add registerListener()

Author: ahornace

opengrok-indexer/src/main/java/org/opengrok/indexer/configuration/RuntimeEnvironment.java

@@ -41,6 +41,7 @@
 import java.util.SortedSet;
 import java.util.TreeSet;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArraySet;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadFactory;
@@ -124,6 +125,8 @@ public final class RuntimeEnvironment {
 
     public WatchDogService watchDog;
 
+    private final Set<ConfigurationChangedListener> listeners = new CopyOnWriteArraySet<>();
+
     public List<String> getSubFiles() {
         return subFiles;
     }
@@ -1679,6 +1682,10 @@ public void applyConfig(Configuration config, boolean reindex, CommandTimeoutTyp
         getAuthorizationFramework().reload();
 
         messagesContainer.setMessageLimit(getMessageLimit());
+
+        for (ConfigurationChangedListener l : listeners) {
+            l.onConfigurationChanged();
+        }
     }
 
     public void setIndexTimestamp() throws IOException {
@@ -1943,4 +1950,8 @@ public Set<String> getAuthenticationTokens() {
     public void setAuthenticationTokens(Set<String> tokens) {
         syncWriteConfiguration(tokens, Configuration::setAuthenticationTokens);
     }
+
+    public void registerListener(ConfigurationChangedListener listener) {
+        listeners.add(listener);
+    }
 }