RFR: 8365400: enhance JFR to emit file and module metadata for class loading

[Markus Grönlund]

On Thu, 9 Oct 2025 21:04:41 GMT, Larry Cable <duke at openjdk.org> wrote:

> the existing` jdk.classDefine` and `jdk.ClassLoad` events do not include metadata regarding the location/source of the ClassFile.
> 
> The location of the class file for a class defined can be of utility in both debugging and auditing.
> 
> this addition introduces a new `jdk.ClassFileDefine` event which records the class defined and the location (path/url) of the class file that contained the implementation thereof

Can you please give an example URL for a class definition? I am concerned about whether this is high cardinality strings (for path/name.class) or a lot of reuse (for paths). We should only represent a URL once, which makes me think that the field type should be symbol instead of string.

For that, we would need a concurrent symbol table, which I have already planned in other changes.

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PR Comment: https://git.openjdk.org/jdk/pull/27738#issuecomment-3390552142