Hallo,

I’m having trouble reading Data from the OPC UA Server. I have a subscription which gets triggered every minute and is supposed to
read Data from the OPC UA Server. For this action I tried to use the following two methods. (readValues(List) and readAttribute(NodeId, UnsignedInteger).

The first Method uses the Method “readValues” of the UaClient. This Methods reads alle the Values from all the Nodes I need at once and is very fast.
It is exactly what I need, but the is ONE BIG PROBLEM. If the Data I read every Minute changes, the “readValues” Method will not read the changed
new values und just reads the old values. It seems like this methods caches the old value in some way and just retruns me the old values instead of reading
the current values of the nodeId.

Because of this Issue I was forced to use the second Method “readAttribute” which uses the Method “read” of the UaClient. I have to call this Method for every single
Node I want to read the Value from. It does the job an gives me the current Values of the Node. The only problem here is that I now have a single reading request
for every Node and this slows down the reading quit a lot. In my case it takes about 10 times longer than the first Method.

It would be perfect beeing able to disable to caching for the “readValues” Method. This would give me the current Data of the Node in very little time. Please can
someone give me a hint how I can achive this 🙂

protected UaClient client;

public DataValue[] readValues(List nodeids){
NodeId[] nodes= new NodeId[nodeids.size()];
try {
DataValue[] values= client.readValues(nodeids.toArray(nodes));
return values;
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}

public DataValue readAttribute(NodeId nodeId, UnsignedInteger attributeId){
ReadResponse response = null;
ReadValueId readValue = new ReadValueId(nodeId, attributeId, null, null);
try {
response= client.read(0.0, TimestampsToReturn.Both, readValue);
DataValue[] values = response.getResults();
return values[0];
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}