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KumuluzEE OpenAPI MicroProfile

KumuluzEE CI

KumuluzEE OpenAPI MicroProfile project provides powerful tools to incorporate the OpenAPI 3 specification to your microservices in a standardized way.

KumuluzEE OpenAPI MicroProfile project allows you to document microservice APIs using OpenAPI v3 compliant annotations. Project will automatically hook-up servlet that will serve your API specifications on endpoint /openapi. The project implements the MicroProfile OpenAPI specification.

More details:


You can enable KumuluzEE OpenAPI MicroProfile support by adding the following dependency:


OpenAPI configuration

When kumuluzee-openapi-mp dependency is included in the project, you can start documenting your REST API using MicroProfile OpenAPI annotations.

Documenting application class

@SecurityScheme(securitySchemeName = "openid-connect", type = SecuritySchemeType.OPENIDCONNECT,
        openIdConnectUrl = "http://auth-server-url/.well-known/openid-configuration")
@OpenAPIDefinition(info = @Info(title = "CustomerApi", version = "v2.0.0", contact = @Contact(), license = @License(name="something")), servers = @Server(url = "http://localhost:8080"), security
        = @SecurityRequirement(name = "openid-connect"))
public class CustomerApplication extends Application {

Documenting resource class and operations

public class CustomerResource {

    @Operation(summary = "Get customers details", description = "Returns customer details.")
            @APIResponse(description = "Customer details", responseCode = "200", content = @Content(schema = @Schema(implementation =
    public Response getCustomer(@PathParam("customerId") String customerId) {
        // ...


Accessing API specification

Build and run project using:

mvn clean package
java -jar target/${}.jar

After startup API specification will be available at:




Serving OpenAPI specification can be disabled by setting property kumuluzee.openapi-mp.enabled to false. By default serving API spec is enabled.


The KumuluzEE OpenAPI MicroProfile extension can be configured with the standard KumuluzEE configuration mechanism. For example with the config.yml file:

    enabled: true
      mapping: /openapi-custom-mapping

Some interesting configuration properties are:

  • kumuluzee.openapi-mp.enabled - If set to false disables the extension (and OpenAPI servlet). Default value: true
  • kumuluzee.openapi-mp.servlet.mapping - The endpoint at which the OpenAPI specification is available. Appended to optional server context path. Default value: /openapi
  • kumuluzee.openapi-mp.scan.packages - Comma separated list of packages which are scanned for the OpenAPI annotations. By default, all packages are scanned.

Full list of configuration properties can be found in MicroProfile OpenAPI specification.


By default KumuluzEE OpenAPI MP uses optimized scanning in order to reduce startup times. This means that only the main application JAR will be scanned (main artifact). In order to scan additional artifacts you need to specify them using the scan-libraries mechanism. You need to include all dependencies which contain JAX-RS application and resources as well as dependencies containing models returned from JAX-RS resources. If all your models and resources are in the main artifact you don't need to include anything. For example to include my-models artifact use the following configuration:

      - my-models

If you are unsure if your configuration is correct you can try to disable optimized scanning by using the following configuration:

      optimize: false

You can also enable scan debugging by setting the following key to true: kumuluzee.openapi-mp.scanning.debug. This will output a verbose log of scanning configuration and progress.

Adding Swagger UI

To serve API specification in visual form and to allow API consumers to interact with API resources you can add Swagger UI by including the kumuluzee-swagger-ui dependency:


Swagger UI is automatically enabled and is available at /api-specs/ui. In order to disable Swagger UI you can set the configuration key kumuluzee.openapi-mp.ui.enabled to false. You can also remap the Swagger UI to another location by setting the kumuluzee.openapi-mp.ui.mapping key (default value: /api-specs/ui). Path is appended to optional server context path.

Swagger UI needs to know where the OpenAPI specification is served from. It tries to define it from the following sources:

  1. Static: <protocol>://localhost:<port> (useful when nothing is defined, lowest priority)
  2. From the servers parameter in @OpenAPIDefinition annotation (useful when OpenAPI specification is available from the same hostname as Swagger UI)
  3. Configuration property: kumuluzee.server.base-url (useful for overriding above values)
  4. Configuration property: kumuluzee.openapi-mp.ui.specification-server (same as above but in a namespace specific to this extension)

Swagger UI server auto configuration

Server auto configuration allows for dynamic resolution of parameters like kumuluzee.openapi-mp.ui.specification-server instead of need to set it. This is done by retrieving necessary information from request during runtime and based on that setting correct redirect. It is especially useful when service is being deployed in multiple environments. This feature also updates list of servers in Swagger UI and reorder them, so it will be first one. It is also possible to resolve correct redirect when service is behind for example Ingres (Ingress must have enabled feature which forwards original URL).

By default, this feature is disabled for backward compatibility. To enable it set to true. To enable (Ingress) URI check set to true.

Default settings for server auto configuration:

        enabled: false
        original-uri-check: false

note: localhost server with same port is added only once (if not already specified in @OpenAPIDefinition) and in case in which is used localhost address in different format (for example instead of http://localhost:8080), no new server will be added to list and because of this Swagger UI will be unable to do API calls (this is due to issue with cors)

OpenAPI Maven Plugin

Maven plugin can be used to generate OpenAPI schema when building the application. To use it add the following to pom.xml:


By default, the schema is generated in target/generated/ directory in JSON and YAML formats.

If the schema is defined across multiple artefacts you must define the <scanLibraries></scanLibraries> configuration property with comma-separated list of dependencies in the same format as described in the Scanning section above.

Maven plugin uses SmallRye implementation in order to generate the schema. For more configuration options see the following document:


Recent changes can be viewed on Github on the Releases Page


See the contributing docs

When submitting an issue, please follow the guidelines.

When submitting a bugfix, write a test that exposes the bug and fails before applying your fix. Submit the test alongside the fix.

When submitting a new feature, add tests that cover the feature.