PreferenceConverters can now be registered through OSGi service registry

java/com.sap.sse.security/src/com/sap/sse/security/PreferenceConverter.java

@@ -7,6 +7,8 @@ package com.sap.sse.security;
  * @param <PREF> The type of preference object, this converter handles.
  */
 public interface PreferenceConverter<PREF> {
+    public final String KEY_PARAMETER_NAME = "key";
+    
     String toPreferenceString(PREF preference);
 
     PREF toPreferenceObject(String stringPreference);

java/com.sap.sse.security/src/com/sap/sse/security/PreferenceConverterRegistrationManager.java

@@ -0,0 +1,77 @@
+package com.sap.sse.security;
+
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import org.osgi.framework.BundleContext;
+import org.osgi.framework.ServiceReference;
+import org.osgi.util.tracker.ServiceTracker;
+import org.osgi.util.tracker.ServiceTrackerCustomizer;
+
+/**
+ * Automatically registers/removes {@link PreferenceConverter} instances found in the OSGi service registry on the given
+ * {@link UserStore}.
+ *
+ * {@link PreferenceConverter} found are required to have a property with the key
+ * {@link PreferenceConverter#KEY_PARAMETER_NAME} defining the preference key the converter should be registered with.
+ */
+public class PreferenceConverterRegistrationManager {
+    private static final Logger logger = Logger.getLogger(PreferenceConverterRegistrationManager.class.getName());
+
+    private final BundleContext context;
+    private final UserStore userStore;
+
+    private final ServiceTracker<PreferenceConverter<?>, PreferenceConverter<?>> tracker;
+
+    public PreferenceConverterRegistrationManager(BundleContext bundleContext, UserStore userStore) {
+        this.context = bundleContext;
+        this.userStore = userStore;
+        tracker = createTracker(bundleContext);
+        tracker.open();
+    }
+
+    @SuppressWarnings({ "unchecked", "rawtypes" })
+    private ServiceTracker<PreferenceConverter<?>, PreferenceConverter<?>> createTracker(BundleContext bundleContext) {
+        return new ServiceTracker<PreferenceConverter<?>, PreferenceConverter<?>>(bundleContext,
+                (Class) PreferenceConverter.class, new Cutomizer());
+    }
+
+    public void stop() {
+        tracker.close();
+    }
+
+    private class Cutomizer implements ServiceTrackerCustomizer<PreferenceConverter<?>, PreferenceConverter<?>> {
+
+        @Override
+        public PreferenceConverter<?> addingService(ServiceReference<PreferenceConverter<?>> reference) {
+            String preferenceKey = (String) reference.getProperty(PreferenceConverter.KEY_PARAMETER_NAME);
+            PreferenceConverter<?> converter = context.getService(reference);
+            if (preferenceKey == null) {
+                logger.log(Level.SEVERE,
+                        "Found PreferenceConverter \"" + converter + "\" in OSGi registry without property "
+                                + PreferenceConverter.KEY_PARAMETER_NAME + " defining the preference key");
+            } else {
+                logger.log(Level.FINE, "Registering PreferenceConverter \"" + converter
+                        + "\" found as OSGi service with key \"" + preferenceKey + "\"");
+                userStore.registerPreferenceConverter(preferenceKey, converter);
+            }
+            return converter;
+        }
+
+        @Override
+        public void modifiedService(ServiceReference<PreferenceConverter<?>> reference,
+                PreferenceConverter<?> service) {
+            // Should we do anything here?
+        }
+
+        @Override
+        public void removedService(ServiceReference<PreferenceConverter<?>> reference, PreferenceConverter<?> service) {
+            String preferenceKey = (String) reference.getProperty(PreferenceConverter.KEY_PARAMETER_NAME);
+            if (preferenceKey != null) {
+                logger.log(Level.FINE,
+                        "Removing PreferenceConverter \"" + service + "\" with key \"" + preferenceKey + "\"");
+                userStore.removePreferenceConverter(preferenceKey);
+            }
+        }
+    }
+}

java/com.sap.sse.security/src/com/sap/sse/security/UserStore.java

@@ -55,14 +55,38 @@ public interface UserStore extends Named {
     String getPreference(String username, String key);
     
     /**
+     * <p>
+     * In an OSGi environment, this shouldn't be called manually, but instead automatically managed by setting a
+     * {@link PreferenceConverterRegistrationManager} up. {@link PreferenceConverter}s should be registered in the OSGi
+     * service registry with {@link PreferenceConverter#KEY_PARAMETER_NAME} containing the associated preference key
+     * added as property of the service registration.
+     * </p>
+     * 
+     * <p>
      * Registers a converter objects for a preference key that is used to convert preference Strings to Objects. This
      * makes it possible to access deserialized settings without the need to do the deserialization over and over again.
+     * </p>
      * 
-     * @param key the key to associate the converter with
-     * @param converter the converter to use for (de)serialization
+     * @param key
+     *            the key to associate the converter with
+     * @param converter
+     *            the converter to use for (de)serialization
      */
     void registerPreferenceConverter(String key, PreferenceConverter<?> converter);
     
+    /**
+     * <p>
+     * In an OSGi environment, this shouldn't be called manually, but instead automatically managed by setting a
+     * {@link PreferenceConverterRegistrationManager} up.
+     * </p>
+     * 
+     * <p>
+     * Removes a registered {@link PreferenceConverter}  with the given key.
+     * </p>
+     * 
+     * @param key
+     *            the key of the {@link PreferenceConverter} to remove
+     */
     void removePreferenceConverter(String key);
     
     /**