added extension point for HttpSessionListener

scm-webapp/src/main/java/sonia/scm/HttpSessionListenerHolder.java

@@ -0,0 +1,170 @@
+
+package sonia.scm;
+
+//~--- non-JDK imports --------------------------------------------------------
+
+import com.google.common.collect.Sets;
+import com.google.inject.Injector;
+import com.google.inject.Key;
+import com.google.inject.TypeLiteral;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+//~--- JDK imports ------------------------------------------------------------
+
+import java.util.Set;
+import javax.servlet.ServletContext;
+
+import javax.servlet.http.HttpSession;
+import javax.servlet.http.HttpSessionEvent;
+import javax.servlet.http.HttpSessionListener;
+import sonia.scm.plugin.ext.Extension;
+
+/**
+ * Dispatcher for {@link HttpSessionEvent}. The {@link HttpSessionListenerHolder}
+ * loads all registered {@link HttpSessionListener}s from the {@link Injector}
+ * and delegates the events to the them. {@link HttpSessionListener} can be 
+ * registered with the {@link Extension} annotation.
+ *
+ * @author Sebastian Sdorra <sebastian.sdorra@gmail.com>
+ * @since 1.42
+ */
+public class HttpSessionListenerHolder implements HttpSessionListener
+{
+
+  /** key type of the session listeners */
+  private static final Key<Set<HttpSessionListener>> KEY =
+    Key.get(new TypeLiteral<Set<HttpSessionListener>>() {}
+  );
+
+  /** logger for HttpSessionListenerHolder */
+  private static final Logger logger =
+    LoggerFactory.getLogger(HttpSessionListenerHolder.class);
+
+  //~--- constructors ---------------------------------------------------------
+
+  /**
+   * Constructs a new HttpSessionListenerHolder.
+   *
+   */
+  public HttpSessionListenerHolder()
+  {
+    if (logger.isDebugEnabled())
+    {
+      logger.debug("create instance of {}",
+        HttpSessionListenerHolder.class.getName());
+    }
+  }
+
+  //~--- methods --------------------------------------------------------------
+
+  /**
+   * Delegates the create session event to all registered 
+   * {@ĺink HttpSessionListener}s.
+   *
+   *
+   * @param event session event
+   */
+  @Override
+  public void sessionCreated(HttpSessionEvent event)
+  {
+    if (listenerSet == null)
+    {
+      listenerSet = loadListeners(event);
+    }
+
+    dispatch(event, true);
+  }
+
+  /**
+   * Delegates the destroy session event to all registered 
+   * {@ĺink HttpSessionListener}s.
+   *
+   *
+   * @param event session event
+   */
+  @Override
+  public void sessionDestroyed(HttpSessionEvent event)
+  {
+    dispatch(event, false);
+  }
+
+  /**
+   * Dispatch session events.
+   *
+   *
+   * @param event session event
+   * @param create {@code true} if the event is a create event
+   */
+  private void dispatch(HttpSessionEvent event, boolean create)
+  {
+    if (listenerSet != null)
+    {
+      for (HttpSessionListener listener : listenerSet)
+      {
+        if (create)
+        {
+          listener.sessionCreated(event);
+        }
+        else
+        {
+          listener.sessionDestroyed(event);
+        }
+      }
+    }
+    else
+    {
+      logger.warn(
+        "could not dispatch session event, because holder is not initialized");
+    }
+  }
+
+  /**
+   * Load listeners from {@link Injector} which is stored in the 
+   * {@link ServletContext}.
+   *
+   *
+   * @param event session event
+   *
+   * @return set of session listeners
+   */
+  private synchronized Set<HttpSessionListener> loadListeners(
+    HttpSessionEvent event)
+  {
+    Set<HttpSessionListener> listeners = null;
+    HttpSession session = event.getSession();
+
+    if (session != null)
+    {
+      Injector injector = (Injector) session.getServletContext().getAttribute(
+                            Injector.class.getName());
+
+      if (injector != null)
+      {
+        logger.debug("load HttpSessionListeners from injector");
+        listeners = injector.getInstance(KEY);
+      }
+      else
+      {
+        logger.error("could not find injector in servletContext");
+      }
+
+      if (listeners == null)
+      {
+        listeners = Sets.newHashSet();
+      }
+    }
+    else
+    {
+      logger.warn("received session event without session");
+    }
+
+    return listeners;
+  }
+
+  //~--- fields ---------------------------------------------------------------
+
+  /** listener set */
+  private Set<HttpSessionListener> listenerSet;
+}

scm-webapp/src/main/java/sonia/scm/plugin/DefaultPluginLoader.java

@@ -77,6 +77,7 @@ import java.util.Set;
 
 import javax.servlet.ServletContext;
 import javax.servlet.ServletContextListener;
+import javax.servlet.http.HttpSessionListener;
 
 import javax.xml.bind.JAXB;
 
@@ -563,12 +564,20 @@ public class DefaultPluginLoader implements PluginLoader
 
     //J-
     extensionPoints = extensionPointCollector.getAnnotatedClasses();
+    // add ServletContextListener to list of extension points
     extensionPoints.add(
       new AnnotatedClass<ExtensionPoint>(
         Extensions.createExtensionPoint(true), 
         ServletContextListener.class
       )
     );
+    // add HttpSessionListener to list of extension points
+    extensionPoints.add(
+      new AnnotatedClass<ExtensionPoint>(
+        Extensions.createExtensionPoint(true), 
+        HttpSessionListener.class
+      )
+    );
 
     extensions = extensionCollector.getAnnotatedClasses();
     extensions.add(