LambdaFetchingSupport is broken for cross class loader method access after JDK >= 14 #3369
Description
Describe the bug
Whilst working on #2789 I found this bug.
Java changed the way MethodHandles.privateLookupIn behaves in JDK 14 (?):
A new Lookup::hasFullPrivilegeAccess method for testing full privilege access
This effectively breaks LambdaFetchingSupport.createGetter in cross class loader situations and always silently goes into the try (... ignore) {} and falls back to the original reflection:
To Reproduce
Run the LambdaFetchingSupportTest.'different class loaders induce certain behaviours' on a JDK 14+ (triggered for me on JDK 17)
How to fix
Jackson fixed this by (if I understand correctly) creating a dummy class in the same package as the 'hidden' class that has a static reference to the MethodHandle.Lookup instance, which can then be resolved using reflection:
To fix this for GraphQL Java the GrantAccess.java would need to be edited a bit to give the "dummy" class a different name i.e, GraphQLJavaAccess, running this will create the necessary class bytes
Then the CrossLoaderAccess would be copied and the bytes would be modified with the correct class bytes that were generated.
Then the class would have to be "opened up" in LambdaFetchingSupport.getLookup (see CrossLoaderAccess.apply) after which it will work like normal again
Other
I am unsure of how many deployments this applies to, but considering that having GraphQL Java in one class loader and the target classes in another is not the craziest idea, it should probably be fixed. Especially considering the performance gains (#2985 )
It probably wasn't noticed because the tests have not been run JDK>11 because of Gradle toolchains: 091710c#diff-335d1791aad84b00e8762546a158726200525fa06a55b73d8284ff0fea4ac7deR186
#2789 would of course fix this by testing on newer releases
This was also implemented in OpenJ9: eclipse-openj9/openj9#8571
After JDK 17 some things might again be slightly different: https://bugs.openjdk.org/browse/JDK-8221255
Email chain from Jackson Blackbird to lib-core-devs: https://www.mail-archive.com/core-libs-dev@openjdk.java.net/msg83157.html