Subject: Netscape 3.01 CLASS VERIFIER BUG From: Anatoli Krassavine <kras@nmr1.ioc.ac.ru> Date: 1997/01/17 Message-Id: <32DFC60F.167E@nmr1.ioc.ac.ru> Newsgroups: comp.lang.java.programmer [More Headers] Hi everyone, I experienced strange problems with running my applets on Netscape 3.01. Has anybody experienced the same? Any work-around? Ok, below is small description: ^^^^^^^^^^^^^^^^^ HTML page contains 2 different independent applets. Although applets are different they are inherited from the same applet class, written by me, i.e. CommonInterfaceApplet / \ / \ Applet1 Applet2 Ok, on all the previous versions of Netscape the system downloads both applets correctly, runs them, etc. But with Netscape 3.01 I have the following error message VERIFIER CLASS ERROR Applet2: Class Applet2 overrides final method init.()V VERIFIER CLASS .......... .......................... and so on - the same for a dozen different methods in Applet2 ........................... finally I have # Applet exception: class Applet2 got a security violation: method verification error Naturally Applet2 stop, although Applet1 runs fine. Sometimes the message referes to Applet1, but usually Applet2 - probably it is initialized second, since it is much bigger then Applet1 NOW THE INTERESTING PART: If I put just one of this applets on the page - either of them - it will run fine!!! It looks like the Java virtual machine downloads the classes for Applet1 and starts to initialize them. When machine starts to download classes for Applet2 - something clashes - naturally both applets contain certain methods which are overwritten from CommonInterfaceApplet. As I said, I never experienced anything like that in previous versions. Any help? JUST some answers to obvious questions: 1) All the classes are downloaded from the same directory on the same site 2) No ZIPping is used Sincerely yours, Toly kras@nmr1.ioc.ac.ru
Subject: Re: security violation: method verification error From: David Hopwood <hopwood@zetnet.co.uk> Date: 1997/05/20 Message-Id: <1997052001301674952@zetnet.co.uk> Newsgroups: comp.lang.java.security [More Headers] In message <337CCC92.6AF0@hbp.com> Don Rude <donr@hbp.com> writes: > The Java Console output of Netscape(3.01) follows: > > AppAccelerator(tm) 1.0.2a for Java, x86 version. > > Copyright (c) 1996 Borland International. All Rights Reserved. > > VERIFIER ERROR p6.action(Ljava/awt/Event;Ljava/lang/Object;)Z: Expecting to find object on stack If I remember correctly this bug was fixed in 4.0 (and maybe 3.02?). To work around it in previous versions, avoid casting from an array type to another type. David Hopwood david.hopwood@lmh.ox.ac.uk, hopwood@zetnet.co.uk
Subject: Re: Problem running Java applets in Navigator 3.01 From: Jay Guidos <jayman@cadvision.com> Date: 1996/12/06 Message-Id: <32A84A81.683B@cadvision.com> Newsgroups: comp.lang.java.programmer [More Headers] Vinh D. Nguyen wrote: > > I wrote an applet in Visual J++ and it ran fine in IE 3.0. However, when I > tried to run the same applet in Navigator 3.01, I kept getting a method > verification error. I realize from reading the postings in this news group > that several others have had the same problem; however, no answer was ever > offered! Please help! > > Vinh Hi Vinh, I have had this problem many times. Others have noted here and elsewhere that Netscape has acknowledged problems with the verifier on NS3.1 that generates these kinds of problems, but I am not aware of any FAQ or bug report that details this. Let me tell you how I beat Verifier errors when they happen to me. 1) delete all your .class files, remove all debug options from your compile setup, and re-compile ALL classes together. Although many times that is sufficient, you may also have problems with accessing static class methods (the JVM throws exceptions when accessing perfectly valid references to a static method of a particular class). The only solution to that one I have found is to : 2) make some small change in the method of the static class that NS3.1 hates. Ensure that the change will result in a different set of byte codes! Recompile. Good luck, Jay -- Jay Guidos mailto:jayman@cadvision.com I&J Scientific Software Ltd http://wndx.com/wndx/gaia/gaia.html Calgary, AB, Canada