Obtain node anomalies through BrowseNodes

[DreamToffee]

I encountered an issue when using BrowseNodes for node traversal. In most cases, this method can traverse the correct nodes, but when the nodes in the image appear, it cannot parse them properly. After checking with UaExpert, I found that the arrays that cannot be traversed are displayed as node icons structurally, but w

hen clicked, their types are variables. How should I handle this for nodes

[DreamToffee]

Errors and Num are both arrays, with the contents of the Errors and Num arrays being variables, and the nodes under Num being nodes, with the internal nodes being variables

[kevinherron]

Which one of these can't your browse?

I think you'll need to share the code you're using to browse and a Wireshark capture that shows what happens when you try to browse these.

[DreamToffee]

There are two nodes under AlarmCV-DB in the picture, Error Code and num. Error Code can be traversed normally, but accessing num node will result in an exception. The exception content is as follows

2024-08-05T09:17:43.481+08:00 WARN 27644 --- [PLCService] [d-thread-pool-1] o.e.milo.opcua.sdk.client.AddressSpace : Failed to create Node from Reference to ExpandedNodeId{ns=4, id=|var|Inovance-ARM-Linux.Application.AlarmCV_DB.num, serverIndex=0}

java.util.concurrent.CompletionException: UaException: status=Bad_UnexpectedError, message=java.lang.IllegalArgumentException: expected NodeClass.Object, got NodeClass.Variable
at java.base/java.util.concurrent.CompletableFuture.encodeRelay(CompletableFuture.java:368) ~[na:na]
at java.base/java.util.concurrent.CompletableFuture.completeRelay(CompletableFuture.java:377) ~[na:na]
at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1152) ~[na:na]
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510) ~[na:na]
at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2147) ~[na:na]
at org.eclipse.milo.opcua.stack.client.UaStackClient.lambda$deliverResponse$5(UaStackClient.java:318) ~[stack-client-0.6.13.jar:0.6.13]
at org.eclipse.milo.opcua.stack.core.util.ExecutionQueue$Task.run(ExecutionQueue.java:119) ~[stack-core-0.6.13.jar:0.6.13]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) ~[na:na]
at java.base/java.lang.Thread.run(Thread.java:833) ~[na:na]
Caused by: org.eclipse.milo.opcua.stack.core.UaException: java.lang.IllegalArgumentException: expected NodeClass.Object, got NodeClass.Variable
at org.eclipse.milo.opcua.sdk.client.AddressSpace.newObjectNode(AddressSpace.java:1243) ~[sdk-client-0.6.13.jar:0.6.13]
at org.eclipse.milo.opcua.sdk.client.AddressSpace.lambda$getObjectNodeAsync$2(AddressSpace.java:215) ~[sdk-client-0.6.13.jar:0.6.13]
at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1150) ~[na:na]
... 7 common frames omitted
Caused by: java.lang.IllegalArgumentException: expected NodeClass.Object, got NodeClass.Variable
at com.google.common.base.Preconditions.checkArgument(Preconditions.java:143) ~[guava-33.0.0-jre.jar:na]
at org.eclipse.milo.opcua.sdk.client.AddressSpace.newObjectNode(AddressSpace.java:1214) ~[sdk-client-0.6.13.jar:0.6.13]
... 9 common frames omitted

[DreamToffee]

The access code is as follows

    public void listNode(OpcUaClient client, UaNode uaNode) throws Exception {
        List<? extends UaNode> nodes;
        if (uaNode == null) {
            nodes = client.getAddressSpace().browseNodes(Identifiers.ObjectsFolder);
        } else {
            nodes = client.getAddressSpace().browseNodes(uaNode);
        }

        for (UaNode nd : nodes) {
            System.out.println("Node= " + nd.getBrowseName().getName());
            listNode(client, nd);
        }
    }

[kevinherron]

I think what's happening is that in the ReferenceDescription returned when browsing AlarmCV_DB the Server is indicating that num is an Object, but in the subsequent code that reads the attributes while creating a UaNode instance the Server indicates the NodeClass is Variable.

This would be something that needs to be fixed in the server. The only work around I can see on the Client side is to stop using the browseNodes methods that create UaNode instances and use the lower-level browse methods.