Callable Task is not executing properly

Question

Hi I have created a simple task which is hitting one of the third party apis,

I tried to create a callable task and execute it in parallel with ExecutorService

       for (String script : allScripts) {
            callableTasks.add(new DataFetchTask(script,TimeInterval.get(interval),
                    Range.get(range)).newCallable());
        }
        final ExecutorService executorService = new ThreadPoolExecutor(1, 10,
                10000, TimeUnit.MILLISECONDS,
                new SynchronousQueue<Runnable>());
        try {
            System.out.println("Callable Tasks"+callableTasks.size());
            final Future<YahooFinResponse> yahooFinResponseFuture = executorService.submit(callableTasks.get(0));
            /*final List<Future<YahooFinResponse>> futures = executorService.invokeAll(callableTasks);
            for(Future<YahooFinResponse> future : futures) {
                yahooFinResponses.add(future.get());
            }*/
            return FinDataServiceUtil.writeResponsesToCSVFile(yahooFinResponses);
        } catch (Exception e) {
            e.printStackTrace();
        }

Task Class

@RequiredArgsConstructor
public class DataFetchTask {

    private final String script;
    private final TimeInterval timeInterval;
    private final Range timeRange;

    @Autowired
    YahooFinDataFetcher yahooFinDataFetcher;

    public Callable<YahooFinResponse> newCallable() {

        return new Callable<YahooFinResponse>() {

            public YahooFinResponse call() {
                System.out.println("Starting Job for Script"+script);
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("After wait");
                final YahooFinResponse yahooFinResponse = yahooFinDataFetcher.fetchData(script +
                        ".NS", timeInterval, timeRange);
                System.out.println("Returning from call"+yahooFinResponse.chart.error);
                return yahooFinResponse;
            }
        };
    }

}

Service class

@Component
public class YahooFinDataFetcher {

    private static final OkHttpClient client = new OkHttpClient();
    private static final Gson gson = new Gson();

    private static final String BASE_URL = "***;
    private static final String DOMAIN = "**";
    private static final String CORS_DOMAIN = "***";

    public YahooFinResponse fetchData (final String scriptName, final TimeInterval timeInterval,
            final Range range) {
        System.out.println("Calling Service");
        final Request request = new Request.Builder()
                .url(createUrl(scriptName, timeInterval, range))
                .build();

        final Call call = client.newCall(request);
        try {
            final Response response = call.execute();
            final String responseStr = response.body().string();
            final YahooFinResponse yahooFinResponse = gson.fromJson(responseStr,
                    YahooFinResponse.class);
            System.out.println(String.format("Returning Data For YahooFInResponse %s "
                    + "\n",yahooFinResponse));
            return yahooFinResponse;
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println(String.format("Returning null from fetchData for %s  TimeInterval %s, "
                + "Range %s \n",scriptName,timeInterval,range));
        return null;
    }

I am getting output as

Size5list[RELIANCE, SBIN, YESBANK, ITC, VEDL]
Callable Tasks5
Starting Job for ScriptRELIANCE
After wait

But not getting output of job completion,

I tried with reducing job size, Changing creation of ExecutorService with FixedThreadPool and CachedThreadPool

Changing DataFetchTask to newCallable as method and earlier this class itself was implementing Callable<T> directly

When i try to get future.get() it is giving NullPointerException

I tried multiple things, but not sure what is wrong with Callable task creation.

I am hitting service through the controller

Answer 1

Your yahooFinDataFetcher is probably null since IOC was not able to inject an instance of it. DataFetchTask is not being handle as a component.

Try to manually instantiate yahooFinDataFetcher at DataFetchTask and see if it was reallly the case

@RequiredArgsConstructor
public class DataFetchTask {

    private final String script;
    private final TimeInterval timeInterval;
    private final Range timeRange;

    @Autowired
    YahooFinDataFetcher yahooFinDataFetcher = new YahooFinDataFetcher();

   ...