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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
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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
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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
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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
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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
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