1 files changed, 167 insertions, 0 deletions
diff --git a/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/lifecycle/LifecycleHook.java b/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/lifecycle/LifecycleHook.java
new file mode 100644
index 0000000000..07a57b3d1f
--- /dev/null
+++ b/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/lifecycle/LifecycleHook.java
@@ -0,0 +1,167 @@
+/*
+ * Copyright (c) 2018 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.net4j.util.lifecycle;
+
+import org.eclipse.net4j.util.event.IEvent;
+import org.eclipse.net4j.util.event.IListener;
+
+/**
+ * @author Eike Stepper
+ * @since 3.8
+ */
+public class LifecycleHook<T extends ILifecycle> extends Lifecycle
+{
+  private final IListener delegateListener = new LifecycleEventAdapter()
+  {
+    @Override
+    protected void notifyOtherEvent(IEvent event)
+    {
+      delegateEvent(delegate, event);
+    }
+
+    @Override
+    protected void onAboutToActivate(ILifecycle lifecycle)
+    {
+      delegateAboutToActivate(delegate);
+    }
+
+    @Override
+    protected void onAboutToDeactivate(ILifecycle lifecycle)
+    {
+      delegateAboutToDeactivate(delegate);
+    }
+
+    @Override
+    protected void onActivated(ILifecycle lifecycle)
+    {
+      delegateActivated(delegate);
+      hookDelegateIfPossible();
+    }
+
+    @Override
+    protected void onDeactivated(ILifecycle lifecycle)
+    {
+      unhookDelegateIfPossible();
+      delegateDeactivated(delegate);
+    }
+  };
+
+  private T delegate;
+
+  private boolean listening;
+
+  private boolean delegateHooked;
+
+  public LifecycleHook()
+  {
+  }
+
+  protected final T getDelegate()
+  {
+    return delegate;
+  }
+
+  protected final void setDelegate(T delegate)
+  {
+    T oldDelegate = this.delegate;
+
+    if (oldDelegate != delegate)
+    {
+      unhookDelegateIfPossible();
+      this.delegate = delegate;
+      hookDelegateIfPossible();
+
+      delegateChanged(oldDelegate, delegate);
+    }
+  }
+
+  protected void delegateChanged(T oldDelegate, T newDelegate)
+  {
+  }
+
+  protected void delegateEvent(T delegate, IEvent event)
+  {
+  }
+
+  protected void delegateAboutToActivate(T delegate)
+  {
+  }
+
+  protected void delegateActivated(T delegate)
+  {
+  }
+
+  protected void delegateAboutToDeactivate(T delegate)
+  {
+  }
+
+  protected void delegateDeactivated(T delegate)
+  {
+  }
+
+  @Override
+  protected void doActivate() throws Exception
+  {
+    hookDelegateIfPossible();
+  }
+
+  @Override
+  protected void doDeactivate() throws Exception
+  {
+    unhookDelegateIfPossible();
+  }
+
+  protected void hookDelegate(T delegate)
+  {
+  }
+
+  protected void unhookDelegate(T delegate)
+  {
+  }
+
+  protected boolean hookInactiveDelegates()
+  {
+    return false;
+  }
+
+  private void hookDelegateIfPossible()
+  {
+    if (!listening && delegate != null)
+    {
+      delegate.addListener(delegateListener);
+      listening = true;
+    }
+
+    if (listening && !delegateHooked && (hookInactiveDelegates() || delegate.isActive()))
+    {
+      hookDelegate(delegate);
+      delegateHooked = true;
+    }
+  }
+
+  private void unhookDelegateIfPossible()
+  {
+    if (delegate != null)
+    {
+      if (delegateHooked)
+      {
+        unhookDelegate(delegate);
+        delegateHooked = false;
+      }
+
+      if (listening)
+      {
+        delegate.removeListener(delegateListener);
+        listening = false;
+      }
+    }
+  }
+}