Configure content type for update service

application/src/main/java/org/thingsboard/server/service/update/DefaultUpdateService.java

@@ -21,6 +21,9 @@ import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.info.BuildProperties;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
 import org.springframework.stereotype.Service;
 import org.springframework.web.client.RestTemplate;
 import org.thingsboard.common.util.ThingsBoardThreadFactory;
@@ -65,8 +68,8 @@ public class DefaultUpdateService implements UpdateService {
 
     private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1, ThingsBoardThreadFactory.forName("tb-update-service"));
 
-    private ScheduledFuture checkUpdatesFuture = null;
+    private ScheduledFuture<?> checkUpdatesFuture = null;
-    private RestTemplate restClient = new RestTemplate();
+    private final RestTemplate restClient = new RestTemplate();
 
     private UpdateMessage updateMessage;
 
@@ -94,7 +97,7 @@ public class DefaultUpdateService implements UpdateService {
         Path instanceIdPath = Paths.get(INSTANCE_ID_FILE);
         if (instanceIdPath.toFile().exists()) {
             byte[] data = Files.readAllBytes(instanceIdPath);
-            if (data != null && data.length > 0) {
+            if (data.length > 0) {
                 try {
                     result = UUID.fromString(new String(data));
                 } catch (IllegalArgumentException e) {
@@ -124,13 +127,15 @@ public class DefaultUpdateService implements UpdateService {
     Runnable checkUpdatesRunnable = () -> {
         try {
             log.trace("Executing check update method for instanceId [{}], platform [{}] and version [{}]", instanceId, platform, version);
+            var headers = new HttpHeaders();
+            headers.setContentType(MediaType.APPLICATION_JSON);
             ObjectNode request = new ObjectMapper().createObjectNode();
             request.put(PLATFORM_PARAM, platform);
             request.put(VERSION_PARAM, version);
             request.put(INSTANCE_ID_PARAM, instanceId.toString());
             UpdateMessage prevUpdateMessage = updateMessage;
-            updateMessage = restClient.postForObject(UPDATE_SERVER_BASE_URL + "/api/v2/thingsboard/updates", request, UpdateMessage.class);
+            updateMessage = restClient.postForObject(UPDATE_SERVER_BASE_URL + "/api/v2/thingsboard/updates", new HttpEntity<>(request.toString(), headers), UpdateMessage.class);
-            if (updateMessage.isUpdateAvailable() && !updateMessage.equals(prevUpdateMessage)) {
+            if (updateMessage != null && updateMessage.isUpdateAvailable() && !updateMessage.equals(prevUpdateMessage)) {
                 notificationRuleProcessor.process(NewPlatformVersionTrigger.builder()
                         .updateInfo(updateMessage)
                         .build());