RFR: 8359707: Add classfile modification code to RedefineClassHelper [v6]

[Coleen Phillimore]

On Thu, 26 Jun 2025 07:30:13 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Made it even shorter.
>
> test/lib/RedefineClassHelper.java line 29:
> 
>> 27: import java.lang.classfile.ClassFile;
>> 28: import java.lang.classfile.ClassModel;
>> 29: import java.util.Map;
> 
> Nit: import out of order

I like the imports when they're grouped by things they support.  Map isn't being used in the final version though.

> test/lib/RedefineClassHelper.java line 92:
> 
>> 90:         byte[] buf = getBytecodes(loader, oldClassName);
>> 91:         ClassModel classModel = ClassFile.of().parse(buf);
>> 92:         return ClassFile.of().build(ClassDesc.of(newClassName), classModel::forEach);
> 
> That's cool! I have no idea how to read it to understand what it does, but it is cool it can be done in one line. :)
> 
> Seriously though, which part of that is doing the actual replace??

Java's gone overly terse, but if you look at the n-1 commit, the classModel::forEach copies everything in the class to the new class.  At least that's what Chen told me and it seems to do.  Isn't this cool?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25857#discussion_r2168886521
PR Review Comment: https://git.openjdk.org/jdk/pull/25857#discussion_r2168884543