JDK 12 support

[dje1990]

Will JDK 12 be supported by the docker-gradle image? Thanks

[keeganwitt]

It's my plan to support it as soon as an image with the Linux version (Alpine/Debian) I publish for is available from my base image (openjdk). Currently the only Java 12 images available for me to build on top of are Oracle Linux and Windows.

[dje1990]

Ok thanks @keeganwitt I will check back again in a few days. Thanks.

[keeganwitt]

I'm not sure if it will be done quickly. I know the Docker guys need to have Alpine/Debian package maintainers create a new package so they can use it in their Docker image as well. I'm not sure yet how far those maintainers are with that.

[davidkarlsen]

#92 could be a start for one flavour at least

[vvanholl]

@davidkarlsen This is not as simpler as it looks

You have differences between openjdk:11-jdk and openjdk:12-jdk
First : wget and unzip are absent, you need install them
Then : LANG environment variable is not set

[re-thc]

Maybe better to use AdoptOpenJDK images? 12 is already there.

[keeganwitt]

There's a discussion on this in the openjdk image repo: docker-library/openjdk#302. Tianon asked that folks who think they need an official OpenJDK image based on Debian in addition to Oracle Linux respond with thumbs up to this comment. I think there are likely images folks have made with the Debian based Gradle image as a base image that would take significant migration to move to Oracle Linux. So I think it's a +1 for users of this image.

For this image, we could add Oracle Linux in addition to Debian and Alpine based images, but not as a replacement for either.

The AdoptOpenJDK images, while closer than Oracle Linux, aren't a perfect replacement either since they're based on Ubuntu rather than Debian. But their Alpine images might be a potential replacement for the official OpenJDK Alpine images.

Another option would be for me to install both OpenJDK tarball and Gradle into a vanilla Debian image. I think either this or the AdoptOpenJDK option are gonna be the way to go. I don't know when we'll get an OpenJDK 12+ image we can use.

[keeganwitt]

My discussion with folks at Docker suggested AdoptOpenJDK is a better approach since that team tests against Ubuntu, and thus will be closer to upstream than a manually installed tarball by us. I like that it's less for me to maintain, though it does change the base from Debian to Ubuntu. For the time being, that's the direction I'll proceed with.

[keeganwitt]

Actually, we have to wait until AdoptOpenJDK is available as an official base image (docker-library/official-images#5710) before this can go live.