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

    • 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

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

    Gradle AWS Database Example Download completed 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.

    1. Open the GDK Launcher in advanced mode.

    2. 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)
    3. 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:

    gdk create-app com.example.aws-db-demo \
 --clouds=aws \
 --services=database \
 --features=graalvm \
 --build=gradle \
 --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:

    build.gradle

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

    Note: Flyway migrations are not compatible with the default automatic schema generation that is configured in aws/src/main/resources/application.properties. If schema-generate is active, it will conflict with Flyway. So edit aws/src/main/resources/application.properties and either delete the datasources.default.schema-generate=CREATE_DROP line or change that line to datasources.default.schema-generate=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 VPC, Security Group, Subnets, and Subnet Group (Optional)

    Define the subnet group name:

    export DB_SUBNET_GROUP_NAME=micronaut-guides-mysql-sng

    To allow connections to the database from your local computer, create a VPC, and a security group that allows access to the database default port from your current public IP address.

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

    You will also create two subnets in different availability zones and a subnet group to associate them.

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

    # VPC, internet gateway and route table
export VPC_ID=$(aws ec2 create-vpc --cidr-block 10.0.0.0/16 --tag-specification "ResourceType=vpc,Tags=[{Key=Name,Value=GcnAutomatedTestVPC}]" | jq -r '.Vpc.VpcId')
export IG_ID=$(aws ec2 create-internet-gateway  --tag-specification "ResourceType=internet-gateway,Tags=[{Key=Name,Value=GcnAutomatedTestIG}]" | jq -r '.InternetGateway.InternetGatewayId')
aws ec2 attach-internet-gateway --internet-gateway-id $IG_ID --vpc-id $VPC_ID
aws ec2 modify-vpc-attribute --enable-dns-hostnames --vpc-id $VPC_ID
export RT_ID=$(aws ec2 describe-route-tables --filters "Name=vpc-id,Values=$VPC_ID" --query "RouteTables[].RouteTableId" --output text)
export TMP_RES=$(aws ec2 create-route --route-table-id $RT_ID --destination-cidr-block 0.0.0.0/0 --gateway-id $IG_ID)

# Security group
export SG_ID=$(aws ec2 create-security-group --group-name gcn-test-guides-mysql-sg --description "Security Group for the Test GCN MySQL 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]'

# Subnets and 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 $SN1_ID --map-public-ip-on-launch
export DBSubnetGroup=$(aws rds create-db-subnet-group --db-subnet-group-name $DB_SUBNET_GROUP_NAME --db-subnet-group-description "DB subnet group for Testing the GCN  MySQL guide" --subnet-ids "$SN0_ID" "$SN1_ID")

    3.3. Create a MySQL Instance

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

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

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

      export DBInstanceArn=$(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')

    3. Wait for the instance to become available:

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

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

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

    5. Finally, test connectivity to the database using the MySQL client CLI:

      mysql -u admin -p

    3.4. Create a Database and a Database User

    1. Connect to the database using the MySQL client CLI (as shown earlier).

    2. Create the database. You can use any valid database name (for example, awsdb):

      CREATE DATABASE awsdb;

    3. 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!';

    4. Grant access to the database for the new user:

      GRANT ALL ON awsdb.* TO 'awsdb_user';

    5. Exit the MySQL console by entering "exit".

    4. Test the Application

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

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

    2. 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

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

      Note: If you use Windows Command Prompt, replace export with set, for example, set DATASOURCES_DEFAULT_USERNAME=awsdb_user. If you use Windows PowerShell, replace export with $ and surround the value with double quote marks, for example, $DATASOURCES_DEFAULT_USERNAME="awsdb_user".

    Run the tests:

    ./gradlew :aws:test

    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.

    1. To generate a native executable, use the following command:

      ./gradlew :aws:nativeCompile

      The native executable is created in the aws/build/native/nativeCompile/ directory

    2. You can then run the native executable with the following command:

      aws/build/native/nativeCompile/aws-db-demo-aws

      You can customize the name of the resulting binary by updating the Maven/Gradle plugin for GraalVM Native Image configuration.

    3. 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"

    4. 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:

    export DB_INSTANCE=$(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.