Introduce ByProducerIdOrFirstField as the default event routing

client-testlib/src/main/java/io/spine/testing/client/TestActorRequestFactory.java

@@ -53,13 +53,31 @@
 })
 public class TestActorRequestFactory extends ActorRequestFactory {
 
+    /**
+     * Creates a new factory with the specified actor and time zone.
+     *
+     * @param actor
+     *         the ID of the user who performs operations
+     * @param zoneId
+     *         the time zone in which the actor operates
+     */
     public TestActorRequestFactory(UserId actor, ZoneId zoneId) {
         super(ActorRequestFactory.newBuilder()
                       .setActor(actor)
                       .setZoneId(zoneId)
         );
     }
 
+    /**
+     * Creates a new factory with the specified tenant, actor and time zone.
+     *
+     * @param tenantId
+     *         the ID of the tenant in a multi-tenant application
+     * @param actor
+     *         the ID of the user who performs operations
+     * @param zoneId
+     *         the time zone in which the actor operates
+     */
     public TestActorRequestFactory(@Nullable TenantId tenantId, UserId actor, ZoneId zoneId) {
         super(ActorRequestFactory.newBuilder()
                       .setTenantId(tenantId)
@@ -68,29 +86,74 @@ public TestActorRequestFactory(@Nullable TenantId tenantId, UserId actor, ZoneId
         );
     }
 
+    /**
+     * Creates a new factory with an actor ID created from the string and specified time zone.
+     *
+     * @param actor
+     *         the string to create actor ID from
+     * @param zoneId
+     *         the time zone in which the actor operates
+     */
     public TestActorRequestFactory(String actor, ZoneId zoneId) {
         this(GivenUserId.of(actor), zoneId);
     }
 
+    /**
+     * Creates a new factory using the test class name as the actor ID and system default time zone.
+     *
+     * @param testClass
+     *         the class whose name will be used as the actor ID
+     */
     public TestActorRequestFactory(Class<?> testClass) {
         this(testClass.getName(), ZoneIds.systemDefault());
     }
 
+    /**
+     * Creates a new factory with the specified actor and system default time zone.
+     *
+     * @param actor
+     *         the ID of the user who performs operations
+     */
     public TestActorRequestFactory(UserId actor) {
         this(actor, ZoneIds.systemDefault());
     }
 
+    /**
+     * Creates a new factory with the specified actor, tenant and system default time zone.
+     *
+     * @param actor
+     *         the ID of the user who performs operations
+     * @param tenantId
+     *         the ID of the tenant in a multi-tenant application
+     */
     public TestActorRequestFactory(UserId actor, TenantId tenantId) {
         this(tenantId, actor, ZoneIds.systemDefault());
     }
 
+    /**
+     * Creates a new factory using the test class name as the actor ID,
+     * specified tenant and system default time zone.
+     *
+     * @param testClass
+     *         the class whose name will be used as the actor ID
+     * @param tenantId
+     *         the ID of the tenant in a multi-tenant application
+     */
     public TestActorRequestFactory(Class<?> testClass, TenantId tenantId) {
         this(tenantId,
              GivenUserId.of(testClass.getName()),
              ZoneIds.systemDefault());
     }
 
-    /** Creates new command with the passed timestamp. */
+    /**
+     * Creates a new command with the given message and timestamp.
+     *
+     * @param message
+     *         the command message
+     * @param timestamp
+     *         the time when the command was created
+     * @return new command instance with the specified timestamp
+     */
     public Command createCommand(CommandMessage message, Timestamp timestamp) {
         var command = command().create(message);
         return withTimestamp(command, timestamp);
@@ -111,6 +174,13 @@ private static Command withTimestamp(Command command, Timestamp timestamp) {
         return result;
     }
 
+    /**
+     * Creates a new command with the given message.
+     *
+     * @param message
+     *         the command message
+     * @return new command instance
+     */
     public Command createCommand(CommandMessage message) {
         var command = command().create(message);
         return command;

dependencies.md

@@ -1,6 +1,6 @@
 
 
-# Dependencies of `io.spine:spine-client:2.0.0-SNAPSHOT.348`
+# Dependencies of `io.spine:spine-client:2.0.0-SNAPSHOT.349`
 
 ## Runtime
 1.  **Group** : com.google.android. **Name** : annotations. **Version** : 4.1.1.4.
@@ -1085,14 +1085,14 @@
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Thu Nov 06 20:06:57 WET 2025** using 
+This report was generated on **Tue Nov 11 19:50:43 WET 2025** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:spine-client-testlib:2.0.0-SNAPSHOT.348`
+# Dependencies of `io.spine.tools:spine-client-testlib:2.0.0-SNAPSHOT.349`
 
 ## Runtime
 1.  **Group** : com.google.android. **Name** : annotations. **Version** : 4.1.1.4.
@@ -2273,14 +2273,14 @@ This report was generated on **Thu Nov 06 20:06:57 WET 2025** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Thu Nov 06 20:06:57 WET 2025** using 
+This report was generated on **Tue Nov 11 19:50:43 WET 2025** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine:spine-core:2.0.0-SNAPSHOT.348`
+# Dependencies of `io.spine:spine-core:2.0.0-SNAPSHOT.349`
 
 ## Runtime
 1.  **Group** : com.google.code.findbugs. **Name** : jsr305. **Version** : 3.0.2.
@@ -3301,14 +3301,14 @@ This report was generated on **Thu Nov 06 20:06:57 WET 2025** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Thu Nov 06 20:06:57 WET 2025** using 
+This report was generated on **Tue Nov 11 19:50:43 WET 2025** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:spine-core-testlib:2.0.0-SNAPSHOT.348`
+# Dependencies of `io.spine.tools:spine-core-testlib:2.0.0-SNAPSHOT.349`
 
 ## Runtime
 1.  **Group** : com.google.android. **Name** : annotations. **Version** : 4.1.1.4.
@@ -4375,14 +4375,14 @@ This report was generated on **Thu Nov 06 20:06:57 WET 2025** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Thu Nov 06 20:06:57 WET 2025** using 
+This report was generated on **Tue Nov 11 19:50:43 WET 2025** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine:spine-server:2.0.0-SNAPSHOT.348`
+# Dependencies of `io.spine:spine-server:2.0.0-SNAPSHOT.349`
 
 ## Runtime
 1.  **Group** : com.google.android. **Name** : annotations. **Version** : 4.1.1.4.
@@ -5479,14 +5479,14 @@ This report was generated on **Thu Nov 06 20:06:57 WET 2025** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Thu Nov 06 20:06:57 WET 2025** using 
+This report was generated on **Tue Nov 11 19:50:43 WET 2025** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:spine-server-testlib:2.0.0-SNAPSHOT.348`
+# Dependencies of `io.spine.tools:spine-server-testlib:2.0.0-SNAPSHOT.349`
 
 ## Runtime
 1.  **Group** : com.google.android. **Name** : annotations. **Version** : 4.1.1.4.
@@ -6719,6 +6719,6 @@ This report was generated on **Thu Nov 06 20:06:57 WET 2025** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Thu Nov 06 20:06:57 WET 2025** using 
+This report was generated on **Tue Nov 11 19:50:43 WET 2025** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).

pom.xml

@@ -10,7 +10,7 @@ all modules and does not describe the project structure per-subproject.
  -->
 <groupId>io.spine</groupId>
 <artifactId>spine-core-jvm</artifactId>
-<version>2.0.0-SNAPSHOT.348</version>
+<version>2.0.0-SNAPSHOT.349</version>
 
 <inceptionYear>2015</inceptionYear>
 

server/src/main/java/io/spine/server/aggregate/AggregateRepository.java

@@ -111,13 +111,13 @@ public abstract class AggregateRepository<I,
     private final Supplier<CommandRouting<I>> commandRouting;
 
     /** The routing schema for events to which aggregates react. */
-    private final EventRouting<I> eventRouting;
+    private final Supplier<EventRouting<I>> eventRouting;
 
     /**
      * The routing for event import, which by default obtains the target aggregate ID as the
      * {@linkplain io.spine.core.EventContext#getProducerId() producer ID} of the event.
      */
-    private final EventRouting<I> eventImportRouting;
+    private final Supplier<EventRouting<I>> eventImportRouting;
 
     /**
      * The {@link Inbox} for the messages, which are sent to the instances managed by this
@@ -134,8 +134,12 @@ public abstract class AggregateRepository<I,
     protected AggregateRepository() {
         super();
         this.commandRouting = memoize(() -> CommandRouting.newInstance(idClass()));
-        this.eventRouting = EventRouting.withDefaultByProducerId();
-        this.eventImportRouting = EventRouting.withDefaultByProducerId();
+        this.eventRouting = memoize(
+                () -> EventRouting.withDefaultByProducerIdOrFirstField(idClass())
+        );
+        this.eventImportRouting = memoize(
+                () -> EventRouting.withDefaultByProducerIdOrFirstField(idClass())
+        );
     }
 
     /**
@@ -174,7 +178,7 @@ public void registerWith(BoundedContext context) {
     private void setupRouting() {
         doSetupCommandRouting();
         doSetupEventRouting();
-        setupImportRouting(eventImportRouting);
+        setupImportRouting(eventImportRouting.get());
     }
 
     private void doSetupCommandRouting() {
@@ -185,8 +189,8 @@ private void doSetupCommandRouting() {
     }
 
     private void doSetupEventRouting() {
-        EventRoutingSetup.apply(entityClass(), eventRouting);
-        setupEventRouting(eventRouting);
+        EventRoutingSetup.apply(entityClass(), eventRouting.get());
+        setupEventRouting(eventRouting.get());
     }
 
     @Override
@@ -478,7 +482,7 @@ private RouteFn<? extends EventMessage, EventContext, I> eventImportRouting() {
      *          if {@link #eventImportRouting} returns more than one ID
      */
     private I idForImported(EventMessage message, EventContext context) {
-        var ids = eventImportRouting.invoke(message, context);
+        var ids = eventImportRouting.get().invoke(message, context);
         var numberOfTargets = ids.size();
         var messageType = message.getClass()
                                  .getName();
@@ -515,7 +519,7 @@ private CommandRouting<I> commandRouting() {
      * Obtains event routing instance used by this repository.
      */
     private EventRouting<I> eventRouting() {
-        return eventRouting;
+        return eventRouting.get();
     }
 
     /**

server/src/main/java/io/spine/server/entity/EventDispatchingRepository.java

@@ -37,8 +37,10 @@
 import io.spine.server.type.EventEnvelope;
 
 import java.util.Set;
+import java.util.function.Supplier;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Suppliers.memoize;
 
 /**
  * Abstract base for repositories that deliver events to entities they manage.
@@ -56,11 +58,13 @@ public abstract class EventDispatchingRepository<I,
         extends DefaultRecordBasedRepository<I, E, S>
         implements EventDispatcher {
 
-    private final EventRouting<I> eventRouting;
+    private final Supplier<EventRouting<I>> eventRouting;
 
     protected EventDispatchingRepository() {
         super();
-        this.eventRouting = EventRouting.withDefaultByProducerId();
+        this.eventRouting = memoize(
+                () -> EventRouting.withDefaultByProducerIdOrFirstField(idClass())
+        );
     }
 
     /**
@@ -76,8 +80,8 @@ public void registerWith(BoundedContext context) {
         context.internalAccess()
                .registerEventDispatcher(this);
 
-        EventRoutingSetup.apply(entityClass(), eventRouting);
-        setupEventRouting(eventRouting);
+        EventRoutingSetup.apply(entityClass(), eventRouting.get());
+        setupEventRouting(eventRouting.get());
     }
 
     /**
@@ -129,7 +133,7 @@ public final DispatchOutcome dispatch(EventEnvelope event) {
      * @return a set of IDs of projections to dispatch the given event to
      */
     protected Set<I> route(EventEnvelope event) {
-        var targets = route(eventRouting, event);
+        var targets = route(eventRouting.get(), event);
         @SuppressWarnings("unchecked")
         var result = (Set<I>) targets.orElse(ImmutableSet.of());
         return result;

server/src/main/kotlin/io/spine/server/route/ByFirstField.kt

@@ -54,9 +54,8 @@ internal class ByFirstField<I : Any, M : Routable, C : SignalContext>(
     /**
      * Obtains a descriptor of the first field of the passed.
      *
-     * @throws IllegalStateException
-     * if the passed message does not declare fields, or
-     * the field is a repeated field or a map
+     * @throws IllegalStateException if the passed message does not declare fields, or
+     *   the field is a repeated field or a map.
      */
     @Suppress("ThrowsCount")
     private fun fieldIn(message: M): FieldDescriptor {