<@U02AB5P2XU6> I wonder if you could possibly help...

# kobweb

[Ryan Scott]

@David Herman I wonder if you could possibly help me with something else. I'm trying to make a fullstack app, and am encountering an issue if I ever use the @Api annotation.

[Ryan Scott]

java.lang.NoSuchMethodError: 'java.lang.Object java.util.List.removeFirst()'
  	at com.varabyte.kobweb.navigation.RouteTree.register(RouteTree.kt:360)
  	at com.varabyte.kobweb.api.Apis.register(Apis.kt:57)

[Ryan Scott]

That happens if my app ever tries to access the api.

[Ryan Scott]

Or if I start up the app from a clean slate.

[David Herman]

Oh wow, I've never seen that.

[David Herman]

Maybe it's an issue with the JDK being used to build the project?

[Ryan Scott]

I feel like there may be a java version difference or something.

[Ryan Scott]

Yah. I'm using:

ryan[wagemix] (main)$ java -version
openjdk version "17.0.7" 2023-04-18 LTS
OpenJDK Runtime Environment Zulu17.42+19-CA (build 17.0.7+7-LTS)
OpenJDK 64-Bit Server VM Zulu17.42+19-CA (build 17.0.7+7-LTS, mixed mode, sharing)

[Ryan Scott]

Do you think I should downgrade to 11 or something?

[David Herman]

I've been building with 22 so it shouldn't be necessary

[Ryan Scott]

I also notice other things as I was attempting to work around this. For example, I tried to create a kobweb server plugin and add api routes. I was indeed able to add routes to the server this way. However, The class loader could not find classes that were there if I looked at the classes available within the server jar.

[David Herman]

I once ran into a similar list issue where a Kotlin extension changed behavior after a Java update.

[David Herman]

Like, I think the Java API took over the Kotlin extension but then if your JDK was too old it would crash

[David Herman]

https://docs.oracle.com/en/java/javase//21/docs/api/java.base/java/util/List.html#removeFirst()

[Ryan Scott]

Do you think I need to update to JDK 21 or something?

[David Herman]

Looks like this was introduced recently

[David Herman]

If you update to JDK 21 that should work, yes

[Ryan Scott]

Ooh.

[David Herman]

Meanwhile, crazy more people haven't been yelling about this

[Ryan Scott]

Okay. I can just upgrade. I'm only using 17 because I tend to use it for most of my projects.

[Ryan Scott]

I think mostly people don't use the full stack features.

[Ryan Scott]

You may want to list JDK 21 that as a dependency on the documentation site (if it's not already listed)

[David Herman]

Oh, no way

[David Herman]

I'm going to fix it so that it stops crashing in JDK 17 🙂

[Ryan Scott]

Thanks.

[Ryan Scott]

That would be helpful.

[Ryan Scott]

In any case, When I upgraded to JDK 21, It started working. Thanks.

[Ryan Scott]

And just FYI, the class loader still cannot find classes that it should be able to find inside of my kobweb server plugin.

[David Herman]

https://www.reddit.com/r/androiddev/comments/1gspjrs/dont_use_kotlins_removefirst_and_removelast_when/

[David Herman]

(Same problem, different domain!)

[David Herman]

https://jakewharton.com/kotlins-jdk-release-compatibility-flag/

[Ryan Scott]

Oh--The IDE provides a warning for this now.

[Ryan Scott]

(The removeFirst issue)

[David Herman]

I think the safest thing for me to do is use

kotlin.targets.withType(KotlinJvmTarget::class.java) { target ->
  target.compilations.configureEach {
    it.kotlinOptions.freeCompilerArgs += listOf(
      "-Xjdk-release=$javaVersion",
    )
  }
}

if that works. My intention 100% is to be compatible with JDK11.

[Ryan Scott]

To be honest, I'd rather just write a kobweb server plugin and then configure Ktor with all the things I want to configure it with.

[Ryan Scott]

But that may just be because I don't know all the goodness I get from kobweb.

[David Herman]

Well, the class that's calling the problematic code here is multiplatform, so I'm surprised it's not breaking on client code either. (It's the same class that registers routes for your page and handles navigation)

[David Herman]

https://github.com/varabyte/kobweb/commit/ec3dbb619f466dfcbe53da8d6de020c6245ab68f

[David Herman]

Should be fixed in 0.21.2+, thanks for reporting