How to read JSON array of arrays with mixed values in Retrofit 2?

Question

I'm trying to read the following data from the API:

[
    [
        1724180400000,
        "59191.45000000",
        "59597.28000000",
        "59137.78000000",
        "59511.99000000",
        "544.56764000",
        1724183999999,
        "32351755.73378980",
        51002,
        "290.20494000",
        "17241827.16012430",
        "0"
    ],
    [
        1724184000000,
        "59512.00000000",
        "59722.72000000",
        "59421.38000000",
        "59589.07000000",
        "301.58055000",
        1724187599999,
        "17968010.37382020",
        23563,
        "169.48375000",
        "10099057.30721750",
        "0"
    ]
]

But Retrofit expects a JSON response starting with '{' instead of '['.

I tried serializing the data with the following dependencies:

implementation(libs.retrofit)
implementation(libs.retrofit2.kotlinx.serialization.converter)
implementation(libs.okhttp)
implementation(libs.kotlinx.serialization.json)

When I tell Retrofit to expect a list with lists it states that 'Serializer for class 'Any' is not found'. How to serialize this response type with only arrays containing mixed types (String and Int)?

Answer 1

If type does not matter, you can just use type String.

@GET("test")
fun test(): Call<List<List<String>>>

If type matters, you can use JsonPrimitive.

@GET("test")
fun test(): Call<List<List<JsonPrimitive>>>

After you received data, you can parse it as List<List<Any>> like this.

val result: List<List<JsonPrimitive>> = response.body()!!

val parsedResult: List<List<Any>> = result.map { innerItem ->
    innerItem.map {
         if (it.isNumber) it.asInt
         else it.asString
    }
}

println(parsedResult)