feat: allow Spanner and Datastore Transaction Manager in same project

docs/src/main/asciidoc/datastore.adoc

@@ -854,6 +854,13 @@ This feature requires a bean of `DatastoreTransactionManager`, which is provided
 If a method annotated with `@Transactional` calls another method also annotated, then both methods will work within the same transaction.
 `performTransaction` cannot be used in `@Transactional` annotated methods because Cloud Datastore does not support transactions within transactions.
 
+Other Google Cloud database-related integrations like Spanner and Firestore can introduce `PlatformTransactionManager` beans, and can interfere with Datastore Transaction Manager. To disambiguate, explicitly specify the name of the transaction manager bean for such `@Transactional` methods. Example:
+
+[source,java]
+----
+@Transactional(transactionManager = "datastoreTransactionManager")
+----
+
 ==== Read-Write Support for Maps
 
 You can work with Maps of type `Map<String, ?>` instead of with entity objects by directly reading and writing them to and from Cloud Datastore.

docs/src/main/asciidoc/spanner.adoc

@@ -956,6 +956,14 @@ This feature requires a bean of `SpannerTransactionManager`, which is provided w
 If a method annotated with `@Transactional` calls another method also annotated, then both methods will work within the same transaction.
 `performReadOnlyTransaction` and `performReadWriteTransaction` cannot be used in `@Transactional` annotated methods because Cloud Spanner does not support transactions within transactions.
 
+Other Google Cloud database-related integrations like Spanner and Firestore can introduce `PlatformTransactionManager` beans, and can interfere with Datastore Transaction Manager. To disambiguate, explicitly specify the name of the transaction manager bean for such `@Transactional` methods. Example:
+
+[source,java]
+----
+@Transactional(transactionManager = "spannerTransactionManager")
+----
+
+
 ==== DML Statements
 
 `SpannerTemplate` supports https://cloud.google.com/spanner/docs/dml-tasks:[DML] `Statements`.

docs/src/main/md/datastore.md

@@ -944,6 +944,15 @@ same transaction. `performTransaction` cannot be used in
 `@Transactional` annotated methods because Cloud Datastore does not
 support transactions within transactions.
 
+Other Google Cloud database-related integrations like Spanner and Firestore can
+introduce `PlatformTransactionManager` beans, and can interfere with Datastore
+Transaction Manager. To disambiguate, explicitly specify the name of the
+transaction manager bean for such `@Transactional` methods. Example:
+
+```java
+@Transactional(transactionManager = "datastoreTransactionManager")
+```
+
 #### Read-Write Support for Maps
 
 You can work with Maps of type `Map<String, ?>` instead of with entity

docs/src/main/md/spanner.md

@@ -1123,6 +1123,15 @@ same transaction. `performReadOnlyTransaction` and
 annotated methods because Cloud Spanner does not support transactions
 within transactions.
 
+Other Google Cloud database-related integrations like Spanner and Firestore can
+introduce `PlatformTransactionManager` beans, and can interfere with Datastore
+Transaction Manager. To disambiguate, explicitly specify the name of the
+transaction manager bean for such `@Transactional` methods. Example:
+
+```java
+@Transactional(transactionManager = "spannerTransactionManager")
+```
+
 #### DML Statements
 
 `SpannerTemplate` supports

spring-cloud-gcp-autoconfigure/src/main/java/com/google/cloud/spring/autoconfigure/datastore/DatastoreTransactionManagerAutoConfiguration.java

@@ -26,7 +26,6 @@
 import org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration;
 import org.springframework.boot.autoconfigure.transaction.TransactionManagerCustomizers;
 import org.springframework.context.annotation.Bean;
-import org.springframework.transaction.PlatformTransactionManager;
 
 /**
  * Auto-configuration for {@link DatastoreTransactionManager}.
@@ -59,7 +58,7 @@ static class DatastoreTransactionManagerConfiguration {
     }
 
     @Bean
-    @ConditionalOnMissingBean(PlatformTransactionManager.class)
+    @ConditionalOnMissingBean
     public DatastoreTransactionManager datastoreTransactionManager() {
       DatastoreTransactionManager transactionManager =
           new DatastoreTransactionManager(this.datastore);

spring-cloud-gcp-autoconfigure/src/main/java/com/google/cloud/spring/autoconfigure/spanner/SpannerTransactionManagerAutoConfiguration.java

@@ -28,7 +28,6 @@
 import org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration;
 import org.springframework.boot.autoconfigure.transaction.TransactionManagerCustomizers;
 import org.springframework.context.annotation.Bean;
-import org.springframework.transaction.PlatformTransactionManager;
 
 /**
  * Auto-configuration for {@link SpannerTransactionManager}.
@@ -61,7 +60,7 @@ static class DatabaseClientTransactionManagerConfiguration {
     }
 
     @Bean
-    @ConditionalOnMissingBean(PlatformTransactionManager.class)
+    @ConditionalOnMissingBean
     public SpannerTransactionManager spannerTransactionManager() {
       SpannerTransactionManager transactionManager =
           new SpannerTransactionManager(this.databaseClientProvider);

spring-cloud-gcp-samples/spring-cloud-gcp-data-multi-sample/README.adoc

@@ -1,6 +1,7 @@
 = Spring Framework on Google Cloud Cloud Spanner and Datastore Combined Usage Example
 
 This code sample demonstrates how to use both link:../../spring-cloud-gcp-starters/spring-cloud-gcp-starter-data-spanner[Spring Data Cloud Spanner] and link:../../spring-cloud-gcp-starters/spring-cloud-gcp-starter-data-datastore[Spring Data Cloud Datastore] using the Spring Data Cloud Datastore modules in a single Spring application.
+This sample also demonstrates usage of transactions with both modules.
 
 == Running the example
 

spring-cloud-gcp-samples/spring-cloud-gcp-data-multi-sample/src/main/java/com/example/MultipleDataModuleExample.java

@@ -26,11 +26,11 @@
 @SpringBootApplication
 public class MultipleDataModuleExample {
 
-  // A Spring Data Datastore repository
-  @Autowired PersonRepository personRepository;
+  // Internally uses a Spring Data Datastore repository
+  @Autowired private PersonService personService;
 
-  // A Spring Data Cloud Spanner repository
-  @Autowired TraderRepository traderRepository;
+  // Internally uses a Spring Data Cloud Spanner repository
+  @Autowired private TraderService traderService;
 
   public static void main(String[] args) {
     SpringApplication.run(MultipleDataModuleExample.class, args);
@@ -41,19 +41,19 @@ ApplicationRunner applicationRunner() {
     return args -> {
       System.out.println("Deleting all entities.");
 
-      this.personRepository.deleteAll();
-      this.traderRepository.deleteAll();
+      this.personService.deleteAll();
+      this.traderService.deleteAll();
 
-      System.out.println("The number of Person entities is now: " + this.personRepository.count());
-      System.out.println("The number of Trader entities is now: " + this.traderRepository.count());
+      System.out.println("The number of Person entities is now: " + this.personService.count());
+      System.out.println("The number of Trader entities is now: " + this.traderService.count());
 
       System.out.println("Saving one entity with each repository.");
 
-      this.traderRepository.save(new Trader("id1", "trader", "one"));
-      this.personRepository.save(new Person(1L, "person1"));
+      this.traderService.save(new Trader("id1", "trader", "one"));
+      this.personService.save(new Person(1L, "person1"));
 
-      System.out.println("The number of Person entities is now: " + this.personRepository.count());
-      System.out.println("The number of Trader entities is now: " + this.traderRepository.count());
+      System.out.println("The number of Person entities is now: " + this.personService.count());
+      System.out.println("The number of Trader entities is now: " + this.traderService.count());
     };
   }
 }

spring-cloud-gcp-samples/spring-cloud-gcp-data-multi-sample/src/main/java/com/example/PersonService.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2023 Google LLC
+ *
+ * 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 com.example;
+
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@Transactional(transactionManager = "spannerTransactionManager")
+public class PersonService {
+
+  private final PersonRepository personRepository;
+
+  public PersonService(PersonRepository personRepository) {
+    this.personRepository = personRepository;
+  }
+
+  public Person save(Person person) {
+    return this.personRepository.save(person);
+  }
+
+  public void deleteAll() {
+    this.personRepository.deleteAll();
+  }
+
+  public Long count() {
+    return this.personRepository.count();
+  }
+}

spring-cloud-gcp-samples/spring-cloud-gcp-data-multi-sample/src/main/java/com/example/TraderService.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2023 Google LLC
+ *
+ * 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 com.example;
+
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@Transactional(transactionManager = "datastoreTransactionManager")
+public class TraderService {
+
+  private final TraderRepository traderRepository;
+
+  public TraderService(TraderRepository traderRepository) {
+    this.traderRepository = traderRepository;
+  }
+
+  public Trader save(Trader trader) {
+    return this.traderRepository.save(trader);
+  }
+
+  public void deleteAll() {
+    this.traderRepository.deleteAll();
+  }
+
+  public Long count() {
+    return this.traderRepository.count();
+  }
+}