Applets and IE

Question

I have an applet I am trying to view in IE. I have it in a jar archive. When I try to view it I get the following in the console:
java.lang.ClassNotFoundException: MyClass
     at com/ms/vm/loader/URLClassLoader.loadClass
     at com/ms/vm/loader/URLClassLoader.loadClass
     at com/ms/applet/AppletPanel.securedClassLoad
     at com/ms/applet/AppletPanel.processSentEvent
     at com/ms/applet/AppletPanel.processSentEvent
     at com/ms/applet/AppletPanel.run
     at java/lang/Thread.run
It doesn't find my base class. If I put my class files in a cab file, it works.
Here is the issue: I have to sign the jar file with a verisign certificate. I put the signed jar in a cab file. I continue to get the message that the base class cannot be found. I can load the applet in another client (Lotus Notes)
Does anyone have any ideas what I need to do
Thanks in advance!
Chris

Answer 1

As IanSchneider pointed out, you are experiencing the joys of the m$ vm. If you want your applet to run under both the m$ vm and the sun jvm, you must purchase two separate Code Signing Digital IDs -- a Sun Java Signing Digital ID and a Microsoft Authenticode Digital ID. Then place your applet in a cab file and a jar file and sign each. Then you can use the following HTML:
<APPLET CODE = 'MyApplet' ARCHIVE = 'MyApplet.jar' NAME = 'MyApplet'>
    <PARAM name='cabbase' value='MyApplet.cab'>
</APPLET>Doing this will allow your applet to run in both IE with the m$ vm or in IE with the Sun JVM installed. (One caveat: I have not found a way to make an applet that is part of a package to work inside the m$ vm, even when placed in the cab file. I really never spent much time looking for a solution since it was just as easy to make the applet a stand alone class rather than part of a package.)
A better (and cheaper) strategy is to only use the Sun JVM, especially since the m$ vm is limited to Java 1.2 support and Microsoft will soon stop supporting their vm -- which means no more security fixes.
To deal with the situation of an end-user only having the m$ vm installed or having both installed but the m$ vm set as the default, you can "force" the applet to run using the Sun JVM by using the HTML <OBJECT> and <EMBED> tags instead of the <APPLET> Tag. The easiest way to do this is to use Sun's HTML converter. See http://java.sun.com/j2se/1.4.1/docs/guide/plugin/developer_guide/contents.html for more details (specifically chapter 4). This will create HTML markup similar to:
<OBJECT
    classid = "clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
    codebase = "http://java.sun.com/products/plugin/autodl/jinstall-1_4-windows-i586.cab#Version=1,4,0,0"
    NAME = 'MyApplet' >
    <PARAM NAME = CODE VALUE = 'MyApplet' >
    <PARAM NAME = ARCHIVE VALUE = 'MyApplet.jar' >
    <PARAM NAME = NAME VALUE = 'MyApplet' >
    <PARAM NAME = "type" VALUE = "application/x-java-applet;version=1.4">
    <PARAM NAME = "scriptable" VALUE = "false">
    <PARAM NAME = 'cabbase' VALUE='MyApplet.cab'>
    <COMMENT>
     <EMBED
            type = "application/x-java-applet;version=1.4"
            CODE = 'MyApplet'
            ARCHIVE = 'MyApplet.jar'
            NAME = 'MyApplet'
            'cabbase' ='MyApplet.cab'
         scriptable = false
         pluginspage = "http://java.sun.com/products/plugin/index.html#download">
         <NOEMBED>
            </NOEMBED>
     </EMBED>
    </COMMENT>
</OBJECT>With this markup, even if the user has the m$ vm set as the default, the applet will run using the Sun JVM. If the user does not have it installed, they will be prompted asking if they want to download and install it. Be sure to read the plugin documentation (linked to above) carefully. You can "configure" the Object tag (by the values set for the classid and codebase attributes) so that only a specific version of a JVM is used, or only JVMs newer than a certain version, etc. The HTMLConverter has Template files that will do this for you, or you can manually edit the <Object> tag.
Good Luck.