1 files changed, 72 insertions, 0 deletions
diff --git a/plugins/infra/emf/org.eclipse.papyrus.infra.emf/src/org/eclipse/papyrus/infra/emf/spi/resolver/EObjectResolverService.java b/plugins/infra/emf/org.eclipse.papyrus.infra.emf/src/org/eclipse/papyrus/infra/emf/spi/resolver/EObjectResolverService.java
new file mode 100644
index 00000000000..9b2e0ecb239
--- /dev/null
+++ b/plugins/infra/emf/org.eclipse.papyrus.infra.emf/src/org/eclipse/papyrus/infra/emf/spi/resolver/EObjectResolverService.java
@@ -0,0 +1,72 @@
+/*****************************************************************************
+ * Copyright (c) 2016 Christian W. Damus 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:
+ *   Christian W. Damus - Initial API and implementation
+ *   
+ *****************************************************************************/
+
+package org.eclipse.papyrus.infra.emf.spi.resolver;
+
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.stream.Stream;
+
+import org.osgi.framework.BundleContext;
+import org.osgi.framework.ServiceReference;
+import org.osgi.util.tracker.ServiceTracker;
+
+/**
+ * A resolver that delegates to registered OSGi services in a <em>Chain of Command</em>
+ * pattern to provide the first available service result.
+ */
+public class EObjectResolverService extends ServiceTracker<IEObjectResolver, IEObjectResolver> implements IEObjectResolver {
+	private final AtomicReference<IEObjectResolver> delegate = new AtomicReference<>(IEObjectResolver.identity());
+
+	/**
+	 * Initializes me with the bundle context in which I track resolver services.
+	 * 
+	 * @param context
+	 *            the bundle context
+	 */
+	public EObjectResolverService(BundleContext context) {
+		super(context, IEObjectResolver.class, null);
+	}
+
+	@Override
+	public Object resolve(Object object) {
+		IEObjectResolver delegate = this.delegate.get();
+		if (delegate == null) {
+			// Recompute
+			delegate = Stream.of(getServices(new IEObjectResolver[getTrackingCount()]))
+					.filter(Objects::nonNull) // If the array has more slots than we have services
+					.reduce(IEObjectResolver.identity(), IEObjectResolver::compose);
+			this.delegate.set(delegate);
+		}
+
+		return delegate.resolve(object);
+	}
+
+	@Override
+	public IEObjectResolver addingService(ServiceReference<IEObjectResolver> reference) {
+		IEObjectResolver result = super.addingService(reference);
+
+		// We will have to recompute our delegates
+		delegate.set(null);
+
+		return result;
+	}
+
+	@Override
+	public void removedService(ServiceReference<IEObjectResolver> reference, IEObjectResolver service) {
+		super.removedService(reference, service);
+
+		// We will have to recompute our delegates
+		delegate.set(null);
+	}
+}