Pavel

Posted onSep 7, 2023 • Edited onSep 11, 2023 • Originally published atpakisan.github.io

Spring Boot 3 with MongoDB transactions

#springboot #mongodb #transactions #tutorial

Transactions won't work without next things:

replica set

Since transactions are built on concepts of logical sessions they require mechanics (like oplog) which are only available in replica set environment.
You can always convert a standalone to a single noded replica set and transactions will work with this one node.
https://docs.mongodb.com/manual/tutorial/convert-standalone-to-replica-set/

Reference

MongoTransactionManager

Unless you specify aMongoTransactionManager within your application context, transaction support is DISABLED. You can usesetSessionSynchronization(ALWAYS) to participate in ongoing non-native MongoDB transactions.

Reference

That's main reason why newly created Spring Boot project with MongoDB will fail with next error:

java.lang.IllegalStateException: Failed to retrieve PlatformTransactionManager for @Transactional test:

What to do:

Create replica set
ConfigureMongoTransactionManager asPlatformTransactionManager
Update application properties
Fix DataMongoTest tests

Create replica set

Choose preferred way to create replica set:

Configure PlatformTransactionManager

importorg.jetbrains.annotations.NotNull;importorg.springframework.beans.factory.annotation.Value;importorg.springframework.context.annotation.Bean;importorg.springframework.context.annotation.Configuration;importorg.springframework.data.mongodb.MongoDatabaseFactory;importorg.springframework.data.mongodb.MongoTransactionManager;importorg.springframework.data.mongodb.config.AbstractMongoClientConfiguration;@ConfigurationpublicclassMongoClientConfigurationextendsAbstractMongoClientConfiguration{@Value("${spring.data.mongodb.database}")privateStringdatabaseName;@BeanpublicMongoTransactionManagertransactionManager(MongoDatabaseFactorymongoDatabaseFactory){returnnewMongoTransactionManager(mongoDatabaseFactory);}@NotNull@OverrideprotectedStringgetDatabaseName(){returndatabaseName;}}

Update application properties

spring.data.mongodb.replica-set-name=myReplicaSet

Fix DataMongoTest tests

Looks like@DataMongoTest still not activates autoconfiguration for MongoDB transactions.

References:

Proposal to importTransactionAutoConfiguration didn't help me

@ImportAutoConfiguration(TransactionAutoConfiguration.class)

So I decided to replace it with MongoDBConfig import

importapp.config.MongoDBConfig;importorg.junit.jupiter.api.Test;importorg.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;importorg.springframework.context.annotation.Import;importorg.springframework.transaction.annotation.Transactional;@DataMongoTest@Transactional@Import(MongoDBConfig.class)publicclassMongoTest{@TestpublicvoidtestTransaction(){}}