and ktor.http.jvm
error: module kotlinx.coroutines.core reads package io.ktor.util from both ktor.server.core and ktor.utils.jvm
...................

Support of Java 8 ends quite soon, so it makes sense to start supporting Jigsaw. IMHO, this should be prioritized, as it will require breaking backward compatibility. The less Ktor is popular, the easier would be to break backward compatibility. And Ktor will definitely become more popular over time.

Ktor Version

1.2.0

JVM Version, Operating System and Relevant Context

JDK 12

[remal]

I'd like to add that Java 8 support ends in 3 years. No serious project can rely on such short period of platform support.

[robstoll]

I have the same problem here, I see multiple solutions to circumvent the split package problematic:

• cleanup the packages, prefix all according to domain, e.g. ktor.server.core rewrites package io.ktor.http to io.ktor.server.http and ktor.http.jvm can keep io.ktor.http
• create fat-jars which contain all sources so that it is treated as one module

In the long run I would suggest to go with the first approach, IMO the second is more a workaround. Of course, this implies a breaking change and is therefore only valid for 2.x (migrating to it/deprecate old packages could already be done in 1.x though)

[alkoclick]

This issue also affects any other kotlin web framework that uses ktor as a dependency, such as kweb. I think that @robstoll's suggestions both make sense - a fat jar is an immediate fix that will unlock Java 9+ users, while solving the split packages is the eventual mid/long term solution

[chris-hatton]

This is surely a critical issue to solve; with Ktor being such a new and forward looking framework and others trying to create similarly forward looking libraries and Applications that reference it - we can't afford to be stuck in Java 8 land any more.

Ktor is already well modularised by artifact; that just needs to be formalised for Java, with a Java Module per Ktor module. There will have to be a brief 'breaking' pain of renaming the packages-per-module - but considering the number of dependents on Ktor is set to grow fast - the sooner the better!

[Dico200]

Perhaps it would be better for the compiler to provide a workaround by moving some definitions between packages and delegating from the original? There wouldn't be any breaking change. I don't know what these package restrictions are about though...

[rajohns08]

Does Ktor still not support anything above Java 8?

[marshallpierce]

FWIW I've been running ktor on java 11 for years now (via the classpath, not the module path), and ./gradlew jvmTest passes locally for me on 11.0.7, albeit with one test occasionally failing from a timeout. It won't run on 14 because the version of gradle is too old.

[rajohns08]

Is there an official Ktor page somewhere that mentions supported java versions?

[e5l]

We're continuously testing against JDK 11 for a year and everything works well!

I think that issue is obsolete. Closed.

[robstoll]

@e5l and do you use module-path or classpath?

[alkoclick]

I think the underlying problem remains unaddressed, unless I missed something? Does Ktor run in the modulepath? If not we'll have to immediately open up a new issue and closing this one feels a bit off

[e5l]

Sure. I will setup the CI test with that check

[Patresss]

FWIW I've been running ktor on java 11 for years now (via the classpath, not the module path),

@marshallpierce Could you provide an example? Did you use the build.gradle file for this?

[marshallpierce]

@Patresss I maintain a demo of some patterns I've used successfully with ktor at https://bitbucket.org/marshallpierce/ktor-demo/src/master/. It's pretty similar to a number of services that I work with that are serving real traffic.

[Patresss]

Thanks! I thought that you have added the Ktor library via the classpath and the rest of all via the module path. That's why I was curious about how you could do it.

[remal]

Guys, isn't it a good time for 2.* version with renamed packages? I understand that nobody wants to implement a change that breaks backward compatibility, but sooner or later it should be fixed anyway. And the sooner it's fixed, the less people and projects are affected.

Despite a lot of hacks with compiler arguments can be found on the Internet, they are still hacks and are very inconvenient to use.

[Patresss]

@remal I am also waiting for this fix, but I am not sure that it is possible at a library level. I found the same issue in project Kotest. Please look at this comment: https://github.com/kotest/kotest/issues/1495#issuecomment-640303895

with Kotlin MPP you can't just rename them because you implement platform specific code by use of actual / expect keywords for functions in the same package.

[remal]

@Patresss looks like a design issue for me. In this case I think it should be fixed ASAP to minimize affected projects count.

[robstoll]

IMO should be possible also in MPP project, you usually don't consume two platforms of the same artifact. I.e no split package problematic there. I did not run into issues so far with Atrium (https://github.com/robstoll/atrium) though I have never checked it with jlink. so far I relied on the checks of the Kotlin compiler and unfortunately it is buggy (so :crossed_fingers:).

[oleg-larshin]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.

[WIPShriharsh]

Hello team, I am working on a project where Ktor is implemented already. Now, we are trying to move to modular approach with Java11. I am getting following error while building the project

error: the unnamed module reads package io.ktor.network.sockets from both ktor.network.jvm and ktor.client.core.jvm
error: the unnamed module reads package io.ktor.network.tls.certificates from both ktor.network.tls.certificates.jvm and ktor.network.tls.jvm
error: the unnamed module reads package io.ktor.util from both ktor.server.core.jvm and ktor.utils.jvm
error: the unnamed module reads package io.ktor.util.date from both ktor.server.core.jvm and ktor.utils.jvm
error: the unnamed module reads package io.ktor.http from both ktor.server.core.jvm and ktor.http.jvm
error: the unnamed module reads package io.ktor.http.content from both ktor.server.core.jvm and ktor.http.jvm
error: module ktor.server.core.jvm reads package io.ktor.network.sockets from both ktor.network.jvm and ktor.client.core.jvm
error: module ktor.server.core.jvm reads package io.ktor.network.tls.certificates from both ktor.network.tls.certificates.jvm and ktor.network.tls.jvm
+120 more lines

Since, I have been studying Jigsaw implementation for long now and have faced this issue in my projects as well, I can tell u few things.

I believe ktor is not build to support java modules. That is why gradle is creating unnamed modules while building. That is why, we are getting an "unnamed module" Now, starting from java9, we should "not "have 2 packages of same name in 2 modules. Comes the second part of error: ktor.network.jvm and ktor.client.core.jvm both have a package io.ktor.network.sockets. You need to rename at least one package.

Please fix this ASAP. Java modularity approach is being implemented in lot of places now.

[david-gang]

Hello team, I am working on a project where Ktor is implemented already. Now, we are trying to move to modular approach with Java11. I am getting following error while building the project

error: the unnamed module reads package io.ktor.network.sockets from both ktor.network.jvm and ktor.client.core.jvm
error: the unnamed module reads package io.ktor.network.tls.certificates from both ktor.network.tls.certificates.jvm and ktor.network.tls.jvm
error: the unnamed module reads package io.ktor.util from both ktor.server.core.jvm and ktor.utils.jvm
error: the unnamed module reads package io.ktor.util.date from both ktor.server.core.jvm and ktor.utils.jvm
error: the unnamed module reads package io.ktor.http from both ktor.server.core.jvm and ktor.http.jvm
error: the unnamed module reads package io.ktor.http.content from both ktor.server.core.jvm and ktor.http.jvm
error: module ktor.server.core.jvm reads package io.ktor.network.sockets from both ktor.network.jvm and ktor.client.core.jvm
error: module ktor.server.core.jvm reads package io.ktor.network.tls.certificates from both ktor.network.tls.certificates.jvm and ktor.network.tls.jvm
+120 more lines

Since, I have been studying Jigsaw implementation for long now and have faced this issue in my projects as well, I can tell u few things.

I believe ktor is not build to support java modules. That is why gradle is creating unnamed modules while building. That is why, we are getting an "unnamed module" Now, starting from java9, we should "not "have 2 packages of same name in 2 modules. Comes the second part of error: ktor.network.jvm and ktor.client.core.jvm both have a package io.ktor.network.sockets. You need to rename at least one package.

Please fix this ASAP. Java modularity approach is being implemented in lot of places now.

hi @WIPShriharsh i am akso waiting for this issue, the main activity of ktor issues moved to youtrack. you an add the info there https://youtrack.jetbrains.com/issue/KTOR-619

[vidicunt]

I'm waiting for this as well. It's been so long, I really need ktor to support module support.

[e5l]

Fixed with 2.0.0