[izpack-devel] Uninstall before installing

[Christopher Deckers]

Hi,

I needed to trigger the uninstall procedure silently, from the
installer, to ensure that only one instance of my program is
installed. I have this need because my uninstall procedures unlocks
some files that otherwise could not be overriden by the newer
versions, needs to ensure that the registry is cleaned up from past
useless keys, and needs to remove from the install location the
content of the packs that the user decided not to install when
reinstalling.

I managed to get my way through by creating an install listener that
looks for the uninstall string in the Windows registry, fiddles with
it, and triggers the command line uninstall in the beforePacks(xxx)
method. I placed this listener as the first one in the list of
listeners with an OS restriction to be Windows :)

A few points:
- I use the JRE of the currently running installer rather than the one
in the uninstall string, because that one may point to a JRE that was
removed.
- I don't use the $INSTALL_PATH, but the uninstall string, because the
user may decide to install the program to a different location.
- Because the uninstall process is detached, I test the existence of
the target directory until it gets deleted, with a timeout of 5
seconds.

Was there something built in to do the same thing that I overlooked?
I add the file with the code to this e-mail in case someone is
interested or want to comment my approach. I don't know if the list
allows that... if not I will send a second e-mail with the content in
the e-mail itself.

Cheers,
-Christopher
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