I'm kinda stuck with a problem that - I guess - is pretty common.
I run a Wildfly 12 with Java EE 8 profile enabled (including CDI 2.0) and I'm using JTA.
So what's the problem: I have an @ApplicationScoped bean that fires an asynchronous event. Another @ApplicationScoped bean observes this event via @ObservesAsync. Within the observer, I want to process some propagated metadata and also interact with the database. I have a repository class annotated with @Transactional for that. The setup looks like this:
A simple example would look like this:
@ApplicationScoped
public class ClassA {
@Inject
private Event<ApplicationStarted> applicationStartedEvent;
public void initialize(@Observes @Initialized(ApplicationScoped.class) Object init) {
applicationStartedEvent.fireAsync(new ApplicationStarted());
}
}
@ApplicationScoped
public class ClassB {
@Inject
private Repository repository;
public void onApplicationStarted(@ObservesAsync ApplicationStarted applicationStarted) {
repository.getSomethingFromDatabase();
}
}
@Transactional
@Dependent
public class Repository {
@PersistenceContext
private EntityManager entityManager;
public List<Object> getSomethingFromDatabase() {
return entityManager.createQuery("from User").getResultList();
}
}
Unfortunately I can't get this code snippet work. There's a weird exception I don't understand when
repository.getSomethingFromDatabase();
is executed.
17:17:53,611 ERROR [stderr] (Weld Thread Pool -- 3) java.lang.NullPointerException
17:17:53,611 ERROR [stderr] (Weld Thread Pool -- 3) at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:936)
17:17:53,611 ERROR [stderr] (Weld Thread Pool -- 3) at org.wildfly.common.context.ContextManager.getPrivileged(ContextManager.java:271)
17:17:53,611 ERROR [stderr] (Weld Thread Pool -- 3) at org.wildfly.transaction.client.LocalTransactionContext.getCurrent(LocalTransactionContext.java:115)
17:17:53,612 ERROR [stderr] (Weld Thread Pool -- 3) at org.wildfly.transaction.client.ContextTransactionManager.begin(ContextTransactionManager.java:62)
17:17:53,612 ERROR [stderr] (Weld Thread Pool -- 3) at org.wildfly.transaction.client.ContextTransactionManager.begin(ContextTransactionManager.java:54)
17:17:53,612 ERROR [stderr] (Weld Thread Pool -- 3) at com.arjuna.ats.jta.cdi.transactional.TransactionalInterceptorBase.invokeInOurTx(TransactionalInterceptorBase.java:116)
17:17:53,612 ERROR [stderr] (Weld Thread Pool -- 3) at com.arjuna.ats.jta.cdi.transactional.TransactionalInterceptorRequired.doIntercept(TransactionalInterceptorRequired.java:53)
17:17:53,612 ERROR [stderr] (Weld Thread Pool -- 3) at com.arjuna.ats.jta.cdi.transactional.TransactionalInterceptorBase.intercept(TransactionalInterceptorBase.java:79)
17:17:53,613 ERROR [stderr] (Weld Thread Pool -- 3) at com.arjuna.ats.jta.cdi.transactional.TransactionalInterceptorRequired.intercept(TransactionalInterceptorRequired.java:47)
17:17:53,613 ERROR [stderr] (Weld Thread Pool -- 3) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
17:17:53,613 ERROR [stderr] (Weld Thread Pool -- 3) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
17:17:53,614 ERROR [stderr] (Weld Thread Pool -- 3) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
17:17:53,614 ERROR [stderr] (Weld Thread Pool -- 3) at java.lang.reflect.Method.invoke(Method.java:498)
17:17:53,614 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.interceptor.reader.SimpleInterceptorInvocation$SimpleMethodInvocation.invoke(SimpleInterceptorInvocation.java:73)
17:17:53,614 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.interceptor.proxy.InterceptorMethodHandler.executeAroundInvoke(InterceptorMethodHandler.java:84)
17:17:53,614 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.interceptor.proxy.InterceptorMethodHandler.executeInterception(InterceptorMethodHandler.java:72)
17:17:53,614 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.interceptor.proxy.InterceptorMethodHandler.invoke(InterceptorMethodHandler.java:56)
17:17:53,614 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.bean.proxy.CombinedInterceptorAndDecoratorStackMethodHandler.invoke(CombinedInterceptorAndDecoratorStackMethodHandler.java:79)
17:17:53,615 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.bean.proxy.CombinedInterceptorAndDecoratorStackMethodHandler.invoke(CombinedInterceptorAndDecoratorStackMethodHandler.java:68)
17:17:53,615 ERROR [stderr] (Weld Thread Pool -- 3) at com.auroraspotter.kp.Repo$Proxy$_$$_WeldSubclass.getSomethingFromDatabase(Unknown Source)
17:17:53,615 ERROR [stderr] (Weld Thread Pool -- 3) at com.auroraspotter.kp.KpIndexUpdateCronControl.onApplicationStarted(KpIndexUpdateCronControl.java:48)
17:17:53,615 ERROR [stderr] (Weld Thread Pool -- 3) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
17:17:53,616 ERROR [stderr] (Weld Thread Pool -- 3) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
17:17:53,616 ERROR [stderr] (Weld Thread Pool -- 3) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
17:17:53,616 ERROR [stderr] (Weld Thread Pool -- 3) at java.lang.reflect.Method.invoke(Method.java:498)
17:17:53,616 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.injection.StaticMethodInjectionPoint.invoke(StaticMethodInjectionPoint.java:95)
17:17:53,617 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.injection.StaticMethodInjectionPoint.invoke(StaticMethodInjectionPoint.java:85)
17:17:53,617 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.injection.MethodInvocationStrategy$DefaultMethodInvocationStrategy.invoke(MethodInvocationStrategy.java:109)
17:17:53,617 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.event.ObserverMethodImpl.sendEvent(ObserverMethodImpl.java:330)
17:17:53,617 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.event.ObserverMethodImpl.sendEvent(ObserverMethodImpl.java:308)
17:17:53,617 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.event.ObserverMethodImpl.notify(ObserverMethodImpl.java:286)
17:17:53,617 ERROR [stderr] (Weld Thread Pool -- 3) at javax.enterprise.inject.spi.ObserverMethod.notify(ObserverMethod.java:124)
17:17:53,617 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.util.Observers.notify(Observers.java:170)
17:17:53,618 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.event.ObserverNotifier.notifyAsyncObserver(ObserverNotifier.java:413)
17:17:53,618 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.event.ObserverNotifier.lambda$notifyAsyncObservers$5(ObserverNotifier.java:356)
17:17:53,618 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.event.ObserverNotifier.lambda$null$8(ObserverNotifier.java:438)
17:17:53,618 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.security.spi.SecurityServices.lambda$getSecurityContextAssociator$0(SecurityServices.java:80)
17:17:53,618 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.weld.event.ObserverNotifier.lambda$createSupplier$9(ObserverNotifier.java:435)
17:17:53,618 ERROR [stderr] (Weld Thread Pool -- 3) at java.util.concurrent.CompletableFuture$AsyncSupply.run$$$capture(CompletableFuture.java:1590)
17:17:53,618 ERROR [stderr] (Weld Thread Pool -- 3) at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java)
17:17:53,618 ERROR [stderr] (Weld Thread Pool -- 3) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
17:17:53,619 ERROR [stderr] (Weld Thread Pool -- 3) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
17:17:53,619 ERROR [stderr] (Weld Thread Pool -- 3) at java.lang.Thread.run(Thread.java:748)
17:17:53,619 ERROR [stderr] (Weld Thread Pool -- 3) at org.jboss.threads.JBossThread.run(JBossThread.java:485)
If I run the same code with a synchronous event, everything works fine.
So what am I missing?
I finally found the solution.
Since the observer is asynchrounsly there is no container managed transaction available (which makes aboslutely sense, cause the transaction can't span around multiple threads). So I need to start a transaction on my own.
Unfortunately this didn't work either. After hours of debugging I finally found the root cause, though. For some reason Wildfly's ContextManager threw an NPE because there was no class loader available in the observer class (ClassB). Fortunately there is already a bugfix available for the module wildfly-common. So I just upgraded from version 1.3.0.Final to 1.3.1.Final.
The final code looks like this:
@ApplicationScoped
public class Observer {
@Inject
private Repository repository;
public void onApplicationStarted(@ObservesAsync ApplicationStarted applicationStarted) throws Exception {
UserTransaction userTransaction = (UserTransaction) new InitialContext().lookup("java:jboss/UserTransaction");
userTransaction.begin();
try {
repository.getSomethingFromDatabase();
// or repository.persistSomething();
} catch (Exception e) {
e.printStackTrace();
}
userTransaction.commit();
}
}