[JAXRS-spec] Use Microprofile Openapi annotations instead of swagger

[michbeck100]

Description

Moving forward to OAS 3.0 the openapi-generator should have the option to switch from Swagger annotations in the generated code to annotations from the Microprofile OpenAPI Specification.

[jmini]

Yes this would be great...

Related discussion is #27 and the more I participate in the MicroProfile Project, the more I am convinced that it is the way to go.

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My approach was more: we could propose a new generator for MicroProfile (also based on AbstractJavaJAXRSServerCodegen but with new templates). The more I think about it, the more I think that it will take some time to reach the maturity of the current generators.

With version containing breaking changes (4.0.0 or later) we could decided that this version is good enough to existing JaxRS generator that uses Swagger 2 components.

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Is your issue just a wish or are you ready to invest time on it (development, testing, ...)?

Let me know, maybe we can work together on it.

[michbeck100]

Currently my approach is to remove the swagger annotations by using a boolean switch in the mustache templates. Because the microprofile openapi spec allows to merge YAML API definition with annotations, it is enough to have just the YAML definition together with the generated code.

[jmini]

I did not understood your last point:

Because the microprofile openapi spec allows to merge YAML API definition with annotations, it is enough to have just the YAML definition together with the generated code.

[michbeck100]

The Microprofile OpenAPI specification allows to have just the API definition as single YAML file without any annotations in code (see here):

In this case, we refer to the OpenAPI document as the "source of truth", by which the client and provider must abide.

[michbeck100]

And this section describes merging the YAML with annotations.

[arthurdm]

+1 to supporting MP OpenAPI!

that's an interesting approach @michbeck100 - if someone already has an OpenAPI v3 YAML file before the code they're likely (but not exclusively) using a design-first approach, in which case the code should not deviate from the static file..which creates the question on whether or not do we need OAS3 annotations at all?

Looking from the other side of the coin, I think that it's probably good to generate the MP OpenAPI annotations for some reasons:

• puts the documentation closer to the code (i.e. the developer doesn't need to go into the static file to see more information about the method they need to implement)
• allows for the application to be extended, in the cases where the dev team started with a static file, but then wanted to make some additions for v2 using a code-first approach.
• brings more awareness to MP OpenAPI annotations (community education)

So perhaps this issue can be staged:

Stage 1: generate a pure JAX-RS app from an OAS3 doc (also adding META-INF/openapi.yaml)
Stage2: augment Stage 1's generated code to also generate MP OpenAPI annotations.

Thoughts?

[jmini]

As I wrote in #809, I think it would be nice to have 2 generators:

• java-microprofile-without-annotation (your Stage 1)
• java-microprofile-with-annotation (your Stage 2)

=> I am open for better name.

The generators should produce a meaningful project (README, pom.xml, ...) so that it is easy for the user to start.

The generator could also provide the possibility to select the implementation. The "library" option can be (mis)used to allow to pre-configure one app server:

• Spec only (no additional vendor dependencies)
• Open Liberty
• Wildfly Swarm
• ...

As far as I understood switching implementation is only a matter of different libraries in the pom and chapter in the readme.

=> also open for feedback.

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For "Stage 1" we are not that far: JAXRS-spec generator with other config can be almost reused.

[michbeck100]

Stage 1 is already finished with #813. It just removes all swagger parts like annotations, imports and dependencies.

@arthurdm IMHO when using the contract-first approach, there is actually no need for any extra annotations in the first place. Every annotation generated from the static file would be "duplicate code", because of the ability to merge the static file with annotations.
The only thing that makes sense, is to add the dependency to org.eclipse.microprofile.openapi:microprofile-openapi-api, so the developer can start to use the annotations without compile error. But do we need a separate generator for this? If #809 is fixed, i would say no, not necessarily.

For the code-first approach it makes sense to create a new generator. This would translate the static file into annotations and ignore the static file completely. This would then be the java-microprofile generator (stage 2). And i like the idea to pre-configure for one app server.

[jmini]

(Stage 1) But do we need a separate generator for this? I would say no, not necessarily.

I agree.

My reasons are more "marketing" oriented:

• Having something that is microprofile ready would be easier for the user.
• It allows to have something that can be used directly without to have to change a dependency.
• It creates awareness for the microprofile-openapi project.

[igbch]

Hi, I like a lot the contract first approach and I think each change should go first to the contract and then to code, so I like what @michbeck100 is proposing and I follow his changes in the code-generator (which are working using openliberty), but I also share the thoughts of @arthurdm about the possibility of code-first. Out there in the community you always find both flavors and so to have support for both would be great and helps the microprofile community to have full support, I vote for stage 1 and stage 2 and look forward to test it.

[jmini]

Hi @igbch, @michbeck100, @arthurdm,

Any pointer on how what we described as "(Stage 1)" in this issue works? (doc: static OpenAPO files).

I have tried to run a simple project with:

• Open-Liberty
• Thorntail (aka WildFly Swarm)

I did not managed to get it running. A simple project would help to create the corresponding generator.

I think that java-microprofile-spec-file is a better generator name for this approach.

[igbluz]

I just open a sample1-helloworld on github for demonstration how to use openAPI v3 with OpenLiberty v18.0.0.3. It does not use any swagger package. Does it help?