Polishing.

Initialize MongoId also for reactive insertAll(…).

See: #4944
Original pull request: #4945

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveMongoTemplate.java

@@ -1433,11 +1433,16 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 						entity.assertUpdateableIdIfNotSet();
 
 						T initialized = entity.initializeVersionProperty();
-						Document dbDoc = entity.toMappedDocument(writer).getDocument();
+						MappedDocument mapped = entity.toMappedDocument(writer);
 
-						maybeEmitEvent(new BeforeSaveEvent<>(initialized, dbDoc, collectionName));
+						maybeEmitEvent(new BeforeSaveEvent<>(initialized, mapped.getDocument(), collectionName));
+						return maybeCallBeforeSave(initialized, mapped.getDocument(), collectionName).map(toSave -> {
 
-						return maybeCallBeforeSave(initialized, dbDoc, collectionName).thenReturn(Tuples.of(entity, dbDoc));
+							MappedDocument mappedDocument = queryOperations.createInsertContext(mapped)
+									.prepareId(uninitialized.getClass());
+
+							return Tuples.of(entity, mappedDocument.getDocument());
+						});
 					});
 				}).collectList();
 

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/ReactiveMongoTemplateTests.java

@@ -48,6 +48,7 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.dao.DataIntegrityViolationException;
@@ -84,6 +85,7 @@ import org.springframework.data.mongodb.test.util.ReactiveMongoTestTemplate;
 
 import com.mongodb.WriteConcern;
 import com.mongodb.reactivestreams.client.MongoClient;
+import com.mongodb.reactivestreams.client.MongoCollection;
 
 /**
  * Integration test for {@link MongoTemplate}.
@@ -165,6 +167,19 @@ public class ReactiveMongoTemplateTests {
 		assertThat(person.getId()).isNotNull();
 	}
 
+	@Test // GH-4944
+	void insertAllShouldConvertIdToTargetTypeBeforeSave() {
+
+		RawStringId walter = new RawStringId();
+		walter.value = "walter";
+
+		RawStringId returned = template.insertAll(List.of(walter)).blockLast();
+		template.execute(RawStringId.class, MongoCollection::find) //
+				.as(StepVerifier::create) //
+				.consumeNextWith(actual -> assertThat(returned.id).isEqualTo(actual.get("_id"))) //
+				.verifyComplete();
+	}
+
 	@Test // DATAMONGO-1444
 	void saveSetsId() {