MethodHandles.Lookup.defineResource?

[Peter Levart]

On 08/28/2018 08:55 AM, Peter Levart wrote:
>> MethodHandles.Lookup.defineClass() allows a class to be pushed into an
>> existing ClassLoader & Module, but I'm unaware of an equivalent for
>> resources, and that seems like a gap, regardless of use case.
>
> ClassLoader (the Java part of it at least, which is exposed as an API) 
> is a delegate of a VM. VM calls it when it needs the bytecode of a 
> particular class it wants to define lazily. The ClassLoader API is 
> such that at the end, the ClassLoader calls back into the VM to define 
> the class whose bytecode it obtained in its own way. 
> MethodHandles.Lookup.defineClass() in this respect "bypasses" this 
> searching mechanism and ClassLoader API entirely and "eagerly" defines 
> a class in the VM. ClassLoader API and its bytecode resource searching 
> logic is not involved here.
>
> What you are proposing as "defineResource()" API is therefore not a 
> parallel of defineClass(). ClassLoader API is all about "searching" 
> for resources (bytecode and other kinds) while defineClass() has 
> nothing to do with "searching" and everything to do with VM internals. 
> Your proposed defineResource() would have nothing to do with VM and 
> everything to do with searching as it would just augment the search 
> logic of existing ClassLoader instance.

...thinking further... In any way, such defineResource() method would 
have to be empty and declared in java.lang.ClassLoder. Why? Because its 
purpose would be to augment the logic of ClassLoader.findResource(s) 
method(s) and those methods are implemented by ClassLoader subclasses. 
Each ClassLoader subclass implements its own particular strategy of 
searching for resources. There's no way to "generically" inject 
additional resources in each and every ClassLoader implementation. JDK 
ClassLoader implementations could be made to "obey" the 
defineResource(), but this would not be a universal "fix" and code 
relying on defineResource() would only work in environments using JDK 
ClassLoader implementations.

Regards, Peter