encode Structure without DataTypeDefinition

[an-nie]

Hello!

I want to call a method but have problems getting the InputArguments encoding from the server.

Situation

The method is GenerateFileForRead. If I open the "Call" method dialogue window in UaExpert, I can see the argment is of type ProductionDatasetReadOptionsType and has two fields, Storage (an Enum) and Name (String):

The Attributes of the InputArguments reference DataType ns=4;i=3007.

Node ns=4;i=3007 is indeed ProductionDatasetReadOptionsType. But it has no DataTypeDefinition, nor anything else that hints at fields Storage and Name or its DataTypes. Its encoding are defaults.

Goal/Problem

I want to call the method. For that I need to encode the input argument, but it is missing its DataTypeDefinition. I'm trying to repeat the trick of discussion #1703 and define my own DataType with the DataTypeDefinition and StructureFields that I expect, but I still need an encoding for that, and seemingly no way to get it. The referenced Default Binary and Default XML for ProductionDatasetReadOptionsType have null encodings.

But that makes me wonder:

Question

When displaying the "Call" method dialogue, UaExpert somehow knows how to resolve the input argument into its fields Storage and Name, and even correctly resolve the Storage Enum. I should be able to replicate that by following references through the OPC UA structure, and find the encoding. But I cannot figure out how; even igonring the encoding, ProductionDatasetReadOptionsType does not appear to contain or reference this structure (the fields, their types, ...) at all. What am I missing?

[kevinherron]

I would guess that UaExpert is reading/parsing the DataType dictionary XML document...

Does your server have an entry like this (with some other namespace/name than BACnet)?

[kevinherron]

Also - hover over the "Default Binary" reference, UaExpert should tell you its NodeId - that's the NodeId of the binary encoding.

[an-nie]

Re: encoding

I have tried that already. I wrote a custom DataType as a copy of the given DataType, just with a DataTypeDefinition added.

val inputDataType: DataType = ... // ProductionDatasetReadOptionsType
val inputDataTypeExpanded: DataType = new DataType() {
	override def getBinaryEncodingId: NodeId = inputDataType.getBinaryEncodingId  // ns=4;i=5012

	override def getXmlEncodingId: NodeId = inputDataType.getXmlEncodingId

	override def getJsonEncodingId: NodeId = inputDataType.getJsonEncodingId

	override def getBrowseName: QualifiedName = inputDataType.getBrowseName

	override def getNodeId: NodeId = inputDataType.getNodeId

	override def isAbstract: lang.Boolean = inputDataType.isAbstract

	override def getDataTypeDefinition: DataTypeDefinition =
		new StructureDefinition(
			getBinaryEncodingId,
			new NodeId(0,22), // baseDataType: Structure 
			StructureType.Structure,
			new StructureField[] {...}
		)
}
val input = new DynamicStructType(inputDataTypeExpanded, members)
ExtensionObject.encode(client.getDynamicEncodingContext, input)		// throws exception:

// org.eclipse.milo.opcua.stack.core.UaSerializationException: no codec registered for encodingId=ns=4;i=5012

Re: dictionary

Yes, there are two dictionaries!

(The ProductionDatasetReadOptionsType node here has the same EncodingId as the one above: ns=4;i=5012)

I have just tried to access the dictionaries and am already at the next problem:

val namespaceUri = ...  // value of Node "NamespaceUri", child of dictionary Node
val dict = client.getDynamicDataTypeManager.getTypeDictionary(namespaceUri) // dict = null

[kevinherron]

The Milo client is not going to read those dictionaries for you unless you switch it into legacy datatype dictionary mode: https://github.com/eclipse-milo/milo/blob/main/milo-examples/client-examples/src/main/java/org/eclipse/milo/examples/client/LegacyDataTypeDictionaryExample.java

I don't recommend this because it's not a very complete mapping of all the variations of OPC UA types and uses a different "dynamic struct" representation. It's deprecated, so it's provided to you as-is.

Each of those Euromap nodes will have a ByteString value that is a relatively large XML document. Inside the XML document you'll find the datatype/struct definitions.

[an-nie]

I will try that and update with results tomorrow.

Thank you very much for your excellent and quick responses!

[an-nie]

Solved it:

client.setDynamicDataTypeManagerFactory(
  DataTypeManagerFactory.eager(new LegacyDataTypeManagerInitializer(client)))

val method = client.getAddressSpace.getObjectNode(productionDatasetTransferNode)
  .getMethod(new QualifiedName(0, "GenerateFileForRead"))
val inputDataTypeNodeId = method.getInputArguments.head.getDataType
val inputDataType = client.getDataTypeTree.getDataType(inputDataTypeNodeId)

val struct = Struct.builder("ProductionDatasetReadOptionsType")
  .addMember("Storage", storage)
  .addMember("Name", name)
  .build()

val input = new BsdStructWrapper[Struct](inputDataType, struct)
ExtensionObject.encode(client.getDynamicEncodingContext, input)

We will use this as a fallback only if the DataTypeDefinition is missing.

Thank you very much!