<Swing Dev> Remove System.out.println from ImageIcon.loadImage
Volodin, Vladislav
vladislav.volodin at sap.com
Wed Feb 5 23:04:48 UTC 2020
Hi Christoph,
there are two issues that I was planning to resolve:
* the presence of System.out.println
* the absence of the thread interruption
Do you know if a single bug report can contain them both? If yes, I think we need a new bug report and change a status of your as „duplicate“. Is it fair?
I will ping you tomorrow
Thank you,
Vlad
Sent from myFone
On 5. Feb 2020, at 23:50, Langer, Christoph <christoph.langer at sap.com> wrote:
Hi Vlad,
I can help you generate a webrev and upload it to cr.o.j.n. Please ping me tomorrow.
Another question to all: Shall I reopen https://bugs.openjdk.java.net/browse/JDK-6421373 for this?
Thanks
Christoph
-----Original Message-----
From: swing-dev <swing-dev-bounces at openjdk.java.net> On Behalf Of
Volodin, Vladislav
Sent: Mittwoch, 5. Februar 2020 16:59
To: Jason Mehrens <jason_mehrens at hotmail.com>
Cc: swing-dev at openjdk.java.net
Subject: [CAUTION] Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
Hi Jason,
thank you for your advice. I have changed my code, now it simulates the
behavior of the interrupted thread. Can you please check my patch?
I don't have the "bug" ticket, so in my test case "@bug JDK-123456" should
be adjusted.
I will appreciate if you and somebody else can review my patch and submit it
to JDK.
Thanks,
Vlad
-----Original Message-----
From: Jason Mehrens <jason_mehrens at hotmail.com>
Sent: Mittwoch, 29. Januar 2020 17:55
To: Volodin, Vladislav <vladislav.volodin at sap.com>
Cc: swing-dev at openjdk.java.net
Subject: Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
1. Agreed.
2. I was just pulling from the jdk8 source (because I'm lazy) to express the
idea. Feel free to adjust.
3. Reasserting in the finally ensure we are not forcefully setting the
interrupted status on the current thread and calling 'statusID' and
'removeImage'. It also ensures that the interrupt is set even if an
unexpected exception is thrown. Reasserting at the end of 'e1' and never in
'e2' should work too.
The main issue that I'm trying to convey to you is that your test is incomplete
in that it does check that the interrupt was swallowed. Swallowing interrupts
is bad practice. Reasserting in e2 only means that we swallow interrupts
from e1.
Change your test to this and retest:
===
public static void main(String[] args) throws Exception {
Toolkit ignoreToolkit = Toolkit.getDefaultToolkit();
Thread.currentThread().interrupt();
ImageIcon iconInterrupt = new ImageIcon(EMPTY_GIF);
if (iconInterrupt.getImageLoadStatus() != MediaTracker.COMPLETE) {
throw new RuntimeException("Couldn't load GIF from bytes after
interruption");
}
if (!Thread.currentThread().isInterrupted()) {
throw new RuntimeException("Interrupt was swallowed");
}
}
}
===
________________________________________
From: Volodin, Vladislav <vladislav.volodin at sap.com>
Sent: Wednesday, January 29, 2020 9:52 AM
To: Jason Mehrens
Cc: swing-dev at openjdk.java.net
Subject: RE: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
Hi Jason,
I have few questions:
1. The second assignment is probably redundant:
} catch (InterruptedException e1) {
wasInterrupted = true; // line #2, see comment below
try {
mTracker.waitForID(id, 0);
} catch (InterruptedException e2) {
loadStatus = MediaTracker.ABORTED;
wasInterrupted = true; // <-- this is redundant, because of the line #2
}
} finally {
2. I think the first call of "addImage" is not necessary:
boolean wasInterrupted = false;
mTracker.addImage(image, id); // maybe I should remove this, because of
another comment down below.
try {
loadStatus = 0;
mTracker.addImage(image, id); // because of that
May I also ask you a question?
What is the purpose of interrupting the current thread in the finally block,
instead of doing it in the second catch block (where e2 is created)? I assume
that since we were able to handle the exception properly, and plus the
entire block is in the synchronization area, in theory we have only one
importer at the time.
Kind regards,
Vlad
-----Original Message-----
From: Jason Mehrens <jason_mehrens at hotmail.com>
Sent: Mittwoch, 29. Januar 2020 16:35
To: Volodin, Vladislav <vladislav.volodin at sap.com>
Cc: swing-dev at openjdk.java.net
Subject: Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
Bug in that last version:
Thread.currentThread().isInterrupted(); ->
Thread.currentThread().interrupt();
===
protected void loadImage(Image image) {
MediaTracker mTracker = getTracker();
synchronized (mTracker) {
int id = getNextID();
boolean wasInterrupted = false;
mTracker.addImage(image, id);
try {
loadStatus = 0;
mTracker.addImage(image, id);
mTracker.waitForID(id, 0);
} catch (InterruptedException e1) {
wasInterrupted = true;
try {
mTracker.waitForID(id, 0);
} catch (InterruptedException e2) {
loadStatus = MediaTracker.ABORTED;
wasInterrupted = true;
}
} finally {
if (loadStatus == 0) {
loadStatus = mTracker.statusID(id, false);
}
mTracker.removeImage(image, id);
if (wasInterrupted) {
Thread.currentThread().interrupt();
}
}
}
}
===
________________________________________
From: swing-dev <swing-dev-bounces at openjdk.java.net> on behalf of
Jason Mehrens <jason_mehrens at hotmail.com>
Sent: Wednesday, January 29, 2020 9:33 AM
To: Volodin, Vladislav
Cc: swing-dev at openjdk.java.net
Subject: Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
A shorter version is just to reassert at the end of catch e1. It is safer to just
reassert as the last statement in the finally.
===
protected void loadImage(Image image) {
MediaTracker mTracker = getTracker();
synchronized (mTracker) {
int id = getNextID();
boolean wasInterrupted = false;
mTracker.addImage(image, id);
try {
loadStatus = 0;
mTracker.addImage(image, id);
mTracker.waitForID(id, 0);
} catch (InterruptedException e1) {
wasInterrupted = true;
try {
mTracker.waitForID(id, 0);
} catch (InterruptedException e2) {
loadStatus = MediaTracker.ABORTED;
}
} finally {
if (loadStatus == 0) {
loadStatus = mTracker.statusID(id, false);
}
mTracker.removeImage(image, id);
if (wasInterrupted) {
Thread.currentThread().isInterrupted();
}
}
}
}
===
Jason
________________________________________
From: Volodin, Vladislav <vladislav.volodin at sap.com>
Sent: Tuesday, January 28, 2020 4:02 PM
To: Jason Mehrens
Cc: swing-dev at openjdk.java.net
Subject: Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
This is a valid point, because I wasn’t sure that when the thread is
interrupted, I handled the first exception, and my thought was that all other
‘wait’ calls (maybe in other threads) should get the same exception as well.
And since I handled this exceptional case, I am restoring the interrupted
status in case if I don’t know how to handle this exception the second time.
} catch (InterruptedException e1) {
try {
mTracker.waitForID(id, 0);
} catch (InterruptedException e2) {
loadStatus = MediaTracker.ABORTED;
Thread.currentThread().interrupt();
}
If I restore the interrupted status BEFORE waitForID call, then this thread will
immoderately fail. Should I restore it AFTER, e.g.
} catch (InterruptedException e1) {
try {
mTracker.waitForID(id, 0);
Thread.currentThread().interrupt(); // <— Here?
} catch (InterruptedException e2) {
loadStatus = MediaTracker.ABORTED;
Thread.currentThread().interrupt();
}
Thanks,
Vlad
Sent from myPad
On 28. Jan 2020, at 22:27, Jason Mehrens <jason_mehrens at hotmail.com>
wrote:
I see. Well I would have to do some more digging and testing to make
myself more knowledgeable on MediaTracker.
Then the only bug in your current code is that you are not reasserting
interrupted status of the current thread in the case e1 is raised and e2 is not.
It is usually best to reassert the interrupted state at the end of the method.
Jason
________________________________________
From: Volodin, Vladislav <vladislav.volodin at sap.com>
Sent: Tuesday, January 28, 2020 2:54 PM
To: Jason Mehrens
Cc: swing-dev at openjdk.java.net
Subject: Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
Hi Jason,
I am not sure about the loop, because I don’t know if we can trust results
from mTracker.statusID at the moment when an exceptional case occurs. For
example, I was experimenting with the code and found out that the
MediaTracker can spawn a thread to load the image, or might use the current
thread, and the ABORTED state is never returned (I don’t even know how to
raise this state). That is why I don’t even know if your loop will ever stop.
In my solution, I give the second chance only, and in case if the execution
was interrupted the second time, I explicitly assign the ABORTED state to
loadStatus. If the user wants to load this image once again, he can create
ImageIcon again (or even do this in a loop), or reinitialize it with a single
method (I don’t remember its name).
What do you think?
Kind regards,
Vlad
Sent from myPad
On 28. Jan 2020, at 21:34, Jason Mehrens <jason_mehrens at hotmail.com>
wrote:
Vlad,
I assume you would want to wait in a loop and reassert the interrupt at
the end.
===
protected void loadImage(Image image) {
MediaTracker mTracker = getTracker();
synchronized(mTracker) {
int id = getNextID();
mTracker.addImage(image, id);
boolean wasInterrupted = false;
try {
do {
try {
mTracker.waitForID(id, 0);
} catch (InterruptedException e) {
wasInterrupted = true;
}
loadStatus = mTracker.statusID(id, false);
} while (loadStatus == MediaTracker.LOADING);
mTracker.removeImage(image, id);
width = image.getWidth(imageObserver);
height = image.getHeight(imageObserver);
} finally {
if (wasInterrupted) {
Thread.currentThread().interrupt();
}
}
}
}
===
Jason
________________________________________
From: swing-dev <swing-dev-bounces at openjdk.java.net> on behalf of
Volodin, Vladislav <vladislav.volodin at sap.com>
Sent: Monday, January 27, 2020 11:11 AM
To: Sergey Bylokhov
Cc: swing-dev at openjdk.java.net
Subject: Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
Hello Sergey, and others,
here is the patch (made with "git diff") in the attachment. I have read that
sometimes the attachments are lost. So here is my version with few
comments regarding my code. I decided to use your approach with a small
improvement. There is an excerpt of my patch.
The idea is pretty simple:
1. I create an empty gif 1x1;
2. Initialize DefaultToolkit (I plan to interrupt the main thread, and if I do
not initialize the toolkit in advance, my test will fail at the beginning
3. Interrupt the main thread
4. Try to load the icon:
import javax.swing.*;
import java.awt.*;
public class imageIconInterrupted {
static byte[] EMPTY_GIF = new byte[]{
(byte) 0x47, (byte) 0x49, (byte) 0x46, (byte) 0x38, (byte) 0x39, (byte)
0x61, (byte) 0x01, (byte) 0x00,
(byte) 0x01, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte)
0x21, (byte) 0xF9, (byte) 0x04,
(byte) 0x01, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte)
0x2C, (byte) 0x00, (byte) 0x00,
(byte) 0x00, (byte) 0x00, (byte) 0x01, (byte) 0x00, (byte) 0x01, (byte)
0x00, (byte) 0x00, (byte) 0x02
};
public static void main(String[] args) throws Exception {
Toolkit ignoreToolkit = Toolkit.getDefaultToolkit();
Thread.currentThread().interrupt();
ImageIcon iconInterrupt = new ImageIcon(EMPTY_GIF);
if (iconInterrupt.getImageLoadStatus() != MediaTracker.COMPLETE) {
throw new RuntimeException("Couldn't load GIF from bytes after
interruption");
}
}
}
The code of loadImage I have changed as follows:
1. I clear loadStatus for "finally" part;
2. Check the interruption according to your comments;
3. Change the status to ABORTED, if the interruption happened again (this
part I cannot test, because I cannot properly interrupt the thread whenever I
want. Multithreading is quite fragile there :( )
4. update the status "interrupted" again;
5. and then - finally block.
protected void loadImage(Image image) {
...
try {
loadStatus = 0;
mTracker.addImage(image, id);
mTracker.waitForID(id, 0);
} catch (InterruptedException e1) {
try {
mTracker.waitForID(id, 0);
} catch (InterruptedException e2) {
loadStatus = MediaTracker.ABORTED;
Thread.currentThread().interrupt();
}
} finally {
if (loadStatus == 0) {
loadStatus = mTracker.statusID(id, false);
}
mTracker.removeImage(image, id);
}
P.S. if you think that my patch sounds fine, I will find a sponsor for the bug
report and the patch preparation, so you can review it later.
After the second attempt, my EMPTY_GIF was loaded successfully. The
ABORTED part it seems that I don't know if it has ever worked. My patch (in
the attachment) checks also the state ERROR for the URL that doesn't exist.
Something like:
ImageIcon iconNotExist = new ImageIcon(new
URL("http://doesnt.exist.anywhere/1.gif")); // I am not sure if I spelled this
URL grammatically correct
if (iconNotExist.getImageLoadStatus() != MediaTracker.ERRORED) {
throw new RuntimeException("Got unexpected status from non-
existing GIF");
}
Thanks to everyone.
Kind regards,
Vlad
-----Original Message-----
From: Sergey Bylokhov <Sergey.Bylokhov at oracle.com>
Sent: Dienstag, 21. Januar 2020 22:26
To: Volodin, Vladislav <vladislav.volodin at sap.com>
Cc: Jason Mehrens <jason_mehrens at hotmail.com>; swing-
dev at openjdk.java.net
Subject: Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
On 1/21/20 1:14 pm, Volodin, Vladislav wrote:
Hi all,
If I am not mistaken, this method is called from the constructor and
other methods. How long should we try loading the icon using the
unmanaged (by any thread pool, but I am not sure about this statement)
thread?
We don’t even have the flag “interrupted”. So technically this icon has to
be loaded.
I think it is necessary to save the "interrupted" state in the catch
block and try to call waitForID() again. It will be necessary to set
"interrupted" flag for the Thread after that(when the waitForID will
return without exception).
Sent from myFone
On 21. Jan 2020, at 21:55, Sergey Bylokhov
<Sergey.Bylokhov at oracle.com> wrote:
On 1/21/20 12:26 pm, Jason Mehrens wrote:
+1 for Sergey suggestion.
Or probably we need to try to load the image again because of the spec
of the method state this:
"Loads the image, returning only when the image is loaded."
________________________________________
From: Sergey Bylokhov <Sergey.Bylokhov at oracle.com>
Sent: Sunday, January 19, 2020 9:31 PM
To: Volodin, Vladislav; Jason Mehrens
Cc: swing-dev at openjdk.java.net
Subject: Re: <Swing Dev> Remove System.out.println from
ImageIcon.loadImage
I guess there are no objections, probably the best way to fix
it is to drop the System.out.println and set interrupted flag.
On 1/16/20 7:05 am, Volodin, Vladislav wrote:
If people in this distribution list agree, I can start working on a simple
fix and either remove the logging (System.out.println), or replace it with
PlatformLogger. I guess the second solution sounds better, but I don't know
what is the better way to write a test-case for it.
--
Best regards, Sergey.
--
Best regards, Sergey.
--
Best regards, Sergey.
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