Usage of Virtual Threads and ScopedValue

[Alan Bateman]

On 20/08/2025 06:21, Peter Firmstone wrote:
> :
>
> It uses a heavily modified Authorization implementation ...
>
> Basically ScopedValue is used to detect and limit recursion, which can 
> occur when a permission check requires other permission checks to 
> complete.   The implementation is relatively basic, but it works well, 
> eg, for more info see the link above.
>
>
ScopedValue is a good choice for authorization as the current "security 
context" or "identity" is an implicit method parameter. In the JDK, the 
Subject API was recently re-implemented to use a scoped value.

Detecting reentrancy, or limiting recursion in your example, is another 
good usage. In the JDK there are several cases, provider 
lookup/discovery in particular, where reentrancy needs to be detected. 
One of these (Charset) was recently changed to detect reentrancy based 
on whether a ScopedValue a bound or not.

Experience using ScopedValue is always useful. If you have feedback or 
experience to report then bringing it to the loom-dev list would be best.

-Alan