[9] RFR (M): 8050052: Small cleanups in java.lang.invoke code (original) (raw)
Peter Levart peter.levart at gmail.com
Wed Jul 16 18:20:40 UTC 2014
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On 07/16/2014 05:14 PM, Peter Levart wrote:
On 07/15/2014 09:51 PM, John Rose wrote:
On Jul 11, 2014, at 10:56 AM, Remi Forax <forax at univ-mlv.fr> wrote:
On 07/11/2014 06:18 PM, Vladimir Ivanov wrote: http://cr.openjdk.java.net/~vlivanov/8050052/webrev.00 https://bugs.openjdk.java.net/browse/JDK-8050052 I've found myself writing the very same code as MethodHandleStatics.uncaughException several times and I wonder if it should not be an instance method of Throwable. Something like:
public E rethrow(Function<? super Throwable, ?_ _extends E> uncaughtHandler) { if (this instanceof RuntimeException) { throw (RuntimeException)this; } if (this instanceof Error) { throw (Error)this; } return uncaughtHandler.apply(this); } in that case, throw uncaughtException(ex) can be replaced by throw ex.rethrow(::newInternalError); That's not a bad idea, but (odd for me to say this) it is too easy to use. Occasionally there are reasons for locally subverting static checking of exceptions, usually because we are writing a framework (like jli) that is polymorphic across exception types. The checking is suppressed in one place so it can be reasserted elsewhere, usually with some concerted wrapping and unwrapped (aka exception tunnelling). An API which assists in doing this would be helpful, but it should be highly specific. In effect it should say "I am temporarily suppressing all checked exceptions except the locally checked ones X, Y, Z, and tunnelling the rest through a wrapper W." try { ... } catch (X | Y | Z e) { throw e; } catch (Throwable t) { throw new W(t); }
Ops, it should be:
try { ... } catch (X | Y | Z | RuntimeException | Error e) { throw e; } catch (Throwable t) { throw new W(t); }
... and it's not so concise any more.
And it's easy to make a mistake ;-). But Remi is right when he says that an API does not have to be concerned about managing locally checked X, Y, Z since they can be handled by normal catch block(s) before the last catch (Throwable).
About the name of such Throwable instance method (using Stream terminology):
mapIfChecked(Function); // ElseThrow is implicit
An alternative could be:
public Throwable throwIfUnchecked() { if (this instanceof RuntimeException) throw (RuntimeException) this; if (this instanceof Error) throw (Error) this; return this; }
Then use it like:
try {
...
} catch (Throwable t) {
throw new WrapperException(t.throwIfUnchecked());
}Regards, Peter
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