How to get IzPack tocheck for an existing version

Question

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

Answer 1

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.

Answer 2

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.