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10:23, EET
January 30, 2014
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Hi,
I would like to avoid calling the read methods for individual items like:
DataValue shorttext = client.readAttribute(nodeId, Attributes.DisplayName);
DataValue longtext = client.readAttribute(nodeId, Attributes.Description);
DataValue value = client.readAttribute(nodeId, Attributes.Value);
e.g. I would like for one node to read set of specified attributes.
I read from prosys javadoc next sample usage examples:
Sample usage:
ReadValueId[] nodesToRead = new ReadValueId[2];
// Scalar value or complete array
nodesToRead[0] = new ReadValueId(nodeId1, Attributes.Value, null, null);
// Part of an array
NumericRange range = new NumericRange(1, 3);
nodesToRead[10] = new ReadValueId(nodeId2, Attributes.Value, range.toString(), null);
final ReadResponse readResponse = read(UaClient.MAX_CACHE_AGE, TimestampsToReturn.Both, nodesToRead);
final DataValue[] values = readResponse.getResults();
// Use the values:
if (values[0].getStatusCode().isGood()) System.out.println(values[0].getValue());
if (values[1].getStatusCode().isGood()) System.out.println(values[1].getValue());
but I stuck with opc foundation docs. Could you please provide simple example to read set of attribs of one node. Tnks
11:13, EET
December 21, 2011
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Simple answer:
Internally, this translates to
for (int i = 0; i < attributeIds.length; i++)
nodesToRead[i] = new ReadValueId(nodeId, attributeIds[i], null,
null);
final ReadResponse readResponse = read(MAX_CACHE_AGE,
TimestampsToReturn.Both, nodesToRead);
final DataValue[] values = readResponse.getResults();
12:01, EET
January 30, 2014
Offline
Just one small change, readAttributes needs an array as second argument (from Prosys-OPC-UA-Java-SDK-Client-Binary-1.4.8-8731-javadoc):
DataValue[] arrayOfValues = client.readAttributes(node, attribs);
Thank you, it works.
12:33, EET
December 21, 2011
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Oh, yes, you are right. I was sure it was defined as “UnsignedInteger… attributeIds”.
9:23, EET
December 21, 2011
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Jouni Aro said
I was sure it was defined as “UnsignedInteger… attributeIds”.
Will be like that in the next versions.
11:29, EET
January 30, 2014
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Hi,
(1) Regards reading performance is
the same as:
e.g. it is one call to server in both cases, right?
(2) Regards data type
System.out.println(dataValue.getValue());
prints
i=7
Is it possible by using prosys api (or opc fond classes) to transform data type value returned in the form
i=7 directly in java.lang.Class, like Float.class, Double.class, String.class, Integer.class … ?
BR
12:18, EET
December 21, 2011
Offline
(1) Not quite. AddressSpace.getNode() makes a couple of readAttributes: first to determine the node class and then read UaNode.supportedAttributes(). After that it will also read node references and properties – to make the node more complete for use in the application.
Regarding performance, getNode() will put the node into a local cache, but will reread the node, if it’s “too old” anyway. The AddressSpace.getCache().setNodeMaxAgeInMillis() can be used to define what is “too old”.
The nodes are store in the cache with WeakReferences, and will be removed when necessary.
(2)
You can convert Variant values with
but it does not expose the Java class corresponding to the type. It does provide the opposite, though:
Instead, you can get it directly from
dt.getJavaClass();
Note that these are “manually” initialised in the SDK and may be null for some types. But in general they are available both on the client and server side.
12:44, EET
December 21, 2011
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dt above, is of course initialised from
20:21, EET
January 30, 2014
Offline
Thanks Aro for directions, helps me related to UaDataType.
UaVariable v = (UaVariable) uaNode;
dataType = (UaDataType) v.getDataType();
System.out.println("JavaClass: " + dataType.getJavaClass());
I still didn’t find more elegant way with client.read() method except to parse returned value of attribute Attributes.DataType which is not big deal.
DataValue[] arrayOfValues = client.readAttributes(node_id, attribs);
String dataTypeString = arrayOfValues[2].getValue().toString();
int dataTypeIdentifier = Integer.parseInt(dataTypeString.substring(dataTypeString.indexOf("=") + 1));
UaDataType dt = (UaDataType) client.getAddressSpace().getType(new NodeId(0, dataTypeIdentifier));
System.out.println(dt.getJavaClass());
or instead of client.getAddressSpace() maybe it is faster to use:
So, regards performances what you prefer
UaVariable v = (UaVariable) uaNode;
dataType = (UaDataType) v.getDataType();
…
UnsignedInteger[] attribs = v.getSupportedAttributes();
…
or simplier:
?
BR
8:33, EET
December 21, 2011
Offline
You can get the DataTypeId “simply” as:
DataValue[] arrayOfValues = client.readAttributes(node_id, attribs);
NodeId dataTypeId = (NodeId) arrayOfValues[2].getValue().getValue();
I wouldn’t consider performance too much at an early stage. Although it is making several calls to the server, unless you need to read a lot of nodes, it won’t matter very much, I think. A call to a local server will take just a couple of ms (depending on the server, of course).
9:35, EET
January 30, 2014
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(NodeId) arrayOfValues[2].getValue().getValue()
Thank you. BR
9:57, EET
December 21, 2011
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Yes, that’s not very obvious and looks odd, indeed 
The DataValue provides values as Variants, which can be of any type. If you know the type, you can just cast it. There is also a property, compositeClass(), which tells you the actual type – and asClass(), which provides a “safe cast”.
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