GUI -- Base Link View added -- WIP.

Change-Id: Iad0bb3d4a796b420d0fcb071812d320c35941b6b
diff --git a/web/gui/src/main/java/org/onosproject/ui/impl/LinkViewMessageHandler.java b/web/gui/src/main/java/org/onosproject/ui/impl/LinkViewMessageHandler.java
new file mode 100644
index 0000000..59e017b
--- /dev/null
+++ b/web/gui/src/main/java/org/onosproject/ui/impl/LinkViewMessageHandler.java
@@ -0,0 +1,100 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.ui.impl;
+
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.google.common.collect.ImmutableSet;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Link;
+import org.onosproject.net.link.LinkService;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Message handler for link view related messages.
+ */
+public class LinkViewMessageHandler extends AbstractTabularViewMessageHandler {
+
+    /**
+     * Creates a new message handler for the link messages.
+     */
+    protected LinkViewMessageHandler() {
+        super(ImmutableSet.of("linkDataRequest"));
+    }
+
+    @Override
+    public void process(ObjectNode message) {
+        ObjectNode payload = payload(message);
+        String sortCol = string(payload, "sortCol", "src");
+        String sortDir = string(payload, "sortDir", "asc");
+
+        LinkService service = get(LinkService.class);
+        TableRow[] rows = generateTableRows(service);
+        RowComparator rc =
+                new RowComparator(sortCol, RowComparator.direction(sortDir));
+        Arrays.sort(rows, rc);
+        ArrayNode links = generateArrayNode(rows);
+        ObjectNode rootNode = mapper.createObjectNode();
+        rootNode.set("links", links);
+
+        connection().sendMessage("linkDataResponse", 0, rootNode);
+    }
+
+    private TableRow[] generateTableRows(LinkService service) {
+        List<TableRow> list = new ArrayList<>();
+        for (Link link : service.getLinks()) {
+            list.add(new LinkTableRow(link));
+        }
+        return list.toArray(new TableRow[list.size()]);
+    }
+
+    /**
+     * TableRow implementation for {@link Link links}.
+     */
+    private static class LinkTableRow extends AbstractTableRow {
+
+        private static final String SOURCE = "src";
+        private static final String DEST = "dst";
+        private static final String TYPE = "type";
+        private static final String STATE = "state";
+        private static final String DURABLE = "durable";
+
+        private static final String[] COL_IDS = {
+                SOURCE, DEST, TYPE, STATE, DURABLE
+        };
+
+        public LinkTableRow(Link l) {
+            ConnectPoint src = l.src();
+            ConnectPoint dst = l.dst();
+
+            add(SOURCE, src.elementId().toString() + "/" + src.port().toString());
+            add(DEST, dst.elementId().toString() + "/" + dst.port().toString());
+            add(TYPE, l.type().toString());
+            add(STATE, l.state().toString());
+            add(DURABLE, Boolean.toString(l.isDurable()));
+        }
+
+        @Override
+        protected String[] columnIds() {
+            return COL_IDS;
+        }
+    }
+
+}