Hello all
8 months ago we had a thread about 'ImageInputStream.close()' not being
idempotent, which is a violation of 'java.io.Closeable' contract. Joe
Darcy suggested that the best way to address the problem would be to
make those 'close()' method idempotent [1], but I don't know if there is
any follow-up on this topic... But we have just hit another argument in
favour of making 'ImageInputStream.close()' idempotent. Looking in
'javax.imageio.ImageIO' Javadoc, we found the following:
* For ImageIO.read(InputStream), the Javadoc said "This method does
not close the provided InputStream after the read operation has
completed; it is the responsibility of the caller to close the
stream, if desired." [2]
* But for ImageIO.read(ImageInputStream), the Javadoc said "Unlike
most other methods in this class, this method does close the
provided ImageInputStream after the read operation has completed,
unless null is returned, in which case this method does not close
the stream." [3]
So the following code work as expected:
try (InputStream in = getMyImageInputStream()) {
image = ImageIO.read(in);
}
But just replacing InputStream by ImageInputStream in the above snipset
causes unexpected IOException to be thrown with "stream closed" message,
unless (ironically) ImageIO.read(...) fails to recognize the image
format. I guess that we can not change the ImageIO specification, but
making 'ImageInputStream.close()' idempotent would both makes it conform
to the Closeable contract, and avoid the above surprising behaviour.
Is making 'ImageInputStream.close()' idempotent something that could be
done? I could contribute patch, but before doing so I would like to know
if this is something that the Java2D team consider desirable.
Thanks,
Martin Desruisseaux
[1] http://mail.openjdk.java.net/pipermail/2d-dev/2012-June/002607.html
[2]
http://download.java.net/jdk8/docs/api/javax/imageio/ImageIO.html#read%28java.io.InputStream%29
[3]
http://download.java.net/jdk8/docs/api/javax/imageio/ImageIO.html#read%28javax.imageio.stream.ImageInputStream%29
