Openapi fake server

See example source

If you generate external API client using OpenAPI declaration, you can also generate a fake server implementation from the same file.

Sample client and server build:

mport org.openapitools.generator.gradle.plugin.tasks.GenerateTask

plugins {
    id 'org.openapi.generator'
}

java {
    withSourcesJar()
}

dependencies {
    implementation 'io.dropwizard:dropwizard-forms'
    implementation 'com.github.scribejava:scribejava-core:8.3.3'

    // OPENAPI CODEGEN
    // additional dependency required for codegen, but conflicts with dropwizard (need to disable feature)
    implementation 'org.glassfish.jersey.media:jersey-media-json-jackson'

    compileOnly 'io.swagger.core.v3:swagger-annotations:2.2.30'
}

// https://openapi-generator.tech/docs/generators/java
openApiGenerate {
    generatorName = "java"
    inputSpec = "$projectDir/src/main/openapi/petStore.yaml"
    outputDir = "$buildDir/petstore/client"
    apiPackage = "com.petstore.api"
    invokerPackage = "com.petstore"
    modelPackage = "com.petstore.api.model"
    configOptions = [
            library: "jersey3",
            dateLibrary: "java8",
            openApiNullable: "false",
            hideGenerationTimestamp: "true"
    ]
}


// https://openapi-generator.tech/docs/generators/jaxrs-jersey
tasks.register('openApiGenerateServer', GenerateTask) {
    group = 'openapi tools'
    generatorName = "jaxrs-jersey"
    inputSpec = "$projectDir/src/main/openapi/petStore.yaml"
    outputDir = "$buildDir/petstore/server"
    apiPackage = "com.petstore.server.api"
    invokerPackage = "com.petstore.server"
    modelPackage = "com.petstore.server.api.model"
    configOptions = [
            library    : "jersey3",
            dateLibrary: "java8",
            openApiNullable: "false",
            hideGenerationTimestamp: "true"
    ]
}

compileJava.dependsOn 'openApiGenerate', 'openApiGenerateServer'
tasks.sourcesJar.dependsOn 'openApiGenerate', 'openApiGenerateServer'
sourceSets.main.java.srcDir "${openApiGenerate.outputDir.get()}/src/main/java"
// note main folder not attached! (sources were copied manually)
sourceSets.main.java.srcDir "${openApiGenerateServer.outputDir.get()}/src/gen/java"

openApiGenerate creates client in build/petstore/client openApiGenerateServer creates server stub in build/petstore/server

Client

Actual client interfaces are generated in:

/build/petstore/client/src/main/java/com/petstore/api

These are the main client classes:

• PetApi
• StoreApi
• UserApi

Guice bindings:

public class PetStoreApiModule extends DropwizardAwareModule<ExampleConfig> {

    @Override
    protected void configure() {
        ApiClient apiClient = new ApiClient();
        apiClient.setBasePath(configuration().getPetStoreUrl());
        // optional
        apiClient.setDebugging(true);

        bind(ApiClient.class).toInstance(apiClient);
        bind(PetApi.class).toInstance(new PetApi(apiClient));
        bind(StoreApi.class).toInstance(new StoreApi(apiClient));
        bind(UserApi.class).toInstance(new UserApi(apiClient));
    }
}

(target url is in configuration)

Server

Generated server stub:

/build/petstore/server/src/main/java/com/petstore/server

NOTE: server will also generate its own model, but this part will be attached directly (from gen folder).

Now copy server files into the main sources (preserving package):

/build/petstore/server/src/main/java/com/petstore/server -->  /src/main/java/com/petstore/server

(except Bootstrap class)

Implement fakes in impl. For example, to implement getPetById, change PetApiServiceImpl :

@Override
public Response getPetById(Long petId, SecurityContext securityContext) throws NotFoundException {
    final Pet pet = new Pet();
    pet.setId(petId);
    pet.setName("Jack");
    final Tag tag = new Tag();
    tag.setName("puppy");
    pet.getTags().add(tag);
    return Response.ok().entity(pet).build();
}

Now implement root fake resource:

@Path("/fake/petstore/")
public class FakePetStoreServer {

    // IMPORTANT: paths in console would contain /pet/pet duplicate, but ACTUAL path matching would IGNORE
    // @Path("/pet") declared on ApiApi class, so such declaration is correct for runtime

    @Path("/pet")
    public Class<PetApi> getPetApi() {
        return PetApi.class;
    }

    @Path("/store")
    public Class<StoreApi> getStoreApi() {
        return StoreApi.class;
    }

    @Path("/user")
    public Class<UserApi> getUserApi() {
        return UserApi.class;
    }
}

Bundle

Use GuiceyBundle for activation:

public class PetStoreBundle implements GuiceyBundle {

    @Override
    public void run(GuiceyEnvironment environment) throws Exception {
        // because of required conflicting dependency jersey-media-json-jackson
        // https://github.com/dropwizard/dropwizard/issues/1341#issuecomment-251503011
        environment.environment().jersey()
                .property(CommonProperties.FEATURE_AUTO_DISCOVERY_DISABLE, Boolean.TRUE);

        // register client api
        environment.modules(new PetStoreApiModule());

        // optional fake server start
        if (environment.<ExampleConfig>configuration().isStartFakeStore()) {
            environment.register(FakePetStoreServer.class);
        }
    }
}

Registration in app:

@Override
public void initialize(Bootstrap<ExampleConfig> bootstrap) {
    bootstrap.addBundle(GuiceBundle.builder()
            .bundles(new PetStoreBundle())
            .build());
}

Usage

@TestDropwizardApp(value = ExampleApp.class,
        configOverride = {
                "petStoreUrl: http://localhost:8080/fake/petstore",
                "startFakeStore: true"})
public class FakeServerTest {

    @Inject
    SampleService sampleService;

    @Test
    void testServer() {

        final Pet pet = sampleService.findPet(1);
        Assertions.assertNotNull(pet);
        Assertions.assertEquals("Jack", pet.getName());
    }
}