Add the following dependency to your project’s pom.xml file:

Version 2.x.x of this extension supports Quarkus 3, and version 1.x.x supports Quarkus 2. We strongly recommend you to use version 2.x.x. No updates are planned for version 1.x.x. 
<dependency>
  <groupId>io.quarkiverse.openapi.generator</groupId>
  <artifactId>quarkus-openapi-generator</artifactId>
  <version>3.0.0-SNAPSHOT</version>
</dependency>

You will also need to add or update the quarkus-maven-plugin configuration with the following:

You probably already have this configuration if you created your application with Code Quarkus. That said, double-check your configuration not to add another plugin entry. 
<plugin>
  <groupId>io.quarkus</groupId>
  <artifactId>quarkus-maven-plugin</artifactId>
  <extensions>true</extensions>
  <executions>
    <execution>
      <goals>
        <goal>build</goal>
        <goal>generate-code</goal>
        <goal>generate-code-tests</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Now, create the directory openapi under your src/main/ path and add the OpenAPI spec files there. We support JSON, YAML and YML extensions.

If you want to change the directory where OpenAPI files must be found, use the property quarkus.openapi-generator.codegen.input-base-dir. IMPORTANT: it is relative to the project base directory. For example, if you have a project called MyJavaProject and decide to place them in MyJavaProject/openapi-definitions, use the following property:

quarkus.openapi-generator.codegen.input-base-dir=openapi-definitions

If you want to change the directory where template files must be found, use the property quarkus.openapi-generator.codegen.template-base-dir. If not set the templates will be expected in the build directory under classes/templates IMPORTANT: it is relative to src/main. For example, if you want your custom templates in src/main/resources/custom-templates, use the following property:

quarkus.openapi-generator.codegen.template-base-dir=resources/custom-templates

To fine tune the configuration for each spec file, add the following entry to your properties file. In this example, our spec file is in src/main/openapi/petstore.json:

quarkus.openapi-generator.codegen.spec.petstore_json.additional-model-type-annotations=@org.test.Foo;@org.test.Bar

If you want to change the base package in which the classes are generated, use the quarkus.openapi-generator.codegen.spec.<filename>.base-package property. If a base package is not provided, it will default to org.openapi.quarkus.<filename>. For example, org.openapi.quarkus.petstore_json.

quarkus.openapi-generator.codegen.spec.petstore_json.base-package=org.acme

Configuring additional-model-type-annotations will add all annotations to the generated model files (extra details can be found in OpenApi Generator Doc).

You can customize the name of generated classes. To do that, you must define the following properties:

quarkus.openapi-generator.codegen.spec.petstore_json.api-name-suffix=CustomApiSuffix
quarkus.openapi-generator.codegen.spec.petstore_json.model-name-suffix=CustomModelSuffix
quarkus.openapi-generator.codegen.spec.petstore_json.model-name-prefix=CustomModelPrefix

You can remove operationId prefix (e.g. User_findAll⇒ findAll). To do that, you must define the following properties:

quarkus.openapi-generator.codegen.spec.petstore_json.remove-operation-id-prefix=true

Character to use as a delimiter for the prefix. Default is '_'.You can define the prefix delimiter (e.g. User.findAll⇒ findAll):

quarkus.openapi-generator.codegen.spec.petstore_json.remove-operation-id-prefix-delimiter=.

You can define count of delimiter for the prefix (e.g. org.acme.UserResource.findAll⇒ findAll). Use -1 for last Default:

quarkus.openapi-generator.codegen.spec.petstore_json.remove-operation-id-prefix-count=3

The same way you can add any additional annotations to the generated api files with additional-api-type-annotations. Given you want to include Foo and Bar annotations, you must define additional-api-type-annotations as:

quarkus.openapi-generator.codegen.spec.petstore_json.additional-api-type-annotations=@org.test.Foo;@org.test.Bar
Note that the file name`petstore_json`is used to configure the specific information for each spec. We follow the Environment Variables Mapping Rules from Microprofile Configuration to sanitize the OpenAPI spec filename. Any non-alphabetic characters are replaced by an underscore _.

Run mvn compile to generate your classes in target/generated-sources/open-api-json path:

- org.acme.openapi
  - api
    - PetApi.java
    - StoreApi.java
    - UserApi.java
  - model
    - Address.java
    - Category.java
    - Customer.java
    - ModelApiResponse.java
    - Order.java
    - Pet.java
    - Tag.java
    - User.java

You can reference the generated code in your project, for example:

import jakarta.inject.Inject;
import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.core.MediaType;

import org.acme.openapi.api.PetApi;
import org.eclipse.microprofile.rest.client.inject.RestClient;
import org.jboss.resteasy.annotations.jaxrs.PathParam;

@Produces(MediaType.APPLICATION_JSON)
@Path("/petstore")
public class PetResource {

    @RestClient
    @Inject
    PetApi petApi;
}

See the integration-tests module for more information of how to use this extension. Please be advised that the extension is on experimental, early development stage.