The most elegant practice found so far is to use retrofit, gson converter, and kudos to ensure the empty security of kotlin data.

build.gradle.kts

plugins {
    kotlin("jvm")
    id("com.kanyun.kudos") version "1.9.20-1.1.1"
}

group = "org.example"
version = "1.0-SNAPSHOT"

repositories {
    mavenCentral()
}

kudos {
    gson = true
}

dependencies {
    implementation("com.google.code.gson:gson:2.10.1")
    implementation("com.squareup.retrofit2:retrofit:2.9.0")
    implementation("com.squareup.retrofit2:converter-gson:2.9.0")
    implementation("com.squareup.okhttp3:logging-interceptor:3.14.9")

    testImplementation("org.jetbrains.kotlin:kotlin-test")
}

tasks.test {
    useJUnitPlatform()
}
kotlin {
    jvmToolchain(11)
}

RetrofitKotlinNullSafety.kt

package org.example

import com.google.gson.annotations.SerializedName
import com.kanyun.kudos.annotations.Kudos
import okhttp3.OkHttpClient
import okhttp3.logging.HttpLoggingInterceptor
import retrofit2.Call
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory
import retrofit2.http.GET

/**
 * retrofit + gson converter + kudos 来做 kotlin 数据的空安全保证
 * 目前找到的最优雅的实践
 */

fun main() {
    val response = serverApi.getData().execute()
    if (response.isSuccessful) {
        println("请求成功，http code: ${response.code()}, message: ${response.message()}")
        val serverResponse = response.body()
        println("请求到的数据: $serverResponse")
    } else {
        println("失败了！http code: ${response.code()}, message: ${response.message()}")
    }
}

@Kudos
data class Data(
    @SerializedName("id")
    val id: Int,

    @SerializedName("imagePath")
    val imagePath: String,

    @SerializedName("url")
    val url: String,

    @SerializedName("not_existed_field")
    val noExistedField: String = "default value" // 服务器端不会返回这个数据，kudos 会使用这个默认值，而不是 null，确保空安全
)

data class ServerResponse(
    @SerializedName("errorCode")
    val code: Int,

    @SerializedName("errorMsg")
    val message: String,

    @SerializedName("data")
    val dataList: List<Data>
)

interface IServerApi {
    @GET("banner/json")
    fun getData(): Call<ServerResponse>
}

val serverApi: IServerApi by lazy {
    val loggingInterceptor = HttpLoggingInterceptor()
    loggingInterceptor.level = HttpLoggingInterceptor.Level.BASIC

    val okHttpClient = OkHttpClient.Builder()
        .addInterceptor(loggingInterceptor)
        .build()

    val retrofit = Retrofit.Builder()
        .client(okHttpClient)
        .baseUrl("https://www.wanandroid.com")
        .addConverterFactory(GsonConverterFactory.create())
        .build()

    retrofit.create(IServerApi::class.java)
}

Running Result

12月 20, 2023 11:42:36 上午 okhttp3.internal.platform.Platform log
信息: --> GET https://www.wanandroid.com/banner/json
12月 20, 2023 11:42:36 上午 okhttp3.internal.platform.Platform log
信息: <-- 200 OK https://www.wanandroid.com/banner/json (235ms, unknown-length body)
请求成功，http code: 200, message: OK
请求到的数据: ServerResponse(code=0, message=, dataList=[Data(id=30, imagePath=https://www.wanandroid.com/blogimgs/42da12d8-de56-4439-b40c-eab66c227a4b.png, url=https://www.wanandroid.com/blog/show/3352, noExistedField=default value), Data(id=6, imagePath=https://www.wanandroid.com/blogimgs/62c1bd68-b5f3-4a3c-a649-7ca8c7dfabe6.png, url=https://www.wanandroid.com/navi, noExistedField=default value), Data(id=10, imagePath=https://www.wanandroid.com/blogimgs/50c115c2-cf6c-4802-aa7b-a4334de444cd.png, url=https://www.wanandroid.com/blog/show/2, noExistedField=default value)])