如何使用 hurence 在 java 中读取 opc-ua 变量

Question

I'm try to read a variable from a OPC-UA server. I'm using com.hurence.opc library. My code is

    OpcUaConnectionProfile connectionProfile = new OpcUaConnectionProfile()
            .withConnectionUri(URI.create("opc.tcp://localhost:62541/Quickstarts/ReferenceServer"))
            .withClientIdUri("imp:ladisa").withClientName("GestionaleLadisa")
            .withSocketTimeout(Duration.ofSeconds(15));

    // Create an instance of a ua operations
    OpcUaOperations opcUaOperations = new OpcUaTemplate();
    // connect using our profile
    opcUaOperations.connect(connectionProfile).doOnError(throwable -> System.out.println(throwable.getMessage()))
            .ignoreElement().blockingAwait();

    
      OpcUaSessionProfile sessionProfile = new OpcUaSessionProfile()
                //the publication window
                .withPublicationInterval(Duration.ofMillis(100));
      
      
      
        try (OpcSession session = opcUaOperations.createSession(sessionProfile).blockingGet()) {
            List<OpcData> result = session.read("Objects.CTT.Scalar.Scalar_Instructions").blockingGet();
            for(var dt:result) {
                System.out.println( dt.getValue());
            }
            
            
            
        }         

I'm testing with opc server reference implementation. But I'm not able to reference the variable and I get an Exception

java.util.NoSuchElementException: No value present
at java.base/java.util.Optional.get(Optional.java:141)
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
at java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)

What is the correct way to point to a node in the OPC-UA tree?

Answer 1

The way I found is:

List<OpcData> result = session.read("ns=2;s=Scalar_Instructions").blockingGet();

using nodeId. I hope that this can help somebody.