@echo off

:: At this point you can place assumptions about Java version. It is still better than nothing anyway. In this particular case, we rely on a knowledge of Java version during installation time (with IzPack). Or you can just specify default value here, for example by default assume that 32 version is being run
set JVM_VERSION=""
if $SYSTEM_os_arch==x86 (
  set JVM_VERSION=32
) else (
  set JVM_VERSION=64
)
:: End of assumption section

:: Now trying to find out, what is current jvm version.

set TEMP_FILE=%TEMP%\javaCheck%RANDOM%%TIME:~9,5%.txt

java -version 2>%TEMP_FILE%
FOR /F "tokens=*" %%i in (%TEMP_FILE%) do (
  echo %%i | find "HotSpot" >nul
  if not errorlevel 1 (
    echo %%i | find "64-Bit" >nul
    if not errorlevel 1 (
      set JVM_VERSION=64
    ) else (
      set JVM_VERSION=32
    )
  )
)

del %TEMP_FILE%

if %JVM_VERSION%==32 (
  set NATIVE_JARS=$INSTALL_PATH/lib/32
) else (
  set NATIVE_JARS=$INSTALL_PATH/lib/64
)

start "App" javaw -classpath .;"%NATIVE_JARS%/*" my.app.App

The trick is to redirect java -version to a temporary file. Then try to find a line with "HotSpot" substring. If that line contains "64-Bit", then it is 64bit version Java. Otherwise it is 32bit.

To start with, I will notice that in installpath you can always use IzPack way of interpreting environmental variables. For example:

<installpath>${ENV[APPDATA]}\3Dfacto\installers\glassfish</installpath>

Next, ordinary IzPack variables to be used in BAT files.
In your silent configuration files you would like to see something like:

<AutomatedInstallation langpack="eng">
   ...
  <com.izforge.izpack.panels.UserInputPanel id="UNKNOWN (com.izforge.izpack.panels.UserInputPanel)">
    <userInput>
      <entry key="myVar" value="%HOMEDRIVE%\location\file.txt"/>
   ...
</AutomatedInstallation>

Here are some ideas which may help you make it work.

Now, when you use ProcessPanel to launch your bat file, you pass a environmental variable inside a variable. Once you realize it, it is easy to make small trick to make everything work. For example, if in silent installation configuration file (in example above), you provide environmental variable to myVar variable. And then you pass it to the bat file with ProcessPanel in processPanelSpec.xml:

<processing>
  <job name="Install configuratorPortal">
    <executefile name="$INSTALL_PATH/script.bat">
      <env>myVar=$myVar</env>
  ...
</processing>

When ProcessPanel launches that bat file, your myVar will be substituted once. But you need to get it substituted two times! What you may do is to simply add shell call command in front of the expression, where myVar is used. In this case, variable will be substituted twice.
However, it will not work in some cases, for example:

call echo hi> %myVar%

or

call if exist %myVar% echo "hi"

What you can do in this case is to use a wrapper. For instance, if you want to call echo command to substitute variable twice:

call echo hi> %myVar%

Then create a helper parameterDumper.bat:

echo off

:: %1 -- what
:: %2 -- where

call echo %~1>> %~2

Include it into installation and simply call that instead:

call "%INSTALL_PATH%\parameterDumper.bat" "hi" "%myVar%"

Then two call commands will be executed and the parameter will be evaluated twice.

One may want to modularize installer's components and support them separately. It is easy to do with IzPack too!
In this example, we suppose, that installers are built with Maven.

Ok, now we assume, that we have two other installers project1-installer and project2-installer. Then we create another project for "master" installer. In "master" installer's pom.xml file we specify project1-installer and project2-installer as a dependencies:

<dependency>
  <groupId>company</groupId>
  <artifactId>project1-installer</artifactId>
  <version>version</version>
  <classifier>standard</classifier>
</dependency>

<dependency>
  <groupId>company</groupId>
  <artifactId>project2-installer</artifactId>
  <version>version</version>
  <classifier>standard</classifier>
</dependency>

Then we use a dependency plugin to dump project1-installer and project2-installer. And then in install.xml in the "master" installer in the pack section we specify, that we want to include those dependencies in our "master" installation:

<packs>
  <pack name="main" required="yes">
    <description>Master Installation</description>

    <file src="${dependencies.dir}/project1-installer-standard.jar" targetdir="$INSTALL_PATH/install" override="true" />
    <file src="${dependencies.dir}/project2-installer-standard.jar" targetdir="$INSTALL_PATH/install" override="true" />
  </pack>
</packs>

All we left to do is just to call these project1-installer and project2-installer in order. So we create a ProcessPanel and in configuration file of that panel we specify, that we want to run a bat file:

<processing>
  <job name="Install">
    <executefile name="$INSTALL_PATH/install/dependenciesInstall.bat" />
  </job>
</processing>

Where the dependenciesInstall.bat would be the following:

echo off

echo.
echo -------------------------------------------------------
echo Launching Project1 Installer
"${INSTALL_PATH}\install\project1-installer-standard.jar

echo.
echo -------------------------------------------------------
echo Launching Project1 Installer
"${INSTALL_PATH}\install\project2-installer-standard.jar

echo.
echo -------------------------------------------------------
echo Done

And of course we need to include that dependenciesInstall.bat into our installer by specifying in pack section of install.xml:

<parsable targetfile="$INSTALL_PATH/install/dependenciesInstall.bat" />

copy /Y fileToBackup fileToBackup.bak_%date%_%time:~0,2%%time:~3,2%

Which gives a nice timestamp in the filename, for example:

fileToBackup.bak_29-06-2010_1738

ProcessPanel can be configured to run at specific point, for example right after the point when user specified some input fields. <executable> is run right after InstallPanel.

Sometimes you want to run an executable two times during the installation. For example, when user specified some data, you run one executable. After he specified another piece of data, you run another executable. Unfortunately, there is no easy way to do that using ProcessPanel or <executable>

In your install.xml you need to add a resources, where you will specify a configuration of your bat file (where it exists and what parameters should be passed to it):

<resources>
  <res id="ProcessPanel.Spec.xml" src="processPanelSpec.xml" />
</resources>

Then, you will need to create a file named processPanelSpec.xml. If you run the example from my previous post, the location of this file should be src/main/resources. In this file you specify, what file needs to be run and what parameters should be passed to it:

<?xml version="1.0" encoding="UTF-8"?>

<processing>

  <job name="Say Hello">
    <executefile name="$INSTALL_PATH/sayHello.bat">
      <env>name=Max</env>
    </executefile>
  </job>

</processing>

In two words, $INSTALL_PATH/sayHello.bat is location of our bat file -- we will cover this later. arg is passed argument.

Then in src/main/resources create a sayHello.bat file:

echo Hello %name%

And then in install.xml file in main pack (<packs><pack>..) say, that you want to include that bat file:

  <packs>
    <pack name="main" required="yes">
      ...

      <file src="sayHello.bat" targetdir="$INSTALL_PATH" override="true" />
    </pack>
  </packs>

And in install.xml in panels you need to specify three panels. The first is either TargetPanel or DefaultTargetpanel which would tell IzPack where it is possible to extract installation filees. Another one is InstallPanel which tells when to unpack the installation files. And the last one is ProcessPanel which specifies when a file needs to be processed:

<panels>
  <panel classname="HelloPanel" />
  <panel classname="TargetPanel" />
  <panel classname="ProcessPanel" />
  <panel classname="SimpleFinishPanel" />
</panels>

And then you can run mvn install. You will find your installer in standard target folder. And you should be able to see a message "Hello Max".

Here is a complete install.xml which I used for this example:

<?xml version="1.0" encoding="UTF-8"?>

<installation version="1.0">

  <info>
    <appname>test</appname>
    <appversion>1</appversion>
    <uninstaller write="no" />
    <javaversion>1.6</javaversion>

    <pack200 />
  </info>

  <guiprefs resizable="no" width="480" height="360">
    <laf name="looks">
      <param name="variant" value="windows" />
      <os family="windows" />
    </laf>
  </guiprefs>

  <locale>
    <langpack iso3="eng" />
  </locale>

  <resources>
    <res id="ProcessPanel.Spec.xml" src="processPanelSpec.xml" />
  </resources>

  <panels>
    <panel classname="HelloPanel" />
    <panel classname="TargetPanel" />
    <panel classname="InstallPanel" />
    <panel classname="ProcessPanel" />
    <panel classname="SimpleFinishPanel" />
  </panels>

  <packs>
    <pack name="main" required="yes">
      <description>Test Installation</description>

      <file src="sayHello.bat" targetdir="$INSTALL_PATH" override="true" />
    </pack>
  </packs>

</installation>

For example you can change the backslashes to slashes in the URL parameter when you pass it to the Java file:

echo %resources.home:\=/%