Java基于系统api监控文件新增事件

得益于jvm对系统api的封装，本文的方法实际是对jvm封装后的方法的再次封装。

在linux上，对应的api为inotify，在windows上，对应的api则为ReadDirectoryChangesW。

本文应用的jdk版本为8。

业务字段：

@Data
public class FileMessageDto {

  private LocalDateTime createTime;

  private String hostName;

  private String channel;

  private String directory;

  private String fileName;

  private String filePath;

}

主类：

@Slf4j
@Service
public class ListenerService {

  @Value("#{${listenerservice.paths}}")
  private Map<String, String> watchPaths;

  @Value("#{${listenerservice.directory}}")
  private Map<String, String> directoryMap;

  private static final BlockingQueue<FileMessageDto> QUEUE = new LinkedBlockingQueue<>();

  private static final int CONCURRENT_SUBMIT_THREADS = Runtime.getRuntime().availableProcessors() * 2;

  @Value("${listenerservice.duplicationRemoveTime:15}")
  private int redisDuplicationRemoveTime;

  @Value("#{'${listenerservice.fastChannels:}'.split(',')}")
  private Set<String> fastChannels;

  @Autowired
  private KafkaTemplate<String, KafkaMessage<FileMessageDto>> kafkaTemplate;

  @Autowired
  private RedisLockService redisLockService;

  public int getQueueSize() {
    return QUEUE.size();
  }


  @PostConstruct
  public void init() {
    Runnable kafkaPusher = () -> {
      while (true) {
        FileMessageDto dto;
        try {
          dto = QUEUE.take();
        } catch (InterruptedException e) {
          Thread.currentThread().interrupt();
          return;//不可达
        }
        KafkaMessage<FileMessageDto> msg = new KafkaMessage<>();
        msg.setData(dto);
        String topic;
        if (fastChannels.contains(dto.getChannel())) {
          topic = KafkaMsgTopics.FILE_NAME_FAST;
        } else {
          topic = KafkaMsgTopics.FILE_NAME_SLOW;
        }
        try {
          kafkaTemplate.send(topic, msg);
          log.info(topic + "发送" + msg);
        } catch (Exception e) {
          log.error("", e);
        }
      }
    };
    ExecutorService committerPool = getThreadsPool(CONCURRENT_SUBMIT_THREADS, "_COMMITTER_");
    for (int i = 0; i < CONCURRENT_SUBMIT_THREADS; i++) {
      committerPool.execute(kafkaPusher);
    }
    ExecutorService listenerPool = getThreadsPool(watchPaths.size(), "_LISTENER_");
    for (Map.Entry<String, String> e : watchPaths.entrySet()) {
      String directory = directoryMap.get(e.getKey());
      if (directory == null) {
        throw new IllegalArgumentException("未正确配置路径");
      }
      Task task = new Task(e.getKey(), directory, e.getValue());
      listenerPool.execute(task.listener);
    }
  }

  private ExecutorService getThreadsPool(int concurrentSubmitThreads, String threadNamePrefix) {
    return new ThreadPoolExecutor(
        concurrentSubmitThreads, concurrentSubmitThreads, 60L,
        TimeUnit.SECONDS, new SynchronousQueue<>(),
        new CustomizableThreadFactory(this.getClass().getSimpleName() + threadNamePrefix));
  }


  @RequiredArgsConstructor
  @EqualsAndHashCode(of = {"channel"})
  static class Task {
    @NonNull
    private final String channel;
    @NonNull
    private final String directory;
    @NonNull
    private final String pathStr;
    private final Runnable listener;

    @SuppressWarnings("all")
    public Task(@NonNull String channel, @NonNull String directory, @NonNull String pathStr) {
      this.channel = channel;
      this.directory = directory;
      this.pathStr = pathStr;
      this.listener = () -> {
        while (true) {
          try {
            watcherWrap();
          } catch (Exception e) {
            log.error(this.channel + "监控出错,重启监控", e);
          }
          try {
            Thread.sleep(10000);
          } catch (InterruptedException e) {
            throw new BusinessException(e.getMessage());
          }
        }

      };
    }

    private void watcherWrap() {
      try (WatchService watchService = FileSystems.getDefault().newWatchService()) {
        Path path = Paths.get(this.pathStr);
        path.register(watchService, StandardWatchEventKinds.ENTRY_CREATE);
        log.info("监控开始,渠道:{},路径:{}", channel, pathStr);

        while (true) {
          WatchKey key = watchService.take();
          List<WatchEvent<?>> watchEvents = key.pollEvents();
          for (WatchEvent<?> event : watchEvents) {
            FileMessageDto dto = new FileMessageDto();
            dto.setCreateTime(LocalDateTime.now());
            dto.setHostName(HostNameUtil.getHostName());
            dto.setChannel(this.channel);
            dto.setDirectory(this.directory);
            dto.setFileName(event.context().toString());
            dto.setFilePath(path.toString());

            QUEUE.put(dto);
          }
          boolean valid = key.reset();
          if (!valid) {
            throw new SystemException(String.format("监控中断，渠道:%s,路径:%s", channel, pathStr));
          }
        }

      } catch (IOException e) {
        log.error("监控失败,渠道:{},路径:{}", channel, pathStr);
        log.error("", e);
      } catch (InterruptedException e) {
        log.error("监控中断,渠道:{},路径:{}", channel, pathStr);
        log.error("", e);
        Thread.currentThread().interrupt();
      }
    }


  }

实际上，BlockingQueue<FileMessageDto> QUEUE = new LinkedBlockingQueue<>()这个队列应该可以不要或者设置一个比较小的容量，此处是为了能察觉kafka推送是否顺畅。