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--- programmatic_sample_code [2024/10/08 19:38] – created wikiadmin
+++ programmatic_sample_code [2024/10/15 11:28] (current) – wikiadmin
@@ Line 1: / Line 1: @@
+Once you have the OPC Gateway running, it's possible access the OPC Legacy server from any system using pure Java code.  Here's a sample that shows how to do that.
 <code java>
 import com.ergotech.util.SimulationManager;
@@ Line 65: / Line 67: @@
             // Assign the host and item to connect to in the OPC server.
-            opc.setHost("localhost");
+            opc.setHost("localhost"); // the host that is running the OPCGateway
             opc.setItem("GEMToolSimulator.VIDs.SVIDs.Temperature");
         } catch (BadParameterException e) {
@@ Line 93: / Line 95: @@
         // Access current values as various types
+        // Force the server to register for value updates even though there are no listeners
+        opc.setAutoSuspend(SimpleDataSource.AUTOSUSPEND_NEVER);
+        // read the data
         System.out.println("Current value as String: " + opc.getValueObject().getStringValue());
         System.out.println("Current value as Double: " + opc.getValueObject().getDoubleValue());
@@ Line 112: / Line 117: @@
     }
+}
+</code>
+The OPC DA standard is optimized for a subscription model. Here's an example of reading multiple servers.  Each will update when the value changes at the server and the updated value will be stored in a HashMap.  Multiple listeners/HashMaps could be used to build "groups" of data, especially if you're looking to use ErgoTech's "TriggeredHistorical" component to periodically save these straight to a database.
+<code java>
+import com.ergotech.util.SimulationManager;
+import com.ergotech.util.TargetLicenseManager;
+import com.ergotech.vib.exceptions.BadParameterException;
+import com.ergotech.vib.exceptions.VIBUpdateFailedException;
+import com.ergotech.vib.servers.SimpleDataSource;
+import com.ergotech.vib.servers.opc.opcclient.OPC;
+import com.ergotech.vib.utils.DataSourceContainer;
+import com.ergotech.vib.valueobjects.ValueChangedEvent;
+import com.ergotech.vib.valueobjects.ValueObjectInterface;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.HashMap;
+public class OPCDemo {
+    // HashMap to store the latest values for each item
+    private HashMap<String, ValueObjectInterface> itemValueMap = new HashMap<>();
+    public static void main(String[] args) throws InterruptedException {
+        OPCDemo opcDemo = new OPCDemo();
+        // Configure the license, required for OPC component to function.
+        opcDemo.setupLicense();
+        // Disable simulation mode to connect to the actual OPC server.
+        SimulationManager.getSimulationManager().setSimulating(false);
+        // Initialize and start the OPC setup.
+        opcDemo.setupOpc();
+        // Keep the application running for 5 minutes to receive updates from the OPC server.
+        Thread.sleep(1000 * 60 * 5);
+    }
+    public void setupLicense() {
+        try (InputStream license = Files.newInputStream(Path.of("resources/MIX.trg"))) {
+            // Initialize the license manager with the appropriate target.
+            final TargetLicenseManager manager = new TargetLicenseManager("MIX",
+                    license,
+                    OPCDemo.class.getClassLoader());
+            // Set the license manager for components.
+            SimpleDataSource.setClassLicenseManager(manager);
+        } catch (Exception e) {
+            // Handle any failure during license setup.
+            throw new RuntimeException("Failed to setup license", e);
+        }
+    }
+    public void setupOpc() {
+        DataSourceContainer container;
+        try {
+            // Create a new OPC container to hold the OPC components.
+            container = DataSourceContainer.getRootContainer().createNewChildContainer("OPCExample");
+        } catch (BadParameterException e) {
+            // Occurs if a container with the same name already exists.
+            throw new RuntimeException("Failed to create OPC container", e);
+        }
+        // List of items to monitor
+        String[] items = {
+                "GEMToolSimulator.VIDs.SVIDs.Temperature",
+                "GEMToolSimulator.VIDs.SVIDs.Pressure",
+                "GEMToolSimulator.VIDs.SVIDs.Humidity"
+        };
+        // Create a single listener instance
+        ValueChangedCallback listener = new ValueChangedCallback();
+        for (String item : items) {
+            OPC opc = new OPC();
+            try {
+                // Assign a unique, case-insensitive name to the OPC component.
+                opc.setName("OPC_" + item);
+                // Assign the host and item to connect to in the OPC server.
+                opc.setHost("localhost"); // the host that is running the OPCGateway
+                opc.setItem(item);
+            } catch (BadParameterException e) {
+                // Handle invalid configuration for the OPC component.
+                throw new RuntimeException("Invalid OPC configuration", e);
+            }
+            try {
+                // Add the configured OPC component to the container.
+                container.addComponent(opc, opc.getName());
+            } catch (BadParameterException e) {
+                // Occurs if a component with the same name is already added to the container.
+                throw new RuntimeException("Failed to add OPC component to container", e);
+            }
+            // Register the same listener to handle value change events from the OPC server.
+            opc.addValueChangedListener(listener);
+            try {
+                // Initialize and start the OPC component.
+                opc.init();
+                opc.start();
+            } catch (BadParameterException | VIBUpdateFailedException e) {
+                // Handle any failure during initialization or startup.
+                throw new RuntimeException("Failed to start OPC component", e);
+            }
+            // Force the server to register for value updates even though there are no listeners
+            opc.setAutoSuspend(SimpleDataSource.AUTOSUSPEND_NEVER);
+        }
+        // Access current values from the HashMap
+        for (String item : items) {
+            ValueObjectInterface valueObject = itemValueMap.get(item);
+            if (valueObject != null) {
+                System.out.println("Current value of " + item + " as String: " + valueObject.getStringValue());
+                System.out.println("Current value of " + item + " as Double: " + valueObject.getDoubleValue());
+                System.out.println("Current value of " + item + " as Float: " + valueObject.getFloatValue());
+                System.out.println("Current value of " + item + " as Integer: " + valueObject.getIntValue());
+                System.out.println("Current value of " + item + " as Long: " + valueObject.getLongValue());
+                System.out.println("Current value of " + item + " as Boolean: " + valueObject.getBoolValue());
+            } else {
+                System.out.println("No value yet for " + item);
+            }
+        }
+    }
+    // Callback to process value changes from the OPC component.
+    public class ValueChangedCallback {
+        // Any object with a method "valueInput(ValueChangedEvent)" can be used as a callback
+        public void valueInput(ValueChangedEvent valueChangedEvent) {
+            // Logic to handle changes in OPC data, triggered whenever the OPC value changes.
+            ValueObjectInterface valueObject = valueChangedEvent.getValueObject();
+            OPC opc = (OPC) valueChangedEvent.getSource();
+            String itemName = opc.getItem();
+            // Update the HashMap with the new value
+            itemValueMap.put(itemName, valueObject);
+            System.out.println("Value Changed for item " + itemName + ": " + valueObject + " [quality: " + valueObject.getQuality() + "]");
+        }
+    }
 }
 </code>