为什么我的线程在调用服务方法时阻塞

Question

我的线程和服务类：

public class InterfaceThread implements Runnable {

    private static final Logger logger = Logger.getLogger(InterfaceThread.class);

    @Autowired
    private ScanService scanService;
    
    @Override
    public void run() {
        String accessToken = getAccessTokenFromJSON(getResponse(null, URL_UPDATE_ACCESS_TOKEN, METHOD_POST).getText());
        logger.debugv("Access Token Found {0}", accessToken);
        
        String pendingOrdersJson = getResponse(accessToken, URL_PENDING_ORDERS, METHOD_GET).getText();
        logger.infov("Pending Orders {0}", pendingOrdersJson);

        String singleOrderJson = getResponse(accessToken, String.format(URL_SINGLE_ORDER, "3353246000022471593"), METHOD_GET).getText();
        logger.infov("Single Order {0}", singleOrderJson);
        
        doProcess(accessToken);
    }
    
    private void doProcess(String accessToken) {
        // read tblScan for any records that have an order number and serial number that are not completed sent and not 5 tries
        // loop through serialNumbers and find a detail record and update it

        System.out.println("getting List");
        List<Scan> scans = scanService.listReadyForTransmission();
        System.out.println(Arrays.toString(scans.toArray()));
        for (Scan scan : scans) {
            processScan(accessToken, scan);
        }
    }
}
    
@Service
public class ScanServiceImpl implements ScanService {

    @Autowired 
    ScanDao scanDao;
    
    @Override
    @Transactional
    public List<Scan> listReadyForTransmission() {
        System.out.println("Calling the dao for list");
        return scanDao.listReadyForTransmission();
    }
}

我的日志：

14:42:08 INFO [pool-5-thread-1]:web.InterfaceThread.run()72 - Pending Orders {Returned JSON}
14:42:09 INFO [pool-5-thread-1]:web.InterfaceThread.run()75 - Single Order {Returned JSON}
getting List

所以你可以从日志中看到 Pending Orders 有效，Single Order 有效，然后进入“getting list”，后面应该紧跟着“Calling the dao for list”，但是线程被阻塞了.为什么会这样，我该如何阻止它？

Answer 1

您很可能会陷入处理 @Transactional 注释的任何拦截器中。

要调试它，我建议使用 JDK 附带的the jstack utility（与java 在同一目录中）；它将转储所有正在运行的线程的堆栈跟踪，因此您可以看到该线程挂起的位置。