Thanks Matti.

I have used prosys java sdk for UA client server developement.

In my UAClient, I would like to subscribe to a parent node of opcua server whose child nodes can be dynamically updated(added or removed) at run time.
I assumed that on addition of any child node, MonitoredEventItemListener’s onEvent() method will be called (similar to calling onDataChange() method in AtoMonitoredDataItemListener on value change when subscribed to Valued attributes).
I am not getting notified with below code which is similar to sample client code. Could you please help me here:

///////Inside createMonitoredItem method which is called from subscribe() method
MonitoredEventItem eventItem = createMonitoredEventItem(nodeId); //nodeId of parent node
item = eventItem;
double requestedSamplingInterval = item.getSamplingInterval();
sub.addItem(item);
monitoredItemId = item.getMonitoredItemId();
double revisedSamplingInterval = item.getSamplingInterval();

protected MonitoredEventItem createMonitoredEventItem(NodeId nodeId) {
initEventFieldNames();
EventFilter filter = createEventFilter(eventFieldNames);

// Create the item
MonitoredEventItem eventItem = new MonitoredEventItem(nodeId, filter);
eventItem.setEventListener(eventListener);
return eventItem;
}

In createEventFilter method below filter is added as per Sample Uaclient. Could you please let me know if below filter doesn’t allow GeneralModelChangeEventType? I also tried removing/changing this filter but couldn’t get notification on addition/removal of child node.

// Event filtering: the following sample creates a
// “Not OfType GeneralModelChangeEventType” filter
ContentFilterBuilder fb = new ContentFilterBuilder();
// The element operand refers to another operand –
// operand #1 in this case which is the next,
// LiteralOperand
fb.add(FilterOperator.Not, new ElementOperand(UnsignedInteger.valueOf(1)));
final LiteralOperand filteredType = new LiteralOperand(Identifiers.GeneralModelChangeEventType);
fb.add(FilterOperator.OfType, filteredType);

// Apply the filter to Where-clause
filter.setWhereClause(fb.getContentFilter())

Any help here would really be appreciated.

Thanks
Nan

Sure Jimmy.

What I basically want to know is how do we subscribe to GeneralModelChangeEventType events. The code above is just the sample client code provided with prosys sdk.

My further analysis show that I could listen to GeneralModelChangeEventType event when I subscribed to “Server” node instead of “Objects ” node. But with subscribing to the server node, how do I know the exact node which is changed i.e. nodeId for parent node in which child node is added or removed and know the child nodes’ nodeId as well.

I have been struggling with this scenario. Any help here would be highly appreciated.

Thanks
Nan

Thanks Matti.
That means I need to subscribe to Server node only and not Objects node?
i.e. browse path “Objects/0:Server”

I do see onEvent(MonitoredEventItem sender, Variant[] eventFields) method of MonitoredEventItemListener class being called now.
I am doubtful of how to access GeneralModelChangeEventType object here inside onEvent method so I can get array of ModelChangeStructureDataType and eventually nodeId of the affected nodes.
or some other way to access GeneralModelChangeEventType object in client, when event is triggered from the server.

Thanks
Nan

Thanks a lot Matti.
That worked for me!!

1)
In my case an instance is added to the Parent node. for which I get Verb-“4” which as per document is
” DataTypeChanged 4 This verb may be used only for affected Nodes that are Variables or VariableTypes. It indicates that the DataType Attribute has changed.”
where as in my case a new instance node is just added and no data type changed.

When the instance is deleted the Verb is “8” which is not mentioned/explained in the doc.
If you could please help me if I am understanding the Verbs wrong here.

2)Is there a way to get NodeId of the node/instance that is added or deleted from parent node?

Thanks
Nan

Is there a way to get NodeId of the node/instance that is added or deleted from parent node?
or some information about the added/deleted reference.

1)Does that mean in my case where Reference was added to parent node(Verb=4), I can only get NodeId of the parent node it was added to and no information about the reference itself?
For my use case, where i want to get information about the Reference added, Is browsing the parent node only option?

2)When you say “If the Reference was birectional” , does that mean when Refence is removed from 1 node and added to other?