How to get IzPack tocheck for an existing version of the software?

I have an application for which we use IzPack to create the installer. The installer is working fine in its current state, however, I need to add functionality that enables it to check whether an existing version of the software has been installed.

I understand IzPack supports this out of the box using its CheckedHelloPanel, unfortunately that only works for Windows, as it appears to depend on the windows registry.

Is there a way to configure IzPack such that it is able to detect existing installations?

I need to be able to detect whether there is one and merely display a message notifying the user... Bonus points for how to give the user the option to trigger the uninstaller of the existing installation.

Assume that the software will only be installed using the new installer
IzPack only: please do not suggest alternatives, as we cannot change that now
If you suggest using <validator>, please include a code sample of the validator class, because I have considered this, but don't know where to start

Tim Williscroft

I wrote this to allow my application to be installed over the jboss install.

public class JBossChecker {

 private static boolean tempJBossEnv;
 private static boolean tempJBossDirectoryExists;

 static {
  String s = System.getenv("JBOSS_HOME");
  tempJBossEnv= (s!=null);

  if( tempJBossEnv) {
   File f = new File(s);
   tempJBossDirectoryExists= ( f.exists() && f.isDirectory());
  }
  hasJBossEnv =tempJBossEnv;
  hasJBossDir = tempJBossDirectoryExists;
 }

 public static boolean hasJBossDir;
 public static boolean hasJBossEnv;

 public static void main(String[] args){
  System.out.println("Jboss environment "+hasJBossEnv);
  System.out.println("Jboss directory "+hasJBossDir);

 }
}

Then the installer has a section like

<conditions>
     <condition type="java" id="jbossEnv">
             <java> 
                 <class>au.com.codarra.ela.installer.JBossChecker</class
                 <field>hasJBossEnv</field>
             </java>
             <returnvalue type="boolean">true</returnvalue>
 </condition> 

 <condition type="java" id="jbossDir">
             <java>
                 <class>au.com.codarra.ela.installer.JBossChecker</class>
                 <field>hasJBossDir</field>
             </java>
             <returnvalue type="boolean">true</returnvalue>
 </condition> 

</conditions>

<installerrequirements>
 <installerrequirement condition="jbossEnv" message="Your system does not have the environment variable JBOSS_HOME set. Cannot update your system. Is XXXX installed on this system?" />
 <installerrequirement condition="jbossDir" message="Your system does not have a directory at the location in the environement variable JBOSS_HOME . Cannot update your system. Is XXXX installed on this system?" />
</installerrequirements>

<dynamicvariables>
 <variable name="INSTALL_PATH" value="${ENV[JBOSS_HOME]}"/>
</dynamicvariables>

<jar src="c:\dev\xxxx\build\installer.jar" />

The bit at the end makes sure izpack adds it to the installer jar.

It only works on Windows, because only Windows has a registry. However, in Linux apps traditionally don't have customized unified locations. For example your run scripts would go in a bin folder, your binaries would go in /opt, your documentation would go in /var, etc. The idea that there's one single "your-app" directory that is selected by the user and contains everything related to the application is a Windows concept.

So anyway, the way to solve this in Linux is to install the various parts of your app in non-user-defined locations. That way you know exactly where your app would be if it was already installed.

来源：https://stackoverflow.com/questions/1845166/how-to-get-izpack-tocheck-for-an-existing-version-of-the-software

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