WIP: Refactoring the Intent REST API.
NOTE: All changes are Work-in-Progress, and they are in the process
of being actively updated and refactored.

 * The new implementation is in onos/core/intent/runtime/web
   The old implementation in the onos/core/datagrid/web is kept until
   the refactoring is completed.

 * The new REST API base path is /wm/onos/intent

 * The initial set of (new) APIs is the following:
   - /wm/onos/intent/high
     GET all high-level intent
     POST (create) a collection of high-level intents
     DELETE all intents

   - /wm/onos/intent/high/{intent-id}
     GET a high-level intent object
     DELETE a high-level intent object

   - /wm/onos/intent/low
     GET all low-level intents

   - /wm/onos/intent/low/{intent-id}
     GET a low-level intent object

   - /wm/onos/intent/path/switch/{src-dpid}/shortest-path/{dst-dpid}
     GET a Shortest Path between two Switch DPIDs

  * The Application-Level Intent object is specified in class
    onos/api/intent/ApplicationIntent.java

TODO (list incomplete):
 - Return the appropriate REST codes and return values for each REST operation
 - Add the appropriate Java APIs so each REST call would make a single
   Java call.
 - If necessary, rename API class ApplicationIntent to something more
   appropriate, and use it in the Java API.
 - Re-think/refactor the ApplicationIntent so it becomes a more solid base for
   all (high-level) intents.
 - The corresponding Java APIs for each REST call should be synchronous
   (for some definition of the expected operation outcome).
 - Implement intent/intents Java API delete operation that requires a
   single call instead of two calls (delete and purge)
 - Refactor the High and Low Level intents, such that they don't use
   inheritance from a common base class.
 - Cleanup the return Intent objects representation in JSON. E.g.,
   the Dpid JSON should be just "dpid": <value> instead of
   "dpid": {
        "value": <value>
    }

Change-Id: Ia994a2026f57a1f176c5321c1952325e3b986097
diff --git a/src/main/java/net/onrc/onos/core/intent/runtime/web/IntentLowResource.java b/src/main/java/net/onrc/onos/core/intent/runtime/web/IntentLowResource.java
new file mode 100644
index 0000000..bf0b527
--- /dev/null
+++ b/src/main/java/net/onrc/onos/core/intent/runtime/web/IntentLowResource.java
@@ -0,0 +1,39 @@
+package net.onrc.onos.core.intent.runtime.web;
+
+import java.io.IOException;
+import java.util.Collection;
+
+import net.onrc.onos.core.intent.Intent;
+import net.onrc.onos.core.intent.IntentMap;
+import net.onrc.onos.core.intent.runtime.IPathCalcRuntimeService;
+
+import org.restlet.resource.Get;
+import org.restlet.resource.ServerResource;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A class to access the low-level intents.
+ */
+public class IntentLowResource extends ServerResource {
+    private static final Logger log = LoggerFactory.getLogger(IntentLowResource.class);
+
+    /**
+     * Gets all low-level intents.
+     *
+     * @return a collection of all low-leve intents.
+     */
+    @Get("json")
+    public Collection<Intent> retrieve() throws IOException {
+        IPathCalcRuntimeService pathRuntime = (IPathCalcRuntimeService) getContext().
+                getAttributes().get(IPathCalcRuntimeService.class.getCanonicalName());
+
+        //
+        // Get all low-level intents
+        //
+        IntentMap intentMap = pathRuntime.getPathIntents();
+        Collection<Intent> intents = intentMap.getAllIntents();
+
+        return intents;
+    }
+}