On 05/05/2014 11:31 AM, Alan Bateman wrote:
On 03/05/2014 01:04, Bernd Eckenfels wrote:
Hello,
back in 2011 there was a discussion about the new changed behavior of
FilterOutputStream (and BufferedOutputStream) in regards to not anymore
swalloging IOExceptions from flush() on this list (thats where I got
the subject from).
This was generally a very good improvement (and I am glad that
https://bugs.openjdk.java.net/browse/JDK-6335274 thereby got fixed).
However the implementation with the try-with-resource has a problem:
when flush() and close() report the same exception instance the
construction of the suppressed exception will actually fail with an
IllegalArgumentException.
This IllegalArgumentException of Throwable.addSuppressed is very
unfortunate (it would be better simply ignore it).
Anyway, this new behavior broke a Unit-Test for Apache VFS as you can
see here: https://issues.apache.org/jira/browse/VFS-521
I think this can only be fixed in Throwable by avoiding this
IllegalArgumentException or by the close() method not using
try-with-resource.
For reference, according to this changeset other locations are affected
as well:
http://hg.openjdk.java.net/jdk8/jdk8/jdk/rev/759aa847dcaf
Thanks this bug report, I've created JDK-8042377 to track it. I don't
think this has come up before, probably because flush and close are
more likely to throw new exceptions rather than equal (cached)
exceptions.
Hi Alan,
There has been a discussion about a year ago on this list:
http://mail.openjdk.java.net/pipermail/core-libs-dev/2013-April/015947.html
I don't see this issue as driver to changing Throwable to support self
suppression but we can change BufferedWriter and FilteredOuputStream
to only add the suppressed exception when they are not equal.
It's try-with-resources construct that adds suppressed exceptions to
other exceptions, OuputStreams are just throwing them. And
(Buffered)FilteredOuputStream doesn't do any exception caching - it just
propagates exceptions thrown by underlying OuputStream. If underlying
OuputStream is throwing the same instance on flush() and on close() than
we have problem. The only thing a FilteredOuputStream could do was to
actually cache the exception thrown by underlying stream's flush()
method and compare it by reference with the exception thrown by
underlying stream's close() method and clone it if it happens to be the
same instance before throwing it. But that's probably not a very clean
approach and it would only be effective for FilteredOuputStreams and
subclasses.
I think it would be better to just change the Throwable.addSuppressed()
method to treat self-suppression as a no-op. Or change javac to generate
code that only calls target.addSuppressed(t) when t != target ...
Regards, Peter
-Alan.
