@Override
    protected void mapAndProcess(Object eventObject, InputEventHandler inputEventHandler)
            throws MappingFailedException, InterruptedException {
        if (eventObject != null) {
            if (eventObject instanceof Event) {
                Event event = ((Event) eventObject);
                event.getData()[0] = sourceOptionHolder.validateAndGetOption("topic").getValue(event);
                event.getData()[1] = sourceType;
                inputEventHandler.sendEvent((Event) eventObject);
            } else {
                throw new MappingFailedException(Collections.singletonList(
                        new ErroneousEvent(eventObject, "Event object must be Event " +
                                "but found " + eventObject.getClass().getCanonicalName())));
            }
        }

    }
Event Mapper implementation to handle pass-through scenario where user does not need to do any mapping.
modules/siddhi-core/src/test/java/io/siddhi/core/transport/TestSourceOptionSourceMapper.java