Guava EventBus Multiple subscribers same tpe - guava

Question

import com.google.common.eventbus.EventBus;
import com.google.common.eventbus.Subscribe;
public class Test {
public static class Processing { }
public static class ProcessingResults { }
public static class ProcessingFinished { }
public static EventBus bus = new EventBus();
#Subscribe
public void receiveStartRequest(Processing evt) {
System.out.println("Got processing request - starting processing");
}
#Subscribe
public void processingStarted(Processing evt) {
System.out.println("Processing has started");
}
#Subscribe
public void resultsReceived(ProcessingResults evt) {
System.out.println("got results");
}
#Subscribe
public void processingComplete(ProcessingFinished evt) {
System.out.println("Processing has completed");
}
public static void main(String[] args) {
Test t = new Test();
bus.register(t);
bus.post(new Processing());
}
}
So, in above example, it can be seen that there are 2 subscribers accepting same type Processing. Now, at the time of post(), which all functions will get called? If the 2 functions receiveStartRequest and processingStarted will get called, then in which order they will be get called?

Answer 1

Both your methods will be called and in no predefinite order.
To counter this, just create two extra classes: ProcessingStarted and ProcessingRequested.
public class ProcessingStarted {
private Processing processing;
// Constructors
// Getters/Setters
}
public class ProcessingStarted {
private Processing processing;
// Constructors
// Getters/Setters
}
Then call post(new ProcessingRequested(processing)) and post(new ProcessingStarted(processing)) when needed, instead of a single post(processing).