bugfix: got null execption when no url for download found.

src/main/java/logic/GEManager.java

@@ -150,18 +150,31 @@ public class GEManager {
             SimpleHttpResponse httpFileUrlResp = httpClient.processRequest(httpRequest);
             if (httpFileUrlResp.getStatusCode() != 200) {
                 logHttpError("ge.getLatestMediaFile/getLatestMediaURL", httpFileUrlResp);
-                return errorHttpResponse(httpFileUrlResp);
+                return errorHttpResponse(httpFileUrlResp, "getLatestMediaFile() failed");
             }
+            // get url
+            String url = null;
             contentObj = objMapper.readTree(httpFileUrlResp.getContent());
             JsonNode arrNode = contentObj.get("content");
-            String url = arrNode.get(0).get("url").asText();
+            if (arrNode != null  &&  arrNode.isNull() == false) {
+
+                JsonNode mediaInfo = arrNode.get(0);
+                if (mediaInfo != null &&  mediaInfo.isNull() == false) {
+                    JsonNode jsUrl = mediaInfo.get("url");
+                    if (jsUrl != null &&  jsUrl.isNull() == false)
+                        url = jsUrl.asText();
+                }
+            }
+            if (url == null) {
+                return errorResponse("No latest media file found for camId: " + camId);
+            }
 
             // step 2: get/download latest media file data (e.g: https://ie-cities-media.run.asv-pr-pub.ice.predix.io/v2/file/CAMERA-STG-HYP1052-CAM-L_1487807853000_0_IMAGE.JPG)
             httpRequest = buildDownloadLatestMediaFileRequest(url);
             SimpleHttpResponse httpFileDataResp = httpClient.processRequest(httpRequest);
             if (httpFileDataResp.getStatusCode() != 200) {
                 logHttpError("ge.getLatestMediaFile/downloadLatestMediaFile", httpFileDataResp);
-                return errorHttpResponse(httpFileDataResp);
+                return errorHttpResponse(httpFileDataResp, "failed to download file: " + url);
             }
             String fileData = httpFileDataResp.getContent();
 
@@ -202,7 +215,7 @@ public class GEManager {
                 brr = buildCameraListResp(httpResp);
             else {
                 logHttpError("getCameraList", httpResp);
-                return errorHttpResponse(httpResp);
+                return errorHttpResponse(httpResp, "getCameraList() faild");
             }
 
         } catch (Exception e) {
@@ -228,7 +241,7 @@ public class GEManager {
                 brr = buildCameraDetailsResp(httpResp);
             else {
                 logHttpError("ge.getCameraDetails", httpResp);
-                return errorHttpResponse(httpResp);
+                return errorHttpResponse(httpResp, "getCameraDetails() failed");
             }
 
         } catch (Exception e) {
@@ -270,7 +283,7 @@ public class GEManager {
                 brr = buildSensorLatestEventResp(httpResp);
             else {
                 logHttpError("getSensorLatestEvent", httpResp);
-                return errorHttpResponse(httpResp);
+                return errorHttpResponse(httpResp, "getSensorLatestEvent() failed");
             }
 
         } catch (Exception e) {
@@ -366,7 +379,7 @@ public class GEManager {
                 brr = buildSensorListResp(httpResp);
             else {
                 logHttpError("getSensorList", httpResp);
-                return errorHttpResponse(httpResp);
+                return errorHttpResponse(httpResp, "failed to fetch sensor list");
             }
 
         } catch (Exception e) {
@@ -707,10 +720,11 @@ public class GEManager {
         return apiString;
     }
 
-    private BaseRestResponse errorHttpResponse(SimpleHttpResponse httpResp) {
+    private BaseRestResponse errorHttpResponse(SimpleHttpResponse httpResp, String description) {
 
         BaseRestResponse errResp = new BaseRestResponse(false, null);
         ObjectNode objectNode = objMapper.createObjectNode();
+        objectNode.put("description", description);
         objectNode.put("statusCode", httpResp.getStatusCode());
         objectNode.put("content", httpResp.getContent());
         errResp.objectNode = objectNode;