Kotlin Multiplatform - 使用 Ktor 处理响应 http 代码和异常答案

【问题标题】：Kotlin Multiplatform - Handle response http code and exceptions with KtorKotlin Multiplatform - 使用 Ktor 处理响应 http 代码和异常
【发布时间】：2020-12-27 22:13:24
【问题描述】：

我刚开始探索 KMM，目前看来真的很不错。

基本上，我想要在一个地方全局处理所有 http 错误代码（如 401、404、500）。

但是，我不确定如何与响应交互。

我在 HttpClient 中安装了 ResponseObserver，但它只有在 http 状态为 200 时才会出现。

我也尝试使用 HttpResponseValidator，但它从不到那里。

代码如下：

class ApiImpl : Api {

    private val httpClient = HttpClient {

        install(JsonFeature) {

            val json = kotlinx.serialization.json.Json { ignoreUnknownKeys = true }

            serializer = KotlinxSerializer(json)
        }

        install(ResponseObserver) {

            onResponse { response ->

                //*** We get here only if http status code is 200 ***/

                println("HTTP status: ${response.status.value}")
            }
        }

        HttpResponseValidator {

            validateResponse { response: HttpResponse ->

                val statusCode = response.status.value

                //*** We never get here ***/

                println("HTTP status: $statusCode")

                when (statusCode) {

                    in 300..399 -> throw RedirectResponseException(response)
                    in 400..499 -> throw ClientRequestException(response)
                    in 500..599 -> throw ServerResponseException(response)
                }

                if (statusCode >= 600) {
                    throw ResponseException(response)
                }
            }

            handleResponseException { cause: Throwable ->

                throw cause
            }
        }
    }

    override suspend fun getUsers(): List<User> {

        try {

            return httpClient.get("some url....")

        } catch (e: Exception) {

            //*** We get here in case of 404 (for example), but I don't want to repeat it in every request ***/

            println(e.message)
        }

        return emptyList()
    }
}

【问题讨论】：

你在你的HttpClient中设置expectSuccess = false了吗？这可能是您在 ResponseObserver/Validator 中仅获得 200 的原因。

标签： ktor kotlin-multiplatform

【解决方案1】：

我已经用这个示例类（从official ktor github rep 获取和修改）测试了你的场景，我可以在你想要获取错误代码的所有断点处（例如500）

package com.example.kmmtest001.shared

import io.ktor.client.*
import io.ktor.client.features.*
import io.ktor.client.features.json.*
import io.ktor.client.features.json.serializer.*
import io.ktor.client.features.observer.*
import io.ktor.client.request.*
import io.ktor.client.statement.*
import io.ktor.http.*
import kotlinx.coroutines.*

internal expect val ApplicationDispatcher: CoroutineDispatcher

class ApplicationApi {
    private val client = HttpClient {
        install(JsonFeature) {
            val json = kotlinx.serialization.json.Json { ignoreUnknownKeys = true }
            serializer = KotlinxSerializer(json)
        }

        install(ResponseObserver) {
            onResponse { response ->
                println("HTTP status: ${response.status.value}")
            }
        }

        HttpResponseValidator {
            validateResponse { response: HttpResponse ->
                val statusCode = response.status.value

                println("HTTP status: $statusCode")

                when (statusCode) {
                    in 300..399 -> throw RedirectResponseException(response)
                    in 400..499 -> throw ClientRequestException(response)
                    in 500..599 -> throw ServerResponseException(response)
                }

                if (statusCode >= 600) {
                    throw ResponseException(response)
                }
            }

            handleResponseException { cause: Throwable ->
                throw cause
            }
        }
    }

    var address = Url("https://tools.ietf.org/rfc/rfc1866.txt")

    fun about(callback: (String) -> Unit) {
        GlobalScope.apply {
            launch(ApplicationDispatcher) {
                val result: String = client.get {
                    url(this@ApplicationApi.address.toString())
                }

                callback(result)
            }
        }
    }

    fun get500ServerError(callback: (String) -> Unit) {
        GlobalScope.apply {
            launch(ApplicationDispatcher) {
                try {
                    val result: String = client.get {
                        url("https://www.versionestabile.it/_sw/so/63812313/index500.php")
                    }

                    callback(result)
                } catch (se: ServerResponseException) {
                    val statusCode = se.response?.status?.value
                    callback("HTTP status code: $statusCode --> ${se.message}")
                } catch (ce: ClientRequestException) {
                    val statusCode = ce.response?.status?.value
                    callback("HTTP status code: $statusCode --> ${ce.message}")
                }
            }
        }
    }
}

我还测试了401 和404 错误。

【讨论】：