Throw exception from Guava EventBus subscriber

Question

I am using Guava EventBus in sync. How can I rollback the complete transaction if any of the subscribers throw an Exception? How can I throw an Exception which will not be caught by the EventBus Subscriber?

Answer 1

I solved it using java.lang.ThreadLocal variable across the publisher and the subscriber.

Publisher needs to be wrapped in a class which reads thread local exception and throws it

public void publish(Event event) {
  eventBus.post(event);
  if(threadLocalException != null) {
    Store threadLocalException in some variable say e
    Clear threadLocalException variable
    throw e;
  }
}

Subscriber needs to be wrapped in a class to set the exception in thread local variable

public abstract class EventSubscriber<T extends Event> {

  @Subscribe
  public void invoke(T event) {
    try {
      handle(event);
    } catch (Exception e) {
      Set thread local variable to e
    }
  }

  protected abstract void handle(T event);

}