Access Properties of a new Stream in Esper

Question

I'm starting a new stream by using the statement:

insert into middleLayerStream 
    select id, 'response' as constraint 
    from[...]

Afterwards I'm starting a SELECT-query to the middleLayerStream. In die update-function of my middleLayerStream I want to print out the properties of the stream.

This is my update function:

public class MiddleLayerListener implement UpdateListener {
   public void update(EventBean[] newEvents, EventBean[] oldEvents) {
      EventBeant[] event = newEvents[0];
      System.out.println(event.getUnderlying());
   }
}

When the update-function is called, I don't get the properties but this statement instead:

{a=MapEventBean eventType=com.espertech.esper.event.map.MapEventType@52500920, b=MapEventBean eventType=com.espertech.esper.event.map.MapEventType@52500920}

How do I get access to the properties?

I just found out, that event is not a simple EventBean but a MapEventBean. Maybe it's because two different types of events (but with the same properties) are inserted into the stream. But how can i handle a MapEventBean and get the properties out of it?

Thank you very much for your help.

Answer 1

The EventBean interface offers a "get" method that returns an event property value by name.

public void update(EventBean[] newEvents, EventBean[] oldEvents){
  for (EventBean event : newEvents) {
    System.out.println(event.get("id"));
  }
}

You left off the "from" in your post so it wasn't possible to see what was selected. I assume that you have a pattern in the "from" such as "a=A -> b=B".

In the case of a pattern returning a nested event event.get("a.id") or event.get("a") or event.getFragment("a") or select a.id as id from [...] would do.

Answer 2

Ok I got it.. In my SELECT Query that ist starting the update function of MiddleLayerListener I selected * like

SELECT * from pattern[every a=.... -> b=...]

So of course there a both events in a MapEventBean (a and b). By specifying the SELECT Query like:

SELECT a.id as id from pattern...

In now have only the wanted properties in my stream and can access them as normal.

Wow.. that took me a whole day of desperation :D

Thank your very much for your help :)