OpenApi Generator Usage on Sample Quarkus Application

This example covers the approach adopted on the Natwest Identity project when generating API clients with Resteasy for Identity Service Provider Interfaces which they are using Quarkus native libraries.

For Spring, with the help of the boat-plugin, we have the default configuration to use open-api-generator with Spring. It's already documented and is well known in Backbase.

Also, multi-tenancy (while creating api-client) and aspects of tracing will be covered with the examples.

NOTE: Please take a look at the BOAT Golden Example to understand how to use boat-plugin.

For Quarkus, to use openapi-generator the plugin must be configured.

Configuration of OpenApiGenerator Plugin

The input spec of this sample application can be found here.

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <executions>
        <execution>
            <id>todo-api</id>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/src/main/resources/todo.yaml</inputSpec>
                <configOptions>
                    <modelPackage>org.quarkus.openapi.todo.model</modelPackage>
                    <apiPackage>org.quarkus.openapi.todo.api</apiPackage>
                </configOptions>
            </configuration>
        </execution>
    </executions>
    <configuration>
        <output>${codegen.openapi.generated-sources-dir}</output>
        <generatorName>java</generatorName>
        <generateApiTests>false</generateApiTests>
        <generateModelTests>false</generateModelTests>
        <generateModelDocumentation>false</generateModelDocumentation>
        <generateApiDocumentation>false</generateApiDocumentation>
        <configOptions>
            <library>resteasy</library>
            <dateLibrary>java8</dateLibrary>
            <openApiNullable>false</openApiNullable>
            <invokerPackage>org.quarkus.openapi.todo.api</invokerPackage>
        </configOptions>
    </configuration>
</plugin>

<library>resteasy</library>

The resteasy library is used to generate resteasy client.

<dateLibrary>java8</dateLibrary>

Java8 date library is used.

<openApiNullable>false</openApiNullable>

OpenAPI Jackson Nullable library is disabled.

<invokerPackage>org.quarkus.openapi.todo.api</invokerPackage>

Root package for generated code

Config Class for API(s)

We have TodoApiConfig class, by using this config class, the API(s) usage is/are can be easy. At this example, we only have one API,

if we would have multiple API's, the new API Clients would be created in the TodoApiConfigFactory class and would be ready to use by any service calling the TodosApiConfig.

In TodoApiConfig class, we are simply adding the generated TodosApi.

TodoApiConfig

public class TodoApiConfig {
    private final TodosApi todosApi;

    public TodoApiConfig(TodosApi todosApi) {
        this.todosApi = todosApi;
    }

    public TodosApi getTodosApi() {
        return todosApi;
    }
}

In TodoApiConfigFactory class, we have simply one method for creating TodoApiConfig which TodosApi will be created for the Config class.

TodoApiConfigFactory

public class TodoApiConfigFactory {

    /**
     * Create Todo Api Config without tenant data.
     *
     * @return {@link TodoApiConfig}
     */
    public static TodoApiConfig createTodoApiConfig() {
        return createTodoApiConfig(null);
    }

    /**
     * Create Todo Api Config for a given tenant.
     * Global scope is used to get base url.
     *
     * @return {@link TodoApiConfig}
     */
    public static TodoApiConfig createTodoApiConfig(Tenant tenant) {
        Config.Scope scope = ConfigUtils.getGlobalScope();

        Optional<String> tenantId = Optional.ofNullable(tenant).map(Tenant::getId);

        TodosApi todosApi =
            createTodoApi(tenantId.orElse(null), scope.get(TODO_API_BASE_URL_KEY));

        if (Objects.isNull(todosApi)) {
            log.error("Can't initialize Todos api for tenant: {}", tenantId.orElse("<no tenant>"));
            return null;
        }

        return new TodoApiConfig(todosApi);
    }

    private static TodosApi createTodoApi(String tenantId, String baseUrl) {
        if (Objects.isNull(baseUrl)) {
            log.error("TodoApi base url is null");
            return null;
        }

        return new TodosApi(ApiClientFactory.createTenantApiClient(tenantId, baseUrl));
    }

Tracing

It’s becoming more important than ever before to be able to see what’s going on inside our requests as they span across multiple microservices.

As a first step, we need to create ApiClient with the base path. After that, we can register our newly created ApiClient to the OpenTracing.

We are using JAXRS Default Client Builder to create JAXRS Client. OpenTracing's Global Tracer is used for this sample quarkus application.

If any logger is defined for debugging in ApiClient class, the logger class will be registered while creating JAXRS Client. Last step is setting the HttpClient. An HttpClient can be used to send requests and retrieve their responses. An HttpClient is created through a builder.

(Since we are going to create a new JAX-RS - Client, we used JAX-RS - Client Builder)

    /**
     * Getting ApiClient configured for given tenant.
     */
    public static ApiClient createTraceApiClient(String basePath) {
        ApiClient apiClient = new ApiClient().setBasePath(basePath);
        Tracer tracer = GlobalTracer.get();
        ClientBuilder clientBuilder = ClientBuilder.newBuilder()
            .executorService(new TracedExecutorService(Executors.newCachedThreadPool(), tracer))
            .register(new SmallRyeClientTracingFeature(tracer))
            .register(apiClient.getJSON());

        if (LoggerFactory.getLogger(ApiClient.class).isDebugEnabled()) {
            clientBuilder.register(Logger.class);
        }

        return apiClient.setHttpClient(clientBuilder.build());
    }

Multi-tenancy

Each time an API request is performed, we need to know to tenant identifier to correctly route the persistence operations.

There are around three most common ways to provide tenant identifier.

1. Providing the tenant identifier as a URL Part
2. Using a custom HTTP Request header
3. Using JWTs to provide the tenant identifier as a JSON token claim

For this sample-app, second option through a custom HTTP header called 'X-TID' is used.

    public class ApiClientFactory {

    private ApiClientFactory() {
    }

    /**
     * Getting ApiClient configured for given tenant.
     */
    public static ApiClient createTraceApiClient(String basePath) {
        ApiClient apiClient = new ApiClient().setBasePath(basePath);
        Tracer tracer = GlobalTracer.get();
        ClientBuilder clientBuilder = ClientBuilder.newBuilder()
            .executorService(new TracedExecutorService(Executors.newCachedThreadPool(), tracer))
            .register(new SmallRyeClientTracingFeature(tracer))
            .register(apiClient.getJSON());

        if (LoggerFactory.getLogger(ApiClient.class).isDebugEnabled()) {
            clientBuilder.register(Logger.class);
        }

        return apiClient.setHttpClient(clientBuilder.build());
    }

    /**
     * Getting ApiClient configured for given tenant (or without tenant if tenantId is null).
     */
    public static ApiClient createTenantApiClient(String tenantId, String basePath) {
        ApiClient apiClient = createTraceApiClient(basePath);
        if (Objects.isNull(tenantId)) {
            return apiClient;
        }

        return apiClient.addDefaultHeader("X-TID", tenantId);
    }
}

After the trace api client is created, the custom HTTP request header (X-TID) is added.

Tests

We have basic tests for Factory classes, TodoApiConfig and Provider class to ensure that our ApiClient and ApiConfig are initialized correctly.

TodoApiConfigTest

   @ExtendWith(MockitoExtension.class)
    class TodoApiConfigTest {

    @Mock
    private TodosApi todosApi;

    @InjectMocks
    private TodoApiConfig todoApiConfig;

    @Test
    void shouldReturnAllApis() {
        assertNotNull(todoApiConfig.getTodosApi());
    }
}

For factory class tests: there are different methods to verify the ApiClient is created correctly.

Detailed test can be found (creating ApiConfig with the tenant/without tenant) on TodoApiConfigFactoryTest class.

Running the application in dev mode

You can run your application in dev mode that enables live coding using:

./mvnw compile quarkus:dev

NOTE: Quarkus now ships with a Dev UI, which is available in dev mode only at http://localhost:8080/q/dev/.

Packaging and running the application

The application can be packaged using:

./mvnw package

It produces the quarkus-run.jar file in the target/quarkus-app/ directory. Be aware that it’s not an über-jar as the dependencies are copied into the target/quarkus-app/lib/ directory.

The application is now runnable using java -jar target/quarkus-app/quarkus-run.jar.

If you want to build an über-jar, execute the following command:

./mvnw package -Dquarkus.package.type=uber-jar

The application, packaged as an über-jar, is now runnable using java -jar target/*-runner.jar.

Creating a native executable

You can create a native executable using:

./mvnw package -Pnative

Or, if you don't have GraalVM installed, you can run the native executable build in a container using:

./mvnw package -Pnative -Dquarkus.native.container-build=true

You can then execute your native executable with: ./target/code-with-quarkus-1.0.0-SNAPSHOT-runner

If you want to learn more about building native executables, please consult https://quarkus.io/guides/maven-tooling.

Provided Code

RESTEasy Reactive

Easily start your Reactive RESTful Web Services

Related guide section...