I am testing out the alarm functionality of the Java SDK. I am using version 2.0.2-275. My goal is simple: Create an alarm for a variable, that will trigger if the variable’s value goes under a low limit or over a high limit. However, I have had some issues.

Here is the closest I’ve gotten to a working solution:

Regardless of the alarm, this is my starting point. It follows the example very closely.

final NodeId li1DataId = new NodeId(ns, “LI” + number + “001” + “Data”);
UaType doubleType = this.getServer().getNodeManagerRoot().getType(Identifiers.Double);
UaVariableNode li1data = new CacheVariable(this, li1DataId, “DataItem”,
LocalizedText.NO_LOCALE);
li1data.setDataType(doubleType);
li1data.setTypeDefinitionId(Identifiers.BaseDataVariableType);
li1data.setValue(0.5);
li1.addComponent(li1data);

this.createAlarmNode(li1data, boiler, 500, 0.2, 0.3, 0.8, 0.9);
// + EventSource, the target of the EventSource is normally the
// source of the HasCondition reference
boiler.addReference(li1data, Identifiers.HasEventSource, false);

// + HasNotifier, these are used to link the source of the EventSource
// up in the address space hierarchy
myObjectsFolder.addReference(li1data, Identifiers.HasNotifier, false);

public void createAlarmNode(UaVariable source, UaObjectNode myDevice, int severity, double lowLowLimit, double lowLimit, double highLimit, double highHighLimit) throws StatusException,
UaInstantiationException {

// Level Alarm from the LevelMeasurement

// See the Spec. Part 9. Appendix B.2 for a similar example

int ns = this.getNamespaceIndex();
final NodeId myAlarmId = new NodeId(ns, source.getNodeId().getValue()
+ “.Alarm”);
String name = source.getBrowseName().getName() + “Alarm”;
//MyLevelAlarmType myAlarm = new MyLevelAlarmType(this, this, myAlarmId, new QualifiedName(name), new LocalizedText(name));
//MyLevelAlarmType myAlarm = createInstance(MyLevelAlarmType.class, name, myAlarmId);
ExclusiveLevelAlarmTypeNode myAlarm= createInstance(ExclusiveLevelAlarmTypeNode.class, name, myAlarmId);

// ConditionSource is the node which has this condition
myAlarm.setSource(source);
// Input is the node which has the measurement that generates the alarm
myAlarm.setInput(source);

myAlarm.setMessage(“Level exceeded”); // Default locale
myAlarm.setSeverity(severity); // Medium level warning
myAlarm.setHighHighLimit(highHighLimit);
myAlarm.setHighLimit(highLimit);
myAlarm.setLowLowLimit(lowLowLimit);
myAlarm.setLowLimit(lowLimit);
myAlarm.setEnabled(true);
myDevice.addComponent(myAlarm); // addReference(…Identifiers.HasComponent…)

// + HasCondition, the SourceNode of the reference should normally
// correspond to the Source set above
source.addReference(myAlarm, Identifiers.HasCondition, false);

}

As you can see, I have three different possibilities for creating the actual alarm node. Here, MyLevelAlarmType is exactly the same as the one in the samples.

MyLevelAlarmType myAlarm = new MyLevelAlarmType(this, this, myAlarmId, new QualifiedName(name), new LocalizedText(name));

MyLevelAlarmType myAlarm = createInstance(MyLevelAlarmType.class, name, myAlarmId);

ExclusiveLevelAlarmTypeNode myAlarm= createInstance(ExclusiveLevelAlarmTypeNode.class, name, myAlarmId);

Using MyLevelAlarmType, I run into two possible problems:
When creating as new MyLevelAlarmType(…), an error is thrown because NodeBuilder was not used.
When creating as createInstance(MyLevelAlarmType.class …), an eror is thrown because the custom class MyLevelAlarmType does not have a TypeDefinition.

Using ExclusiveLevelAlarmTypeNode, I succesfully create the alarm node with the right values but it does not trigger (ActiveState= “Inactive”, does not change) when I change the variable’s value so that it exceeds the limits. I assume this is because the Node does not have the right kind of DataChangeListener. However, I cannot create a DataChangeListener that can access the alarm’s variables and methods, except in a custom class, which I haven’t been able to get to work (see above).

So, how will I be able to make a working alarm? Should I be working on creating a non-error-throwing custom Alarm, or somehow get the ExclusiveLevelAlarmTypeNode to work? It is also entirely possible that I have missed or misunderstood something very basic, I am new to this.