Create and Connect a Micronaut Application to an Amazon Web Services RDS MySQL Database

This guide describes how to create a database application using the Graal Development Kit for Micronaut (GDK). The application presents REST endpoints and stores data in an Amazon Web Services (AWS) Relational Database Service (RDS) for MySQL database using Micronaut® Data JDBC.

AWS RDS for MySQL is a service for MySQL database to set up, operate, and scale MySQL deployments in the cloud. AWS RDS supports MySQL Community Edition versions 5.7 and 8.0.

Micronaut Data is a database access toolkit that uses ahead-of-time compilation to precompute queries for repository interfaces that are then executed by a thin, lightweight runtime layer. Micronaut Data supports the following back ends: JPA (Hibernate and Hibernate Reactive); SQL (JDBC, R2DBC); and MongoDB.

Prerequisites

JDK 17 or higher. See Setting up Your Desktop.
An Amazon Web Services (AWS) account with enough user permissions to create and manage DB instances in RDS. See Setting up Your Cloud Accounts.
The AWS CLI. Follow the AWS documentation for installing or updating the latest version of the AWS CLI.
The MySQL client CLI.
An Amazon Virtual Private Cloud to which you have management permissions.
An Internet Gateway attached to your Virtual Private Cloud. See How to create and attach an internet gateway to your VPC.
The GDK CLI. See Setting up Your Desktop. (Optional.)

Follow the steps below to create the application from scratch. However, you can also download the completed example:

Gradle
Maven

Gradle AWS Database Example

The application ZIP file will be downloaded in your default downloads directory. Unzip it and proceed to the next steps.

A note regarding your development environment

Consider using Visual Studio Code, which provides native support for developing applications with the Graal Development Kit for Micronaut Extension Pack.

Note: If you use IntelliJ IDEA, enable annotation processing.

Windows platform: The GDK guides are compatible with Gradle only. Maven support is coming soon.

1. Create the Application

Create an application using the GDK Launcher.

Open the GDK Launcher in advanced mode.
Create a new project using the following selections.
- Project Type: Application (Default)
- Project Name: aws-db-demo
- Base Package: com.example (Default)
- Clouds: AWS
- Build Tool: Gradle (Groovy) or Maven
- Language: Java (Default)
- Test Framework: JUnit (Default)
- Java Version: 17 (Default)
- Micronaut Version: (Default)
- Cloud Services: Database
- Features: GraalVM Native Image (Default)
- Sample Code: Yes (Default)
Click Generate Project, then click Download Zip. The GDK Launcher creates an application with the package com.example in a directory named aws-db-demo. The application ZIP file will be downloaded to your default downloads directory. Unzip it, open it in your code editor, and proceed to the next steps.

Alternatively, use the GDK CLI as follows:

Gradle
Maven

gdk create-app com.example.aws-db-demo \
 --clouds=aws \
 --services=database \
 --features=graalvm \
 --build=gradle \
 --jdk=17  \
 --lang=java

gdk create-app com.example.aws-db-demo \
 --clouds=aws \
 --services=database \
 --features=graalvm \
 --build=maven \
 --jdk=17  \
 --lang=java

Open the micronaut-cli.yml file, you can see what features are packaged with the application:

features: [app-name, data, data-jdbc, flyway, gdk-aws-cloud-app, gdk-aws-database, gdk-bom, gdk-license, graalvm, http-client, java, java-application, jdbc-hikari, junit, logback, maven, maven-enforcer-plugin, micronaut-http-validation, mysql, netty-server, properties, readme, serialization-jackson, shade, static-resources, test-resources, validation]

The GDK Launcher creates a multi-module project with two subprojects: aws for Amazon Web Services, and lib for common code and configuration shared across cloud platforms. You develop the application logic in the lib subproject, and keep the Amazon Web Services-specific configurations in the aws subproject.

If you enable sample code generation, the GDK Launcher creates the main controller, repository interface, entity, service classes, and tests for you. Consider checking this guide where each sample class is closely examined.

2. Configure Datasource

The GDK Launcher included Flyway for database migrations. It uses the Micronaut integration with Flyway that automates schema changes, significantly simplifies schema management tasks, such as migrating, rolling back, and reproducing in multiple environments. The GDK Launcher enables Flyway in the aws/src/main/resources/application.properties file and configures it to perform migrations on the default datasources.

flyway.datasources.default.enabled=true

If you specified Flyway as a project feature in the GDK Launcher the build file includes it as a dependency:

Gradle
Maven

aws/build.gradle

implementation("io.micronaut.flyway:micronaut-flyway")
runtimeOnly("org.flywaydb:flyway-mysql")

aws/pom.xml

<dependency>
    <groupId>io.micronaut.flyway</groupId>
    <artifactId>micronaut-flyway</artifactId>
    <scope>compile</scope>
</dependency>
<dependency>
    <groupId>org.flywaydb</groupId>
    <artifactId>flyway-mysql</artifactId>
    <scope>runtime</scope>
</dependency>

Note: Flyway migrations require full control over schema management. By default, the project does not generate schema automatically in aws/src/main/resources/application.properties. If you manually configure datasources.default.schema-generate=CREATE_DROP set it to NONE to ensure that only Flyway manages your schema.

Configuring multiple datasources is as simple as enabling Flyway for each one. You can also specify directories that will be used for migrating each datasource. For more information, see Micronaut integration with Flyway.

Flyway migration is automatically triggered before your application starts. Flyway reads migration file(s) in the lib/src/main/resources/db/migration/ directory. The migration file with the database schema, lib/src/main/resources/db/migration/V1__schema.sql, was also created for you by the GDK Launcher.

DROP TABLE IF EXISTS genre;

CREATE TABLE genre (
   id    BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
   name  VARCHAR(255) NOT NULL UNIQUE
);

During application startup, Flyway runs the commands in the SQL file and creates the schema needed for the application.

3. Create a MySQL Database Instance Using AWS RDS

You will create a MySQL Database instance with the AWS CLI. See the AWS CLI rds Command Reference to learn more about AWS RDS.

3.1. Create an Administrator Account

Instead of using your AWS root account, use an administrator account. If you do not have one already, see Setting up Your Cloud Accounts.

3.2. Create Security Group, Subnets, and Subnet Group (Optional)

To allow connections to the database from your local computer, create the following resources in addition to your VPC to allow access to the database default port from your current public IP address.

First, export your VPC Id and Internet Gateway Id:

export VPC_ID=<your-vpc-id>
export IG_ID=<your-ig-id>

set VPC_ID=<your-vpc-id>
set IG_ID=<your-ig-id>

$ENV:VPC_ID="<your-vpc-id>"
$ENV:IG_ID="<your-ig-id>"

Define the subnet group name and the security group name:

export SECURITY_GROUP_NAME="<SecurityGroupName>"
export DB_SUBNET_GROUP_NAME="<SubnetGroupName>"

Make sure DNS hostname is enabled on your VPC, if not run the following command:

aws ec2 modify-vpc-attribute --enable-dns-hostnames --vpc-id $VPC_ID

Some of the following commands use jq, which is a lightweight and flexible command-line JSON processor.

Now let’s create a Route :

export RT_ID=$(aws ec2 describe-route-tables \
      --filters "Name=vpc-id,Values=$VPC_ID" \
      --query "RouteTables[].RouteTableId" --output text)
export RTD_RES=$(aws ec2 create-route --route-table-id $RT_ID \
      --destination-cidr-block 0.0.0.0/0 \
      --gateway-id $IG_ID)

Create security group and allow TCP traffic on port 3306 :

export SG_ID=$(aws ec2 create-security-group --group-name $SECURITY_GROUP_NAME \
      --description "Security Group for the GDK DB guide" \
      --vpc-id $VPC_ID | jq -r '.GroupId')
aws ec2 authorize-security-group-ingress --group-id $SG_ID \
      --protocol tcp --port 3306 \
      --cidr $(curl ifconfig.me)/32 | jq -r '.SecurityGroupRules[0]'

Create two subnets on two different availability zones and add them to a subnet group :

export AZ_0=$(aws ec2 describe-availability-zones \
      --filters "Name=state,Values=available" \
      --query "AvailabilityZones[0].ZoneName" --output text)
export AZ_1=$(aws ec2 describe-availability-zones \
      --filters "Name=state,Values=available" \
      --query "AvailabilityZones[1].ZoneName" --output text)
export SN0_ID=$(aws ec2 create-subnet --vpc-id $VPC_ID \
      --cidr-block 10.0.0.0/20 \
      --availability-zone $AZ_0 | jq -r '.Subnet.SubnetId')
export SN1_ID=$(aws ec2 create-subnet --vpc-id $VPC_ID \
      --cidr-block 10.0.16.0/20 \
      --availability-zone $AZ_1 | jq -r '.Subnet.SubnetId')
aws ec2 modify-subnet-attribute --subnet-id $SN0_ID --map-public-ip-on-launch
aws ec2 modify-subnet-attribute --subnet-id $SN1_ID --map-public-ip-on-launch

And finally create a subnet group and add the subnets to it :

export DBSubnetGroup=$(aws rds create-db-subnet-group \
      --db-subnet-group-name $DB_SUBNET_GROUP_NAME \
      --db-subnet-group-description "DB subnet group for the GDK Oracle DB guide" \
      --subnet-ids "$SN0_ID" "$SN1_ID")

Note: Exposing a database port to the internet is a security risk. This should be done only for development purposes.

3.3. Create a MySQL Instance

Set the following environment variables (you can change the values to any of your choice):

export DB_INSTANCE_NAME=awsguidetemp
export ADMIN_USERNAME=admin
export ADMIN_PASSWORD=Passw0rd1234!

Run this command to create a MySQL instance in AWS RDS:

aws rds create-db-instance \
     --db-instance-identifier $DB_INSTANCE_NAME \
     --db-instance-class db.t3.micro \
     --engine mysql \
     --master-username $ADMIN_USERNAME \
     --master-user-password $ADMIN_PASSWORD \
     --allocated-storage 20 \
     --db-subnet-group-name $DB_SUBNET_GROUP_NAME \
     --vpc-security-group-ids $SG_ID \
     --publicly-accessible \
     --output json | jq -r '.DBInstance.DBInstanceArn'

Wait for the instance to become available:

aws rds wait db-instance-available --output text \
      --db-instance-identifier "$DB_INSTANCE_NAME"

Once the instance is available, set the value of an environment variable (named ORACLEDB_HOST) to represent its hostname:

export MYSQL_HOST=$(aws rds describe-db-instances  --output text \
      --query 'DBInstances[?DBInstanceIdentifier==`awsguidetemp`].Endpoint.Address')

Finally, test connectivity to the database using the MySQL client CLI:
```
mysql -u admin -p
```

3.4. Create a Database and a Database User

Connect to the database using the MySQL client CLI (as shown earlier).
Create the database. You can use any valid database name (for example, awsdb):
```
CREATE DATABASE awsdb;
```
Create a database user. You can use any valid MySQL username (for example, awsdb_user) and any valid password:
```
CREATE USER 'awsdb_user' IDENTIFIED BY 'M1cr0n4ut!';
```
Grant access to the database for the new user:
```
GRANT ALL ON awsdb.* TO 'awsdb_user';
```
Exit the MySQL console by entering "exit".

4. Test the Application

With almost everything in place, you can run the tests.

Return to your local IDE where you have opened the Micronaut database application, and open the aws/src/main/resources/application.properties file.

The settings configure the datasource for MySQL, specifying the database type, dialect, and driver class:

datasources.default.db-type=mysql
datasources.default.dialect=MYSQL
datasources.default.driver-class-name=com.mysql.cj.jdbc.Driver

Set values for the missing datasources.default.url, datasources.default.username, and datasources.default.password properties by exporting them as environment variables as follows:

export DATASOURCES_DEFAULT_PASSWORD=M1cr0n4ut!
export DATASOURCES_DEFAULT_URL=jdbc:mysql://$MYSQL_HOST:3306/awsdb
export DATASOURCES_DEFAULT_USERNAME=awsdb_user

set DATASOURCES_DEFAULT_PASSWORD=M1cr0n4ut!
set DATASOURCES_DEFAULT_URL=jdbc:mysql://%MYSQL_HOST%:3306/awsdb
set DATASOURCES_DEFAULT_USERNAME=awsdb_user

$ENV:DATASOURCES_DEFAULT_PASSWORD="M1cr0n4ut!"
$ENV:DATASOURCES_DEFAULT_URL="jdbc:mysql://$MYSQL_HOST:3306/awsdb"
$ENV:DATASOURCES_DEFAULT_USERNAME="awsdb_user"

where the value of MYSQL_HOST is the private IP address of your MySQL database instance (see section 2.3).

Run the tests:

Gradle
Maven

./gradlew :aws:test

./mvnw install -pl lib -am
./mvnw mn:test -pl aws

Then open the file aws/build/reports/tests/test/index.html in a browser to view the results.

Next, you can package this application as a native executable and deploy from the virtual machine, connected to the MySQL database. Deploying as a native executable does not require a Java VM to run, so you can transfer it to another Linux host and run easily.

5. Generate a Native Executable Using GraalVM

The GDK supports compiling Java applications ahead-of-time into native executables using GraalVM Native Image. You can use the Gradle plugin for GraalVM Native Image building/Maven plugin for GraalVM Native Image building. Packaged as a native executable, it significantly reduces application startup time and memory footprint.

Prerequisites: Make sure you have installed a GraalVM JDK. The easiest way to get started is with SDKMAN!. For other installation options, visit the Downloads section.

To generate a native executable, use the following command:
- Gradle
- Maven
```
./gradlew :aws:nativeCompile
```
The native executable is created in the aws/build/native/nativeCompile/ directory
```
./mvnw install -pl lib -am
./mvnw clean package -pl  aws -Dpackaging=native-image
```
The native executable is created in the aws/target/ directory
You can then run the native executable with the following command:
- Gradle
- Maven
```
aws/build/native/nativeCompile/aws-db-demo-aws
```
```
aws/target/aws-db-demo-aws
```
You can customize the name of the resulting binary by updating the Maven/Gradle plugin for GraalVM Native Image configuration.

Run this command to create a new Genre entry in the database table:

TEST_RES=$(curl -X "POST" "http://localhost:8080/genres" \
               -H 'Content-Type: application/json; charset=utf-8' \
               -d $'{ "name": "music" }')

echo "Result: $TEST_RES"

Then list all genres:

TEST_RES=$(curl -s localhost:8080/genres/list)
echo "Result: $TEST_RES"

As a reminder, you do not need to install a Java VM on the virtual machine to run the application. The native executable is a self-contained binary. Deploying from a native executable significantly reduces application startup time and memory footprint.

6. Stop Database Instance and Clean Up

Once you are done with this guide, you can stop and/or delete the AWS resources created to avoid incurring unnecessary charges. Run these commands:

aws rds delete-db-instance --db-instance-identifier $DB_INSTANCE_NAME --skip-final-snapshot --query "DBInstance.DBInstanceIdentifier" --output json
aws rds wait db-instance-deleted --db-instance-identifier $DB_INSTANCE_NAME
aws ec2 delete-subnet --subnet-id $SN0_ID
aws ec2 delete-subnet --subnet-id $SN1_ID
aws rds delete-db-subnet-group --db-subnet-group-name $DB_SUBNET_GROUP_NAME
aws ec2 delete-security-group --group-id $SG_ID
aws ec2 detach-internet-gateway --internet-gateway-id $IG_ID --vpc-id $VPC_ID
aws ec2 delete-internet-gateway --internet-gateway-id $IG_ID
aws ec2 delete-vpc --vpc-id $VPC_ID

Summary

This guide demonstrated how to use the GDK to create and access a database application that stores data in an AWS RDS MySQL database using Micronaut Data JDBC. You also learned how to package this application into a native executable.