DWR call count is not a number

For all our applications we use pretty much the defacto standards. For us DWR is also a defacto standard for doing AJAX with a JEE backend. Like many of our applications we can’t dictate what type of browser the customer should use, so we have to check all browsers. So during the last sprint we checked it on all versions of ie, no problems. We deployed and one of our main testers create a defect ticket.

In the ticket he described the application as always creating alerts with the description call count is not a number . He used ie7, you would expect this from ie6 but not from ie7. However off course other users with ie7 didn’t have this issue. After some googling this seemed related to DWR, however we couldn’t really find the cause for the problem. However we did find a workaround for the issue.

We added this small piece of code

<script type=”text/javascript”>
function errH(msg){}


This might not be the best solution, but after losing quite some time this was the preferred solution

jquery apache tomcat ajp issues , ie6 hangs

The application I work on is accessed from all over the world, we don’t have any control over what kind of browser access it. So we have to check pretty much all possible combinations. After our latest release we had trouble with some users who were running windows 2000 with internet explorer 6.

I know this is an old system, but we can’t force them to upgrade, neither can we force them to install a real browser (i.e. firefox) as they don’t have local admin accounts. I checked windows xp with ie6 and this worked without any problems. So I picked up a windows 2000 cd and installed it in a vm. I upgraded the browser to the same version as the customer but couldn’t reproduce the problem.

After some emailing and friendly help from their local IT sysadmins, I could access an identical vm on their local systems. I user our test environment to do some tests changing settings here and there. After a couple of minutes I found out that the problem had to do with the jquery library. So I tried accessing it with the actual URL, maybe there was a security constraint or something but this worked without any problem. Even stranger when I accessed the applicaiton again everything worked perfectly, normally after the login the page would freeze and you had to kill the iexplore process.

After a while I figured it out. To shrink the size of the html we were using the compression options of apache. This shrinked the actual html sometimes with 80%. However we also shrinked all javascript libraries. JQuery default ships with a minimized library. It seems that some internet explorer versions have problems with accessing this file. I imagine that ie6 can’t handle a file that is minimized file and gziped at the same time.

So any one out there experiencing the same problems, you can check if you didn’t run into the same problem as we did.

Linux vs Windows maven building

I recently received a new Dell laptop. It came with windows 7, I tried it and it didn’t look bad. But for my personal stuff I prefer Linux over Windows. The computer at the office is managed by somebody else, that off course runs windows. It’s a very good machine and the guys who manage it know what what they are doing. As soon as somebody has a virus somewhere (e.g. usb stick from a customer) they are standing next to the person within a matter of minutes. Or if somebody is consuming a lot of bandwith and effecting others, they’ll notice it. However I’m a developer and all these extra monitoring tools (network consumption isn’t on my own computer off course) consume resources from my machine.

As we build all our projects with maven, it’s pretty easy to do the build on another system. I always have a version on my laptop, so I also checked out one to my new Ubuntu 9.10 laptop. If I do a mvn clean install -DskipTests on my laptop it takes about 27 seconds. If I do this on my main workstation (that actually is a dual cpu dual core machine) it takes 4 minutes 30 seconds.

Noted that the maven version isn’t the same and that I’m running 64 bit Linux instead of Windows xp 32 bit. This still seems a big difference, but then again every time I access a file the antivirus kicks in and who knows what else.

If I had a big company I would make all my developers work on Linux machines, reducing licensing costs and gaing time 🙂

If they were .net developers, well that would make it a bit more difficult but I’ld definitely give it a go. Time is money and loosing 4 minutes for every clean build is way to much. Luckily mvn compile and some ant tasks run much faster.