Note that a Neo4j reactive transaction manager is not auto-configured

Closes gh-23629

spring-boot-project/spring-boot-docs/build.gradle

@@ -82,6 +82,7 @@ dependencies {
 	implementation("org.springframework:spring-web")
 	implementation("org.springframework:spring-webflux")
 	implementation("org.springframework.data:spring-data-couchbase")
+	implementation("org.springframework.data:spring-data-neo4j")
 	implementation("org.springframework.data:spring-data-redis")
 	implementation("org.springframework.data:spring-data-r2dbc")
 	implementation("org.springframework.kafka:spring-kafka")

spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc

@@ -4791,6 +4791,17 @@ When Project Reactor is available on the classpath, the reactive style is also a
 
 You can customize the locations to look for repositories and entities by using `@EnableNeo4jRepositories` and `@EntityScan` respectively on a `@Configuration`-bean.
 
+[NOTE]
+====
+In an application using the reactive style, a `ReactiveTransactionManager` is not auto-configured.
+To enable transaction management, the following bean must be defined in your configuration:
+
+[source,java,indent=0]
+----
+include::{code-examples}/neo4j/Neo4jReactiveTransactionManagerExample.java[tag=configuration]
+----
+====
+
 
 
 [[boot-features-solr]]

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/neo4j/Neo4jReactiveTransactionManagerExample.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.docs.neo4j;
+
+import org.neo4j.driver.Driver;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.data.neo4j.core.ReactiveDatabaseSelectionProvider;
+import org.springframework.data.neo4j.core.transaction.ReactiveNeo4jTransactionManager;
+import org.springframework.transaction.ReactiveTransactionManager;
+
+/**
+ * Example to show user-defined registration of a {@link ReactiveTransactionManager}.
+ *
+ * @author Stephane Nicoll
+ */
+@Configuration(proxyBeanMethods = false)
+public class Neo4jReactiveTransactionManagerExample {
+
+	// tag::configuration[]
+	@Bean
+	public ReactiveNeo4jTransactionManager reactiveTransactionManager(Driver driver,
+			ReactiveDatabaseSelectionProvider databaseNameProvider) {
+		return new ReactiveNeo4jTransactionManager(driver, databaseNameProvider);
+	}
+	// end::configuration[]
+
+}