[concurrency-interest] MethodHandles.lookup().findVarHandle alternative not throwing checked exceptions?

Nathan and Ila Reynolds nathanila at gmail.com
Tue Aug 15 10:31:44 EDT 2017


Until findVarHandle() with unchecked exceptions, how about writing a 
utility class that has a static findVarHandle(Class<?>, String, 
Class<?>) with the code you have below?  The initialization code would 
then be...

UPSTREAM = VarHandleUtilities.findVarHandle(A.class, "upstream", 
Flow.Subscription.class);

-Nathan

On 8/15/2017 8:18 AM, Dávid Karnok wrote:
> Hello,
>
> I've been implementing a lot of concurrent code with VarHandles lately 
> and there is a repeated inconvenience of using
>
> MethodHandles.lookup().findVarHandle(...)
>
> because I can't use it to initialize static fields directly but have 
> to use a static initialization block and have try-catch around them:
>
> static {
>    try {
>        UPSTREAM = MethodHandles.lookup().findVarHandle(A.class, 
> "upstream", Flow.Subscription.class);
>    } catch (Throwable ex) {
>       throw new InternalError(ex);
>    }
> }
>
> Apart from writing the above by hand all the time, there is a slight 
> annoyance that a well parameterized findVarHandle will never throw 
> thus the throw new InternalError remains uncovered by code-coverage.
>
> Factoring out the lookup part doesn't work if the target class and/or 
> field is non accessible from the point of the common routine, plus I 
> lose the nice IntelliJ feature of validating the findVarHandle 
> parameters in the IDE itself.
>
> Would it be possible to have some versions of findVarHandle and co in 
> Java 10+ that don't throw checked exceptions?
>
> (Tools such as Lombok may (eventually) help with hiding the VarHandle 
> setup via annotation, but the generated catch code would still remain 
> uncovered.)
>
> -- 
> Best regards,
> David Karnok
>
>
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-- 
-Nathan

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