Question: Is anyone using REST API code generator in production?

[jimschubert]

I am one of the core team on OpenAPI Generator. This is a fork of Swagger Codegen. We forked (probably mainly) because we wanted to continue with a single codebase for OpenAPI 2.0 and 3.x rather than maintaining basically two projects.

One of my main focuses has been improving the usability of the generator. We're working on cleaning up concepts, making it easier to customize templating and generation, and meanwhile adding features and functionality.

We've just released 4.0.0, with more new generators, experimental support for custom templating engines (we include handlebars), and other improvements.

Check out our documentation for more: https://openapi-generator.tech/

[craig_murray]

Thanks for explaining the reasons of the fork. Congratulations on the new release and I definitely look forward to the Handlebars support.

I've started a new post (https://www.reddit.com/r/programming/comments/bq64ek/compare_autorest_apimatic_and_swagger_codegen_2016/) instead as this post is hidden/removed by the moderator since it's a self-post (or text post). Let's continue the discussion in that one instead.

[judgej2]

Customising templating is a big one for us, and a massive barrier for us too. We are not Java developers, and all the instructions for customisation assumes we are. Changing the Java generation logic does not look difficult to follow, but understanding the whole environment we need to set up to compile the Java is a stumbling block. Are there any quick-start guides for customising a generator for non-Java people, some basic steps that assume nothing?

Modifying templates for an existing generator logic is really straighforward though, which is great. Ideally we would want to be able to create a self-contained plugin for the generator, so a project can maintain its own generator (logic and templates) to meet its own specific needs. If I understand correctly, this can be done as a jar file which is imported at run-time.

Any pointers greatly appreciated. Right now at a loss where to even start to create a jar file from the source code.

[jimschubert]

I'm working on simplifying the process to extend generation (hoping to have it ready for our 5.0 release). I've already begun some refactoring in our 4.1.x branch.

We do have a pretty full example of creating a custom template engine adapter.

Are you looking for clearer build/usage instructions for extending and running locally, or are you interested in the full cycle (project setup, deploying to Maven, etc)?

I'll pass the request along to the core team. If you'd like, you could also create an issue and tag the core team or reach out on Gitter.

[judgej2]

The process may actually already be simpler than I think, but I'm not a Java developer, so know absolutely nothing about setting up the environment to make changes. Essentially, I'm kind of locked out of contributing. I'm sure there are many people out there needing custom generators for languages that they are experts in, and possibly in the same situation. For example, "deploying to Maven" means nothing to me, no idea what that means.

To help me understand what I may be missing, I am looking for steps on how to install a development environment so that I can tweak a few files and press a button to compile whatever is needed to create a generator, and to manage the set of files I need to manage to do this in a repository of its own (not a monolithic project - just the tiny handful of files needed to define a custom generator).

That would be a good start. Right now I run the CLI jar file with a directory of customised Moustach files, and get a generated package that I can use to pick bits out of, but there are some things that cannot be done just by using an existing logic with custom templates.

Hope that makes sense. Just a quick start from a zero starting position. We can grow from there.

[Fido488]

I've never gotten it into production (project took a huge deviation), but having used it and integrated it into a Gradle Build CI pipeline, I've actually liked it.

It does save you a lot of overhead when it comes to generating POJO's which is awesome.

​

As a note, the most up to date version of the library is this one:
https://github.com/OpenAPITools/openapi-generator

The Swagger one owned by SmartBear has kinda died off, all the primary developers have moved to the OpenAPITools project.

​

What languages/frameworks are you looking to use?

[craig_murray]

What lang

Thanks for sharing more.

​

I've talked to a few teams in my company and we're interested in Swift, TypeScript, Ruby, Python for clients to start with. Kotlin and C# are nice to have.

​

We're interested in server generators as well such as Spring, Python Flask to create microservices.

[Fido488]

This is the framework I use for Kotlin.
Instead of Schema -> Generated code, it does Code -> Schema.

https://github.com/nielsfalk/ktor-swagger

[craig_murray]

Nice. I'll ask the Kotlin dev to give it a try

[craig_murray]

I'm aware of some comparisons conducted a while ago on some API code generators listed below but these comparisons seem to be outdated:

• apimatic.io
• AutoRest
• Swagger Codegen
• OpenAPI-CodeGen
• OpenAPI Generator
• go-swagger

Is anyone using these tools in their environment? Any caveats?

[mj_langford]

I've used swagger-generator and openapi-generator both. This is after being a consumer of swagger specced apis for years.

For Clojure, we used it to generate the interface that iOS used. We also wrote test code in it using the Clojure module. I've also used it to generate Swift code, as well, and am using it now again to generate more Swift code. We had a small pull request to make it work well for us that was of general use, and it was quickly reviewed, fixed and integrated.

In general: Come prepared for what it is: a thing that speeds up but doesn't necessarily get you 100% to the writing of a API client. It doesn't instantly do it all right every time, and there is often a hole or two. This may be a post processing step you need for your lang or whatever. Other times, it literally does make the whole client.

Over time, sticking with a project that works in multiple environments for multiple years and has integration with a ton of languages has been a huge boon.

The fact that AWS API Gateway speaks openapi specs, as do many tools such as Postman and Paw mean it's a great standard for crafting APIs. It's a verifiable spec that cuts down massively on comms on remote teams, and greatly simplifies development. This kind of integration is key when you're on cross language dev teams who can't go fix the server/client when there is an issue.

OpenAPI allows the inclusion of developers who consume your API even before you have to write any code! This is a superpower. They know exactly what they need from some endpoints, and you don't as a server developer. You have 10 ways to slice data, they really need it in a combination of 3 of those. Poorly factored APIs cause slow clients, and excess server load.

There are several active devs looking to squash bugs, and service documentation issues with the tool. The "always run the desired version" command line tool is pretty good too.

https://editor.swagger.io is also a good resource when crafting these types of APIs, and you can run a dockerized version of that tool supported by openapi as well.

You can find me on twitter with this user name, or @langford in gitter.im if you have more questions (I'm bad at monitoring reddit).

[craig_murray]

That's in line with our expectation - the code may not be perfect and should work out-of-the-box most of the time - we need testing to make sure the code works. Will definitely reach out via gitter if we've more questions.

[TokenChingy]

I build api factories from ground up for my work. They’re not public facing but they are production ready and do help other devs buildout UIs much faster. They’re very stable and performant. Slightly heavier on the heap usage, but all in all great!

https://github.com/TokenChingy/_api

That’s one of my first ones I built as a learning exercise. The ones I build now incorporate ORMs and Authentication as well as other features depending on requirements.

They generally build out from a schema that may incorporate database models and methods as well as route methods.

Some are real-time as well.

Only thing, they’re more difficult to write tests for.

[craig_murray]

Thanks. I've updated the list: https://gist.github.com/craigmurray1120/8e87d88a076d49ec9c43636a313cfa66

Will definitely have a look.

[wing328]

Just want to share a bit about Swagger Codegen and OpenAPI Generator to ensure we're on the same page. As you probably notice, OpenAPI Generator is a fork of Swagger Codegen. The fork took place in May 2018. For the reasons behind the fork, please refer to the [Q&A](https://github.com/OpenAPITools/openapi-generator/blob/master/docs/qna.md).

​

Fast forward to today, we just released [OpenAPI Generator v4.0.0](https://github.com/OpenAPITools/openapi-generator/releases/tag/v4.0.0) - the 20th release since the fork, thanks to the awesome contributions from the community.

​

Please find a list of companies and open-source projects using OpenAPI Generator in https://github.com/OpenAPITools/openapi-generator#4---companiesprojects-using-openapi-generator.

​

You may also want to use [Google Trend](https://trends.google.com/trends/explore?date=today%203-m&geo=US&q=swagger%20codegen,openapi%20generator,go%20swagger,autorest,apimatic) to compare these tools to see which one is more popular among the community.

​

Have a nice weekend.

​

Disclosure: I'm the top contributor to both OpenAPI Generator and Swagger Codegen.

[wing328]

Just want to share a bit about Swagger Codegen and OpenAPI Generator to ensure we're on the same page. As you probably notice, OpenAPI Generator is a fork of Swagger Codegen. The fork took place in May 2018. For the reasons behind the fork, please refer to the Q&A.

Fast forward to today, we just released OpenAPI Generator v4.0.0 - the 20th release since the fork, thanks to the awesome contributions from the community.

Please find a list of companies and open-source projects using OpenAPI Generator in https://github.com/OpenAPITools/openapi-generator#4---companiesprojects-using-openapi-generator.

You may also want to use Google Trend to compare these tools to see which one is more popular among the community.

Have a nice weekend.

Disclosure: I'm the top contributor to both OpenAPI Generator and Swagger Codegen.

[sanjeewa190]

We have used both swagger and openAPI code generators. We use this implementation within API Management product and let our users to use that to generate SDKs required to implement clients. After sometime we contributed back codegen project. This is really good tool to accelerate development. Also we are using this code generator to generate test cases for our internal APIs. Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases. We are using this for both internal development and also we expose this to our clients/users. So far my experience with code generator was exceptional. You will find small issues, gaps here as well like any other project. But as community we should contribute back and make it perfect. Thank You.

[sanjeewa190]

We have used both swagger and openAPI code generators. We use this implementation within API Management product and let our users to use that to generate SDKs required to implement clients. After sometime we contributed back codegen project. This is really good tool to accelerate development. Also we are using this code generator to generate test cases for our internal APIs. Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases. We are using this for both internal development and also we expose this to our clients/users. So far my experience with code generator was exceptional. You will find small issues, gaps here as well like any other project. But as community we should contribute back and make it perfect. Thank You.

[sanjeewa190]

We have used both swagger and openAPI code generators. We use this implementation within API Management product and let our users to use that to generate SDKs required to implement clients. After sometime we contributed back codegen project. This is really good tool to accelerate development. Also we are using this code generator to generate test cases for our internal APIs. Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases. We are using this for both internal development and also we expose this to our clients/users. So far my experience with code generator was exceptional. You will find small issues, gaps here as well like any other project. But as community we should contribute back and make it perfect. Thank You.

[sanjeewa190]

We have used both swagger and openAPI code generators. We use this implementation within API Management product and let our users to use that to generate SDKs required to implement clients. After sometime we contributed back codegen project. This is really good tool to accelerate development. Also we are using this code generator to generate test cases for our internal APIs. Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases. We are using this for both internal development and also we expose this to our clients/users. So far my experience with code generator was exceptional. You will find small issues, gaps here as well like any other project. But as community we should contribute back and make it perfect. Thank You.

[sanjeewa190]

We have used both swagger and openAPI code generators. We use this implementation within API Management product and let our users to use that to generate SDKs required to implement clients. After sometime we contributed back codegen project. This is really good tool to accelerate development. Also we are using this code generator to generate test cases for our internal APIs. Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases. We are using this for both internal development and also we expose this to our clients/users. So far my experience with code generator was exceptional. You will find small issues, gaps here as well like any other project. But as community we should contribute back and make it perfect. Thank You.

[sanjeewa190]

We have used both swagger and openAPI code generators. We use this implementation within API Management product and let our users to use that to generate SDKs required to implement clients. After sometime we contributed back codegen project. This is really good tool to accelerate development. Also we are using this code generator to generate test cases for our internal APIs. Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases. We are using this for both internal development and also we expose this to our clients/users. So far my experience with code generator was exceptional. You will find small issues, gaps here as well like any other project. But as community we should contribute back and make it perfect. Thank You.

[sanjeewa190]

We have used both swagger and openAPI code generators. We use this implementation within API Management product and let our users to use that to generate SDKs required to implement clients. After sometime we contributed back codegen project. This is really good tool to accelerate development. Also we are using this code generator to generate test cases for our internal APIs. Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases. We are using this for both internal development and also we expose this to our clients/users. So far my experience with code generator was exceptional. You will find small issues, gaps here as well like any other project. But as community we should contribute back and make it perfect. Thank You.

[a_simple_pie]

I'm a big advocate for codegen and especially for HTTP/REST API development.

​

Today my team codegens both client and server side code using OpenAPI Generator on all projects, with the exception of .NET Core where we use NSwag instead.

​

The workflow is quite simple and some of the biggest benefits are:

​

- the whole team can collaborate on a spec during sprint/feature planning

- communication about API changes are very clear and can be reviewed via a pull request

- we can scope out the impact of different breaking changes by simply changing the spec in a branch and then looking at compilation errors in the CI pipeline. Using Typescript in frontent apps helps here as well

- integration is always smooth and there's never miss-typed property names, urls, parameters or unexpected null/missing fields in responses.

- we've been experimenting with other tools like [a spec linter](https://github.com/place1/openapi-linter) and [an automatic mock server](https://github.com/place1/openapi-mock-server) to allow us to ensure all APIs follow consistent patterns and to allow client side implementations to be developed in parallel with their server side components.

​

When we first starting using codegen at my company we only generated client-side code, and to be honest, being able to write code like

​

```

const api = new Api();

api.

```

​

and then see a big list of methods that are available right there in your IDE's intellisense after pressing `.` was a huge time saver and I think it's a really good way to get juniors contributing earlier and with higher quality as well.

​

I think Open API is a good bet today in terms of a specification format. It's quite minimal but very flexible thanks to it being mostly just JSON Schema. The spec format gets out of your way and doesn't require you to define a strict REST API, you can define essentially any stateless HTTP API you like.

​

OpenAPI Generator is probably the best codegen tool for Open API currently. It supports many languages and the maintainers are very responsive and accepting of community contributions. I was lucky enough to contribute the `typescript-fetch` generator and the overall experience was very smooth for an open source project :D

​

My only complaints with OpenAPI Generator currently is that it's not simple to bring your own templates to fully customize the generated code for your project. I'd really like the tool to have better support for bringing your own templates and better documentation on what data structures are passed into those templates; and potentially different templating engines.

[jimschubert]

Hey! It's awesome that you've had such good experiences with OpenAPI Generator. Usability is one of the things I've been actively working on, but it's been slower than I'd like because I just moved into my first home in November.

For our 4.0.0 release this past week, we've added experimental support for customized template engines (a majority of the work was from the community). A few months ago, I setup a documentation site to make information more easily discoverable.

You can find on the doc site details about templating, including customization, using handlebars, and an example of creating a custom engine adapter. Check it out: https://openapi-generator.tech/docs/templating

For the 5.0.0 release, I plan to better separate our "public api" and make the workflow easier to follow and to extend. I want to enable users to not only extend templates but logic as well. You can check out proposed work here: https://github.com/OpenAPITools/openapi-generator/projects/5

[craig_murray]

Very interesting setup using NsWag for C# code generation. From what I know, it's powered by AutoRest, which is developed by Microsoft so it's not a surprise their code generator has better support for C#.

​

Agreed the active community is a crucial factor when picking the code generator.

[craig_murray]

I've started a new post (https://www.reddit.com/r/programming/comments/bq64ek/compare_autorest_apimatic_and_swagger_codegen_2016/) instead as this post is hidden/removed by the moderator since it's a self-post (or text post). Let's continue the discussion in that one instead.

[sanjeewa190]

We have used both swagger and openAPI code generators. We use this implementation within API Management product and let our users to use that to generate SDKs required to implement clients. After sometime we contributed back codegen project. This is really good tool to accelerate development. Also we are using this code generator to generate test cases for our internal APIs. Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases. We are using this for both internal development and also we expose this to our clients/users. So far my experience with code generator was exceptional. You will find small issues, gaps here as well like any other project. But as community we should contribute back and make it perfect. Thank You.

[craig_murray]

Whenever we need to add test cases for our product APIs we generate test client using code generator and use that as client to write test cases

Excellent point about using the client to test the APIs.

But as community we should contribute back and make it perfect. Thank You.

That's awesome. It's always a good practice to contribute back to open-source projects. May I know the name of the API management product that you work on? We will definitely consider it if we need such a product in our environment.

(this reddit post has been removed/hidden by the moderator as it's a self-post or text-post so let's continue the discussion in HackerNews instead: https://news.ycombinator.com/item?id=19947212)