Create and Connect a Micronaut Application to an Oracle Cloud Infrastructure Autonomous Database

This guide describes how to create a Micronaut database application using GCN. The application presents REST endpoints and stores data in an Oracle Cloud Infrastructure Autonomous Database using Micronaut Data.

Oracle Cloud Infrastructure Autonomous Database is a fully automated database service that makes it easy for all organizations to develop and deploy application workloads regardless of complexity, scale, or criticality. All Oracle Cloud Infrastructure accounts (whether free or paid) get two Always Free Oracle Autonomous Databases. You can use these databases for transaction processing, data warehousing, Oracle APEX application development, or JSON-based application development. For current regional availability, see the Always Free Cloud Services table in Cloud Regions—Infrastructure and Platform Services.

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 backends: JPA (Hibernate) and Hibernate Reactive; SQL (JDBC, R2DBC); and MongoDB.

Prerequisites #

• JDK 17 or higher. See Setting up Your Desktop.
• An Oracle Cloud Infrastructure account. See Setting up Your Cloud Accounts.
• An Oracle Cloud Infrastructure compartment.
• The GCN 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 in Java:

A note regarding your development environment

Consider using Visual Studio Code that provides native support for developing applications with the Graal Cloud Native Tools extension.

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

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

1. Create the Application #

Create an application using the GCN Launcher.

1. Open the GCN Launcher in advanced mode.

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

Alternatively, use the GCN CLI as follows:

gcn create-app com.example.oci-adb-demo \
    --clouds=oci \
    --services=database \
    --features=graalvm,oracle-cloud-atp \
    --build=gradle \
    --jdk=17 \
    --lang=java

gcn create-app com.example.oci-adb-demo \
    --clouds=oci \
    --services=database \
    --features=graalvm,oracle-cloud-atp \
    --build=maven \
    --jdk=17 \
    --lang=java

1.1. Domain Entity #

The GCN Launcher created the sample domain entity in the lib/src/main/java/com/example/domain/Genre.java file:

package com.example.domain;

import io.micronaut.data.annotation.GeneratedValue;
import io.micronaut.data.annotation.Id;
import io.micronaut.data.annotation.MappedEntity;
import io.micronaut.serde.annotation.Serdeable;

import jakarta.validation.constraints.NotNull;

@Serdeable
@MappedEntity
public class Genre {

    @Id
    @GeneratedValue
    private Long id;

    @NotNull
    private String name;

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Genre{" + "id=" + id + ", name='" + name + "'}";
    }
}

1.2. Repository Interface #

A repository interface defines the operations to access the database. Micronaut Data implements the interface at compilation time. A sample repository interface was created for you in lib/src/main/java/com/example/repository/GenreRepository.java:

package com.example.repository;

import com.example.domain.Genre;
import io.micronaut.core.annotation.NonNull;
import io.micronaut.data.annotation.Id;
import io.micronaut.data.jdbc.annotation.JdbcRepository;
import io.micronaut.data.repository.PageableRepository;

import jakarta.validation.constraints.NotBlank;

import static io.micronaut.data.model.query.builder.sql.Dialect.ORACLE;

@JdbcRepository(dialect = ORACLE) // <1>
public interface GenreRepository extends PageableRepository<Genre, Long> { // <2>

    Genre save(@NonNull @NotBlank String name);

    long update(@Id long id, @NonNull @NotBlank String name);
}

1 @JdbcRepository with a specific dialect.

2 Genre, the entity to treat as the root entity for the purposes of querying, is established either from the method signature or from the generic type parameter specified to the GenericRepository interface.

The repository extends from PageableRepository. It inherits the hierarchy PageableRepository → CrudRepository → GenericRepository.

1.3. Controller #

Hibernate Validator is a reference implementation of the Validation API. Micronaut has built-in support for validation of beans that use jakarta.validation annotations. The necessary dependencies are included by default when creating a project.

The GCN Launcher created the main controller that exposes a resource with the common CRUD operations for you in lib/src/main/java/com/example/controller/GenreController.java:

package com.example.controller;

import com.example.domain.Genre;
import com.example.service.GenreService;
import io.micronaut.data.model.Pageable;
import io.micronaut.http.HttpResponse;
import io.micronaut.http.annotation.Body;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Delete;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Post;
import io.micronaut.http.annotation.Put;
import io.micronaut.http.annotation.Status;
import io.micronaut.scheduling.TaskExecutors;
import io.micronaut.scheduling.annotation.ExecuteOn;

import jakarta.validation.Valid;
import jakarta.validation.constraints.NotBlank;
import java.net.URI;
import java.util.List;
import java.util.Optional;

import static io.micronaut.http.HttpHeaders.LOCATION;
import static io.micronaut.http.HttpStatus.NO_CONTENT;

@ExecuteOn(TaskExecutors.IO) // <1>
@Controller("/genres") // <2>
class GenreController {

    private final GenreService genreService;

    GenreController(GenreService genreService) { // <3>
        this.genreService = genreService;
    }

    @Get("/{id}") // <4>
    public Optional<Genre> show(Long id) {
        return genreService.findById(id);
    }

    @Put("/{id}/{name}") // <5>
    public HttpResponse<?> update(long id, String name) {
        genreService.update(id, name);
        return HttpResponse
                .noContent()
                .header(LOCATION, URI.create("/genres/" + id).getPath());
    }

    @Get("/list") // <6>
    public List<Genre> list(@Valid Pageable pageable) {
        return genreService.list(pageable);
    }

    @Post // <7>
    public HttpResponse<Genre> save(@Body("name") @NotBlank String name) {
        Genre genre = genreService.save(name);

        return HttpResponse
                .created(genre)
                .headers(headers -> headers.location(URI.create("/genres/" + genre.getId())));
    }

    @Delete("/{id}") // <8>
    @Status(NO_CONTENT)
    public void delete(Long id) {
        genreService.delete(id);
    }
}

1 It is critical that any blocking I/O operations (such as fetching the data from the database) are offloaded to a separate thread pool that does not block the event loop.

2 The class is defined as a controller with the @Controller annotation mapped to the path /genres.

3 Uses constructor injection to inject a bean of type GenreRepository.

4 Maps a GET request to /genres/{id}, which attempts to show a genre. This illustrates the use of a URL path variable (id).

5 Maps a PUT request to /genres/{id}/{name}, which attempts to update a genre. This illustrates the use of URL path variables (id and name).

6 Maps a GET request to /genres/list, which returns a list of genres. This mapping illustrates URL parameters being mapped to a single POJO.

7 Maps a POST request to /genres, which attempts to create a new genre.

8 Maps a DELETE request to /genres/{id}, which attempts to remove a genre. This illustrates the use of a URL path variable (id).

1.4. Service #

A service contains business logic and facilitates communication between the controller and the repository. The domain is used to communicate between the controller and service layers.

The GCN Launcher created a sample service class, lib/src/main/java/com/example/service/GenreService.java, for you:

package com.example.service;

import com.example.domain.Genre;
import com.example.repository.GenreRepository;
import io.micronaut.data.model.Pageable;
import jakarta.inject.Singleton;

import jakarta.transaction.Transactional;
import java.util.List;
import java.util.Optional;

@Singleton
public class GenreService {

    private final GenreRepository genreRepository;

    GenreService(GenreRepository genreRepository) {
        this.genreRepository = genreRepository;
    }

    public Optional<Genre> findById(Long id) {
        return genreRepository.findById(id);
    }

    @Transactional
    public long update(long id, String name) {
        return genreRepository.update(id, name);
    }

    public List<Genre> list(Pageable pageable) {
        return genreRepository.findAll(pageable).getContent();
    }

    @Transactional
    public Genre save(String name) {
        return genreRepository.save(name);
    }

    @Transactional
    public void delete(long id) {
        genreRepository.deleteById(id);
    }
}

1.5. Tests #

The GCN Launcher wrote tests for you, in oci/src/test/java/com/example/GenreControllerTest.java, to verify the CRUD operations:

package com.example;

import com.example.domain.Genre;
import com.example.repository.GenreRepository;
import io.micronaut.core.type.Argument;
import io.micronaut.context.env.Environment;
import io.micronaut.http.HttpRequest;
import io.micronaut.http.HttpResponse;
import io.micronaut.http.client.HttpClient;
import io.micronaut.http.client.annotation.Client;
import io.micronaut.http.client.exceptions.HttpClientResponseException;
import io.micronaut.test.extensions.junit5.annotation.MicronautTest;
import jakarta.inject.Inject;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Test;

import java.util.Collections;
import java.util.List;

import static io.micronaut.http.HttpHeaders.LOCATION;
import static io.micronaut.http.HttpStatus.CREATED;
import static io.micronaut.http.HttpStatus.NOT_FOUND;
import static io.micronaut.http.HttpStatus.NO_CONTENT;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertThrows;

@MicronautTest
class GenreControllerTest {

    @Inject
    @Client("/")
    HttpClient client;

    @Test
    void testFindNonExistingGenreReturns404() {
        HttpClientResponseException thrown = assertThrows(HttpClientResponseException.class, () -> {
            client.toBlocking().exchange(HttpRequest.GET("/genres/99999"));
        });

        assertNotNull(thrown.getResponse());
        assertEquals(NOT_FOUND, thrown.getStatus());
    }

    @Test
    void testGenreCrudOperations() {

        HttpResponse<?> response = client.toBlocking().exchange(
                HttpRequest.POST("/genres", Collections.singletonMap("name", "DevOps")));
        assertEquals(CREATED, response.getStatus());

        response = client.toBlocking().exchange(
                HttpRequest.POST("/genres", Collections.singletonMap("name", "Microservices")));
        assertEquals(CREATED, response.getStatus());

        Long id = entityId(response);

        Genre genre = client.toBlocking().retrieve(
                HttpRequest.GET("/genres/" + id), Genre.class);
        assertEquals("Microservices", genre.getName());

        response = client.toBlocking().exchange(
                HttpRequest.PUT("/genres/" + id + "/Micro-services", null));
        assertEquals(NO_CONTENT, response.getStatus());

        genre = client.toBlocking().retrieve(
                HttpRequest.GET("/genres/" + id), Genre.class);
        assertEquals("Micro-services", genre.getName());

        List<Genre> genres = client.toBlocking().retrieve(
                HttpRequest.GET("/genres/list"), Argument.listOf(Genre.class));
        assertEquals(2, genres.size());

        genres = client.toBlocking().retrieve(
                HttpRequest.GET("/genres/list?size=1"), Argument.listOf(Genre.class));
        assertEquals(1, genres.size());
        assertEquals("DevOps", genres.get(0).getName());

        genres = client.toBlocking().retrieve(
                HttpRequest.GET("/genres/list?size=1&sort=name,desc"), Argument.listOf(Genre.class));
        assertEquals(1, genres.size());
        assertEquals("Micro-services", genres.get(0).getName());

        genres = client.toBlocking().retrieve(
                HttpRequest.GET("/genres/list?size=1&page=2"), Argument.listOf(Genre.class));
        assertEquals(0, genres.size());

        response = client.toBlocking().exchange(
                HttpRequest.DELETE("/genres/" + id));
        assertEquals(NO_CONTENT, response.getStatus());
    }

    private Long entityId(HttpResponse<?> response) {
        String value = response.header(LOCATION);
        if (value == null) {
            return null;
        }
        String path = "/genres/";
        int index = value.indexOf(path);
        return index == -1 ? null : Long.valueOf(value.substring(index + path.length()));
    }

    @Inject
    GenreRepository genreRepository;

    @AfterEach
    void cleanup() {
        genreRepository.deleteAll();
    }
}

2. Create an Oracle Autonomous Database #

1. In the Oracle Cloud Console, open the navigation menu, click Oracle Database. Under Autonomous Database, click Autonomous Transaction Processing.

2. Click Create Autonomous Database and accept the default name for the database.

3. Select Transaction Processing and Serverless. If you are using a trial account, make sure you select Always Free.

4. Create an admin password (must be at least 12 characters and contain a number and an uppercase letter) and select Secure access from everywhere as the network access type.

5. Click Create Autonomous Database to create your database.

6. On the Autonomous Database Details screen click Copy to copy the OCID of the database. (This is a unique identifier which you will need later.)

2.1. Create a User #

1. When the database has been provisioned, on the Autonomous Database Details page, click Database Actions. (If necessary, log in with username “ADMIN” and the admin password you created earlier.)

2. Click SQL to open the SQL console.

3. Copy and paste the following SQL commands into the worksheet:

    CREATE USER gcn_user IDENTIFIED BY "XXXXXXXXX";
    GRANT CONNECT, RESOURCE TO gcn_user;
    GRANT UNLIMITED TABLESPACE TO gcn_user;
   

   Create a schema user password (must be at least 12 characters and contain a number and an uppercase letter) and replace the text “XXXXXXXXX” with that password.

4. Click Run Script to run the SQL commands.

3. Configuration #

Before you can test or run your application, provide configuration for Flyway and the application’s datasources.

3.1. Configure Flyway #

The GCN Launcher included Flyway for database migrations. It uses the Micronaut integration with Flyway project that automates schema changes, significantly simplifies schema management tasks, such as migrating, rolling back, and reproducing in multiple environments.

Flyway migration is automatically triggered before your application starts. Flyway reads migration file(s) in the lib/src/main/resources/db/migration/ directory, runs them if necessary, and verifies that the configured datasource is consistent with them.

The migration file with the database schema, lib/src/main/resources/db/migration/V1__schema.sql, was also created for you by the GCN Launcher.

CREATE TABLE "GENRE" (
   "ID"    NUMBER(19) PRIMARY KEY NOT NULL,
   "NAME"  VARCHAR(255) NOT NULL
);
CREATE SEQUENCE "GENRE_SEQ" MINVALUE 1 START WITH 1 NOCACHE NOCYCLE;

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

3.2. Configure Datasources #

The connection information and credentials for an Oracle Cloud Infrastructure Autonomous Database are stored in an Oracle Wallet. See Micronaut Oracle Cloud integration for more details and options for working with Oracle Cloud Infrastructure.

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

export DATASOURCES_DEFAULT_OCID=<ocid> # 1
export DATASOURCES_DEFAULT_WALLET_PASSWORD=<wallet_password> # 2
export DATASOURCES_DEFAULT_USERNAME=<username> # 3
export DATASOURCES_DEFAULT_PASSWORD=<password> # 4

set DATASOURCES_DEFAULT_OCID=<ocid> # 1
set DATASOURCES_DEFAULT_WALLET_PASSWORD=<wallet_password> # 2
set DATASOURCES_DEFAULT_USERNAME=<username> # 3
set DATASOURCES_DEFAULT_PASSWORD=<password> # 4

$ENV:DATASOURCES_DEFAULT_OCID = "<ocid>" # 1
$ENV:DATASOURCES_DEFAULT_WALLET_PASSWORD = "<wallet_password>" # 2
$ENV:DATASOURCES_DEFAULT_USERNAME = "<username>" # 3
$ENV:DATASOURCES_DEFAULT_PASSWORD = "<password>" # 4

1 Replace <ocid> with the OCID of the database you copied when creating the database.

2 Replace <wallet_password> with a password to encrypt the wallet keys (must be at least eight characters and include at least one letter and either one numeric or special character).

3 Replace the <username> with “gcn_user” (the name of the user you created).

4 Replace the <password> with the “gcn_user” password you created.

Note: This guide assumes that you are using the DEFAULT profile to authenticate with Oracle Cloud Infrastructure. If you are using a different profile, specify its name in the oci/src/main/resources/application.properties file, and optionally add a value for the path to the config file if necessary as described in the Authentication section of the Micronaut Oracle Cloud documentation.

4. Run the Application #

To run the application, use the following command, which starts the application on port 8080.

./gradlew :oci:run

./mvnw install -pl lib -am
./mvnw mn:run -pl oci

5. Test the Application #

Test the application by accessing its REST endpoints.

Run this command to test creating and storing a new Genre in the database:

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

You should see a response similar to:

{"id":1,"name":"music"}

Confirm that the new Genre is saved in the database by listing its contents:

curl localhost:8080/genres/list

You should see a response similar to:

[{"id":1,"name":"music"}]

Retrieve a single Genre from the database as follows:

curl -i http://localhost:8080/genres/1

You should see a response similar to:

{"id":1,"name":"music"}

Delete the Genre you added and then list the contents of the database to confirm that it has been deleted:

curl -X "DELETE" "http://localhost:8080/genres/1"
curl localhost:8080/genres/list

6. Generate a Native Executable Using GraalVM #

GCN supports compiling a Java application ahead-of-time into a native executable 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.

To generate a native executable, run the following command:

./gradlew :oci:nativeCompile

oci/build/native/nativeCompile/oci

./mvnw install -pl lib -am
./mvnw package -pl oci -Dpackaging=native-image

oci/target/oci

7. Run and Test the Native Executable #

Run the native executable, and then perform the same tests as in step 5.

8. Clean Up Cloud Resources #

When you finish using the database, you can terminate it from the Oracle Cloud Console. For more information, see Terminate an Autonomous Database Instance.

Summary #

This guide demonstrated how to use GCN to create a database application that stores data in an Oracle Cloud Infrastructure Autonomous Database using Micronaut Data. You also saw how to package this application into a native executable.

Related Documentation #

• Micronaut Data
• Oracle Cloud Infrastructure Autonomous Database
• Native Build Tools
• GraalVM Native Image