java.net.malformedurlexception when using the JS.call method

For the love of all that is good in this world, do not attempt to display an alert from the applet. Either the applet trying to call out to javascript to display a javascript alert, or display a real java alert. Doing so is a great way to crash a browser (I’ve seen probably 2-3 different ways of hanging from trying this). Just return the error from the applet and let the calling javascript display an error.

The IE eolas thing affects visible applets but shouldn’t bother you if your applet is hidden.

Make sure your applet isn’t in an area that will be overwritten by some fancy ajax framework. Put it in the very top or bottom of your html & don’t let anything overwrite it.

That’s all I can remember in addition to what’s posted here. My overall thought is to avoid applets whenever possible but for the scenarios that you have to use them make sure you’re code has a fall back mechanism if the applet dies. Remember, your code can work beautifully but all it takes is one Microsoft patch and you’ve got endless customers crying about how your product is unusable.

I have a related question.

I am using a hidden applet to do file I/O from a javascript context. I have the policy set up to allow this, and it works fine if I open/create the file from the init() method of the applet. However, if I try to open/create the file from a public applet method that is called from a non-init script context, such as onload or onclick, I get a file permission exception, same as I would have if the policy weren’t in place. Any insight? Why should the policy cover the init() context but not a public method context?

Another option I just thought of might be to send the compressed preview thumbnails to Flash as strings/byte arrays, and have Flash render them out individually. But unless the entire uploader is built in Flash (don’t really want to do this), this means the UI would need a lot of separate SWFs and might get rather expensive to render.

I’m considering using this technique to build a photo uploader whose UI is constructed in the DOM. The problem I face is how I’ll show thumbnail previews of images on the local filesystem.

My first idea was to try storing temporary files somewhere and embed images with file:///, but that fell flat on its face when I realized that browsers don’t like mixing internet and local filesystem content on the same document (even with iframes). My next idea is to try running a small web server and bind to the loopback interface only, but I suspect this might cause significant security and firewall warnings/confusing user experience on, say, Vista and even XP SP2+. And I don’t even want to know what might happen if the user is running some 3rd party product like Norton Internet Security. I haven’t tested this yet and was hoping that binding to only the loopback interface might avoid these errors, but won’t hold my breath.

Do you have any suggestions on how I could use a hidden applet to show rescaled thumbnail images from the local filesystem in the DOM?

Maybe you know this already, but your site has been flagged by google as being infected with some malware. See http://safebrowsing.clients.google.com/safebrowsing/diagnostic?client=Firefox&hl=en-GB&site=http://windyroad.org/2006/08/14/reintroducing-javascript-and-hidden-applets-jaha/.

When trying to access it using FireFox3, I get a scary warning each time I access any URL on your site.

// Mike