Can not run few methods sequentially when Spring Boot starts - spring

Question

I have to run a few methods when Application starts, like the following:
#SpringBootApplication
public class Application implements CommandLineRunner {
private final MonitoringService monitoringService;
private final QrReaderServer qrReaderServer;
#Override
public void run(String... args) {
monitoringService.launchMonitoring();
qrReaderServer.launchServer();
}
However, only the first one is executed! And the application is started:
... Started Application in 5.21 seconds (JVM running for 6.336)
... START_MONITORING for folder: D:\results
The second one is always skipped!
If change the call order - the only the second one will be executed.
Could not find any solution for launching both at the beginning - tried #PostConstruct, ApplicationRunner, #EventListener(ApplicationReadyEvent.class)...
Looks like they are blocking each other somehow. Despite the fact that both have void type.
Monitoring launch implementation:
#Override
public void launchMonitoring() {
log.info("START_MONITORING for folder: {}", monitoringProperties.getFolder());
try {
WatchKey key;
while ((key = watchService.take()) != null) {
for (WatchEvent<?> event : key.pollEvents()) {
WatchEvent.Kind<?> kind = event.kind();
if (kind == ENTRY_CREATE) {
log.info("FILE_CREATED: {}", event.context());
// some delay for fully file upload
Thread.sleep(monitoringProperties.getFrequency());
String fullFileName = getFileName(event);
String fileName = FilenameUtils.removeExtension(fullFileName);
processResource(fullFileName, fileName);
}
}
key.reset();
}
} catch (InterruptedException e) {
log.error("interrupted exception for monitoring service", e);
} catch (IOException e) {
log.error("io exception while processing file", e);
}
}
QR Reader start (launch TCP server with Netty configuration):
#Override
public void launchServer() {
try {
ChannelFuture serverChannelFuture = serverBootstrap.bind(hostAddress).sync();
log.info("Server is STARTED : port {}", hostAddress.getPort());
serverChannel = serverChannelFuture.channel().closeFuture().sync().channel();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
shutdownQuietly();
}
}
How to solve this issue?

Answer 1

Start launchMonitoring() asynchronously.
The easiest way to do this is to enable Async by adding #EnableAsync on your Application
and then annotate launchMonitoring() with #Async
Not sure if launchServer() should also be started asynchronously.
EDIT: completed Answer
No task executor bean found for async processing: no bean of type TaskExecutor and no bean named 'taskExecutor' either
By default Spring will create a SimpleAsyncTaskExecutor, but you can provide your taskExecutor
Example:
#EnableAsync
#Configuration
public class AsyncConfig implements AsyncConfigurer {
#Override
public Executor getAsyncExecutor() {
ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
executor.set... // your custom configs
executor.initialize();
return executor;
}
...
}