Retrofit Moshi Unable to create @Body converter for java.util.HashMap

Question

The line EarthlingsApi.retrofitService.register(params)

in my code below

fun clickLogin(){
    val params = HashMap<String, String>()
    params["email"] = email
    params["idToken"] = idToken
    viewModelScope.launch {
        try {
            val userRegisterResult = EarthlingsApi.retrofitService.register(params)
        } catch (e: Exception) {
            Timber.d("exception? " + e.toString())
            _response.value = "Failure: ${e.message}"
        }
    }
}

will always return the error exception? java.lang.IllegalArgumentException: Unable to create @Body converter for java.util.HashMap<java.lang.String, java.lang.String> (parameter #1) for method ApiService.register

And below is the code for EarthlingsApi

private val moshi = Moshi.Builder()
    .add(KotlinJsonAdapterFactory())
    .build()
private val retrofit = Retrofit.Builder()
    .addConverterFactory(MoshiConverterFactory.create(moshi))
    .baseUrl(BASE_URL)
    .build()

interface ApiService {
    @POST("/user/register")
    suspend fun register(@Body params: HashMap<String, String>?): UserRegister?
}

object EarthlingsApi {
    val retrofitService : ApiService by lazy {retrofit.create(ApiService::class.java) }
}

Previously I use Gson and never faced this error. Is there anything else I should do when using Moshi?

score 2 · Answer 1 · answered Feb 09 '21 at 18:29

It seems Moshi supports fields declared as Map but not as HashMap. So just change the HashMap inside suspend fun register(@Body params: HashMap<String, String>?): UserRegister? to Map and it will work. This answer helped me in solving this, but unfortunately, the questioner there doesn't mark it as an answer. So maybe anyone later who bumped into this same issue can upvote the answer there.

Retrofit Moshi Unable to create @Body converter for java.util.HashMap

1 Answers1