How can I write System preferences with Java? Can I invoke UAC?

Question

How can I write system preferences with Java, using Preferences.systemRoot()?

I tried with:

Preferences preferences = Preferences.systemRoot();
preferences.put("/myapplication/databasepath", pathToDatabase);

But I got this error message:

2010-maj-29 19:02:50 java.util.prefs.WindowsPreferences openKey
VARNING: Could not open windows registry node Software\JavaSoft\Prefs at root 0x80000002. Windows RegOpenKey(...) returned error code 5.
Exception in thread "AWT-EventQueue-0" java.lang.SecurityException: Could not open windows registry node Software\JavaSoft\Prefs at root 0x80000002: Access denied
    at java.util.prefs.WindowsPreferences.openKey(Unknown Source)
    at java.util.prefs.WindowsPreferences.openKey(Unknown Source)
    at java.util.prefs.WindowsPreferences.openKey(Unknown Source)
    at java.util.prefs.WindowsPreferences.putSpi(Unknown Source)
    at java.util.prefs.AbstractPreferences.put(Unknown Source)
    at org.example.install.Setup$2.actionPerformed(Setup.java:43)

I would like to do this, because I want to install an embedded JavaDB database, and let multiple users on the computer to use the same database with the application.

How to solve this? Can I invoke UAC and do this as Administrator from Java? And if I log in as Administrator when writing, can I read the values with my Java application if I'm logged in as a User?

Answer 1

You cannot write to any arbitrary registry location from java preferences - all preferences are stored under a subkey Software\Javasoft\Prefs. With user preferences mapping to the HKEY_CURRENT_USER hive, and system mapping to the HKEY_LOCAL_MACHINE hive.

To write to the registry, you could use the windows "REG" command line tool. This page details other ways of modifying the registry. including use of .reg files.

I had the same need - to write to the registry from java - I solved it by writing a small .NET command line utility to do it.

The Sun Windows JDK does ship with generic code to write to arbitrary portions of the registry (WindowsPreferences), but it's not public. This article describes how to access this class using reflection.