7015589: (spec) BufferedWriter.close leaves stream open if close of underlying Writer fails

[Rémi Forax]

On 08/09/2011 01:43 PM, Alan Bateman wrote:
>
> A few months back there was a bug report [1] pointing out that it's 
> possible to continue writing to a BufferedWriter after invoking its 
> close method and the close fails. A similar issue arises with 
> BufferedOutputStream and other classes. At issue is whether a stream 
> (or more generally a resource) is considered closed in the event that 
> the close method fails. This isn't something that Closeable is clear 
> on. Joe tells me that this didn't come up in the Coin discussions on 
> try-with-resources either.
>
> I think it's safe to say that it would be desirable that close 
> releases the resources for failing cases as otherwise the resources 
> may never be released (esp. with try-with-resources usages). 
> Furthermore, when there are multiple resources involved, or cases like 
> the bug report where one stream wraps another, then it would be 
> desirable to keep the state of the resources in sync. To that end, the 
> changes here propose adding an advisory note to AutoCloseable to 
> advise implementers to release the underlying resources and to mark 
> the resource as closed prior to throwing the exception.
>
> For the specific buffering classes discussed at the time, these are 
> changed to follow this advise (but their javadoc isn't changed as 
> there may be other implementations or these classes extended in many 
> ways). In the case of BufferedWriter it is also fixed so that any 
> exception from flushing the underlying writer isn't supplanted by the 
> exception from close. In the case of FilterOutputStream 
> (BufferedOutputStream extends it) then it is fixed so that it doesn't 
> ignore the exception thrown when flushing the underlying stream. This 
> is clearly the right thing to do but it does mean that close can now 
> throw an IOException for a case where it didn't before. For now I 
> don't propose to include a compatibility switch but this may be 
> something that has to revisited later. There are other classes in 
> java.io that could also be cleaned up but I don't propose to do a 
> complete audit at this time.
>
> The webrev with the changes is here:
>   http://cr.openjdk.java.net/~alanb/7015589/webrev/
>
> Thanks,
> Alan.
>
> [1] 
> http://mail.openjdk.java.net/pipermail/core-libs-dev/2011-January/005732.html

Let's close() close :)
Patch looks good.

Rémi