Minimal changes make IDEA 2023.2 work out-of-box

[shifujun]

Correct maven-compiler-plugin JDK version for IDEA import Compiler bytecode version.

Remove JvstTestRoot's constructor, otherwise IDEA cannot show Run icon aside testMethod. Another way is adding suite() static method to those classes.

Now we can clone and open project with IDEA 2023.2. Debug single test case with IDEA is very useful.

BTW, some test case failed in IDEA due to some file path problem.

[wuwen5]

This is a very significant change，Many JDK8 projects may not be able to upgrade dependencies.
I think this will reduce compatibility, it seems unnecessary.

[chibash]

OK... I understand that moving to JDK 11 is too early. Shall we move this back to 1.8?

[shifujun]

I thought we already needed JDK 11.

javassist/.github/workflows/maven.yml

Line 19 in 8b1296e

java-version: [ 11.0.3, 11 ]

I cannot compile master branch under JDK8. Cannot find com.sun.jdi.

[wuwen5]

I thought we already needed JDK 11.

javassist/.github/workflows/maven.yml

Line 19 in 8b1296e

java-version: [ 11.0.3, 11 ]

I cannot compile master branch under JDK8. Cannot find com.sun.jdi.

You should at least use JDK-11 for compilation, but the recommended compilation target version is 1.8.

[wuwen5]

OK... I understand that moving to JDK 11 is too early. Shall we move this back to 1.8?

Sure, I agree. I suggest back to 1.8.

For example, this.
https://github.com/mybatis/mybatis-3/actions/runs/7239276219/job/19720962511?pr=3043#step:11:23

At least currently, there are many basic libraries that are compatible with 1.8.

[shifujun]

I need some missing knowledge here.

Say if we have a Scratch.java, which refs JDI class.

class Scratch {
    public static void main(String[] args) {
        System.out.println(com.sun.jdi.Bootstrap.class.getName());
    }
}

We can compile it with javac -target 11 Scratch.java, test with javap -c -verbose Scratch.class | grep "major version" | cut -d " " -f5.

But I can't comiple it with javac -J-Duser.language=en -target 8 Scratch.java,
it outputs:
warning: target release 8 conflicts with default source release 11
and NO Scratch.class output.

But I tested output of maven before this PR: javap -c -verbose ./target/classes/javassist/util/HotSwapper.class | grep "major version" | cut -d " " -f5. It is 52. I don't understand how did maven compile it ?

[shifujun]

I figured it out. Please review #473

[Subrhamanya]

We are having issues upgrading this dependency. There was no documentation/any release notes telling java 8 support is stopped. We really can't upgrade to java 11 suddenly.