Use Spring Data R2DBC with Azure Database for MySQL

This topic demonstrates creating a sample application that uses Spring Data R2DBC to store and retrieve information in Azure Database for MySQL by using the R2DBC implementation for MySQL from the r2dbc-mysql GitHub repository.

R2DBC brings reactive APIs to traditional relational databases. You can use it with Spring WebFlux to create fully reactive Spring Boot applications that use non-blocking APIs. It provides better scalability than the classic "one thread per connection" approach.

Prerequisites

  • An Azure account. If you don't have one, get a free trial.
  • Azure Cloud Shell or Azure CLI. We recommend Azure Cloud Shell so you'll be logged in automatically and have access to all the tools you'll need.
  • A supported Java Development Kit, version 8 (included in Azure Cloud Shell).
  • cURL or a similar HTTP utility to test functionality.

Sample application

In this article, we will code a sample application. If you want to go faster, this application is already coded and available at https://github.com/Azure-Samples/quickstart-spring-data-r2dbc-mysql.

Prepare the working environment

First, set up some environment variables by using the following commands:

AZ_RESOURCE_GROUP=database-workshop
AZ_DATABASE_NAME=<YOUR_DATABASE_NAME>
AZ_LOCATION=<YOUR_AZURE_REGION>
AZ_MYSQL_USERNAME=spring
AZ_MYSQL_PASSWORD=<YOUR_MYSQL_PASSWORD>
AZ_LOCAL_IP_ADDRESS=<YOUR_LOCAL_IP_ADDRESS>

Replace the placeholders with the following values, which are used throughout this article:

  • <YOUR_DATABASE_NAME>: The name of your MySQL server. It should be unique across Azure.
  • <YOUR_AZURE_REGION>: The Azure region you'll use. You can use eastus by default, but we recommend that you configure a region closer to where you live. You can have the full list of available regions by entering az account list-locations.
  • <YOUR_MYSQL_PASSWORD>: The password of your MySQL database server. That password should have a minimum of eight characters. The characters should be from three of the following categories: English uppercase letters, English lowercase letters, numbers (0-9), and non-alphanumeric characters (!, $, #, %, and so on).
  • <YOUR_LOCAL_IP_ADDRESS>: The IP address of your local computer, from which you'll run your Spring Boot application. One convenient way to find it is to point your browser to whatismyip.akamai.com.

Next, create a resource group:

az group create \
    --name $AZ_RESOURCE_GROUP \
    --location $AZ_LOCATION \
    | jq

Note

We use the jq utility, which is installed by default on Azure Cloud Shell to display JSON data and make it more readable. If you don't like that utility, you can safely remove the | jq part of all the commands we'll use.

Create an Azure Database for MySQL instance

The first thing we'll create is a managed MySQL server.

Note

You can read more detailed information about creating MySQL servers in Create an Azure Database for MySQL server by using the Azure portal.

In Azure Cloud Shell, run the following script:

az mysql server create \
    --resource-group $AZ_RESOURCE_GROUP \
    --name $AZ_DATABASE_NAME \
    --location $AZ_LOCATION \
    --sku-name B_Gen5_1 \
    --storage-size 5120 \
    --admin-user $AZ_MYSQL_USERNAME \
    --admin-password $AZ_MYSQL_PASSWORD \
    | jq

This command creates a small MySQL server.

Configure a firewall rule for your MySQL server

Azure Database for MySQL instances are secured by default. They have a firewall that doesn't allow any incoming connection. To be able to use your database, you need to add a firewall rule that will allow the local IP address to access the database server.

Because you configured our local IP address at the beginning of this article, you can open the server's firewall by running:

az mysql server firewall-rule create \
    --resource-group $AZ_RESOURCE_GROUP \
    --name $AZ_DATABASE_NAME-database-allow-local-ip \
    --server $AZ_DATABASE_NAME \
    --start-ip-address $AZ_LOCAL_IP_ADDRESS \
    --end-ip-address $AZ_LOCAL_IP_ADDRESS \
    | jq

Configure a MySQL database

The MySQL server that you created earlier is empty. It doesn't have any database that you can use with the Spring Boot application. Create a new database called demo:

az mysql db create \
    --resource-group $AZ_RESOURCE_GROUP \
    --name demo \
    --server-name $AZ_DATABASE_NAME \
    | jq

Create a reactive Spring Boot application

To create a reactive Spring Boot application, we'll use Spring Initializr. The application that we'll create uses:

  • Spring Boot 2.3.4.RELEASE.
  • The following dependencies: Spring Reactive Web (also known as Spring WebFlux) and Spring Data R2DBC.

Generate the application by using Spring Initializr

Generate the application on the command line by entering:

curl https://start.spring.io/starter.tgz -d dependencies=webflux,data-r2dbc -d baseDir=azure-database-workshop -d bootVersion=2.3.4.RELEASE -d javaVersion=8 | tar -xzvf -

Add the reactive MySQL driver implementation

Open the generated project's pom.xml file to add the reactive MySQL driver from the r2dbc-mysql repository on GitHub.

After the spring-boot-starter-webflux dependency, add the following snippet:

<dependency>
   <groupId>dev.miku</groupId>
   <artifactId>r2dbc-mysql</artifactId>
   <version>0.8.1.RELEASE</version>
   <scope>runtime</scope>
</dependency>

Configure Spring Boot to use Azure Database for MySQL

Open the src/main/resources/application.properties file, and add:

logging.level.org.springframework.data.r2dbc=DEBUG

spring.r2dbc.url=r2dbc:pool:mysql://$AZ_DATABASE_NAME.mysql.database.azure.com:3306/demo
spring.r2dbc.username=spring@$AZ_DATABASE_NAME
spring.r2dbc.password=$AZ_MYSQL_PASSWORD
  • Replace the two $AZ_DATABASE_NAME variables with the value that you configured at the beginning of this article.
  • Replace the $AZ_MYSQL_PASSWORD variable with the value that you configured at the beginning of this article.

Note

For better performance, the spring.r2dbc.url property is configured to use a connection pool using r2dbc-pool.

You should now be able to start your application by using the provided Maven wrapper:

./mvnw spring-boot:run

Here's a screenshot of the application running for the first time:

The running application

Create the database schema

Inside the main DemoApplication class, configure a new Spring bean that will create a database schema, using the following code:

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.r2dbc.connectionfactory.init.ConnectionFactoryInitializer;
import org.springframework.data.r2dbc.connectionfactory.init.ResourceDatabasePopulator;

import io.r2dbc.spi.ConnectionFactory;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Bean
    public ConnectionFactoryInitializer initializer(ConnectionFactory connectionFactory) {
        ConnectionFactoryInitializer initializer = new ConnectionFactoryInitializer();
        initializer.setConnectionFactory(connectionFactory);
        ResourceDatabasePopulator populator = new ResourceDatabasePopulator(new ClassPathResource("schema.sql"));
        initializer.setDatabasePopulator(populator);
        return initializer;
    }
}

This Spring bean uses a file called schema.sql, so create that file in the src/main/resources folder, and add the following text:

DROP TABLE IF EXISTS todo;
CREATE TABLE todo (id SERIAL PRIMARY KEY, description VARCHAR(255), details VARCHAR(4096), done BOOLEAN);

Stop the running application, and start it again. The application will now use the demo database that you created earlier, and create a todo table inside it.

./mvnw spring-boot:run

Here's a screenshot of the database table as it's being created:

Creation of the database table

Code the application

Next, add the Java code that will use R2DBC to store and retrieve data from your MySQL server.

Create a new Todo Java class, next to the DemoApplication class, using the following code:

package com.example.demo;

import org.springframework.data.annotation.Id;

public class Todo {

    public Todo() {
    }

    public Todo(String description, String details, boolean done) {
        this.description = description;
        this.details = details;
        this.done = done;
    }

    @Id
    private Long id;

    private String description;

    private String details;

    private boolean done;

    public Long getId() {
        return id;
    }

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

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getDetails() {
        return details;
    }

    public void setDetails(String details) {
        this.details = details;
    }

    public boolean isDone() {
        return done;
    }

    public void setDone(boolean done) {
        this.done = done;
    }
}

This class is a domain model mapped on the todo table that you created before.

To manage that class, you'll need a repository. Define a new TodoRepository interface in the same package, using the following code:

package com.example.demo;

import org.springframework.data.repository.reactive.ReactiveCrudRepository;

public interface TodoRepository extends ReactiveCrudRepository<Todo, Long> {
}

This repository is a reactive repository that Spring Data R2DBC manages.

Finish the application by creating a controller that can store and retrieve data. Implement a TodoController class in the same package, and add the following code:

package com.example.demo;

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.*;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@RestController
@RequestMapping("/")
public class TodoController {

    private final TodoRepository todoRepository;

    public TodoController(TodoRepository todoRepository) {
        this.todoRepository = todoRepository;
    }

    @PostMapping("/")
    @ResponseStatus(HttpStatus.CREATED)
    public Mono<Todo> createTodo(@RequestBody Todo todo) {
        return todoRepository.save(todo);
    }

    @GetMapping("/")
    public Flux<Todo> getTodos() {
        return todoRepository.findAll();
    }
}

Finally, halt the application and start it again using the following command:

./mvnw spring-boot:run

Test the application

To test the application, you can use cURL.

First, create a new "todo" item in the database using the following command:

curl --header "Content-Type: application/json" \
    --request POST \
    --data '{"description":"configuration","details":"congratulations, you have set up R2DBC correctly!","done": "true"}' \
    http://127.0.0.1:8080

This command should return the created item, as shown here:

{"id":1,"description":"configuration","details":"congratulations, you have set up R2DBC correctly!","done":true}

Next, retrieve the data by using a new cURL request with the following command:

curl http://127.0.0.1:8080

This command will return the list of "todo" items, including the item you've created, as shown here:

[{"id":1,"description":"configuration","details":"congratulations, you have set up R2DBC correctly!","done":true}]

Here's a screenshot of these cURL requests:

Test with cURL

Congratulations! You've created a fully reactive Spring Boot application that uses R2DBC to store and retrieve data from Azure Database for MySQL.

Clean up resources

To clean up all resources used during this quickstart, delete the resource group using the following command:

az group delete \
    --name $AZ_RESOURCE_GROUP \
    --yes

Next steps

To learn more about Spring and Azure, continue to the Spring on Azure documentation center.

Additional resources

For more information about Spring Data R2DBC, see Spring's reference documentation.

For more information about using Azure with Java, see Azure for Java developers and Working with Azure DevOps and Java.