How do I go about generating and using Openapi specs?

[mikybars]

I came across Mill a couple of weeks ago and I'm trying to integrate it in a Spring Boot project that currently uses Gradle as build tool with the corresponding Openapi Generator plugin.

The thing is I don't know how to replace the openApiGenerate task in Gradle necessary for creating the Java files from the yaml spec. I searched the official Mill docs, this repo and Google and nothing came out.

My best try so far is generate those Java files from outside the build (java -jar openapi-generator-cli-7.13.0.jar generate...) and configure a custom sources task to include this new path. Ideally I'd like to achieve the same thing with a simple mill compile.

Can you point me in the right direction?

[lihaoyi]

@mikybars you should be able to do something like

object foo extends JavaModule{
  def openapiYaml = Task.Source("openapi.yaml")
  def generator = Task{
    os.write(Task.dest / "generator.jar", requests.get("url...to...openapi-generator-cli-7.13.0.jar"))
  }
  override def generatedSources = Task{
    os.call(("java", "-jar", generator().path, openapiYaml().path))
    Seq(PathRe(Task.dest))
  }
}

[mikybars]

Yes, that would do it!

I had to tweak your code example a little bit though. You were missing a return value here:

def generator = Task {
  val jarPath = Task.dest / "generator.jar"
  os.write(jarPath, requests.get("https://repo1.maven.org/maven2/org/openapitools/openapi-generator-cli/7.13.0/openapi-generator-cli-7.13.0.jar"))
  PathRef(jarPath)
}

I leave here the complete generate task with the right syntax for those with the same needs:

override def generatedSources = Task{
  os.call(("java", "-jar", generator().path, "generate",
    "-i", openapiYaml().path,
    "-g", "spring",
    "-o", Task.dest,
    "--api-package", "..adapters.in.rest",
    "--model-package", "..adapters.in.rest",
    "--model-name-suffix", "Dto",
    "--additional-properties=useSpringBoot3=true,interfaceOnly=true,skipDefaultInterface=true,dateLibrary=java8-localdatetime,openApiNullable=false"))
  Seq(PathRef(Task.dest))  // PathRe -> PathRef
}

However I feel it a bit hacky to spawn a new JVM just for the generation process. I wish there was a more streamlined way to do it. Do you think it would be valuable to have a Openapi generator plugin for Mill?

[mikybars]

Do you think it would be valuable to have a Openapi generator plugin for Mill?

@lihaoyi I finally found the time to give it a spin and here you have it https://github.com/mikybars/openapi-generator-mill-plugin in case you'd like to list it on the Third-party Plugins page on your website

And here mikybars/spring-boot-prices-mic-mill@68a6ec3 you can see it in action

[lefou]

• Add OpenApi plugin to thirdparty plugin section #5655

[lostiniceland]

@mikybars thanks for your contribution, just what I was looking for.

How could I use the plugin to have multiple runs with different specs? When using the OpenApiModule it looks like I can only give it a single spec. Due to our frontend requirements, we've splitted the apis in multiple files.

Also it currently looks like the plugin is designed to run the server generators. Is it possible to also run the client generators?

[mikybars]

Response 👉🏼 mikybars/openapi-generator-mill-plugin#1 (comment)