JavaScript Memory Leak in IE

Yes, I knew there was JavaScript memory leak in IE. I developed JavaScript codes mainly by Firefox/Mozilla, so I won’t notice the codes were leaking memory. These days I was developing J2S application in Eclipse, and found that the J2S applications were runnig more and more slowly in the J2S Console, which embed IE Browser widget. Once I did not think that memory leaking will make such poor performance. The slowness that I couldn’t stand finally taught me the lesson and I decided to fix the leaking codes.

Searching the net, I found that lots of articles were talking about this problem. I mainly read Justin Rogers’ Understanding and Solving Internet Explorer Leak Patterns. And after finishing the articles, I monitored one J2S SWT application (SWT Tree Snippet) while tring to refresh the page. I found 5 times of refreshing will leaking the memory from about 22M to 31M! Then I knew that maybe about 100M+ of memories was leaked in developing J2S applications when I felt the slowness of J2S Console.

I added a handler to the “onunload” event to break those circular references, codes like following:

/*
* Only IE need to release the resources so that no memory is leaked
*/
if (window.attachEvent) {
window.attachEvent (“onunload”, function () {
try {
org.eclipse.swt.widgets.Display.releaseAllResources ();
} catch (e) {
}
return true;
});
}
In the static method org.eclipse.swt.widgets.Display.releaseAllResources, I set those elements’ on* handlers to null and set those Controls’ parent and children to null. Things did work much better. But it was not fixed compeletely. Once I refreshed for a couple of times, I noticed that the browser will leak some 10~100k gradually. That was to say it will take about 10~100 times of refreshing for about 1M leaking and users will only perceive the slowness after about 1000 times of refreshing. So it was considered as working better.
I tried other ways to solve this leaking but did not get the right entrance.The current Java2Script library is almost built on closures of JavaScript, which will leak memory easily and hide leadking codes deep inside the whole codes. Replacing all those codes that using closures? No. Without closures, it’s somewhat hard to implement the Java Class inheritance.

It’s as Justin Roger’s saying “not all memory leaks are easy to find”. Memory leaking is just awful enough! 😦

Inside Java2Script: Reusing

There are two advances of Java2Script technologies:

1. Reusing existed Java codes
2. Reusing existed Java tools

It’s totally about reusing. Reusing is the most important things in the programming world: source codes reusing, binary library reusing, model pattern reusing, framework reusing. Without reusing, it will mean that everyone should have to re-inhevent the wheel and then we will always stay in the stage of round wheels. Thanks to the reusing, we have great world now.

Java2Script Pacemaker is developed to give developers a toolkit of reusing existed codes and tools. And Java2Script Pacemaker is reusing other codes and tools:

1. J2S is reusing Eclipse JDT (J2S won’t exist without JDT)
2. J2S is reusing Java SDK’s java.* sources
3. J2S is reusing SWT sources and models (org.eclipse.swt.*) and Visual Editor

Reusing does not mean that the sources or tools should be reused without modifications. In above reusings, I extend some extension points of JDT to given new functions, and I modify parts of the sources java.* so that the generated JavaScript is simple, and I have to reinvent the SWT Widgets inside Browser beside reusing the Events and Layouts of SWT.

Reusing already saves me a lot of time. Without JDT, I won’t have the abilities to parse the Java sources and building the DOM tree and binding. Without DOM tree and binding, I can’t generated the JavaScript codes. Without reusing java.* sources, I will have to spend times to re-write those complicated Map, Set and List implementations. Without org.eclipse.swt.layout.*, I will dedicate most of my time in tunning the layout! Without all these reusing, J2S and the related JavaScript version of SWT won’t come out in a short time. Thanks to the reusing.

Following is the questions and answers I am thinking these days:
Q: Does the Java2Script Pacemaker focus on reusing source codes only?
A: Always reusing source codes is the first of step of reusing others. But you should have already noticed that J2S is also reusing tools including Visual Editor and the Eclipse Platform.

Q: Is Java2Script Pacemaker have the abilities to reuse existed frameworks?
A: I think we should not make too much expectation on the JavaScript codes. But we can integrate the Java2Script Pacemaker with other existed frameworks, as Java2Script technology is still developing.

Q: Will Java2Script be hot in the future?
A: I don’t know. But I know, for sure, that reusing existed codes will save people’s efforts in the progress of converting desktop applications into web applications. And reusing will always be the spirit of programming.

Enjoy using Java2Script, enjoy reusing and keep thinking in reusing.

Java2Script Pacemaker Blog is On

Java2Script Pacemaker, in the goal of reusing existed Java codes into JavaScript, was contributed to sourceforge.net under the license of Eclipse Public License 1.0, exactly, one month ago (Dec 19, 2005).

After the release of 0.1.0 experiencing version, 0.2.0 for better integration of Eclipse JDT building and 0.3.0 for Java2Script application launcher, I found that lots of other developers, both AJAX developers and Java programmers, were interested in this project.

And on these days, I post a series of “Hello J2S World” tutorials on j2s.sourceforge.net. Always, some readers may have problems while reading through these articles, or may find some errors between the words, or may have some ideas on the Java2Script technology. But for the poor support for interactions on sourceforge.net, there are no convenient ways for reader to post questions, replies or comments about the tutorials. So this blog on wordpress.com is the choice.

Here, in this blog, I would like to talk to you about technologies of Java2Script: Java, JavaScript, SWT/JFace, AJAX, HTML, CSS or others.

Wish we would hit the ideas.