FAQ

No, we do not support all new features (e.g. callback, anyOf, etc) at the moment. We would definitely welcome contributions from the community to add support for these new features. Please search the issue tracker to see if anyone has opened a ticket to track the new feature. If no ticket has been opened yet, please open a new one and ideally a sample spec so that we can prioritize the feature request accordingly.

How to debug OpenAPI Generator?

Please refer to https://github.com/OpenAPITools/openapi-generator/blob/master/docs/debugging.md

How do "tags" affect the generated code?

tags basically groups endpoints into the same API class file. For example, an endpoint with the "store" tags will be generated in the StoreApi class file.

Ref: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#tagObject

How to import Java objects that are not defined as a model in the OpenAPI v2 or v3 spec?

Please refer to the "Bringing your own models" in the "Customization" guide

Is there a way to disable certificate verification?

Please add -Dio.swagger.parser.util.RemoteUrl.trustAll=true -Dio.swagger.v3.parser.util.RemoteUrl.trustAll=true when generating the code.

How to skip certain files during code generation?

For example, to skip git_push.sh, one can create a file named .openapi-generator-ignore in the output directory and put git_push.sh in that file, which just works like .gitignore.

.openapi-generator-ignore is auto-generated by default.

Or one can manually delete the file(s) after the code generation process completes.

How can I customize the template to add header/footer to the auto-generated code?

You can use the -t option with the customized templates. Here is an example adding header/footer to Ruby templates.

git clone https://github.com/openapitools/openapi-generator
cd openapi-generator
mvn clean package
cp -R modules/openapi-generator/src/main/resources/ruby /var/tmp/ ## copy all Ruby templates to /var/tmp/. You can also selectively copy only the templates (e.g. api.mustache) you want to customize
Edit /var/tmp/ruby/api.mustache to add the footer/header
Run the following command to generate the Ruby API client with customized templates:

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate \
  -i modules/openapi-generator/src/test/resources/2_0/petstore.yaml \
  -t /var/tmp/ruby
  -g ruby -o /var/tmp/ruby_api_client/

What are some of the use cases of the server generators (e.g. Java Spring, C# NancyFx)?

Besides generating the server code as a starting point to implement the API backend, here are some use cases of the server generators:

prototyping - one can generate the server code and have a functional API backend very quickly to try different things or features.
mocking - easily provide an API backend for mocking based on the examples field defined in the response object.
migration - let's say one wants to migrate an API backend from Ruby on Rails to Java Spring. The server generator can save a lot of time in implementing and verify each endpoint in the new API backend.

I just submitted a PR but the CI (continuous integration) tests failed. Do you know what's wrong?

Please do the following:

Click on the failed tests and check the log to see what's causing the errors.
If it's related to connection timeout in downloading dependencies, please restart the CI jobs (which can be done by closing and reopening the PR)

I ran the test locally and got errors (HTTP status code: 500) from the public Petstore server. Is there a way to run the Petstore server locally for testing?

Yes, please run the following commands (assuming you've docker installed):

docker pull swaggerapi/petstore
docker run -d -e SWAGGER_HOST=http://petstore.swagger.io -e SWAGGER_BASE_PATH=/v2 -p 80:8080 swaggerapi/petstore
docker ps -a

Then add the following to your local host table:

127.0.0.1    petstore.swagger.io

I've discovered a security vulnerability with OpenAPI Generator. Who should I report the issue to?

Please contact team@openapitools.org with the details and we'll follow up with you.

Some generators are marked as beta or deprecated. What does that mean?

For "beta", it means the generator is usually newly-added or not that mature in terms of functionality and feature supported.

For "deprecated", it means the generator is no longer maintained due to various reasons such as languages no longer officially support (e.g. Swift 1.x). One can still use the generator or even submit PRs to improve it but users should not have any expectation in terms of the output produced by the generator.

Is it reasonable to expect the output by the generator would work appropriately and securely?

We do not guarantee the output by the generator would work appropriately and securely. It's the responsibility of the users to evaluate and test the output to ensure it can meet their requirements.

How's the primitive type handled in the generator?

The official definition of the primitive type can be found in https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#data-types

Primitive types are usually mapped to primitive types in the corresponding programming language and we do not recommend mapping primitive types to models (e.g. primitive type wrappers) as this does not conform to the specification.

Mustache tags such as isString, isNumber are for enum models only.

How can I update the samples? I couldn't find the script under `./bin/` or Windows batch files under `.\bin\windows`?

As of Jun 2020, we've switched to ./bin/generate-samples.sh for updating Petstore samples. For example, to update Ruby petstore client samples, please run ./bin/generate-samples.sh ./bin/configs/ruby*.

./bin/configs/other/ is another folder that stores the config files for generators that are less active.

For Windows users, please run the script in Git BASH.

How to test with the latest master of OpenAPI Generator?

To test your OpenAPI/Swagger spec with the latest master to confirm whether the issue still exists, please try the following

Docker image for latest openapi-generator-cli: docker pull openapitools/openapi-generator-cli:latest
Docker image for latest openapi-generator-online: docker pull openapitools/openapi-generator-online:latest
Download the latest snapshot version of openapi-generator-cli JAR: https://oss.sonatype.org/content/repositories/snapshots/org/openapitools/openapi-generator-cli/

Build the project locally

git clone https://github.com/OpenAPITools/openapi-generator
cd openapi-generator
Build the project
- Windows: mvnw.cmd clean install -Dmaven.test.skip=true -Dmaven.javadoc.skip=true
- Mac/Linux: ./mvnw clean install

Run the CLI jar locally

Windows:

java -jar modules\openapi-generator-cli\target\openapi-generator-cli.jar generate -g ruby -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml -o C:\temp\ruby-client-test

Mac/Linux:

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g ruby -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml -o /var/tmp/ruby-client-test

git

How can I rebase my PR on the latest master?

Please refer to http://rypress.com/tutorials/git/rebasing, or follow the steps below (assuming the branch for the PR is "fix_issue_9999"):

git checkout master
git pull upstream master (assuming upstream is pointing to the official repo)
git checkout fix_issue_9999
git rebase master
Resolve merge conflicts, if any, and run git commit -a
Rebase done (you may need to add --force when doing git push)

(To setup upstream pointing to the official repo, please run git remote add upstream https://github.com/openapitools/openapi-generator.git)

How can I update commits that are not linked to my Github account?

Please refer to https://stackoverflow.com/questions/3042437/how-to-change-the-commit-author-for-one-specific-commit or you can simply add the email address in the commit as your secondary email address in your Github account.

Any useful git tips to share?

Yes, http://www.alexkras.com/19-git-tips-for-everyday-use/

How can I submit a PR to fix bugs or make enhancements?

Visit https://github.com/openapitools/openapi-generator and then click on the "Fork" button in the upper right corner. Then in your local machine, run the following (assuming your github ID is "your_user_id")

git clone https://github.com/your_user_id/openapi-generator.git
cd openapi-generator
git checkout -b fix_issue9999
make changes
git commit -a (you may need to use git add filename to add new files)
git push origin fix_issue9999
Visit https://github.com/openapitools/openapi-generator in your browser and click on the button to file a new PR based on fix_issue9999

How can I submit a PR for a branch (e.g. 4.2.x)?

Visit https://github.com/openapitools/openapi-generator and then click on the "Fork" button in the upper right corner. Then in your local machine, run the following (assuming your github ID is "your_user_id")

git clone https://github.com/your_user_id/openapi-generator.git
cd openapi-generator
git remote add upstream https://github.com/openapitools/openapi-generator
git checkout 4.2.x
git pull usptream 4.2.x (ensure it has the latest change)
git log (review the latest change to this branch)
git checkout -b 4.2.x-enhance (create a new branch instead of modifying 4.2.x directly)
make changes
git commit -a (you may need to use git add filename to add new files)
git push origin 4.2.x-enhance
Visit https://github.com/openapitools/openapi-generator in your browser and click on the button to file a new PR based on 4.2.x-enhance. Make sure the PR is filed against "4.2.x" branch instead of master.
After the branch is merged, repeat step 3 & 4

Java

Using Java API client to make request results in SSL errors due to an invalid certificate. Is there a way to bypass that?

Yes, please refer to http://stackoverflow.com/a/6055903/677735

I want to use customized templates for Java Feign client. How can I do that?

You will need to provide customized files in Java/libraries/feign under the resources folder and pass the location via the -t option.

In your Gradle build script, please add the following (example):

config.templateDir = 'src/openapi-generator-templates/Java/libraries/feign

Android

How can I generate an Android SDK?

The Java SDK is also compatible with Android.

[RECOMMENDED] To generate the Java SDK with okhttp and gson libraries, run the following:

mvn clean package
java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate \
  -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.json \
  -g java --library=okhttp-gson \
  -D hideGenerationTimestamp=true \
  -o /var/tmp/java/okhttp-gson/

You can also generate the Java SDK with other HTTP libraries by replacing okhttp-gson with retrofit for example. For a list of support libraries, please run

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar config-help -g java

To generate the Android SDK with volley, please run

mvn clean package
java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate \
  -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.json \
  -g android --library=volley \
  -o /var/tmp/android/volley/

We do not recommend using the default HTTP library (Apache HttpClient) with android as it's not actively maintained.

C-Sharp

I got the warning `CSC: warning CS2002: Source file 'Api/FakeApi.cs' specified multiple times` in Xamarin. How can I resolve it?

The warning has no impact on the build process so you should be able to build the solution without issue. The warning should be addressed in the upcoming stable release of Xamarin.

Objective-C

How do I run integration test with Petstore ObjC API client?

Here are the steps:

git clone https://github.com/openapitools/openapi-generator.git
cd openapi-generator/samples/client/petstore/objc/default/OpenAPIClientTests
mvn integration-test

Besides default (folder) ObjC API client, there's also core-data for another ObjC API client with Core Data support.

Swift

How do I run integration test with Petstore Swift API client?

Here are the steps:

git clone https://github.com/openapitools/openapi-generator.git
cd openapi-generator/samples/client/petstore/swift/default/OpenAPIClientTests
mvn integration-test

Besides default (folder), there's another folder promisekit for Swift API client with PromiseKit support

git clone https://github.com/openapitools/openapi-generator.git
cd openapi-generator/samples/client/petstore/swift/promisekit/OpenAPIClientTests
mvn integration-test

Which Swift generator is still actively maintained?

Please use swift5 generator because Swift 4.x is deprecated.

How do I implement bearer token authentication with URLSession on the Swift API client?

First you subclass RequestBuilderFactory

class BearerRequestBuilderFactory: RequestBuilderFactory {
    func getNonDecodableBuilder<T>() -> RequestBuilder<T>.Type {
        BearerRequestBuilder<T>.self
    }

    func getBuilder<T: Decodable>() -> RequestBuilder<T>.Type {
        BearerDecodableRequestBuilder<T>.self
    }
}

Then you subclass URLSessionRequestBuilder and URLSessionDecodableRequestBuilder

class BearerRequestBuilder<T>: URLSessionRequestBuilder<T> {
    @discardableResult
    override func execute(_ apiResponseQueue: DispatchQueue = PetstoreClientAPI.apiResponseQueue, _ completion: @escaping (Result<Response<T>, ErrorResponse>) -> Void) -> RequestTask {

        // Before making the request, we can validate if we have a bearer token to be able to make a request
        BearerTokenHandler.refreshTokenIfDoesntExist {
            
            // Here we make the request
            super.execute(apiResponseQueue) { result in
                
                switch result {
                case .success:
                    // If we got a successful response, we send the response to the completion block
                    completion(result)
                    
                case let .failure(error):
                    
                    // If we got a failure response, we will analyse the error to see what we should do with it
                    if case let ErrorResponse.error(_, data, response, error) = error {
                        
                        // If the error is an ErrorResponse.error() we will analyse it to see if it's a 401, and if it's a 401, we will refresh the token and retry the request
                        BearerTokenHandler.refreshTokenIfUnauthorizedRequestResponse(
                            data: data,
                            response: response,
                            error: error
                        ) { wasTokenRefreshed in
                            
                            if wasTokenRefreshed {
                                // If the token was refreshed, it's because it was a 401 error, so we refreshed the token, and we are going to retry the request by calling self.execute()
                                self.execute(apiResponseQueue, completion)
                            } else {
                                // If the token was not refreshed, it's because it was not a 401 error, so we send the response to the completion block
                                completion(result)
                            }
                        }
                    } else {
                        // If it's an unknown error, we send the response to the completion block
                        completion(result)
                    }
                    
                }
            }
        }
        
        return requestTask
    }
}

class BearerDecodableRequestBuilder<T: Decodable>: URLSessionDecodableRequestBuilder<T> {
    @discardableResult
    override func execute(_ apiResponseQueue: DispatchQueue = PetstoreClientAPI.apiResponseQueue, _ completion: @escaping (Result<Response<T>, ErrorResponse>) -> Void) -> RequestTask {
        // Before making the request, we can validate if we have a bearer token to be able to make a request
        BearerTokenHandler.refreshTokenIfDoesntExist {
            
            // Here we make the request
            super.execute(apiResponseQueue) { result in
                
                switch result {
                case .success:
                    // If we got a successful response, we send the response to the completion block
                    completion(result)
                    
                case let .failure(error):
                    
                    // If we got a failure response, we will analyse the error to see what we should do with it
                    if case let ErrorResponse.error(_, data, response, error) = error {
                        
                        // If the error is an ErrorResponse.error() we will analyse it to see if it's a 401, and if it's a 401, we will refresh the token and retry the request
                        BearerTokenHandler.refreshTokenIfUnauthorizedRequestResponse(
                            data: data,
                            response: response,
                            error: error
                        ) { wasTokenRefreshed in
                            
                            if wasTokenRefreshed {
                                // If the token was refreshed, it's because it was a 401 error, so we refreshed the token, and we are going to retry the request by calling self.execute()
                                self.execute(apiResponseQueue, completion)
                            } else {
                                // If the token was not refreshed, it's because it was not a 401 error, so we send the response to the completion block
                                completion(result)
                            }
                        }
                    } else {
                        // If it's an unknown error, we send the response to the completion block
                        completion(result)
                    }
                    
                }
            }
        }
        
        return requestTask
    }
}

class BearerTokenHandler {
    private static var bearerToken: String? = nil
    
    static func refreshTokenIfDoesntExist(completionHandler: @escaping () -> Void) {
        if bearerToken != nil {
            completionHandler()
        } else {
            startRefreshingToken {
                completionHandler()
            }
        }
    }
    
    static func refreshTokenIfUnauthorizedRequestResponse(data: Data?, response: URLResponse?, error: Error?, completionHandler: @escaping (Bool) -> Void) {
        if let response = response as? HTTPURLResponse, response.statusCode == 401 {
            startRefreshingToken {
                completionHandler(true)
            }
        } else {
            completionHandler(false)
        }
    }
    
    private static func startRefreshingToken(completionHandler: @escaping () -> Void) {
        // Get a bearer token
        let dummyBearerToken = "..."
        
        bearerToken = dummyBearerToken
        PetstoreClientAPI.customHeaders["Authorization"] = "Bearer \(dummyBearerToken)"

        completionHandler()
    }
}

Then you assign the BearerRequestBuilderFactory to the property requestBuilderFactory in the APIs.swift file.

PetstoreClientAPI.requestBuilderFactory = BearerRequestBuilderFactory()

The name PetstoreClientAPI.requestBuilderFactory will change depending on your project name.

Here is a working sample that put's together all of this.

How do I implement bearer token authentication with Alamofire on the Swift API client?