Delay initialization of the UserPreferencesManager.

java/src/jmri/InstanceManager.java

@@ -32,20 +32,26 @@
  * {@link InstanceManager#getNullableDefault} method instead.
  * <p>
  * Multiple items can be held, and are retrieved as a list with
- * {@link    InstanceManager#getList}.
+ * {@link InstanceManager#getList}.
  * <p>
  * If a specific item is needed, e.g. one that has been constructed via a
  * complex process during startup, it should be installed with
  * {@link InstanceManager#store}.
  * <p>
- * If it's OK for the InstanceManager to create an object on first request, have
- * that object's class implement the {@link InstanceManagerAutoDefault} flag
- * interface. The InstanceManager will then construct a default object via the
- * no-argument constructor when one is first requested.
+ * If it is desirable for the InstanceManager to create an object on first
+ * request, have that object's class implement the
+ * {@link InstanceManagerAutoDefault} flag interface. The InstanceManager will
+ * then construct a default object via the no-argument constructor when one is
+ * first requested.
  * <p>
  * For initialization of more complex default objects, see the
  * {@link InstanceInitializer} mechanism and its default implementation in
  * {@link jmri.managers.DefaultInstanceInitializer}.
+ * <p>
+ * Implement the {@link InstanceManagerAutoInitialize} interface when default
+ * objects need to be initialized after the default instance has been
+ * constructed and registered with the InstanceManager. This will allow
+ * references to the default instance during initialization to work as expected.
  * <hr>
  * This file is part of JMRI.
  * <P>
@@ -218,6 +224,7 @@ static public <T> T getNullableDefault(@Nonnull Class<T> type) {
                 try {
                     T obj = (T) type.getConstructor((Class[]) null).newInstance((Object[]) null);
                     l.add(obj);
+                    // obj has been added, now initialize it if needed
                     if (obj instanceof InstanceManagerAutoInitialize) {
                         ((InstanceManagerAutoInitialize) obj).initialize();
                     }
@@ -236,6 +243,7 @@ static public <T> T getNullableDefault(@Nonnull Class<T> type) {
                     T obj = (T) getDefault().initializers.get(type).getDefault(type);
                     log.debug("      initializer created default of {}", type.getName());
                     l.add(obj);
+                    // obj has been added, now initialize it if needed
                     if (obj instanceof InstanceManagerAutoInitialize) {
                         ((InstanceManagerAutoInitialize) obj).initialize();
                     }

java/src/jmri/managers/JmriUserPreferencesManager.java

@@ -25,6 +25,7 @@
 import jmri.ConfigureManager;
 import jmri.InstanceInitializer;
 import jmri.InstanceManager;
+import jmri.InstanceManagerAutoInitialize;
 import jmri.JmriException;
 import jmri.UserPreferencesManager;
 import jmri.beans.Bean;
@@ -57,7 +58,7 @@
  *
  * @author Randall Wood (C) 2016
  */
-public class JmriUserPreferencesManager extends Bean implements UserPreferencesManager {
+public class JmriUserPreferencesManager extends Bean implements UserPreferencesManager, InstanceManagerAutoInitialize {
 
     public final static String SAVE_ALLOWED = "saveAllowed";
 
@@ -1218,6 +1219,11 @@ private void savePreferences() {
         });
     }
 
+    @Override
+    public void initialize() {
+        this.readUserPreferences();
+    }
+
     /**
      * Holds details about the specific class.
      */
@@ -1449,9 +1455,7 @@ public static class Initializer extends AbstractInstanceInitializer {
         @Override
         public <T> Object getDefault(Class<T> type) throws IllegalArgumentException {
             if (type.equals(UserPreferencesManager.class)) {
-                JmriUserPreferencesManager instance = new JmriUserPreferencesManager();
-                instance.readUserPreferences();
-                return instance;
+                return new JmriUserPreferencesManager();
             }
             return super.getDefault(type);
         }