使 FileAlterationListenerAdaptor.onFileCreate() 始終為單線程，apache.commons.io.monitor

Question

我正在覆蓋org.apache.commons.io.monitor.FileAlterationListener接口的onFileCreate()方法。

該方法有效，但我發現有時它會產生兩個線程，我不完全理解是什么觸發了這種行為。

WatchService 類

@Component
@Slf4j(topic="watchService")
public class WatchService {

    private static RestTemplate restTemplate;
    private static Environment env;

    @Autowired
    public WatchService(RestTemplate restTemplate, Environment env) {
        WatchService.restTemplate = restTemplate;
        WatchService.env = env;
    }


    //When a new file is created inside a folder, the file content is sent to kafka
    @Bean
    public static void startFolderPolling() throws Exception {
        FileAlterationObserver observer = new FileAlterationObserver(env.getRequiredProperty("folder"));
        FileAlterationMonitor monitor = new FileAlterationMonitor(5000);
        log.info("setup completed");
        FileAlterationListener listener = new FileAlterationListenerAdaptor() {
            @Override
            public void onFileCreate(File file) {
                log.info("are you single thread ?");
                try {
                    String data = FileUtils.readFileToString(file, "UTF-8");
                    HttpHeaders headers = new HttpHeaders();
                    headers.setContentType(MediaType.APPLICATION_JSON);

                    HttpEntity<String> entity = new HttpEntity<String>(data,headers);
                    log.info("Calling Kakfa microservice");
                    String answer = restTemplate.postForObject("http://kafka/api/messages/receiveSapOrder", entity, String.class);
                    log.info("sending SAP Order result:" + answer);

                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        };
        observer.addListener(listener);
        monitor.addObserver(observer);
        monitor.start();
    }
}

主要方法

@SpringBootApplication
@EnableEurekaClient
public class DirectoryListenerApplication {

   public static void main(String[] args) throws Exception {
       SpringApplication.run(DirectoryListenerApplication.class, args);
       startFolderPolling();
   }
}

對於在文件夾中創建的相同文件，有時該方法在兩個單獨的線程中記錄兩個調用，有時該方法在一個線程中只記錄一個調用。

2022-05-10 09:46:42.382  INFO 88330 --- [           main] watchService                             : setup completed
2022-05-10 09:46:42.397  INFO 88330 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_SAP-LISTENER/192.168.2.63:sap-listener:8095 - registration status: 204
2022-05-10 09:46:57.394  INFO 88330 --- [       Thread-4] watchService                             : are you single thread ?
2022-05-10 09:46:57.423  INFO 88330 --- [       Thread-4] watchService                             : Calling Kakfa microservice
2022-05-10 09:46:58.788  INFO 88330 --- [       Thread-4] watchService                             : sending SAP Order result:{"message":"Uploaded the file successfully"}
2022-05-10 09:47:00.108  INFO 88330 --- [       Thread-2] watchService                             : are you single thread ?
2022-05-10 09:47:00.112  INFO 88330 --- [       Thread-2] watchService                             : Calling Kakfa microservice
2022-05-10 09:47:00.197  INFO 88330 --- [       Thread-2] watchService                             : sending SAP Order result:{"message":"Uploaded the file successfully"}

是否可以強制單線程行為？

Answer 1

我在startFolderPolling方法上刪除了 SprigBoot @Bean表示法，現在只創建了一個線程。