Add REST API for invoking workflow.

Currently, there is no way to invoking using REST API.
I've added REST API.

json data example:

{
  "op": "workflow.invoke",
  "params": {
    "workplace": "Nova-000",
    "id": "of-overlay.workflow-nova",
    "data": {
      "mgmtIp": "192.168.10.8",
      "ovsdbPort": 6641,
      "sshAccessInfo": {
        "remoteIp": "192.168.10.8",
        "port": 22,
        "user": "root",
        "password": "iloveyou",
        "keyfile": "~/.ssh/id_rsa"
      },
      "ovsDatapathType": "system",
      "physicalPorts": [
        "nova0_1"
      ],
      "vtepIp": "120.0.0.200/24",
      "annotations": {
        "rackId": 1,
        "rackPosition": 3
      }
    }
  }
}

Change-Id: I2ce3bc5a59ce1cbe91c8c6f83bd1f25e81933ce3
diff --git a/apps/workflow/app/src/main/java/org/onosproject/workflow/rest/WorkflowRestApi.java b/apps/workflow/app/src/main/java/org/onosproject/workflow/rest/WorkflowRestApi.java
new file mode 100644
index 0000000..fc66e06
--- /dev/null
+++ b/apps/workflow/app/src/main/java/org/onosproject/workflow/rest/WorkflowRestApi.java
@@ -0,0 +1,92 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+ *
+ * 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.workflow.rest;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.JsonNodeFactory;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.onosproject.rest.AbstractWebResource;
+import org.onosproject.workflow.api.WorkflowException;
+import org.onosproject.workflow.api.WorkflowService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.ws.rs.Consumes;
+import javax.ws.rs.POST;
+import javax.ws.rs.Path;
+import javax.ws.rs.Produces;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import java.io.IOException;
+import java.io.InputStream;
+
+import static org.onlab.util.Tools.readTreeFromStream;
+import static javax.ws.rs.core.Response.Status.BAD_REQUEST;
+import static javax.ws.rs.core.Response.Status.INTERNAL_SERVER_ERROR;
+import static org.onosproject.workflow.api.WorkflowDescription.WF_ID;
+import static org.onosproject.workflow.impl.WorkflowNetConfigListener.WORKFLOW_INVOKE;
+
+@Path("workflow")
+public class WorkflowRestApi extends AbstractWebResource {
+
+    private final Logger log = LoggerFactory.getLogger(getClass());
+    private WorkflowService service = get(WorkflowService.class);
+    private static final String OPERATION = "op";
+    private static final String PARAMS = "params";
+
+
+    @POST
+    @Consumes(MediaType.APPLICATION_JSON)
+    @Produces(MediaType.APPLICATION_JSON)
+    @Path("/invoke")
+    public Response invoke(InputStream stream) {
+        ObjectNode ret = JsonNodeFactory.instance.objectNode();
+        try {
+            ObjectNode payload = readTreeFromStream(mapper(), stream);
+            String operation = payload.path(OPERATION).asText();
+
+            if (!(WORKFLOW_INVOKE.equals(operation))) {
+                log.error("Operation is not matched");
+                return Response.status(BAD_REQUEST)
+                        .entity("Operation is not matched!").build();
+            }
+
+            JsonNode wfDescJson = payload.path(PARAMS).deepCopy();
+            service.invokeWorkflow(wfDescJson);
+            ret.put(WF_ID, wfDescJson.path(WF_ID).asText());
+
+            return ok(ret).build();
+        } catch (JsonProcessingException e) {
+            log.error("Failed to get json ", e);
+            ret.put(WF_ID, "Failed to get Json " + e.getCause());
+            return Response.status(BAD_REQUEST)
+                    .entity(ret).build();
+        } catch (IOException e) {
+            log.error("Failed to get request body ", e);
+            ret.put(WF_ID, "Failed to get request body " + e.getCause());
+            return Response.status(INTERNAL_SERVER_ERROR)
+                    .entity(ret).build();
+        } catch (WorkflowException e) {
+            log.error("Failed to invoke workflow ", e);
+            ret.put(WF_ID, "Failed to invoke workflow " + e.getCause());
+            return Response.status(INTERNAL_SERVER_ERROR)
+                    .entity(ret).build();
+
+        }
+    }
+
+}