Multithreading issue with executeService for Dependency Injection inside Runnable class

Support
#1

Hi…
I want to use executeService in a bean for multi threading…

        ExportHelper exportHelper = new ExportHelper();
        ExecutorService executorService = Executors.newFixedThreadPool(4);
        executorService.execute(exportHelper);
        executorService.shutdown();

The Self managed ExportHelper Class implements Runnable, in which we are injecting the bean inside the ExportHelper class specified below.

public class ExportHelper implements Runnable {

    @Autowired
    private NewBean newBean;
    private static final Logger log = LoggerFactory.getLogger(ExportHelper.class);

    @Override
    public void run() {
       String name = newBean.getName();
       log.info(name);
    }
}

@Component
public class NewBean {
    public String getName() {
        return "Hello World!";
    }
}

I am unable to use the newBean service inside the ExportHelper class and getting the below error,

Exception in thread “pool-3-thread-1” java.lang.NullPointerException
at com.company.multithread.core.ExportHelper.run(ExportHelper.java:16)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)

Note: I presume it is because of improper dependency injection (invalid SecurityContext) inside the ExportHelper class, So, plz help how to execute multithreading on Runnable class with dependency injection.

Thanks.

#2

Dependency injection with @Autowired works only in beans (classes annotated with @Component, etc.), that’s why you get NPE.

Why wouldn’t make the ExportHelper a bean?

@Component
public class ExportHelper implements Runnable {
// ...

Of course then you should also inject it or get through ApplicationContext instead of using new.
If it needs some state which is not thread-safe, make it a prototype:

@Component
@Scope(BeanDefinition.SCOPE_PROTOTYPE)
public class ExportHelper implements Runnable {
// ...

and get via ApplicationContext:

ExportHelper exportHelper = applicationContext.getBean(ExportHelper.class);
//...
1 Like
#3

Hi @krivopustov ,
Applicated your solution… Thanks…