Avoid setting the tenant id if one is preset

data-jdbc/src/test/groovy/io/micronaut/data/jdbc/h2/multitenancy/TenancyBook.java

@@ -0,0 +1,19 @@
+package io.micronaut.data.jdbc.h2.multitenancy;
+
+import io.micronaut.core.annotation.Nullable;
+import io.micronaut.data.annotation.GeneratedValue;
+import io.micronaut.data.annotation.Id;
+import io.micronaut.data.annotation.MappedEntity;
+import io.micronaut.data.annotation.TenantId;
+import io.micronaut.serde.annotation.Serdeable;
+
+@Serdeable // <1>
+@MappedEntity // <2>
+public record TenancyBook(@Nullable
+                          @Id // <3>
+                          @GeneratedValue // <4>
+                          Long id,
+                          String title,
+                          @TenantId // <5>
+                          String framework) {
+}

data-jdbc/src/test/groovy/io/micronaut/data/jdbc/h2/multitenancy/TenancyBookController.java

@@ -0,0 +1,26 @@
+package io.micronaut.data.jdbc.h2.multitenancy;
+
+import io.micronaut.context.annotation.Requires;
+import io.micronaut.http.annotation.Controller;
+import io.micronaut.http.annotation.Get;
+import io.micronaut.scheduling.TaskExecutors;
+import io.micronaut.scheduling.annotation.ExecuteOn;
+
+import java.util.List;
+
+@Requires(property = "spec.name", value = "TenancyBookControllerSpec")
+@Controller("/books") // <1>
+class TenancyBookController {
+    private final TenancyBookRepository bookRepository;
+
+    TenancyBookController(TenancyBookRepository bookRepository) { // <2>
+        this.bookRepository = bookRepository;
+    }
+
+    @ExecuteOn(TaskExecutors.BLOCKING) // <3>
+    @Get
+        // <4>
+    List<TenancyBook> index() {
+        return bookRepository.findAll();
+    }
+}

data-jdbc/src/test/groovy/io/micronaut/data/jdbc/h2/multitenancy/TenancyBookControllerSpec.groovy

@@ -0,0 +1,75 @@
+package io.micronaut.data.jdbc.h2.multitenancy
+
+import io.micronaut.context.annotation.Property
+import io.micronaut.core.type.Argument
+import io.micronaut.core.util.StringUtils
+import io.micronaut.http.HttpRequest
+import io.micronaut.http.HttpResponse
+import io.micronaut.http.HttpStatus
+import io.micronaut.http.client.BlockingHttpClient
+import io.micronaut.http.client.HttpClient
+import io.micronaut.http.client.annotation.Client
+import io.micronaut.test.extensions.spock.annotation.MicronautTest
+import jakarta.inject.Inject
+import spock.lang.Specification
+
+import static org.junit.Assert.assertEquals
+
+@Property(name = "datasources.default.schema-generate", value = "CREATE_DROP")
+// <1>
+@Property(name = "datasources.default.url", value = "jdbc:h2:mem:devDb;LOCK_TIMEOUT=10000;DB_CLOSE_ON_EXIT=FALSE")
+@Property(name = "datasources.default.username", value = "sa")
+@Property(name = "datasources.default.password", value = "")
+@Property(name = "datasources.default.dialect", value = "H2")
+@Property(name = "datasources.default.driver-class-name", value = "org.h2.Driver")
+@Property(name = "micronaut.multitenancy.tenantresolver.httpheader.enabled", value = StringUtils.TRUE)
+@Property(name = "spec.name", value = "TenancyBookControllerSpec")
+@MicronautTest(transactional = false)
+// <2>
+class TenancyBookControllerSpec extends Specification {
+
+    @Inject
+    @Client("/")
+    HttpClient httpClient
+
+    @Inject
+    TenancyBookRepository bookRepository
+
+    def multitenancyRequest() {
+
+        given:
+            BlockingHttpClient client = httpClient.toBlocking()
+            save(bookRepository, client, "Building Microservices with Micronaut", "micronaut")
+            save(bookRepository, client, "Introducing Micronaut", "micronaut")
+            save(bookRepository, client, "Grails 3 - Step by Step", "grails")
+            save(bookRepository, client, "Falando de Grail", "grails")
+            save(bookRepository, client, "Grails Goodness Notebook", "grails")
+
+        when:
+            List<TenancyBook> books = fetchBooks(client, "micronaut")
+        then:
+            books
+            books.size() == 2
+
+        when:
+            books = fetchBooks(client, "grails")
+        then:
+            books
+            books.size() == 3
+
+        cleanup:
+            bookRepository.deleteAll()
+    }
+
+    List<TenancyBook> fetchBooks(BlockingHttpClient client, String framework) {
+        HttpRequest<?> request = HttpRequest.GET("/books").header("tenantId", framework)
+        Argument<List<TenancyBook>> responseArgument = Argument.listOf(TenancyBook.class)
+        HttpResponse<List<TenancyBook>> response = client.exchange(request, responseArgument)
+        assertEquals(HttpStatus.OK, response.getStatus())
+        return response.body()
+    }
+
+    void save(TenancyBookRepository bookRepository, BlockingHttpClient client, String title, String framework) {
+        bookRepository.save(new TenancyBook(null, title, framework))
+    }
+}

data-jdbc/src/test/groovy/io/micronaut/data/jdbc/h2/multitenancy/TenancyBookRepository.java

@@ -0,0 +1,17 @@
+package io.micronaut.data.jdbc.h2.multitenancy;
+
+import io.micronaut.context.annotation.Requires;
+import io.micronaut.data.annotation.WithoutTenantId;
+import io.micronaut.data.jdbc.annotation.JdbcRepository;
+import io.micronaut.data.model.query.builder.sql.Dialect;
+import io.micronaut.data.repository.CrudRepository;
+
+@Requires(property = "spec.name", value = "TenancyBookControllerSpec")
+@JdbcRepository(dialect = Dialect.H2) // <1>
+public interface TenancyBookRepository extends CrudRepository<TenancyBook, Long> {  // <2>
+    Long save(String title);
+
+    @WithoutTenantId
+    @Override
+    void deleteAll();
+}

data-runtime/src/main/java/io/micronaut/data/runtime/event/listeners/TenantIdEntityEventListener.java

@@ -76,6 +76,10 @@ protected Predicate<RuntimePersistentProperty<Object>> getPropertyPredicate() {
     public boolean prePersist(@NonNull EntityEventContext<Object> context) {
         for (RuntimePersistentProperty<Object> property : getApplicableProperties(context.getPersistentEntity())) {
             if (property.getAnnotationMetadata().hasStereotype(TenantId.class)) {
+                if (property.getProperty().get(context.getEntity()) != null) {
+                    // Skip existing value
+                    return true;
+                }
                 Argument<Object> argument = property.getArgument();
                 Object newValue = tenantResolver.resolveTenantIdentifier();
                 if (!argument.isInstance(newValue)) {