Question

We’ve developed a custom plugin for Notes 8.5.2. It records a number of custom user preferences. The class that does so is shown below:

import java.util.prefs.Preferences;

/**
 * Provides programmatic access to Windows Registry entries for this plug-in.
 */
public class Registry 
{
    Preferences prefs;    

    /**
     * Initializes a new instance of the Registry class.
     */
    public Registry()
    {
        prefs = Preferences.userNodeForPackage(Registry.class) ;    
    } 

    /**
     * Gets the value of a registry key.
     * 
     * @param keyName  The name of the key to return.
     * 
     * @return A string containing the value of the specified registry key. If a key with the specified name cannot be
     *         found, the return value is an empty string.
     */
    public String GetValue(String keyName)
    {
        try
        {
            return prefs.get(keyName, "NA") ;
        }
        catch(Exception err)
        {
            return  "" ;
        }

    }

    /**
     * Sets the value of a registry key.
     * 
     * @param keyName  The name of the registry key.
     * 
     * @param keyValue The new value for the registry key.
     */
    public void SetValue(String keyName, String keyValue)
    {
        try
        {
            prefs.put(keyName, keyValue);
            prefs.flush();
        }
        catch(Exception err)
        {
        }

    }
}

A sample of the code that uses it is as follows:

Registry wr = new Registry();
String setting1 = wr.GetValue("CustomSetting1");
wr.SetValue("CustomSetting1", newValue);

Now, I’ve scanned the Windows Registry, and these settings do not exist. I’ve indexed my entire hard disk, and I cannot find these entries in any file.

So, where the heck are these settings being stored?

Answer 1

On Windows the Java Preferences API uses the Registry as it’s backing store for the Preferences class. The keys are rooted by package name under HKEY_CURRENT_USER\Software\JavaSoft\Prefs.

Your code doesn’t specify a package, so it uses the following location by default (tested on Windows Vista and 7):

HKEY_CURRENT_USER\Software\JavaSoft\Prefs\<unnamed>

There is an articled titled “Sir, What is Your Preference?” by Ray Djajadinataz at the Sun Developer Network where you can get a little more background on this API with some screen shots showing registry locations.

I wonder if you were searching for the key name, eg CustomSetting1, and not finding it because it is saved as /Custom/Setting1 to note that the C and S are capitalized (see API docs.)