Ktor 2.1.1 Help

Response validation

By default, Ktor doesn't validate a response depending on its status code. If required, you can use the following validation strategies:

  • Use the expectSuccess property to throw exceptions for non-2xx responses.

  • Add stricter validation of 2xx responses.

  • Customize validation of non-2xx responses.

Enable default validation

Ktor allows you to enable default validation by setting the expectSuccess property to true. This can be done on a client configuration level ...

import io.ktor.client.* import io.ktor.client.engine.cio.* val client = HttpClient(CIO) { expectSuccess = true }

... or by using the same property on a request level. In this case, the following exceptions will be thrown for non-2xx error responses:

Custom validation

You can add additional validation for 2xx responses or customize default validation by using the HttpCallValidator plugin. To install HttpCallValidator, call the HttpResponseValidator function inside a client configuration block:

val client = HttpClient(CIO) { HttpResponseValidator { // ... } }

Validate 2xx responses

As mentioned above, default validation throws exceptions for non-2xx error responses. If you need to add stricter validation and check 2xx responses, use the validateResponse function available in HttpCallValidator.

In the example below, a client receives a 2xx response with error details in a JSON format. The validateResponse is used to raise a CustomResponseException:

val client = HttpClient(CIO) { install(ContentNegotiation) { json() } HttpResponseValidator { validateResponse { response -> val error: Error = response.body() if (error.code != 0) { throw CustomResponseException(response, "Code: ${error.code}, message: ${error.message}") } } } }

Handle non-2xx exceptions

If you need to customize default validation and handle exceptions for non-2xx responses in a specific way, use handleResponseExceptionWithRequest. In the example below, a client raises a custom MissingPageException for 404 responses instead of the default ClientRequestException:

val client = HttpClient(CIO) { expectSuccess = true HttpResponseValidator { handleResponseExceptionWithRequest { exception, request -> val clientException = exception as? ClientRequestException ?: return@handleResponseExceptionWithRequest val exceptionResponse = clientException.response if (exceptionResponse.status == HttpStatusCode.NotFound) { val exceptionResponseText = exceptionResponse.bodyAsText() throw MissingPageException(exceptionResponse, exceptionResponseText) } } } }
Last modified: 19 July 2022