Add listener for unloading of plugins

Change-Id: Ib5d65f15c6bda9ec3bee8f43dd20a7e9f40f5013
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-server/src/main/java/com/google/gerrit/server/plugins/PluginGuiceEnvironment.java

@@ -75,6 +75,7 @@ public class PluginGuiceEnvironment {
   private final CopyConfigModule copyConfigModule;
   private final Set<Key<?>> copyConfigKeys;
   private final List<StartPluginListener> onStart;
+  private final List<StopPluginListener> onStop;
   private final List<ReloadPluginListener> onReload;
 
   private Module sysModule;
@@ -111,6 +112,9 @@ public class PluginGuiceEnvironment {
     onStart = new CopyOnWriteArrayList<>();
     onStart.addAll(listeners(sysInjector, StartPluginListener.class));
 
+    onStop = new CopyOnWriteArrayList<>();
+    onStop.addAll(listeners(sysInjector, StopPluginListener.class));
+
     onReload = new CopyOnWriteArrayList<>();
     onReload.addAll(listeners(sysInjector, ReloadPluginListener.class));
 
@@ -165,6 +169,7 @@ public class PluginGuiceEnvironment {
     sshSets = dynamicSetsOf(injector);
     sshMaps = dynamicMapsOf(injector);
     onStart.addAll(listeners(injector, StartPluginListener.class));
+    onStop.addAll(listeners(injector, StopPluginListener.class));
     onReload.addAll(listeners(injector, ReloadPluginListener.class));
   }
 
@@ -187,6 +192,7 @@ public class PluginGuiceEnvironment {
     httpSets = dynamicSetsOf(injector);
     httpMaps = dynamicMapsOf(injector);
     onStart.addAll(listeners(injector, StartPluginListener.class));
+    onStop.addAll(listeners(injector, StopPluginListener.class));
     onReload.addAll(listeners(injector, ReloadPluginListener.class));
   }
 
@@ -233,6 +239,12 @@ public class PluginGuiceEnvironment {
     }
   }
 
+  void onStopPlugin(Plugin plugin) {
+    for (StopPluginListener l : onStop) {
+      l.onStopPlugin(plugin);
+    }
+  }
+
   private void attachItem(Map<TypeLiteral<?>, DynamicItem<?>> items,
       @Nullable Injector src,
       Plugin plugin) {
@@ -545,6 +557,9 @@ public class PluginGuiceEnvironment {
     if (StartPluginListener.class.isAssignableFrom(type)) {
       return false;
     }
+    if (StopPluginListener.class.isAssignableFrom(type)) {
+      return false;
+    }
 
     if (type.getName().startsWith("com.google.inject.")) {
       return false;