Secure Global Desktop Administration Guide > Clients and webtops > Secure Global Desktop and Java™ archives

Secure Global Desktop and Java™ archives

Secure Global Desktop uses Java^™ applets for a variety of purposes. These Java applets must be downloaded from the Secure Global Desktop server to the client device's web browser.

The files that make up each applet can be combined into a Java archive. Java archives are useful because:

They may be compressed, which makes them faster to download.
They may include more than one applet.
They may be digitally signed.
Web browsers can keep local copies of them, which in some cases means they may only need to be downloaded once.

Web browsers can keep local copies of Java archives either by caching them, or locally installing them:

Caching a Java archive means the browser stores the archive in its cache, along with other temporary files. However, when the cache is full, or if an applet isn't used for a while, the browser may delete the archive. Similarly, if a user manually clears their browser's cache, the archive is deleted.
Installing a Java archive is more permanent. The archive can only be removed by the user.

Web browsers usually prompt the user for permission to cache/install an archive. For the archive to be cached/installed, the user must grant permission.

The Java archives in Secure Global Desktop work correctly with all supported browsers. However, some browsers have settings which can disable support for Java archives. If you have changed a particular browser's configuration, the browser may be unable to cache or install Java archives. You can always re-enable Java archive support by returning the browser to its default configuration.

If you are using the classic webtop

Secure Global Desktop provides several types of Java archive, as different web browsers support different types of archive. If you are using the classic webtop, Secure Global Desktop uses the mappings in the /opt/tarantella/etc/data/archives.txt file to control which archive types are used with which browsers.

The table below shows:

the setting required in archives.txt to use an archive type;
a description of the archive type; and
the features of the archive.

Setting	Archive type	Compression	Local copy	Signed
cab	Microsoft cabinet files	Compressed	Cached	Signed
cab4	Microsoft distribution units	Compressed	Installed	Signed
jpsjar	Archives signed using Sun JDK™ suitable for Sun Java Plug-in	Compressed	Cached	Signed
nsjar	Netscape signed installable Java archives	Compressed	Installed	Signed
sjar	Netscape signed non-installable Java archives	Compressed	Cached	Signed
zip	Zip archives	Uncompressed	Cached	Not signed

Note Netscape signed Java archives can be used with non-Netscape browsers.

By default, Secure Global Desktop uses these settings for the following browsers:

Browser/platform	Setting
Microsoft Internet Explorer 5 on Windows	cab4
Microsoft Internet Explorer 6 on Windows using Microsoft Virtual Machine	cab4
Microsoft Internet Explorer 6 on Windows using Sun Java Plug-In	jpsjar
Microsoft Internet Explorer on Apple Mac OS X 10.2+	jpsjar
Netscape 6.x and 7.x	jpsjar

Note The cab4 setting used by default for Internet Explorer users on Windows means that the archive is installed locally. However, the ability to install archives locally requires Administrator privileges. If Secure Global Desktop detects that the user does not have these privileges, it will automatically use the cab archive type instead as this is cached rather than installed.

Customizing which browsers receive which archives

If the archive types used by default are unsuitable, you can edit the /opt/tarantella/etc/data/archives.txt file to change which archive types users receive. The file contains comments to help you customize archive delivery.

If you only need to temporarily override the settings in the archives.txt file so that you use a different Java archive, you can do this by running the Secure Global Desktop CGI program ttaarchives.cgi with a query string. This program sets a cookie which overrides archives.txt. For example, using the URL http://server/tarantella/cgi-bin/ttaarchives.cgi?cab sets your session to use the Microsoft cabinet archive. The cookie lasts for as long as you have your web browser running. The cookie is deleted when you close the web browser.

You can find full details on the query string settings available for ttaarchives.cgi by running:

http://server/tarantella/cgi-bin/ttaarchives.cgi?

Related topics
Which clients are supported? How does Secure Global Desktop use applets?