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Java Forum / General / July 2006Strange behaviour of applet running under Opera
Hello people, I was writing an applet for a challenge site and some people there reported that the applet displayed different results when run under Firefox and Opera. I wrote another one basing on the same applet for testing and the results were different again. I never thought Java was browser-dependent until now. I asked some of my friend to test it again and they experienced the same problem. So can you test it again and if possible have a look at the source code to see what the problem could be? Firefox Screenshot: http://chinhnt2k3.t35.com/strange/firefox.png Opera: http://chinhnt2k3.t35.com/strange/opera.png Test applet: http://chinhnt2k3.t35.com/strange/ Source code: http://chinhnt2k3.t35.com/strange/http://chinhnt2k3.t35.com/strange/Strange.zip Regards, Chinh The link to the source code is: http://chinhnt2k3.t35.com/strange/Strange.zip Copy/paste mistake >< > Hello people, > [quoted text clipped - 5 lines] > and they experienced the same problem. So can you test it again and if > possible have a look at the source code to see what the problem could be? I haven't looked at the source code, but it works fine for me using Opera 9.0 beta on Mac OS X (i.e. the result is 'good', which I guess means the applet is working as required). Safari and Firefox also work, which is to be expected since all three browsers use the same JVM plugin (JavaSE 5.0). The Opera 9.0 beta also works for me on Windows XP. Dan.  SignatureDaniel Dyer http://www.dandyer.co.uk > I was writing an applet for a challenge site and some people there > reported that the applet displayed different results when run under > Firefox and Opera. I wrote another one basing on the same applet for > testing and the results were different again. That was a very good test that you put together. Sadly, despite that, I can't tell you what's going wrong for sure, but I can fill in some of the details, which may help you to find out more. The problem seems to be to do with the fact that Opera uses its own Java plug-in implementation, whereas Firefox uses the plug-in from Sun. In both cases, they use the same underlying JVM implementation (1.5.0_o6-b05 on my machine), but I assume that Opera /uses/ that JVM in a significantly different way (different security manager and so on). In particular it uses its own subclass of java.net.HttpUrlConnection whereas it the Sun plug-in uses the implementation class sun.net.www.protocol.http.HttpUrlConnection (which is a subclass of java.net.HttpUrlConnection which is private to Sun). You can verify that by adding a call to dumpStatus(conn); to your connect() method, where that is defined as: ============= private void dumpStatus(URLConnection conn) { StringBuilder b = new StringBuilder(); b.append("<html><br>"); b.append(conn); Class c = conn.getClass(); while (c != null) { b.append("<br>class: "); b.append(c); c = c.getSuperclass(); } b.append("</html>"); JOptionPane.showMessageDialog( null, b.toString(), "Connection", JOptionPane.INFORMATION_MESSAGE); } ============= If you capture the network traffic (use Ethereal or similar) then you'll see that when Firefox runs the applet the request for the PHP page looks like (with some irrelevant stuff removed): ============= GET /strange/test.php HTTP/1.1 test: test User-Agent: Mozilla/4.0 (Windows XP 5.1) Java/1.5.0_06 Host: chinhnt2k3.t35.com ============= But when you do the same thing with Opera 8.52 (I used a completely brand new installation of Opera -- the very first URL if ever downloaded on this machine was your test !) you see something like: ============= GET /strange/test.php HTTP/1.1 User-Agent: Opera/8.52 (Windows NT 5.1; U; en) Host: chinhnt2k3.t35.com ============= So your custom test: test header isn't being added to the request. I believe that the Opera implementation of HttpUrlConnection is broken in that it doesn't honour setRequestProperty(). It looks as if the only property it allows you to set is "Content-length", all other requests being ignored /silently/. It also does not respect the behaviour of the superclass implementation which throws an exception if you try to use setRequestProperty() after the connection has been connect()-ed. (If that's typical of Opera coding standards in general then I doubt whether Opera is going to stay installed on my machine for very long -- I've been meaning to try it out for a while, but this is a very bad introduction...) -- chris > But when you do the same thing with Opera 8.52 (I used a completely brand new > installation of Opera -- the very first URL if ever downloaded on this machine [quoted text clipped - 5 lines] > > ============= The current Opera version is 8.54 - it might be worth checking that. For that matter Opera 9 is now in beta - haven't tried it myself, but the comments are generally favorable. Signaturemartin@ | Martin Gregorie gregorie. | Essex, UK org | lol, it's been exactly 3 months since the last post, but thanks for your very detailed explanation (if you ever read this topic again :D) Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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