Support custom service sets and additional servers in FindServers

opc-ua-sdk/sdk-server/src/main/java/org/eclipse/milo/opcua/sdk/server/OpcUaServer.java

@@ -47,18 +47,18 @@
 import org.eclipse.milo.opcua.sdk.server.namespaces.OpcUaNamespace;
 import org.eclipse.milo.opcua.sdk.server.namespaces.ServerNamespace;
 import org.eclipse.milo.opcua.sdk.server.nodes.factories.EventFactory;
+import org.eclipse.milo.opcua.sdk.server.servicesets.AttributeServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.DiscoveryServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.MethodServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.MonitoredItemServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.NodeManagementServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.QueryServiceSet;
 import org.eclipse.milo.opcua.sdk.server.servicesets.Service;
+import org.eclipse.milo.opcua.sdk.server.servicesets.SessionServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.SubscriptionServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.ViewServiceSet;
 import org.eclipse.milo.opcua.sdk.server.servicesets.impl.AccessController;
 import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultAccessController;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultAttributeServiceSet;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultDiscoveryServiceSet;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultMethodServiceSet;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultMonitoredItemServiceSet;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultNodeManagementServiceSet;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultQueryServiceSet;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultSessionServiceSet;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultSubscriptionServiceSet;
-import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultViewServiceSet;
 import org.eclipse.milo.opcua.sdk.server.subscriptions.Subscription;
 import org.eclipse.milo.opcua.sdk.server.typetree.DataTypeTreeBuilder;
 import org.eclipse.milo.opcua.sdk.server.typetree.ObjectTypeTreeBuilder;
@@ -189,6 +189,22 @@ public class OpcUaServer extends AbstractServiceHandler {
   private final ServerApplicationContext applicationContext;
 
   public OpcUaServer(OpcUaServerConfig config, OpcServerTransportFactory transportFactory) {
+    this(config, transportFactory, new ServiceSets() {});
+  }
+
+  /**
+   * Create an OpcUaServer using the service set implementations supplied by {@code serviceSets}.
+   *
+   * @param config the {@link OpcUaServerConfig}.
+   * @param transportFactory the {@link OpcServerTransportFactory}.
+   * @param serviceSets the {@link ServiceSets} supplying the service set implementations this
+   *     server uses.
+   */
+  public OpcUaServer(
+      OpcUaServerConfig config,
+      OpcServerTransportFactory transportFactory,
+      ServiceSets serviceSets) {
+
     this.config = config;
     this.transportFactory = transportFactory;
 
@@ -255,19 +271,31 @@ public ServerTable getServerTable() {
             .map(e -> EndpointUtil.getPath(e.getEndpointUrl()))
             .distinct();
 
+    DiscoveryServiceSet discoveryServiceSet = serviceSets.createDiscoveryServiceSet(this);
+    AttributeServiceSet attributeServiceSet = serviceSets.createAttributeServiceSet(this);
+    MethodServiceSet methodServiceSet = serviceSets.createMethodServiceSet(this);
+    MonitoredItemServiceSet monitoredItemServiceSet =
+        serviceSets.createMonitoredItemServiceSet(this);
+    NodeManagementServiceSet nodeManagementServiceSet =
+        serviceSets.createNodeManagementServiceSet(this);
+    QueryServiceSet queryServiceSet = serviceSets.createQueryServiceSet(this);
+    SessionServiceSet sessionServiceSet = serviceSets.createSessionServiceSet(this);
+    SubscriptionServiceSet subscriptionServiceSet = serviceSets.createSubscriptionServiceSet(this);
+    ViewServiceSet viewServiceSet = serviceSets.createViewServiceSet(this);
+
     paths.forEach(
         path -> {
-          addServiceSet(path, new DefaultDiscoveryServiceSet(OpcUaServer.this));
+          addServiceSet(path, discoveryServiceSet);
 
           if (!path.endsWith("/discovery")) {
-            addServiceSet(path, new DefaultAttributeServiceSet(OpcUaServer.this));
-            addServiceSet(path, new DefaultMethodServiceSet(OpcUaServer.this));
-            addServiceSet(path, new DefaultMonitoredItemServiceSet(OpcUaServer.this));
-            addServiceSet(path, new DefaultNodeManagementServiceSet(OpcUaServer.this));
-            addServiceSet(path, new DefaultQueryServiceSet());
-            addServiceSet(path, new DefaultSessionServiceSet(OpcUaServer.this));
-            addServiceSet(path, new DefaultSubscriptionServiceSet(OpcUaServer.this));
-            addServiceSet(path, new DefaultViewServiceSet(OpcUaServer.this));
+            addServiceSet(path, attributeServiceSet);
+            addServiceSet(path, methodServiceSet);
+            addServiceSet(path, monitoredItemServiceSet);
+            addServiceSet(path, nodeManagementServiceSet);
+            addServiceSet(path, queryServiceSet);
+            addServiceSet(path, sessionServiceSet);
+            addServiceSet(path, subscriptionServiceSet);
+            addServiceSet(path, viewServiceSet);
           }
         });
 

opc-ua-sdk/sdk-server/src/main/java/org/eclipse/milo/opcua/sdk/server/ServiceSets.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2026 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.server;
+
+import org.eclipse.milo.opcua.sdk.server.servicesets.AttributeServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.DiscoveryServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.MethodServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.MonitoredItemServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.NodeManagementServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.QueryServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.SessionServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.SubscriptionServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.ViewServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultAttributeServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultDiscoveryServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultMethodServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultMonitoredItemServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultNodeManagementServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultQueryServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultSessionServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultSubscriptionServiceSet;
+import org.eclipse.milo.opcua.sdk.server.servicesets.impl.DefaultViewServiceSet;
+
+/**
+ * Factories for the service set implementations an {@link OpcUaServer} uses.
+ *
+ * <p>Each factory method is invoked once while the server is constructed, and the returned instance
+ * is registered on every applicable endpoint path: the {@link DiscoveryServiceSet} on all paths,
+ * the other service sets on all paths not suffixed with "/discovery".
+ *
+ * <p>All methods have defaults that return the standard implementations, so an implementation only
+ * overrides the service sets it replaces:
+ *
+ * <pre>{@code
+ * var server = new OpcUaServer(config, transportFactory, new ServiceSets() {
+ *     @Override
+ *     public DiscoveryServiceSet createDiscoveryServiceSet(OpcUaServer server) {
+ *         return new DefaultDiscoveryServiceSet(server, additionalServersSupplier);
+ *     }
+ * });
+ * }</pre>
+ */
+public interface ServiceSets {
+
+  default AttributeServiceSet createAttributeServiceSet(OpcUaServer server) {
+    return new DefaultAttributeServiceSet(server);
+  }
+
+  default DiscoveryServiceSet createDiscoveryServiceSet(OpcUaServer server) {
+    return new DefaultDiscoveryServiceSet(server);
+  }
+
+  default MethodServiceSet createMethodServiceSet(OpcUaServer server) {
+    return new DefaultMethodServiceSet(server);
+  }
+
+  default MonitoredItemServiceSet createMonitoredItemServiceSet(OpcUaServer server) {
+    return new DefaultMonitoredItemServiceSet(server);
+  }
+
+  default NodeManagementServiceSet createNodeManagementServiceSet(OpcUaServer server) {
+    return new DefaultNodeManagementServiceSet(server);
+  }
+
+  default QueryServiceSet createQueryServiceSet(OpcUaServer server) {
+    return new DefaultQueryServiceSet();
+  }
+
+  default SessionServiceSet createSessionServiceSet(OpcUaServer server) {
+    return new DefaultSessionServiceSet(server);
+  }
+
+  default SubscriptionServiceSet createSubscriptionServiceSet(OpcUaServer server) {
+    return new DefaultSubscriptionServiceSet(server);
+  }
+
+  default ViewServiceSet createViewServiceSet(OpcUaServer server) {
+    return new DefaultViewServiceSet(server);
+  }
+}

opc-ua-sdk/sdk-server/src/main/java/org/eclipse/milo/opcua/sdk/server/servicesets/impl/DefaultDiscoveryServiceSet.java

@@ -13,9 +13,11 @@
 import static java.util.stream.Collectors.toList;
 import static org.eclipse.milo.opcua.sdk.server.servicesets.AbstractServiceSet.createResponseHeader;
 
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
+import java.util.function.Supplier;
 import org.eclipse.milo.opcua.sdk.server.EndpointConfig;
 import org.eclipse.milo.opcua.sdk.server.OpcUaServer;
 import org.eclipse.milo.opcua.sdk.server.servicesets.DiscoveryServiceSet;
@@ -44,9 +46,32 @@ public class DefaultDiscoveryServiceSet implements DiscoveryServiceSet {
   private final Logger logger = LoggerFactory.getLogger(getClass());
 
   private final OpcUaServer server;
+  private final Supplier<List<ApplicationDescription>> additionalServers;
 
   public DefaultDiscoveryServiceSet(OpcUaServer server) {
+    this(server, List::of);
+  }
+
+  /**
+   * Create a DefaultDiscoveryServiceSet that includes additional servers in the results of the
+   * FindServers service.
+   *
+   * <p>The supplier is invoked each time the FindServers service is invoked, and may return
+   * different results over time. It must not include the ApplicationDescription of {@code server}
+   * itself; that is always included.
+   *
+   * <p>This is intended for use by servers that know of other servers they should advertise, e.g.
+   * the other members of a non-transparent redundant server set.
+   *
+   * @param server the {@link OpcUaServer} this service set belongs to.
+   * @param additionalServers a supplier of additional {@link ApplicationDescription}s to include in
+   *     the results of the FindServers service.
+   */
+  public DefaultDiscoveryServiceSet(
+      OpcUaServer server, Supplier<List<ApplicationDescription>> additionalServers) {
+
     this.server = server;
+    this.additionalServers = additionalServers;
   }
 
   @Override
@@ -94,8 +119,9 @@ public FindServersResponse onFindServers(
             ? List.of(request.getServerUris())
             : Collections.emptyList();
 
-    List<ApplicationDescription> applicationDescriptions =
-        List.of(getFilteredApplicationDescription(request.getEndpointUrl()));
+    List<ApplicationDescription> applicationDescriptions = new ArrayList<>();
+    applicationDescriptions.add(getFilteredApplicationDescription(request.getEndpointUrl()));
+    applicationDescriptions.addAll(additionalServers.get());
 
     applicationDescriptions =
         applicationDescriptions.stream().filter(ad -> filterServerUris(ad, serverUris)).toList();