Closes #466

protege-editor-owl/src/main/java/org/protege/editor/owl/ui/usage/UsageByEntityTreeModel.java

@@ -476,11 +476,6 @@ public void visit(SWRLRule rule) {
 
     protected class UsageTreeNode extends DefaultMutableTreeNode {
 
-        /**
-         * 
-         */
-        private static final long serialVersionUID = -53617232488795863L;
-
         private OWLOntology ont;
 
         private OWLAxiom axiom;

protege-editor-owl/src/main/java/org/protege/editor/owl/ui/usage/UsageTree.java

@@ -3,12 +3,23 @@
 import org.protege.editor.owl.OWLEditorKit;
 import org.protege.editor.owl.ui.renderer.OWLCellRenderer;
 import org.protege.editor.owl.ui.tree.OWLLinkedObjectTree;
+import org.protege.editor.owl.ui.view.ChangeListenerMediator;
+import org.protege.editor.owl.ui.view.Copyable;
 import org.semanticweb.owlapi.model.OWLAxiom;
 import org.semanticweb.owlapi.model.OWLEntity;
+import org.semanticweb.owlapi.model.OWLObject;
 
 import javax.swing.*;
+import javax.swing.event.ChangeListener;
+import javax.swing.event.TreeSelectionEvent;
+import javax.swing.event.TreeSelectionListener;
 import javax.swing.tree.DefaultMutableTreeNode;
+import javax.swing.tree.TreePath;
 import java.awt.*;
+import java.util.*;
+import java.util.List;
+
+import static java.util.stream.Collectors.toList;
 
 
 /**
@@ -17,20 +28,83 @@
  * Bio-Health Informatics Group<br>
  * Date: 21-Feb-2007<br><br>
  */
-public class UsageTree extends OWLLinkedObjectTree {
+public class UsageTree extends OWLLinkedObjectTree implements Copyable {
 
 
     private OWLEditorKit owlEditorKit;
 
     private OWLEntity entity;
 
+    private final ChangeListenerMediator changeListenerMediator = new ChangeListenerMediator();
 
     public UsageTree(OWLEditorKit owlEditorKit) {
         super(owlEditorKit);
         this.owlEditorKit = owlEditorKit;
         setCellRenderer(new UsageTreeCellRenderer(owlEditorKit));
+        getSelectionModel().addTreeSelectionListener(e -> changeListenerMediator.fireStateChanged(UsageTree.this));
+    }
+
+    /**
+     * Determines whether or not at least one <code>OWLObject</code>
+     * can be copied.
+     *
+     * @return <code>true</code> if at least one object can be copied, or
+     * <code>false</code> if no objects can't be copied.
+     */
+    @Override
+    public boolean canCopy() {
+        TreePath[] selectionPaths = getSelectionPaths();
+        if(selectionPaths == null) {
+            return false;
+        }
+        return Arrays.stream(selectionPaths)
+                .map(TreePath::getLastPathComponent)
+                .filter(node -> node instanceof UsageByEntityTreeModel.UsageTreeNode)
+                .findFirst()
+                .isPresent();
+    }
+
+    /**
+     * Gets the objects that will be copied.
+     *
+     * @return A <code>List</code> of <code>OWLObjects</code> that will be
+     * copied to the clip board
+     */
+    @Override
+    public List<OWLObject> getObjectsToCopy() {
+        TreePath[] selectionPaths = getSelectionPaths();
+        if(selectionPaths == null) {
+            return Collections.emptyList();
+        }
+        return Arrays.stream(selectionPaths)
+                .map(TreePath::getLastPathComponent)
+                .filter(node -> node instanceof UsageByEntityTreeModel.UsageTreeNode)
+                .map(node -> ((UsageByEntityTreeModel.UsageTreeNode) node).getAxiom())
+                .collect(toList());
     }
 
+    /**
+     * Adds a change listener.  If the ability to copy OWL objects changes, the
+     * copyable component should notify listeners through a change of state event.
+     *
+     * @param changeListener The listener to be added.
+     * @see ChangeListenerMediator Components may want to use the <code>ChangeListenerMediator</code>
+     * class to manage event notifcation and addition/removal of listeners
+     */
+    @Override
+    public void addChangeListener(ChangeListener changeListener) {
+        changeListenerMediator.addChangeListener(changeListener);
+    }
+
+    /**
+     * Removes a previously added change listener.
+     *
+     * @param changeListener The ChangeListener to be removed.
+     */
+    @Override
+    public void removeChangeListener(ChangeListener changeListener) {
+        changeListenerMediator.removeChangeListener(changeListener);
+    }
 
     public void setOWLEntity(OWLEntity entity) {
         this.entity = entity;