(prefs) AbstractPreferences.isUserNode can cause NPE when customizing preference

Name: gm110360 Date: 05/29/2002


FULL PRODUCT VERSION :
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)

A DESCRIPTION OF THE PROBLEM :
See RFE 4689858 for some background information.

When customizing Preferences in the proper way, and using
the platform backing preferences to do the persistence etc,
the Preferences.userRoot() may not be the same as the nodes
root even when the node is a user node.

The AbstractPreferences isUserNode is making this check,
which is not always correct. In my case it is attempting to
ask if the WindowsPreferences userRoot == TestFactory
userRoot which would return false even though it is a user
node (it actually throws an Exception due to the bug).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run code

EXPECTED VERSUS ACTUAL BEHAVIOR :
Expected: to work
Actual: throws NullPointerException

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.NullPointerException
at java.util.prefs.Preferences.userRoot(Preferences.java:341)
at java.util.prefs.AbstractPreferences$1.run(AbstractPreferences.java:1006)
at java.security.AccessController.doPrivileged(Native Method)
at java.util.prefs.AbstractPreferences.isUserNode(AbstractPreferences.java:1003)
at java.util.prefs.WindowsPreferences.rootNativeHandle(WindowsPreferences.java:1021)
at java.util.prefs.WindowsPreferences.openKey(WindowsPreferences.java:467)
at java.util.prefs.WindowsPreferences.openKey(WindowsPreferences.java:449)
at java.util.prefs.WindowsPreferences.<init>(WindowsPreferences.java:372)
at java.util.prefs.WindowsPreferences.childSpi(WindowsPreferences.java:789)
at java.util.prefs.AbstractPreferences.node(AbstractPreferences.java:816)
at java.util.prefs.AbstractPreferences.node(AbstractPreferences.java:796)
at test.TestFactory.<init>(TestFactory.java:15)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:274)
at java.lang.Class.newInstance0(Class.java:296)
at java.lang.Class.newInstance(Class.java:249)
at java.util.prefs.Preferences.<clinit>(Preferences.java:190)
at TestFactory.main(TestFactory.java:36)



This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.lang.reflect.*;
import java.util.prefs.*;

public class TestFactory implements PreferencesFactory {
  private Preferences systemPreferences;
  private Preferences userPreferences;

  public TestFactory() {
    try {
      Constructor constructor =
Class.forName(System.getProperty("java.util.prefs.DefaultPreferencesFactory")).getDeclaredConstructor(null);
      constructor.setAccessible(true);
      PreferencesFactory defaultPreferencesFactory =
(PreferencesFactory)constructor.newInstance(null);
      systemPreferences = defaultPreferencesFactory.systemRoot().node("test");
      userPreferences = defaultPreferencesFactory.userRoot().node("test");
    }
    catch (Exception ex) {
      System.out.println("Exception: " + ex);
    }
  }

  public Preferences systemRoot() {
    return systemPreferences;
  }

  public Preferences userRoot() {
    return userPreferences;
  }

  public static void main(String[] args) {
    System.setProperty("java.util.prefs.DefaultPreferencesFactory",
System.getProperty("java.util.prefs.PreferencesFactory"));
    System.setProperty("java.util.prefs.PreferencesFactory", "TestFactory");

    Preferences.systemRoot();
  }
}
---------- END SOURCE ----------
(Review ID: 147179)
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###@###.### 11/3/04 20:34 GMT