Since Reactor has taken over the Java world it was inevitable the a reactive sql library would be there.
In this blog we shall use r2dbc with h2 and reactor.

We shall start with the dependencies needed.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>

 <parent>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-parent</artifactId>
 <version>2.5.2</version>
 </parent>

 <groupId>com.gkatzioura</groupId>
 <artifactId>r2dbc-reactor</artifactId>
 <version>1.0-SNAPSHOT</version>

 <properties>
 <maven.compiler.source>11</maven.compiler.source>
 <maven.compiler.target>11</maven.compiler.target>
 </properties>

 <dependencies>
 <dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-data-r2dbc</artifactId>
 </dependency>
 <dependency>
 <groupId>org.springframework.data</groupId>
 <artifactId>spring-data-commons</artifactId>
 </dependency>

 <dependency>
 <groupId>com.h2database</groupId>
 <artifactId>h2</artifactId>
 <scope>runtime</scope>
 </dependency>
 <dependency>
 <groupId>io.r2dbc</groupId>
 <artifactId>r2dbc-h2</artifactId>
 <scope>runtime</scope>
 </dependency>
 <dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-test</artifactId>
 <scope>test</scope>
 </dependency>
 <dependency>
 <groupId>io.projectreactor</groupId>
 <artifactId>reactor-test</artifactId>
 <scope>test</scope>
 </dependency>
 </dependencies>

</project>

We imported spring data from r2dbc, the h2 r2dbc driver, the h2 binary as well as the test utils.

Supposing that this is our schema.
This schema is a postgresql schema.

create table order_request (
	id uuid NOT NULL constraint or_id_pk primary key,
	created_by varchar,
	created timestamp default now() not null,
	updated timestamp default now() not null
);

We shall add it later to test/resources/schema.sql for testing purposes.

Also let’s add a new model

package com.gkatzioura.r2dbc.model;

import java.time.LocalDateTime;
import java.util.UUID;

import org.springframework.data.annotation.Id;
import org.springframework.data.domain.Persistable;
import org.springframework.data.relational.core.mapping.Table;

@Table("order_request")
public class OrderRequest implements Persistable<UUID> {

 @Id
 private UUID id;
 private String createdBy;
 private LocalDateTime created;
 private LocalDateTime updated;

 public void setId(UUID id) {
 this.id = id;
 }

 public String getCreatedBy() {
 return createdBy;
 }

 public void setCreatedBy(String createdBy) {
 this.createdBy = createdBy;
 }

 public LocalDateTime getCreated() {
 return created;
 }

 public void setCreated(LocalDateTime created) {
 this.created = created;
 }

 public LocalDateTime getUpdated() {
 return updated;
 }

 public void setUpdated(LocalDateTime updated) {
 this.updated = updated;
 }

 @Override
 public UUID getId() {
 return id;
 }

 @Override
 public boolean isNew() {
 return created == null;
 }

}

Pay attention to isNew method. This way the repository can identify if the object should be persisted or updated.

Now onwards to our Repository

package com.gkatzioura.r2dbc.repository;

import java.util.UUID;
import org.springframework.data.repository.reactive.ReactiveCrudRepository;
import com.gkatzioura.r2dbc.model.OrderRequest;

public interface OrderRepository extends ReactiveCrudRepository<OrderRequest, UUID> {
}

Let’s put some tests.

As mentioned the schema above will reside in test/resources/schema.sql

We shall add some configuration for the test h2 db. We need to make sure that h2 will pickup the postgresql interface.

package com.gkatzioura.r2dbc;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.r2dbc.config.AbstractR2dbcConfiguration;
import org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories;
import org.springframework.r2dbc.connection.init.CompositeDatabasePopulator;
import org.springframework.r2dbc.connection.init.ConnectionFactoryInitializer;
import org.springframework.r2dbc.connection.init.ResourceDatabasePopulator;

import io.r2dbc.h2.H2ConnectionFactory;
import io.r2dbc.spi.ConnectionFactory;

@Configuration
@EnableR2dbcRepositories
public class H2ConnectionConfiguration extends AbstractR2dbcConfiguration {

 @Override
 public ConnectionFactory connectionFactory() {
 return new H2ConnectionFactory(
 io.r2dbc.h2.H2ConnectionConfiguration.builder()
 .url("mem:testdb;MODE=PostgreSQL;DB_CLOSE_DELAY=-1;")
 .build()
 );
 }

 @Bean
 public ConnectionFactoryInitializer initializer() {
 var initializer = new ConnectionFactoryInitializer();
 initializer.setConnectionFactory(connectionFactory());

 var databasePopulator = new CompositeDatabasePopulator();
 databasePopulator.addPopulators(new ResourceDatabasePopulator(new ClassPathResource("schema.sql")));
 initializer.setDatabasePopulator(databasePopulator);
 return initializer;
 }

}

With this configuration we create a H2 database simulating a Postgresql DB, we create the schemas as well as enable the creation of the R2DBC repositories.

Also let’s add a test.

package com.gkatzioura.r2dbc.repository;

import java.util.UUID;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Import;
import org.springframework.test.context.junit.jupiter.SpringExtension;
import com.gkatzioura.r2dbc.H2ConnectionConfiguration;
import com.gkatzioura.r2dbc.model.OrderRequest;
import reactor.test.StepVerifier;

@ExtendWith({SpringExtension.class})
@Import({H2ConnectionConfiguration.class})
class OrderRepositoryTest {

 @Autowired
 private OrderRepository orderRepository;

 @Test
 void testSave() {
 UUID id = UUID.randomUUID();
 OrderRequest orderRequest = new OrderRequest();
 orderRequest.setId(id);
 orderRequest.setCreatedBy("test-user");

 var persisted = orderRepository.save(orderRequest)
 .map(a -> orderRepository.findById(a.getId()))
 .flatMap(a -> a.map(b -> b.getId()));

 StepVerifier.create(persisted).expectNext(id).verifyComplete();
 }
}

That’s it, you can find the code on github.