1 files changed, 75 insertions, 0 deletions
diff --git a/plugins/infra/misc/org.eclipse.papyrus.infra.sync/src/org/eclipse/papyrus/infra/sync/SyncItem.java b/plugins/infra/misc/org.eclipse.papyrus.infra.sync/src/org/eclipse/papyrus/infra/sync/SyncItem.java
new file mode 100644
index 00000000000..17872f651e8
--- /dev/null
+++ b/plugins/infra/misc/org.eclipse.papyrus.infra.sync/src/org/eclipse/papyrus/infra/sync/SyncItem.java
@@ -0,0 +1,75 @@
+/*****************************************************************************
+ * Copyright (c) 2014, 2015 CEA LIST, 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:
+ *  Laurent Wouters laurent.wouters@cea.fr - Initial API and implementation
+ *  Christian W. Damus - bug 465416
+ *
+ *****************************************************************************/
+package org.eclipse.papyrus.infra.sync;
+
+import java.lang.ref.Reference;
+import java.lang.ref.WeakReference;
+
+/**
+ * Encapsulate an item that can be synchronized with others in a bucket
+ *
+ * @author Laurent Wouters
+ *
+ * @param <M>
+ *            The type of the underlying model element common to all
+ *            synchronized items in a single bucket
+ * @param <T>
+ *            The type of the backend element to synchronize
+ */
+public abstract class SyncItem<M, T> extends SyncObject {
+	private final Reference<T> backend;
+
+	/**
+	 * Initializes this item
+	 *
+	 * @param backend
+	 *            The backend element to synchronize
+	 * @throws NullPointerException
+	 *             when the backend element is null
+	 */
+	public SyncItem(T backend) {
+		if (backend == null) {
+			throw new NullPointerException("The backend element must not be null");
+		}
+
+		this.backend = new WeakReference<>(backend);
+	}
+
+	/**
+	 * Gets the backend element that is being synchronized
+	 *
+	 * @return The backend element (guaranteed to be non-{@code null} if I am {@link ISyncObject#isActive()} active)
+	 */
+	public final T getBackend() {
+		return backend.get();
+	}
+
+	/**
+	 * Gets the model element common to all items in a bucket
+	 *
+	 * @return The model element, or {@code null} if the item is no longer {@link ISyncObject#isActive() enabled}
+	 */
+	public abstract M getModel();
+
+	/**
+	 * I am enabled if my back-end can still be retrieved.
+	 * 
+	 * @return whether my {@link #getBackend() backend} is non-{@code null}
+	 */
+	@Override
+	public boolean isActive() {
+		return backend.get() != null;
+	}
+}