Using Hibernate-Reactive and together R2DBC in one project

Question

I am currently working on a project using Spring-Webflux and R2DBC. I am using an OracleDB 19c and corresponding drivers for R2DBC. Since Hibernate went reactive I want to try it in the existing project - so it needs to run next to R2DBC (for hibernate I used vertx-oracle). But when starting the application I get ClassNotFoundExceptions:

Exception in thread "main" java.lang.NoClassDefFoundError: org/hibernate/engine/jdbc/mutation/spi/MutationExecutorService
    at org.hibernate.reactive.provider.impl.ReactiveServiceInitiators.buildInitialServiceInitiatorList(ReactiveServiceInitiators.java:122)
    at org.hibernate.reactive.provider.impl.ReactiveServiceInitiators.<clinit>(ReactiveServiceInitiators.java:60)
    at org.hibernate.reactive.provider.ReactiveServiceRegistryBuilder.defaultReactiveInitiatorList(ReactiveServiceRegistryBuilder.java:135)
    at org.hibernate.reactive.provider.ReactiveServiceRegistryBuilder.forJpa(ReactiveServiceRegistryBuilder.java:46)
    at org.hibernate.reactive.provider.impl.ReactiveEntityManagerFactoryBuilder.getStandardServiceRegistryBuilder(ReactiveEntityManagerFactoryBuilder.java:39)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.<init>(EntityManagerFactoryBuilderImpl.java:249)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.<init>(EntityManagerFactoryBuilderImpl.java:189)
    at org.hibernate.reactive.provider.impl.ReactiveEntityManagerFactoryBuilder.<init>(ReactiveEntityManagerFactoryBuilder.java:33)
    at org.hibernate.reactive.provider.ReactivePersistenceProvider.getEntityManagerFactoryBuilder(ReactivePersistenceProvider.java:151)
    at org.hibernate.reactive.provider.ReactivePersistenceProvider.getEntityManagerFactoryBuilderOrNull(ReactivePersistenceProvider.java:102)
    at org.hibernate.reactive.provider.ReactivePersistenceProvider.createEntityManagerFactory(ReactivePersistenceProvider.java:50)
    at jakarta.persistence.Persistence.createEntityManagerFactory(Persistence.java:80)
    at jakarta.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
    at org.hibernate.reactive.example.nativesql.Main.main(Main.java:38)
Caused by: java.lang.ClassNotFoundException: org.hibernate.engine.jdbc.mutation.spi.MutationExecutorService
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
    ... 14 more

Process finished with exit code 1

It seems like not all Classes needed are delivered with the hibernate-reactive-core (2.2.0.Final) depenedency. Am I missing something in the documentation or is this some sort of unexpected behaviour?

I tried to import the missing MutationExecutorService interface by adding the dependency

        <dependency>
            <groupId>org.hibernate.orm</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>6.4.0.Final</version>
        </dependency>

to the pom.xml which kind of worked - the class was imported but then I faced problems running both: hibernate and R2DBC. This resulted in a connection timeout for every hibernate-session I tried to open.

I also tried to use the given minimum project from hibernate-reactive examples with less dependencies and even then I faced java.lang.ClassNotFoundException: org.hibernate.engine.jdbc.mutation.spi.MutationExecutorService so that should not be caused by R2DBC.

Do you have some experience and advise for working with hibernate-reactive and R2DBC in one project? And is the missing class normal behaviour or is this an error that should not happen?

Edit I tried the dependencies recommended by [https://stackoverflow.com/a/77620095/23052670)[Davide D'Alto] (hibernate-core 6.3.2.Final + hibernate-reactive-core 2.1.0.Final).

I am still getting a Spring startup freezing for a few seconds and then responding with the Error-Log containing a Timeout.

Edit 2 Even with preparing a SessionFactory-Bean by myself in a @Configuration class I get Timeouts when starting my application.

Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment] due to: io.vertx.core.impl.NoStackTraceThrowable: Timeout

Is this a general Problem to vertx-oracle? Online I've found vertx-postgres examples but no oracle.

Edit 3

I managed to get a connection to a OracleDB with version 21.3c (also a docker container). Still I get an Error: WARN vert.x-eventloop-thread-0 org.hibernate.reactive.provider.service.ReactiveGenerationTarget HR000021: DDL command failed [java.lang.NoClassDefFoundError: oracle/jdbc/OracleCommonPreparedStatement] and therefore the queries have no effect on the database.

I was able to fix that Problem again with a dependency of com.oracle.databas.jdbc.ojdbc11-23.2.0.0.

Answer 1

I figured out how to run it with OracleDB. I took following steps:

1. It seems like Hibernate-Reactive is not compatible with OracleDB 19c at the moment. Using Version 21c worked out (so 'tested with' within project-README should be taken serious at this point)
2. Although a connection to the Database was possible I wasn't able to write to it (at least within autogeneration at startup). This could be fixed by adding following dependency to my pom.xml:

    <dependency>
            <groupId>com.oracle.database.jdbc</groupId>
            <artifactId>ojdbc11</artifactId>
            <version>23.2.0.0</version>
    </dependency>

After these steps the connection was established and the autogeneration worked.

Answer 2

The reason you are having these issues is because the libraries in your project require different Hibernate ORM versions.

I'm not familiar with R2DBC, you should check which dependency it requires and then include the correct Hibernate Reactive version. It's probably going to be Hibernate Reactive 2.1.0.Final (Compatible with Hibernate ORM 6.3.2.Final). But you can check the versions compatibility on the Hibernate website.

Answer 3

Till now(Spring 6.1 and Spring Boot 3.2), there is no official Hibernate Reactive support in Spring and Spring Boot.

If you want to integrate Hibernate Reactive with Spring, esp Spring Reactive stack(WebFlux), it is not difficult, just needs some simple stpes to configure it yourself.

1. Add Hibernate core and Hibernate Reactive deps into a Spring Reactive project.
2. Declare a Java 8 CompletableFuture based or Smallrye Mutiny based Session Factory Bean.
3. Use it in your project to execute JPQL like using generic Hibernate Session or JPA EntityManager.

More details, please read my post: https://itnext.io/integrating-hibernate-reactive-with-spring-5427440607fe

R2dbc is a relatedly new driver for RDBMS, currently most populor database have added R2dbc support. But Hibernate Reactive implementation is based on Vertx reactive driver, there is no relation to R2dbc.

You can use R2dbc in a Spring WebFlux freely, either with Hibernate Reactive or without it.

There are some R2dbc/Spring Data R2dbc example projects from my Github: https://github.com/hantsy/spring-r2dbc-sample

Update: I have created a simple working project with Spring Boot 3.2, Hibernate 6.4.1/Hibernate Reactive 2.2.0.Final(with Vertx pg client), and Spring Data R2dbc(with r2dbc postgres driver), https://github.com/hantsy/spring-puzzles/tree/master/hibernate-reactive-mutiny-r2dbc

Update 2, An working example with Oracle, https://github.com/hantsy/spring-puzzles/tree/master/hibernate-reactive-mutiny-oracle