Spring Bean running in its own thread

Question

Within my web application, I am trying to create a directory polling bean using Java SDK7 WatchService. What I would like to achieve is to run this bean in its own thread so that it does not block the application. Something like:

  <bean id="directoryPoller" class="org...MyDirectoryPoller" scope="thread"/>

Answer 1

I am afraid you will have to create this thread manually with Spring:

<bean id="pollThread" class="java.lang.Thread" init-method="start" destroy-method="interrupt">
    <constructor-arg ref="watchServiceRunnableWrapper"/>
</bean>

<bean id="watchServiceRunnableWrapper" class="WatchServiceRunnableWrapper">
    <constructor-arg ref="watchService"/>
</bean>

<bean id="WatchService" class="java.nio.file.WatchService" destroy-method="close"/>

The WatchServiceRunnableWrapper is simple:

public class WatchServiceRunnableWrapper implements Runnable {

    private WatchService WatchService;

    public WatchServiceRunnableWrapper(WatchService watchService) {
        this.watchService = watchService;
    }

    public void run() {
        watchService.poll();
        //
    }
}

I haven't tested it, but it more-or-less should work and shutdown gracefully.

Answer 2

I'm not familiar with Java 7's WatchService, but you could use Springs' scheduling support for this. Here's yet another tutorial and googling for something like Spring Scheduled probably finds loads more.