Problem with class-based projections since Spring Framework 6.1.x

[sondemar]

According to the Spring Framework issue, the LocalVariableTableParameterNameDiscoverer was completely removed. As a result, the Spring Data JPA project cannot recognize the parameters of constructors for class-based projections in DTO classes that do not include parameter names in the compiled bytecode (i.e., classes compiled without the -parameters flag).

When using such DTO classes from a third-party dependency JAR, the parameter names appear as arg0, arg1, etc. The DefaultParameterNameDiscoverer now only utilizes StandardReflectionParameterNameDiscoverer, which cannot handle these parameter names. Previously, a warning would have been logged for such cases.

I have prepared an example project to demonstrate the issue.

[mp911de]

We rely entirely on Spring's infrastructure to correlate property names to constructor arg names. With the removal of LocalVariableTableParameterNameDiscoverer, there's nothing we can do here really. ReturnedClass.detectConstructorParameterNames doesn't check for parameter absence, so we could introduce some logging to indicate improper usage. I'm moving the ticket into Spring Data Commons as that is the place where projection infrastructure comes from.