The following section in the tutorial describes how automatically
download a Java plugin if a Java VM was not present on the client machine.
The Bambookit GUI's applet is executed if there exists a Java 1.1+ compatible VM.
If not available then a compatible Java VM is loaded and installed with a single click
The VM that gets downloaded should be SMALL, should not ask where it should be installed,
should not popup a download page, but to immediately begin downloading the plug-in
To accomplish this we would need to use the Object tag
(a W3C recognized tag). There are a few compatibilty issues when dealing with earlier versions
of Netscape which we will touch upon a bit later.
Although Object tag has several attributes we will only concern ourselves with CLASSID, CODEBASE, ID, WIDTH, HEIGHT
CLASSID is the only required attribute of the OBJECT tag.
It contains a unique identification tag that is generated whenever the control is compiled.
The aspects of versioning will also be addressed further down the document.
Since this is an Object tag, Windows treats any embedded control as an ActiveX control (even a Java plug-in).
Thus the browser security settings placed on ActiveX controls will affect the Java plug-in.
How can you find the CLASSID of the control you wish to use.
Either the ID is provided to you or you could manually locate them in the registry by using
REGEDIT.exe to find it.
For users to access an ActiveX control on your web page, the control must be installed
and registered on the user's computer.
The CLASSID for Sun's VM is:
The CLASSID for MS's VM is
So how do you ensure the user has the control installed before accessing your web page?
The CODEBASE attribute!
The codebase attribute is used to specify a relative or absolute URL from where the control
should be downloaded.
When the web browser sees the tag >OBJECT< tag in your web page, it checks to see if the control
is already installed user's computer by checking the user's system registry. If the control is
installed then the this control is used on the Web page. If it is not installed then the web browser
downloads the control from the URL specified in the CODEBASE attribute. Installs it and then uses this
control on the web page. This control will then reside on the users computer, serving future requests
without any additional downloads (based on matching CLASSID)
There might be multiple versions of the VM on the database.
If you wish to use a specific version of the VM then you would define the version
Versioning info is passed along in the CODEBASE attribute, the format is
If you wish to ALWAYS download the cab file, you can set the values to
In the case of Bambookit GUI you should ALWAYS be using
dynamic versioning. Meaning that if the user has an older version of the
java plugin then the user will be prompted with a dialog to download
the newer version (the CODEBASE must point to a cab file and not a
To indicate a dynamic version of the Sun Java Plugin you should always use
Thus the codebase version reference would mean at LEAST this version and above,
if below this version then goto the URL reference (either a .cab or html file)
If the CLASSID starts with a
Then that is a static reference, meaning that IF the exact version that is requested is
NOT present than the browser will request the download. (i.e. if the Sun plug-in 1.4.1 is installed and the
version is requesting that version 1.4.0 be installed and there is not a copy of that Java
plugin on the client machine, then the browser will make the request to download that plugin.)
A new addition for Java Plug-in 1.3 (and valid in 1.4.x) was the PARAM scriptable.
The value should be true if the applet requires scripting support and false if it does not.
The value is false by default.
Specifies the base URL of the applet.
The URL should be relative to the document URL.
This PARAM element is required only if the applet is not located in the same directory as the document.
Specifies the name of the Java archive.
The value can be either true or false. Currently not used in Bambookit GUI 2.0.1 but
be used in a later date.
Warning: If you use codebase in the applet tag to centralize the code
then take note below:
Then the direct mapping would be:
The Embed tag is required for the Netscape 4.x browser versions, for more info see the reference
guide at the bottom of this page
The upcoming version of the Java Plugin 1.4.2 for Windows will be 1.3Meg download.
At the times of this writing of this document it was still in beta and not available for download.
(Be warned, for other systems, the plugin could be as high as 13Megs, Linux)
Detecting the Virtual Machine by Scripting?
No methods for determining the browser's Java Virtual Machine are supported in the W3C Document Object Model.
There isn't any support in the Dynamic HTML DOM extensions for Internet Explorer or the DOM for the Netscape browsers.
In a nutshell, that means there's no single cross-browser, script-only method to detecting the user's VM (Virtual Machine) from a Web page.
Can I download the Microsoft VM instead?
If you have the MS Java plugin control, MSJavX86.exe, this can be placed on your local intranet servers
and referenced via the CODEBASE attribute of the OBJECT tag.
Can I use a Personal Java VM instead?
Currently we are unaware of any Personal Java Plugin available to download for free
to use instead of the Java 1.4.2 Plugin.
If any one has any information on such a plugin, please email us so we can add it
to our pages at firstname.lastname@example.org