JDK compatibility issues with jackson-core 2.14 and later due to Multi-Release (MR) jars

[techwhizbang]

The time that the jackson-core library switched from using its own copy of the fasterdoubleparser code to the actual library this can cause JDK incompatibilities. The problem manifests itself if you take any newer version of the jackson-core libraries 2.14 or better and you need to do any type of dependency shading. If you do - the fasterdoubleparser uses a technique of putting all the class files across different JDK's well beyond the advertised JDK8 compatibility (https://github.com/FasterXML/jackson-core?tab=readme-ov-file#jdk) via the Maven assembly plugin (https://github.com/wrandelshofer/FastDoubleParser/blob/main/fastdoubleparser/src/assembly/mrjar.xml).

When shading you end up getting all the class files for all thefasterdoubleparser supported JDK's and if you aren't using the highest JDK version possible you will run into problems like this:

java.lang.IllegalArgumentException: Unsupported class file major version 63
at shadow.org.objectweb.asm.ClassReader.(ClassReader.java:199)
at shadow.org.objectweb.asm.ClassReader.(ClassReader.java:180)
at shadow.org.objectweb.asm.ClassReader.(ClassReader.java:166)
at shadow.org.objectweb.asm.ClassReader.(ClassReader.java:287)

For example I am using JDK17 and the Gradle Shadow plugin. The ASM library aborts when it finds a class file that isn't inline with the JDK you are running.

This is easily reproducible if you use the Gradle Shadow plugin or the Maven Shade plugin and use JDK17 and include the jackson-core 2.15.2 as a dependency for example.

[pjfanning]

Please read https://openjdk.org/jeps/238 -- MR Jars are an important feature of Java.

Please raise this with Gradle and Gradle Shadow plugin. Try upgrading to latest Gradle and Gradle plugin.

I use Gradle and it works fine with jackson-core.

[techwhizbang]

I'm using Gradle 7.x and Gradle 8.x. It works fine with Gradle and in the context of a standard build.

The problem arises if you attempt to use the newer jackson-core library with the dependency on fasterdoubleparser in a shadow jar with either the Maven shade or Gradle shadow plugin.

I suppose your point is that the shadow plugins and libraries may need to be updated to work in harmony with https://openjdk.org/jeps/238.

[GedMarc]

Not quite, The classes are compiled in JDK 19 and you are building with JDK 17.
Version 63 = JDK 19

Also look at updating the ASM library dependency to support JDK 19, or 21 preferred, 9.6 I think it is

[cowtowncoder]

I think it is unfortunate there are issues wrt shading, MR jars. But I am not quite sure what could be done here to help?

Leaving issue open so anyone with problems can find it, and maybe we get some ideas for versions of tools that help, and perhaps workarounds.

[bereng]

I ran into a similar problem and I managed to workaround it by excluding the higher jdk version compiled classes from shading.

Here is the snippet for Gradle shading plugin just before the relocate commands
exclude 'META-INF/versions/17/', 'META-INF/versions/19/', 'META-INF/versions/21/'

Here is the same for the maven-shade-plugin where you add these exclusions

<exclude>META-INF/versions/17/**</exclude>
<exclude>META-INF/versions/19/**</exclude>
<exclude>META-INF/versions/21/**</exclude>

[cowtowncoder]

Thank you for sharing this @bereng ! This should be very helpful for others with Gradle + Shading use case.

One quick question: was the build with JDK 11? Guessing since you are not excluding

<exclude>META-INF/versions/11/**</exclude>

which would make sense? (but someone with Java 8 build, if any, would also need to exclude that)

[bereng]

Yes I was building with JDK11. The actual numbers in compile/shading errors and exclusion commands will vary depending on the JDK versions packed in the jar and that you are running.

This also affects any other jars and plugins where incompatible JDK combinations are hit.

[cowtowncoder]

FWTW, issue has so far been reported for Gradle-builds that use shading (as far as I know).
If anyone has seen problems with other set ups, feel free to add a note.

Similarly if the issue has been resolved with later Gradle versions, that'd be good to know: as far as we know, JDK-specific classes should work the way things are wrt Multi-Release specification.