Java Reference
In-Depth Information
N
OTE
The installer utility finishes its job after the application is installed. Consequently, the
AH Application Support Phase is void in this case because the application, once
installed, is totally independent from the installer.
A final remark concerns the client system resources required during the AH Execution Phase
(that is, while running itself and installing the application) that for large applications could be
demanding. We will take another look at this very popular class of deployment means in
Chapter 3, in which we will discuss a commercial product.
Another Example—The Sun Java Plug-In
As a matter of exercise, let's examine the Sun Java Plug-In in order to illustrate the model at
work. The Sun Java Plug-In was described in some detail in Chapter 1. It will help us to fur-
ther clarify the model with an already discussed case. The Plug-In is bundled with any Sun
JRE package that can be downloaded, for example at
http://javaweb.eng/plugin/
.
The AH consists of the browser together with the Plug-In utility that launches the application.
A normal Web server can work as a Deployment Server because the executables to be
deployed are simple Java applets. The AH Installation Phase occurs whenever the browser and
then the Sun Plug-In are installed.
Only simple Deployment Policies can be enforced by the Software Producer using this prod-
uct. The applet model imposes a relaxed control over end-users attempting to download a given
page containing that applet. Of course, having a dynamic Web server could allow for more
sophisticated control. On the client side, the Application Installation Phase is performed by the
Web browser, which saves the applet locally in the browser cache.
Regarding the AH Application Support Phase, it is interesting to note that the On-The-Run
Management Phase is not void in this case. The Plug-In provides standard runtime services to
the launched applet (that is, the standard applet container).
The following phases are empty in this case:
•
Application Management
Because the application launched as an applet, the runtime
control over it by the AH is very limited.
•
Resources Installation
The Plug-In does not have the capability to download and install
resources on the applet's behalf.
The AH Management Phase, though quite simple, is performed by the Plug-In control panel.
