I'm getting the following error from Guava eventBus when attempting to unregister a handler.
java.lang.IllegalArgumentException: missing event handler for an annotated method. Is [DerivedClass] registered?" at com.google.common.eventbus.EventBus.unregister(EventBus.java:227)
There is an identical question already answered, but the root cause was a client coding error.
In my case, I'm doing everything very simply, and yet still running into the issue.
The client code is an Apache Camel Processor bean, which is running with multiple threads (only 2 in this case). Although eventBus is designed to be thread-safe, the error has only surfaced at time of high traffic, and has only been raised a few times after 1000s of invocations.
The handler instance just stores the Camel Exchange, and if the construction failed, we would fail fast.
public void process(Exchange exchange) throws Exception {
MyHandler evHandler = new MyHandler(exchange);
eventBus.register(evHandler);
try {
doStuff(exchange);
}
catch (Foo bar) {
// stuff
}
finally {
eventBus.unregister(evHandler);
}
}
From reading the EventBus source code, it seems that Guava 14 onwards does sufficient locking to avoid this problem, whereas Guava 13 and below does not do any locking. Can you use a newer version of Guava?
(It's clear from the error message that you're not on the latest Guava, as Guava 16 onwards calls handlers "subscribers" instead.)
Related
Why would you use a Consumer
public Consumer<String> setValue();
instead of direct function call
public void setValue(String value);
for setters?
I only see disadvantages:
the direct method call is more readable
another disadvantage of the Consumer variant is, that the calling code must always handle exceptions explicitly
try {
instance.setValue().accept("newValue");
} catch (Exception e) {
// handle exception
}
Consumer is an interface intended mostly for internal use within RxJava. Since you are getting started with RxJava, you shouldn't worry about it.
The whole purpose of RxJava is to flow data, the more you use it the less you handle state or use setters.
You must use the Consumer, when you cannot use method references for some reason: e.g. when you target older Android versions, that don't support Java8.
Note: with the new Android toolchain, Java8 method references are supported directly (even without Retrolambda, etc.), so this is not required anymore.
Thanks to Jake Wharton who answered in rx-preferences #96
I'm relatively new to REST services in Java. I've created one and everything works fine except error handling. If I make a request with incorrectly formed JSON in it, Jackson JSON processor throws an exception which I unable to catch and I get error 500 in client. Exception follows:
javax.ws.rs.InternalServerErrorException: org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.util.HashSet out of VALUE_STRING token
I have no idea how to handle exceptions raised outside my code.
Google suggests using Exception Mappers or Phase Inteceptors. Though I could miss something in search results.
What is the proper way to handle such situations?
Please, advise something. I'm stuck with this problem...
A JAX-RS ExceptionMapper should do the job. Just add a class like below to your code and if you have the exception type right, then you should get the hook to customize the handling.
#Provider
public class MyExceptionMapper implements ExceptionMapper<MyException> {
#Override
public Response toResponse(MyException ex) {
return Response.status(Response.Status.BAD_REQUEST).build();
}
}
we have multiple instances of JBoss-Server in a clustered environment. For background tasks there is a global queue available, that manages all jobs registered at it. For this queue there is a simple listener (MDB) on each node, manages the incoming messages. This listener does a manual lookup (no injection) for a singleton bean and starts a pre defined method.
Everything works fine so far, but the method in the singleton bean uses some other (no singleton services) that are not available under some circumstances.
For example if a node will be restarted and there are left messages in the queue (not processed yet) the messages will be picked up by the listener and all further beans are null, so the job produces a NPE.
Is it possible to define a delay time in JMS-Listener after messages will be picked up or is it possible to define an "application completely deployed" hook in there? The DependsOn-Annotation does not work, because of the usage of non singletons.
A possibility can be to set the MDB-property "DeliveryActive" to false and start the bean after full deployment. Is there a simple, working way to do this programatically (not in jmx-console)? Any manuals for this I found, redirects me to a manual jndi lookup. I think it have to be possible to inject the Bean per annotation and call startDelivery()? Is there a good place to do this in application?
Another hint takes me to the initialise in order property in application.xml, because the problem might be connected to JBoss Deployment order (some EJBs will be later available than the listener), but there seems to be a bug in JBoss 6.0 and upgrading to 6.1. is not an option. Maybe there is a walkthrough for this?
I hope that the problem is well enough explained, otherwise please ask for further informations.
Thanks in advance,
Danny
Additional informations:
JBoss 6.0.0 Final
HornetQ 2.2.5 Final (already updated, because of the buggy default version of JBoss)
The Listener:
#MessageDriven(activationConfig =
{
#ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"),
#ActivationConfigProperty(propertyName = "destination", propertyValue = "/queue/SchedulerQueue")
})
public class SchedulerQueueListener implements MessageListener {
...
#Override
public void onMessage(Message message) {
...
service = (IScheduledWorkerService) new InitialContext().lookup(jndiName);
EJobResult eJobResult = service.executeJob(message);
...
}
A sample worker:
#Singleton
#LocalBinding(jndiBinding = SampleJobWorkerService.JNDI_NAME)
public class SampleJobWorkerService implements IScheduledWorkerService {
...
#EJB(name = "SampleEJB/local")
private ISampleEJB sampleEjb;
...
#Override
public EJobResult executeJob(Message message) {
int state = sampleEjb.doSomething(message.getLongProperty(A_PROPERTY));
}
In this case the sampleEjb - member will be null sometimes
As a workaround, instead of calling EJB's directly from MDB, you can create a timer with a timeout with some delay. Therefore there will be some delay in execution.
In Timer's timeout method, then you can call singleton EJB, which in case will call other non-singleton EJB's.
JBoss specific : Can try setting the property in the message object before sending.
msg.setLongProperty("JMS_JBOSS_SCHEDULED_DELIVERY", (current + delay));
Other alternative is _JBM_SCHED_DELIVERY.
Edit :
For 1st part, you can have JTA transaction, which may span across JMS & EJB. Therefore failover & other things may be handled accordingly.
You can also increase the redelivery delay for the message object.
<address-setting match="jms.queue.someQueue">
<redelivery-delay>5000</redelivery-delay>
</address-setting>
I am in the same trouble at the moment.
I propose you use EJB 3 startup bean annotation #Startup on your singleton bean to invoke the startDelivery method on your Message listeners.
I have a web service (built using jaxb/jaxws) that invokes a stateless EJB to store some data in the database. The data is being stored as an entity bean. The entity bean has a unique constraint applied to it via the #Column(unique = true) annotation.
When the web service attempts to save data, the transaction fails, and rightfully so. The problem is that since I am using CMP, the transaction is not committed until after the call to the stateless EJB. The end result is that I am not able to trap the exception and it is getting funneled up to the WS stack and results in an ambiguous fault containing the string: Error committing transaction:;nested exception is: weblogic.transaction.internal.AppSetRollbackOnlyException.
Is there a way to catch the exception being thrown so I can provide more information to the caller? Thank you.
Version information:
Application Server: Oracle Weblogic 10.3
Persistence Provider: Hibernate 3.2.5.ga (JPA 1.0)
JDK/JRE: 1.6_0_05 (provided by Weblogic install)
Update:
I tried to implement an EJB 3 interceptor around the method invocation and this does not appear to work.
public class TestInterceptor {
#AroundInvoke
public Object logCall(InvocationContext context) throws Exception {
System.out.println("Invoking method: " + context.getMethod().getName());
try {
return context.proceed();
} catch (Throwable t) {
System.out.println("I caught an exception: " + t.getMessage());
throw new Exception(t);
}
}
The reason I think this doesn't work is because the processing chain is such that the actual persist happens outside of the method (of course).
You could try using Bean Validation. It's nicely connected with the JPA (invoked during pre-persist, pre-update and pre-remove phases and can be used in different layers of your application.
Unfortunately, as far as I know, if a validation constraint violation occurs, the transaction is marked for rollback... I don't know how you could cope with that but one (seems nasty and untested) way I could think of is to inject a ValidatorFactory and validate the object by yourself. Perhaps then you could catch the ValidationException.
EDIT: I'm not sure if the Bean Validation was available in Java EE 5.
EDIT 2: You can create an interceptor which will catch the exception thrown by the JPA (or more precisely by the database). As the interceptor is invoked as a part of the same transaction as the EJB method you might need to explicitly invoke EntityManager#flush(-) to synchronise changes with the database.
I have a stateless bean resposible for persisting entities to a database. This stateless bean is called by a message bean's onMessage method. The wired thing is that on the first message everything works fine, but on the next message the method responsible for persisting is invoked outside a transaction, even though the method is annotated with REQUIRES_NEW.
#TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public StateChange persistChange(long deviceId, ...) {
...
StateChange change = new StateChange(...);
em.persist(change);
em.refresh(change); // To provoke the error
return change;
}
Calling refresh triggers the following exception:
Caused by: javax.persistence.TransactionRequiredException: no transaction is in progress
Any ideas? I'm fairly new to JTA so I might have missed something important?
I tried a lot to solve it and after about 16 hours or so it seems to be working. I'm not sure exactly what did the trick, but it might be the upgrade to Glassfish 2.1.
Finally able to sleep at night again!