WS API improvement

@@ -212,8 +212,12 @@ public class TbEntityDataSubCtx {
     }
 
     public Collection<Integer> clearSubscriptions() {
-        List<Integer> oldSubIds = new ArrayList<>(subToEntityIdMap.keySet());
-        subToEntityIdMap.clear();
-        return oldSubIds;
+        if (subToEntityIdMap != null) {
+            List<Integer> oldSubIds = new ArrayList<>(subToEntityIdMap.keySet());
+            subToEntityIdMap.clear();
+            return oldSubIds;
+        } else {
+            return Collections.emptyList();
+        }
     }
 }

@@ -159,6 +159,95 @@ public class BaseWebsocketApiTest extends AbstractWebsocketTest {
     }
 
     @Test
+    public void testEntityDataLatestWidgetFlow() throws Exception {
+        Device device = new Device();
+        device.setName("Device");
+        device.setType("default");
+        device.setLabel("testLabel" + (int) (Math.random() * 1000));
+        device = doPost("/api/device", device, Device.class);
+
+        long now = System.currentTimeMillis();
+
+        DeviceTypeFilter dtf = new DeviceTypeFilter();
+        dtf.setDeviceNameFilter("D");
+        dtf.setDeviceType("default");
+        EntityDataQuery edq = new EntityDataQuery(dtf, new EntityDataPageLink(1, 0, null, null), Collections.emptyList(),
+                Collections.singletonList(new EntityKey(EntityKeyType.TIME_SERIES, "temperature")), Collections.emptyList());
+
+        EntityDataCmd cmd = new EntityDataCmd(1, edq, null, null, null);
+
+        TelemetryPluginCmdsWrapper wrapper = new TelemetryPluginCmdsWrapper();
+        wrapper.setEntityDataCmds(Collections.singletonList(cmd));
+
+        wsClient.send(mapper.writeValueAsString(wrapper));
+        String msg = wsClient.waitForReply();
+        EntityDataUpdate update = mapper.readValue(msg, EntityDataUpdate.class);
+        Assert.assertEquals(1, update.getCmdId());
+        PageData<EntityData> pageData = update.getData();
+        Assert.assertNotNull(pageData);
+        Assert.assertEquals(1, pageData.getData().size());
+        Assert.assertEquals(device.getId(), pageData.getData().get(0).getEntityId());
+        Assert.assertNotNull(pageData.getData().get(0).getLatest().get(EntityKeyType.TIME_SERIES).get("temperature"));
+        Assert.assertEquals(0, pageData.getData().get(0).getLatest().get(EntityKeyType.TIME_SERIES).get("temperature").getTs());
+        Assert.assertEquals("", pageData.getData().get(0).getLatest().get(EntityKeyType.TIME_SERIES).get("temperature").getValue());
+
+        TsKvEntry dataPoint1 = new BasicTsKvEntry(now - TimeUnit.MINUTES.toMillis(1), new LongDataEntry("temperature", 42L));
+        List<TsKvEntry> tsData = Arrays.asList(dataPoint1);
+        sendTelemetry(device, tsData);
+
+        Thread.sleep(100);
+
+        LatestValueCmd latestCmd = new LatestValueCmd();
+        latestCmd.setKeys(Collections.singletonList(new EntityKey(EntityKeyType.TIME_SERIES, "temperature")));
+        cmd = new EntityDataCmd(1, null, null, latestCmd, null);
+        wrapper = new TelemetryPluginCmdsWrapper();
+        wrapper.setEntityDataCmds(Collections.singletonList(cmd));
+
+        wsClient.send(mapper.writeValueAsString(wrapper));
+        msg = wsClient.waitForReply();
+        update = mapper.readValue(msg, EntityDataUpdate.class);
+
+        Assert.assertEquals(1, update.getCmdId());
+
+        List<EntityData> listData = update.getUpdate();
+        Assert.assertNotNull(listData);
+        Assert.assertEquals(1, listData.size());
+        Assert.assertEquals(device.getId(), listData.get(0).getEntityId());
+        Assert.assertNotNull(listData.get(0).getLatest().get(EntityKeyType.TIME_SERIES));
+        TsValue tsValue = listData.get(0).getLatest().get(EntityKeyType.TIME_SERIES).get("temperature");
+        Assert.assertEquals(new TsValue(dataPoint1.getTs(), dataPoint1.getValueAsString()), tsValue);
+
+        now = System.currentTimeMillis();
+        TsKvEntry dataPoint2 = new BasicTsKvEntry(now, new LongDataEntry("temperature", 52L));
+
+        wsClient.registerWaitForUpdate();
+        sendTelemetry(device, Arrays.asList(dataPoint2));
+        msg = wsClient.waitForUpdate();
+
+        update = mapper.readValue(msg, EntityDataUpdate.class);
+        Assert.assertEquals(1, update.getCmdId());
+        List<EntityData> eData = update.getUpdate();
+        Assert.assertNotNull(eData);
+        Assert.assertEquals(1, eData.size());
+        Assert.assertEquals(device.getId(), eData.get(0).getEntityId());
+        Assert.assertNotNull(eData.get(0).getLatest().get(EntityKeyType.TIME_SERIES));
+        tsValue = eData.get(0).getLatest().get(EntityKeyType.TIME_SERIES).get("temperature");
+        Assert.assertEquals(new TsValue(dataPoint2.getTs(), dataPoint2.getValueAsString()), tsValue);
+
+        //Sending update from the past, while latest value has new timestamp;
+        wsClient.registerWaitForUpdate();
+        sendTelemetry(device, Arrays.asList(dataPoint1));
+        msg = wsClient.waitForUpdate(TimeUnit.SECONDS.toMillis(1));
+        Assert.assertNull(msg);
+
+        //Sending duplicate update again
+        wsClient.registerWaitForUpdate();
+        sendTelemetry(device, Arrays.asList(dataPoint2));
+        msg = wsClient.waitForUpdate(TimeUnit.SECONDS.toMillis(1));
+        Assert.assertNull(msg);
+    }
+
+    @Test
     public void testEntityDataLatestTsWsCmd() throws Exception {
         Device device = new Device();
         device.setName("Device");

@@ -54,12 +54,12 @@ public class TbTestWebSocketClient extends WebSocketClient {
 
     @Override
     public void onClose(int i, String s, boolean b) {
-
+        log.error("CLOSED:");
     }
 
     @Override
     public void onError(Exception e) {
-
+        log.error("ERROR:", e);
     }
 
     public void registerWaitForUpdate() {