[BUG][Java][jaxrs-spec] Codegen creates invalid code for multipart/form-data for quarkus

Description

When creating Java code from a openapi.yml for quakus, the resulting code does not work:

RESTEASY003875: Unable to find a constructor that takes a String param or a valueOf() or fromString() method for javax.ws.rs.FormParam("file") on public abstract void org.openapitools.api.UploadApi.uploadPost(java.io.InputStream,java.lang.String) for basetype: java.io.InputStream

Quarkus cannot handle the geneated method signature of the Rest-resource-class:

@POST
@Consumes({ "multipart/form-data" })
@Produces({ "application/json" })
@ApiOperation(value = "", notes = "", tags={  })
@ApiResponses(value = { 
@ApiResponse(code = 200, message = "", response = Void.class) })
void uploadPost( @FormParam(value = "file") InputStream fileInputStream,@FormParam(value = "name")  String name);

(Additionally, no validation annotations are created!)

openapi-generator version

<groupId>org.openapitools</groupId>
<artifactId>openapi-generator-maven-plugin</artifactId>
<version>4.3.1</version>

OpenAPI declaration file content or url

openapi: 3.0.1
info:
  title: ''
  description: ''
  version: "1.0"

paths:
  /upload:
    post:
      requestBody:
        content:
          multipart/form-data:
            schema:
              $ref: '#/components/schemas/MultipartData'
      responses:
        200:
          description: ''
          content:
            application/json: {}
components:
  schemas:
    MultipartData:
      type: object
      properties:
        file:
          format: binary
          type: string
        name:
          pattern: .*
          type: string

Command line used for generation

Quarkus-Version: 1.9.2.Final

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>4.3.1</version>
    <executions>
        <execution>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/src/main/resources/META-INF/openapi.yml</inputSpec>
                <generatorName>jaxrs-spec</generatorName>
                <configOptions>
                    <library>quarkus</library>
                    <sourceFolder>src/gen/java/main</sourceFolder>
                    <interfaceOnly>true</interfaceOnly>
                </configOptions>
            </configuration>
        </execution>
    </executions>
</plugin>

Steps to reproduce

• clone https://github.com/M-Landwehr/poc/tree/quarkus-file-upload-multipart-form
• run mvnw package quarkus:dev
• the error above is printed to the server log
• delete ExampleResource.java
• rerun mvnw package quarkus:dev
• no error is logged; open http://localhost:8080/swagger-ui/#/default/post_upload

Alternatively simply generate java code from the openapi.yml above using the jaxrs-spec generator and the quarkus library

Related issues/PRs

Suggest a fix/enhancement

The model-class is created but is not used in this case. (althogh is has @JsonProperty annotations insteadod the @FormParam annotations

A possible fix would be to

• For a multipart/form-data request:
  • remove '@JsonProperty' from the generated model class and add @FormParam
  • adjust the generated interface to have methods with a signure simmilar to
    public void uploadPost(@MultipartForm @Valid MultipartData data) {}
    (see https://quarkus.io/guides/rest-client-multipart)

Start by generating the supplied openapi.yml with the jaxrs-spec generator using the quarkus library, then inspect the generated interface and model signatures. Compare the result with the multipart request shape and the suggested @MultipartForm approach; done means the generated Quarkus resource starts without the RESTEasy constructor error and preserves validation annotations.