FAQ: Generators
What are some server generator use cases?
We have around 40+ server generators, with more added regularly. Some of these include Spring in your choice of Java or Kotlin, the Finch and Scalatra frameworks using Scala, and C# generators for ASP.NET and Azure Functions (to name only a few).
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.
- evaluating - when you want to try a new language or framework, and a typical "Hello, World" is too trivial.
Java
The API client has SSL errors due to an invalid certificate. Is there a way to bypass that?
Yes, please refer to http://stackoverflow.com/a/6055903/677735
How can I customize the Feign client templates?
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/3_0/petstore.json \
-l java --library=okhttp-gson \
--additional-properties 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 -l 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/3_0/petstore.json \
-l 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
How do I fix CSC: warning CS2002 in Xamarin?
The full warning might look like this: CSC: warning CS2002: Source file 'Api/FakeApi.cs' specified multiple times
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
Which Swift generator is still actively maintained?
Please use swift5 generator because Swift 4.x is deprecated.
There is a new swift6 generator, that is currently in beta, try it and give us your feedback.
How do I implement bearer token authentication with URLSession on the Swift 5 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.
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. AppDelegate.swift BearerDecodableRequestBuilder.swift
How do I implement bearer token authentication with Alamofire on the Swift 5 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 AlamofireRequestBuilder and AlamofireDecodableRequestBuilder
class BearerRequestBuilder<T>: AlamofireRequestBuilder<T> {
override func createSessionManager() -> SessionManager {
let sessionManager = super.createSessionManager()
let bearerTokenHandler = BearerTokenHandler()
sessionManager.adapter = bearerTokenHandler
sessionManager.retrier = bearerTokenHandler
return sessionManager
}
}
class BearerDecodableRequestBuilder<T: Decodable>: AlamofireDecodableRequestBuilder<T> {
override func createSessionManager() -> SessionManager {
let sessionManager = super.createSessionManager()
let bearerTokenHandler = BearerTokenHandler()
sessionManager.adapter = bearerTokenHandler
sessionManager.retrier = bearerTokenHandler
return sessionManager
}
}
class BearerTokenHandler: RequestAdapter, RequestRetrier {
private static var bearerToken: String? = nil
func adapt(_ urlRequest: URLRequest) throws -> URLRequest {
if let bearerToken = Self.bearerToken {
var urlRequest = urlRequest
urlRequest.setValue("Bearer \(bearerToken)", forHTTPHeaderField: "Authorization")
return urlRequest
}
return urlRequest
}
func should(_: SessionManager, retry request: Request, with _: Error, completion: @escaping RequestRetryCompletion) {
if let response = request.task?.response as? HTTPURLResponse, response.statusCode == 401 {
Self.startRefreshingToken { isTokenRefreshed in
completion(isTokenRefreshed, 0.0)
}
} else {
completion(false, 0.0)
}
}
private static func startRefreshingToken(completionHandler: @escaping (Bool) -> Void) {
// Get a bearer token
let dummyBearerToken = "..."
bearerToken = dummyBearerToken
PetstoreClientAPI.customHeaders["Authorization"] = "Bearer \(dummyBearerToken)"
completionHandler(true)
}
}
Then you assign the BearerRequestBuilderFactory to the property requestBuilderFactory.
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. AppDelegate.swift BearerTokenHandler.swift
How do I implement bearer token authentication with URLSession on the Swift 6 API client?
First you implement the OpenAPIInterceptor protocol.
public class BearerOpenAPIInterceptor: OpenAPIInterceptor {
public init() {}
public func intercept<T>(urlRequest: URLRequest, urlSession: URLSessionProtocol, requestBuilder: RequestBuilder<T>, completion: @escaping (Result<URLRequest, any Error>) -> Void) {
guard requestBuilder.requiresAuthentication else {
// no authentication required
completion(.success(urlRequest))
return
}
refreshTokenIfDoesntExist { token in
// Change the current url request
var newUrlRequest = urlRequest
newUrlRequest.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
// Change the global headers
requestBuilder.openAPIClient.customHeaders["Authorization"] = "Bearer \(token)"
completion(.success(newUrlRequest))
}
}
public func retry<T>(urlRequest: URLRequest, urlSession: URLSessionProtocol, requestBuilder: RequestBuilder<T>, data: Data?, response: URLResponse?, error: Error, completion: @escaping (OpenAPIInterceptorRetry) -> Void) {
// We will analyse the response to see if it's a 401, and if it's a 401, we will refresh the token and retry the request
refreshTokenIfUnauthorizedRequestResponse(
data: data,
response: response,
error: error
) { (wasTokenRefreshed, newToken) in
if wasTokenRefreshed, let newToken = newToken {
// Change the global headers
requestBuilder.openAPIClient.customHeaders["Authorization"] = "Bearer \(newToken)"
completion(.retry)
} 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(.dontRetry)
}
}
}
private var bearerToken: String? = nil
func refreshTokenIfDoesntExist(completionHandler: @escaping (String) -> Void) {
if let bearerToken = bearerToken {
completionHandler(bearerToken)
} else {
startRefreshingToken { token in
completionHandler(token)
}
}
}
func refreshTokenIfUnauthorizedRequestResponse(data: Data?, response: URLResponse?, error: Error, completionHandler: @escaping (Bool, String?) -> Void) {
if let response = response as? HTTPURLResponse, response.statusCode == 401 {
startRefreshingToken { token in
completionHandler(true, token)
}
} else {
completionHandler(false, nil)
}
}
private func startRefreshingToken(completionHandler: @escaping (String) -> Void) {
// Get a bearer token
let dummyBearerToken = "..."
bearerToken = dummyBearerToken
completionHandler(dummyBearerToken)
}
}
Then you assign the BearerOpenAPIInterceptor to the property OpenAPIClient.shared.interceptor.
OpenAPIClient.shared.interceptor = BearerOpenAPIInterceptor()
Here is a working sample that put's together all of this. AppDelegate.swift BearerTokenHandler.swift
How do I implement bearer token authentication with Alamofire on the Swift 6 API client?
First implement the Alamofire RequestInterceptor protocol.
class BearerTokenHandler: RequestInterceptor, @unchecked Sendable {
private var bearerToken: String? = nil
func adapt(_ urlRequest: URLRequest, for session: Session, completion: @escaping (Result<URLRequest, Error>) -> Void) {
if let bearerToken = bearerToken {
var urlRequest = urlRequest
urlRequest.setValue("Bearer \(bearerToken)", forHTTPHeaderField: "Authorization")
completion(.success(urlRequest))
return
}
completion(.success(urlRequest))
}
func retry(_ request: Request, for session: Session, dueTo error: Error, completion: @escaping (RetryResult) -> Void) {
if let response = request.task?.response as? HTTPURLResponse, response.statusCode == 401 {
startRefreshingToken { isTokenRefreshed in
completion(.retry)
}
} else {
completion(.doNotRetryWithError(error))
}
}
private func startRefreshingToken(completionHandler: @escaping (Bool) -> Void) {
// Get a bearer token
let dummyBearerToken = "..."
bearerToken = dummyBearerToken
OpenAPIClient.shared.customHeaders["Authorization"] = "Bearer \(dummyBearerToken)"
completionHandler(true)
}
}
Then you assign the BearerTokenHandler to the property OpenAPIClient.shared.interceptor.
OpenAPIClient.shared.interceptor = BearerTokenHandler()
Here is a working sample that put's together all of this. AppDelegate.swift BearerTokenHandler.swift
How do I migrate from the Swift 5 generator to the swift 6 generator?
- Change the generator to the new
swift6generator, e.g.openapi-generator generate -i https://raw.githubusercontent.com/openapitools/openapi-generator/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml -g swift6 -o /tmp/test/ - Check the
swift6URLSession and Alamofire samples. - The infrastructure files have been moved to a new directory called
Infrastructure. Please delete the old ones. - The
AnyCodabledependency has been removed and replaced with a new enum calledJSONValue, allowing you to use this generator without external dependencies. - The
Combineresponse is now deferred by default, meaning the request will only start when you begin listening to it. To restore the previous behavior, set thecombineDeferredflag tofalse. - A new configuration,
apiStaticMethod, allows you to use instance methods instead of class methods for API calls. For more information, check the sample project apiNonStaticMethod. - The new default response is based on async/await. To revert to the previous behavior, set the
responseAsflag toObjcBlock. - The default project structure now follows the SPM (Swift Package Manager) structure. To revert to the old structure, set the
useSPMFileStructureflag tofalse. - The former
{{projectName}}APIis now calledOpenAPIClient. - You can now set a request interceptor and retrier by configuring
OpenAPIClient.shared.interceptor, making authenticated requests easier to manage.
TypeScript
The JSON response fails to deserialize due to change in variable naming (snake_case to camelCase). Is there any way to keep the original naming?
Yes, please use the following option when generating TypeScript clients:
modelPropertyNaming
Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name (Default: camelCase)