springboot websocket with JPA NullPointerException - spring-mvc

Question

I'm wreting a SpringBoot web service use websocket to send message to client and using JPA to save data.
in project I use a thread to create a data ,and then use JPA to save it ,use Websocket to show data. But it doesn't work with a NullPointExecption.
this is my code:
#RestController
#ServerEndpoint("/websocket")
public class CrawlingController {
private final Logger logger = LoggerFactory.getLogger(CrawlingController.class);
#Autowired
private SimulateDataRepository simulateDataRepository;
private static GlobalStatus globalStatus = GlobalStatus.getInstance();
private Session session;
private static CopyOnWriteArraySet<CrawlingController> crawlingControllers =
new CopyOnWriteArraySet<>();
#OnOpen
public void onOpen(Session session) throws Exception {
this.session = session;
crawlingControllers.add(this);
String message = dataCrawling();
}
#OnMessage
public void onMessage(String message, Session session) throws IOException {
for (CrawlingController controller : crawlingControllers)
sendMessage(message);
}
#OnClose
public void onClose() {
crawlingControllers.remove(this);
if (crawlingControllers.size() == 0)
end();
session=null;
end();
}
private void sendMessage(String message) throws IOException {
this.session.getBasicRemote().sendText(message);
}
public void onError(Session session, Throwable error) {
logger.error(error.getMessage());
System.out.println("websocket found something error!");
}
#RequestMapping("/start")
public String dataCrawling() throws Exception {
if (!globalStatus.isDataCrawling) {
Process process = null;
synchronized (globalStatus) {
process = Utils.crawling();
globalStatus.crawlingProcss = process;
globalStatus.isDataCrawling = true;
}
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
new Thread(() -> {
try {
stuffSimulate(bufferedReader);
} catch (IOException | ParseException e) {
logger.error(e.getMessage());
}
}).start();
return "start Finish!";
} else return "faild";
}
public void stuffSimulate(BufferedReader reader) throws IOException, ParseException {
line = reader.readLine();
while (globalStatus.isDataCrawling) {
SimulateData simulateData = new SimulateData();
.... ...
simulateData.setData(data.toString());
this.saveAndShow(simulateData);
}
}
}
}
private void saveAndShow(SimulateData simulateData) throws IOException {
simulateData = simulateDataRepository.saveAndFlush(simulateData);
SummaryData summaryData = SimulateService.obtainSummary(simulateData);
onMessage(summaryData.printSummary(),this.session);
summaryData.sout();
}
}
simulateDataRepository can be work when i use http://localhost:8080/start.
the mysql can get data.
But it cna't be work when i use websocket!!!
The error meaasge said that:
Exception in thread "Thread-5" java.lang.NullPointerException
at cn.linhos.controller.CrawlingController.saveAndShow(CrawlingController.java:293)
at cn.linhos.controller.CrawlingController.stuffSimulate(CrawlingController.java:172)
at cn.linhos.controller.CrawlingController.lambda$dataCrawling$0(CrawlingController.java:104)
at java.lang.Thread.run(Thread.java:748)
why simulateDataRepository can't saveAndFlush when websocket but can do it when i use "/start"?
how should i do to make websocket work ?