OPCUA milo custom Data Type Structure in Structure possible?

I'm using milo 0.5.4 to setup my own OpCUA server now I try to use a complex Datatype which should include a structure inside a structure.

What works so far is a structure with standard datatypes.

My Custom Structure should include another Structure called StatusStructType which also implements UaStructure.

public class CustomStructType implements UaStructure {

public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse(String.format("nsu=%s;s=%s", Namespace.NAMESPACE_URI, "DataType.CustomStructType"));

public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse(String.format("nsu=%s;s=%s", Namespace.NAMESPACE_URI, "DataType.CustomStructType.BinaryEncoding"));

private final String foo;
private final Integer bar;
private final boolean baz;
private final StatusStructType status;

@Override
public ExpandedNodeId getTypeId() {
    return TYPE_ID;
}

public CustomStructType(String foo, Integer bar, boolean baz, StatusStructType status) {
    this.foo = foo;
    this.bar = bar;
    this.baz = baz;
    this.status = status;
}

public CustomStructType() {
    this(null, 0, false, new StatusStructType());
}

public static class Codec extends GenericDataTypeCodec<CustomStructType> {
    @Override
    public Class<CustomStructType> getType() {
        return CustomStructType.class;
    }

    @Override
    public CustomStructType decode(SerializationContext context, UaDecoder decoder) throws UaSerializationException {

        String foo = decoder.readString("Foo");
        Integer bar = decoder.readInt32("Bar");
        boolean baz = decoder.readBoolean("Baz");
        Object statusStruct = decoder.readStruct("Status", StatusStructType.TYPE_ID);
        StatusStructType statusStructure = new StatusStructType();
        if (statusStruct.getClass().isAssignableFrom(StatusStructType.class)) {
            statusStructure = (StatusStructType) statusStruct;
        }
        return new CustomStructType(foo, bar, baz, statusStructure);
    }

    @Override
    public void encode(SerializationContext context, UaEncoder encoder, CustomStructType value) throws UaSerializationException {

        encoder.writeString("Foo", value.foo);
        encoder.writeInt32("Bar", value.bar);
        encoder.writeBoolean("Baz", value.baz);
        encoder.writeStruct("Status", value.status, StatusStructType.TYPE_ID);
    }
}

}

When I want to read this CustomStructType Node:

UaVariableNode node = client.getAddressSpace().getVariableNode(new NodeId(nodeNamespaceIndex, nodeIdentifier)); 
                DataValue value = node.readValue();

                Variant variant = value.getValue();
                ExtensionObject xo = (ExtensionObject) variant.getValue();

                CustomStructType decoded = (CustomStructType) xo.decode(client.getSerializationContext());

when it comes to xo.decode I get a org.eclipse.milo.opcua.stack.core.UaSerializationException: no codec registered: NodeId{ns=2, id=DataType.StatusStructType} Exception

But I register the codec beforehand with:

NodeId statusbinaryEncodingId = StatusStructType.BINARY_ENCODING_ID.toNodeId(client.getNamespaceTable()).orElseThrow(() -> new IllegalStateException("namespace not found"));
client.getDataTypeManager().registerCodec(statusbinaryEncodingId, new StatusStructType.Codec().asBinaryCodec());

So my question is if it is even possible to have a structure in structure construct with milo UaStructures? And when Yes what am I missing?

When you register your codecs make sure to call both register overloads.

The updated example would look like this:

    NodeId dataTypeId = CustomStructType.TYPE_ID
        .toNodeId(client.getNamespaceTable())
        .orElseThrow(() -> new IllegalStateException("namespace not found"));

    NodeId binaryEncodingId = CustomStructType.BINARY_ENCODING_ID
        .toNodeId(client.getNamespaceTable())
        .orElseThrow(() -> new IllegalStateException("namespace not found"));

    // Register codec with the client DataTypeManager instance
    client.getDataTypeManager().registerCodec(
        binaryEncodingId,
        new CustomStructType.Codec().asBinaryCodec()
    );

    client.getDataTypeManager().registerCodec(
        new QualifiedName(dataTypeId.getNamespaceIndex(), "CustomStructType"),
        dataTypeId,
        new CustomStructType.Codec().asBinaryCodec()
    );