[PATCH] 4851444: Exposing sun.reflect.Reflection#getCallerClass as a public API in Java 8

[Peter Levart]

On 09/20/2013 01:19 PM, Jochen Theodorou wrote:
> that is I think a usecase for some... as I said, getCallerClass(int) 
> is not really ideal for us either. More ideal in this style would be 
> for us
>
>>  public static <T> T findCaller(Predicate<StackFrameInfo> predicate,
>>                                 Function<StackFrameInfo,T> function)
>
> with the predicate indicating when to stop.. 

As I understand the Thread.firstCaller() does exactly that. 
"findFirstCallerMatchingPredicate". Choosen name abbreviation is maybe 
not making the semantic immediately obvious.

> though the usage of this is not that nice:
>
>> Class getCallerClass(final int nonSkippedFramesDepth) {
>>    return findCaller(new Predicate<StackFrameInfo>() {
>>         int depth = 0;
>>         boolean test(StackFrameInfo info) {
>>                     if (haveToSkip(info.getDeclaringClass())) return 
>> false;
>>                     depth++;
>>                     if (depth>=nonSkippedFramesDepth) return 
>> info.getDeclaringClass();
>>                 }
>>           }, StackFrameInfo::getDeclaringClass());
>> }
>

But the API is making it possible without walking entire stack or making 
N partial walks with lengths 1..N, which is O(N^2)...

More compact, using lambda:

Class getCallerClass(int nonSkippedFramesDepth) {
    int[] depth = new int[1];
    return Thread.fistCaller(
       info -> !haveToSkip(info.getDeclaringClass()) && (++depth[0] > 
nonSkippedFramesDepth),
       StackFrameInfo::getDeclaringClass
    );
}

> Have you guys though about exposing the StackStream instead? Then you 
> could use all the existing JDK method for streams on that, which gives 
> you a much more flexible API. I could then for example change the 
> Stream of StackFrameInfo into one of Class.

I don't think StackStream is-a Stream<StackFrameInfo> ...

Peter

>
> bye Jochen