FilterOutputStream.close() throws exception from flush()

[Bernd Eckenfels]

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

Gruss
Bernd

PS: I wrote a german blogpost about the FilterOutputStream here:
http://itblog.eckenfels.net/archives/505-FOS-considered-harmfull.html

The following exception is produced by the testcode:

Exception in thread "main" java.lang.IllegalArgumentException: Self-suppression 
not permitted
        at java.lang.Throwable.addSuppressed(Throwable.java:1043)
        at java.io.FilterOutputStream.close(FilterOutputStream.java:159)
        at testfos.Main.main(Main.java:6)
Caused by: java.io.IOException: remebered IO Exception
        at testfos.FailingOS.<init>(FailingOS.java:10)
        at testfos.Main.main(Main.java:5)

package testfos;

public class Main {
    public static void main(String[] args) throws java.io.IOException {
        java.io.BufferedOutputStream buf = new java.io.BufferedOutputStream(new 
testfos.FailingOS());
        buf.close(); // expected: IOException
    } 
}

package testfos;

public class FailingOS
    extends java.io.OutputStream
{
    private java.io.IOException ex;

    public FailingOS()
    {
        ex = new java.io.IOException("remebered IO Exception");
    }

    public void write(int b) throws java.io.IOException { }

    public void flush() throws java.io.IOException
    { throw ex; }

    public void close() throws java.io.IOException
    { throw ex; }
}