Application Installer
by Roedy Green ©1996-2008 Canadian Mind Products
This essay is about a suggested
student project in
Java programming. This essay gives a rough overview of how it might work. It
does not describe an actual complete program. I have
no source, object,
specifications, file layouts or anything else useful to implementing this
project. Everything I have to say to help you with this project is written below.
I am
not prepared to help you implement it; I have too many other
projects of my own.
I do contract work for a living, which could include writing a program such as
this. However, I don’t do people’s homework
for them. That just robs them of an education.
You have my full permission to implement this project any way you please.
- They are outrageously expensive. They are too expensive for hobbyists or small
businesses.
- They are hideously complicated. They use ugly scripting languages that grew like
Topsy without plan.
- It is hard to do anything out the ordinary. You need clumsy mechanisms to insert
your stub code.
- They are not as smooth as they could be for the end user, particularly in
picking directory names. It should be very easy to take the default suggested
name, but on a different drive. It should be easy to take the default suggested
name, but nested in some other directory. It should allow the user to select
from some most common possibilities, e.g. C:\Program Files\mindprod
or C:\mindprod .
I propose writing a set of Java installer classes. You can then use them to whip
together a custom install program. You don’t need to learn some arcane script
language. If you need to do anything out of the ordinary, you have the full
power of Java at your disposal.
The classes would handle such things as:
- Identifying details about the environment we are installing into, e.g. cpu type,
free space on each disk, the sort of information need/sniff/avoid
provides.
- Inserting/removing lines in autoexec.bat and config.sys.
- putting icons on the screen.
- Adding/removing system menu items.
- Verifying all files are present and accounted for and unmolested.
- Selecting a suitable drive and directory to contain the application.
- Cleaning up after the install to get rid of temp directories.
- Branding with user name and or registration keys.
- Asking the user questions about just what he wants installed and how.
- Displaying a string of entertaining *.gifs during the boring parts.
- Checking and changing the registry.
- Cleaning out aborted previous installs.
- Uninstall and registering the official uninstall.
- Automatic checks for updates with automatic install.
- Prebranded software and software rental.
- On the fly download of files if they are not already present and sufficiently up
to date. you can check if package X is already installed, and if not download
and install it automatically as a precondition to your install.
- The user community of this set of classes might submit additional classes for
inclusion.
You would need to compile your program with a native mode compiler so that you
have all the standard java classes you need embedded in an exe. Further, you
wrap any other files you need with the installer in a self-extracting PKZIP exe.
You don’t want to rely on a working JVM being previously installed.
Alternatively, you insist that a JVM and your installer be preinstalled. It then
unpacks and installs compact download application packages.
Unfortunately the installer will likely be fatter than the app you are trying to
install. Perhaps some advanced Java compilers or optimisers could help put the
installer on a diet.
The first version would focus on Windows 95/98/NT. Later you might add classes
for other platforms. Ideally your mainline program install would be more or less
platform-independent.
Start with a very simple installer and gradually add features. This will keep
you from being overwhelmed by detail. At each stage you will have something
useful other can test. They will provide you feedback on which features are most
important to add next.
- Use the ZIP classes to unpack a zip file to a fixed directory tree.
- Install an icon on the desktop to fire up the application.
- Install an item in the start menu to fire up the application.
- Dynamically configure to allow choice of drive.
- Dynamically configure to allow choice of directory.
- Allow reinstallation of the icons and menut items if they are damaged, without
disturbing anything else.
- Split files into program and data files, so can upgrade without disturbing data
files.
- Run a custom install program after files are in place.
- Allow changes/additions to the registry.
The other half of installing is maintaining an application with automatic
updates. See the Automatic File Updater project.
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