“java -fullversion” triggers ProgressEvent.STANDARD_ERROR_DATA in AIR

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I’m building an AIR app and am using Java to offload some heavy duty work to keep Flash responsive. I want to make sure the end user has a version of Java installed the is compatible with the Jar I ship with my AIR app. To do so I use the following (pseudo) code below:

  1. var args:Vector.<String> = new Vector.<String>();
  2. args.push("-fullversion");
  4. var info:NativeProcessStartupInfo = new NativeProcessStartupInfo();
  5. info.executable = javaLocation;
  6. info.arguments = args;
  8. javaProcess = new NativeProcess();
  9. javaProcess.addEventListener(ProgressEvent.STANDARD_OUTPUT_DATA, versionOutputHandler);
  10. // Fun fact: -fullversion output is considered error data! :s
  11. javaProcess.addEventListener(ProgressEvent.STANDARD_ERROR_DATA, versionOutputHandler);
  12. javaProcess.addEventListener(NativeProcessExitEvent.EXIT, versionExitHandler);
  13. javaProcess.addEventListener(IOErrorEvent.STANDARD_OUTPUT_IO_ERROR, versionErrorHandler);
  14. javaProcess.addEventListener(IOErrorEvent.STANDARD_ERROR_IO_ERROR, versionErrorHandler);
  15. javaProcess.start(info);

To my surprise the result of the call to “java -fullversion” is send to the standard error stream and thus triggering the ProgressEvent.STANDARD_ERROR_DATA to be fired.

Flex + Java = Frankenstein?

Lately I’ve been working on a small upload tool in Flex/AIR.
To verify that an upload has succeeded, I created a hash (md5) of the entire file and sent that to the backend for verification. The AS3CoreLib contains a nice MD5 class, MD5Stream, but it’s much too slow for creating a checksum of files.

Actually, it’s so slow that when I was uploading a 5+ MB file the application would slow down so much that the upload speed dropped to a third of the speed without feeding the MD5Stream data during uploading.
Luckily, with AIR 2.0 NativeProcess has been introduced, it made it much easier to “outsource” complicated calculation to a process that can deal with that much better, i.e. Java.

The nice thing about Java is that it’s cross-platform just as AIR, and these days many people will have the JRE installed.  So first of all, I wrote a small Java class that would print out an MD5 hash of a file based on the path that I passed. I jarred the class and added it to my AIR project.
The second step was to call my Java class instead of the AS3 MD5Stream class. This is surprisingly easy. The NativeProcess documentation comes with a pretty clear example and Piotr Walczyszyn has created a small framework, Flerry, to let Flex talk to Java and vice versa.

Looking at how Flerry is built will give you some more insight on how to deal with NativeProcess.
For my application, I only use the BaseStartupInfoProvider class from Flerry to find where Java is installed on the user’s machine. After that I set up all event listeners as per the NativeProcess documentation and call NativeProcess.start() with a NativeProcessStartupInfo as passed in parameter.
Now my uploads are fast again and I can generate a checksum in a fraction of the time I could before.

There are unfortunately some downsides to this approach. You have to deploy your AIR application as native installer to be able to use the NativeProcess class. So instead of having one AIR file, you’ll end up with four native installers (.exe, .dmg, .deb, .rpm). On the plus side, you can create the native installers from an AIR file without needing to resign the application.
Another downside is that now I’m relying on two runtimes being installed on the end user’s machine, AIR and Java.
My final thought is that now that I am outsourcing some calculations to Java, why not built the whole thing in Java? Then again, building a decent UI can take ages using Java. To me, my application feels like I’m creating a bit of a Frankenstein.

All in all I’m glad I now have a fast way to generate a checksum and my uploads aren’t slowed down by it any more.


We broke Capuchin

While testing our Capuchin application we ran into some trouble with the DataRequest class. It turned out that after an X amount of calls and Y amount of data sent by the DataRequest class it would just fall over.

We were doing a DataRequest every 5 seconds to update the Flash UI and after around 80 to 100 calls it would just freeze. Now I don’t say this is the right approach for a situation like this, however, I don’t think Capuchin should just fail and do nothing either.

We solved the issue by switching to an event driven model and that seems to work very well at the moment.