Do not configure a ReactiveNeo4jTransactionManager

The current arrangement with Neo4j does not allow us to know for sure
that the user intends to use `@Transactional` for reactive or imperative
operations.

The main reason for that is that the only trigger for the reactive
auto-configuration is the presence of reactor on the classpath given
that the Neo4j driver ships with both styles in the same jar. And
reactor can be on the classpath for a number of reasons that are
unrelated to imperative access (typically `WebClient`).

This commits removes the auto-configuration of the
ReactiveNeo4jAutoConfiguration and makes sure that if the user defines
one, the regular `PlatformTransactionManager` backs off. This is
a temporarily situation until we can provide a better signal that the
user intends to primarily use imperative repositories.

Closes gh-22940

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/neo4j/Neo4jDataAutoConfiguration.java

@@ -47,6 +47,7 @@ import org.springframework.data.neo4j.core.schema.Node;
 import org.springframework.data.neo4j.core.transaction.Neo4jTransactionManager;
 import org.springframework.data.neo4j.repository.config.Neo4jRepositoryConfigurationExtension;
 import org.springframework.transaction.PlatformTransactionManager;
+import org.springframework.transaction.TransactionManager;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for Spring Data Neo4j.
@@ -106,7 +107,7 @@ public class Neo4jDataAutoConfiguration {
 	}
 
 	@Bean(Neo4jRepositoryConfigurationExtension.DEFAULT_TRANSACTION_MANAGER_BEAN_NAME)
-	@ConditionalOnMissingBean(PlatformTransactionManager.class)
+	@ConditionalOnMissingBean(TransactionManager.class)
 	public Neo4jTransactionManager transactionManager(Driver driver, DatabaseSelectionProvider databaseNameProvider,
 			ObjectProvider<TransactionManagerCustomizers> optionalCustomizers) {
 		Neo4jTransactionManager transactionManager = new Neo4jTransactionManager(driver, databaseNameProvider);

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/neo4j/Neo4jReactiveDataAutoConfiguration.java

@@ -33,7 +33,6 @@ import org.springframework.data.neo4j.core.ReactiveNeo4jClient;
 import org.springframework.data.neo4j.core.ReactiveNeo4jOperations;
 import org.springframework.data.neo4j.core.ReactiveNeo4jTemplate;
 import org.springframework.data.neo4j.core.mapping.Neo4jMappingContext;
-import org.springframework.data.neo4j.core.transaction.ReactiveNeo4jTransactionManager;
 import org.springframework.data.neo4j.repository.config.ReactiveNeo4jRepositoryConfigurationExtension;
 import org.springframework.transaction.ReactiveTransactionManager;
 
@@ -46,8 +45,7 @@ import org.springframework.transaction.ReactiveTransactionManager;
  * @since 2.4.0
  */
 @Configuration(proxyBeanMethods = false)
-@ConditionalOnClass({ Driver.class, ReactiveNeo4jTransactionManager.class, ReactiveTransactionManager.class,
+@ConditionalOnClass({ Driver.class, ReactiveNeo4jTemplate.class, ReactiveTransactionManager.class, Flux.class })
-		Flux.class })
 @ConditionalOnBean(Driver.class)
 @AutoConfigureAfter(Neo4jDataAutoConfiguration.class)
 @Import(Neo4jDefaultReactiveCallbacksRegistrar.class)
@@ -74,11 +72,4 @@ public class Neo4jReactiveDataAutoConfiguration {
 		return new ReactiveNeo4jTemplate(neo4jClient, neo4jMappingContext, databaseNameProvider);
 	}
 
-	@Bean(ReactiveNeo4jRepositoryConfigurationExtension.DEFAULT_TRANSACTION_MANAGER_BEAN_NAME)
-	@ConditionalOnMissingBean(ReactiveTransactionManager.class)
-	public ReactiveTransactionManager reactiveTransactionManager(Driver driver,
-			ReactiveDatabaseSelectionProvider databaseNameProvider) {
-		return new ReactiveNeo4jTransactionManager(driver, databaseNameProvider);
-	}
-
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/data/neo4j/Neo4jDataAutoConfigurationTests.java

@@ -31,6 +31,8 @@ import org.springframework.data.neo4j.core.Neo4jTemplate;
 import org.springframework.data.neo4j.core.convert.Neo4jConversions;
 import org.springframework.data.neo4j.core.transaction.Neo4jTransactionManager;
 import org.springframework.transaction.PlatformTransactionManager;
+import org.springframework.transaction.ReactiveTransactionManager;
+import org.springframework.transaction.TransactionManager;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
@@ -119,6 +121,13 @@ class Neo4jDataAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void shouldBackoffIfReactiveTransactionManagerIsSet() {
+		this.contextRunner.withBean(ReactiveTransactionManager.class, () -> mock(ReactiveTransactionManager.class))
+				.run((context) -> assertThat(context).doesNotHaveBean(Neo4jTransactionManager.class)
+						.hasSingleBean(TransactionManager.class));
+	}
+
 	@Test
 	void shouldReuseExistingTransactionManager() {
 		this.contextRunner

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/data/neo4j/Neo4jReactiveDataAutoConfigurationTests.java

@@ -30,8 +30,8 @@ import org.springframework.data.neo4j.core.ReactiveDatabaseSelectionProvider;
 import org.springframework.data.neo4j.core.ReactiveNeo4jClient;
 import org.springframework.data.neo4j.core.ReactiveNeo4jOperations;
 import org.springframework.data.neo4j.core.ReactiveNeo4jTemplate;
-import org.springframework.data.neo4j.core.transaction.ReactiveNeo4jTransactionManager;
 import org.springframework.transaction.ReactiveTransactionManager;
+import org.springframework.transaction.TransactionManager;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
@@ -113,23 +113,12 @@ class Neo4jReactiveDataAutoConfigurationTests {
 	}
 
 	@Test
-	void shouldProvideReactiveTransactionManager() {
+	void shouldUseExistingReactiveTransactionManager() {
-		this.contextRunner.withUserConfiguration(CustomReactiveDatabaseSelectionProviderConfiguration.class)
-				.run((context) -> {
-					assertThat(context).hasSingleBean(ReactiveNeo4jTransactionManager.class);
-					assertThat(context.getBean(ReactiveNeo4jTransactionManager.class))
-							.extracting("databaseSelectionProvider")
-							.isSameAs(context.getBean(ReactiveDatabaseSelectionProvider.class));
-				});
-	}
-
-	@Test
-	void shouldReuseExistingReactiveTransactionManager() {
 		this.contextRunner
 				.withBean("myCustomReactiveTransactionManager", ReactiveTransactionManager.class,
 						() -> mock(ReactiveTransactionManager.class))
 				.run((context) -> assertThat(context).hasSingleBean(ReactiveTransactionManager.class)
-						.hasBean("myCustomReactiveTransactionManager"));
+						.hasSingleBean(TransactionManager.class));
 	}
 
 	@Configuration(proxyBeanMethods = false)

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/data/neo4j/Neo4jReactiveRepositoriesAutoConfigurationTests.java

@@ -28,7 +28,7 @@ import org.springframework.boot.autoconfigure.data.neo4j.country.CountryReposito
 import org.springframework.boot.autoconfigure.data.neo4j.country.ReactiveCountryRepository;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.data.neo4j.core.transaction.ReactiveNeo4jTransactionManager;
+import org.springframework.data.neo4j.core.ReactiveNeo4jTemplate;
 import org.springframework.data.neo4j.repository.ReactiveNeo4jRepository;
 import org.springframework.data.neo4j.repository.config.EnableReactiveNeo4jRepositories;
 
@@ -57,7 +57,7 @@ public class Neo4jReactiveRepositoriesAutoConfigurationTests {
 	@Test
 	void configurationWithNoRepositories() {
 		this.contextRunner.withUserConfiguration(EmptyConfiguration.class).run((context) -> assertThat(context)
-				.hasSingleBean(ReactiveNeo4jTransactionManager.class).doesNotHaveBean(ReactiveNeo4jRepository.class));
+				.hasSingleBean(ReactiveNeo4jTemplate.class).doesNotHaveBean(ReactiveNeo4jRepository.class));
 	}
 
 	@Test
@@ -70,7 +70,7 @@ public class Neo4jReactiveRepositoriesAutoConfigurationTests {
 	@Test
 	void autoConfigurationShouldNotKickInEvenIfManualConfigDidNotCreateAnyRepositories() {
 		this.contextRunner.withUserConfiguration(SortOfInvalidCustomConfiguration.class)
-				.run((context) -> assertThat(context).hasSingleBean(ReactiveNeo4jTransactionManager.class)
+				.run((context) -> assertThat(context).hasSingleBean(ReactiveNeo4jTemplate.class)
 						.doesNotHaveBean(ReactiveNeo4jRepository.class));
 	}