在单例 Bean 中调用监视服务的问题

Question

我们想定期监视文件的更改，我们正在使用 jboss 7 。以下是我的代码片段。我在单例 bean 的 postconstruct 方法中初始化了观察程序，并安排了一个轮询监视事件的方法。当我第一次修改文件时，我可以观察到更改，但是没有收到对文件的后续修改。任何人都可以让我知道可能是什么问题

  @Startup
  @ConcurrencyManagement(ConcurrencyManagementType.BEAN)
  @Interceptors(NonThrowingPostConstructInterceptor.class)
  @Singleton
  @Service
  @LocalBinding(jndiBinding=IHeartBeatProducerService.JNDI_LOCAL_BINDING)
 public class HeartBeatProducerService extends EMSingletonService implements IHeartBeatProducerService{
@EJB(mappedName=IMessageService.JNDI_LOCAL_BINDING)
public IMessageService messageService;
@EJB(mappedName=ICommandExecutionService.JNDI_LOCAL_BINDING)
public ICommandExecutionService commandService;
private final static String LAST_OPERATION_COMPLETED="Last Operation Completed";
private final static String STATUS="Status"; 
private WatchService watcher;
private Path dir;
private String concServer; 
public static final String TOPIC="foo";
private IMLogger logger = new IMLogger("foo");
private String content=null; 
@PostConstruct
@Override
public void init() {
    // TODO Auto-generated method stub
    super.init();
    try {

        watcher = FileSystems.getDefault().newWatchService();
        dir=Paths.get("/shared/foo");
        dir.register(watcher, StandardWatchEventKinds.ENTRY_MODIFY);
        logger.entering(0, IHeartBeatProducerService.class.getSimpleName(), "Initializing Heart Beat", new String[]{"Entered"});
    } catch (IOException e) {
        e.printStackTrace();
    }
}
@Schedule(second="*/10", minute = "*", hour="*")
private void checkStatus()
{
    logger.entering(0, IHeartBeatProducerService.class.getSimpleName(), "Checking Status", new String[]{"Entered"});
    final String[] command={"pidof","server"};
    commandService.run(command, null, false);
    concServer=(commandService.getExitCode()==0)?"UP":"DOWN";
    if(concServer.equals("UP"))
    {
        watch();
    }
    else
    {
        content="foo:Failed";
    }
    produce();
}

public void watch()
{       
        logger.entering(0, IHeartBeatProducerService.class.getSimpleName(), "Entering watch()", new String[]{"Entered"});
        WatchKey key = null;
        try 
        {           
         key = watcher.take();
        }
        catch (InterruptedException e)
        {               
            logger.error(HeartBeatProducerService.class.getSimpleName(),"Interupted Exception " +  e.getMessage());
        }
        for ( WatchEvent<?> event: key.pollEvents())
        {
            WatchEvent.Kind kind = event.kind();
            logger.info(HeartBeatProducerService.class.getSimpleName(),"Watch Event :" + kind.name()); 
            if(kind.name().equals("OVERFLOW"))
            {
                continue;
            }
            if(kind.name().equals("ENTRY_MODIFY"))
            {
                Path concLog = (Path) event.context();
                logger.info(HeartBeatProducerService.class.getSimpleName(),"Modified File Name:" + concLog.getFileName()); 
                if(concLog.endsWith("current_status.txt"))
                {
                    logger.info(HeartBeatProducerService.class.getSimpleName(), "Reading Status");                  
                    readStatus();
                }
            }
        }
        boolean valid = key.reset();
        if ( !valid)
        {               
            logger.error(HeartBeatProducerService.class.getSimpleName(),"Key Unregistered"); 
        }
}


private void parse(String output)
{       
    // parse file contents
}
private void readStatus() {
    //read status and parse()
}
private void produce() 
{
    try {
        messageService.publish(TOPIC, content, PublishType.ASync);
    } catch (MessageException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

}

已经有一个链接解释了与@Asynchronous标签相同的内容(EJB 3.1 和 NIO2：监视文件系统(。 但是我需要知道这种方法可能出了什么问题。

Answer 1

监视方法需要在无限循环中运行。现在发生的事情是，在

     try {           
       key = watcher.take();
     }

处理事件，然后 watch(( 方法完成。尝试效果

     for(;;) {

在

上述行之前，在有效性检查后结束 for 块。你看过 Java 教程中的示例吗？