Moshi Retrofit error: "Expected a string but was BEGIN_OBJECT"

Question

I built my Retrofit instance like this:

Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(server.url("/"))
            .addConverterFactory(MoshiConverterFactory.create(moshi))
            .build();

Then I am calling my MockWebServer instance like this:

server.enqueue(new MockResponse().setBody(jsonStr));

Where jsonStr is built like this:

MyModel model = new MyModel("HOME", "AWAY", "ENTERTAIN", "NIGHT", "MUTE",
            "VOLUME", "SCENE 1", "SCENE 2", "SCENE 3");
JsonAdapter<MyModel> jsonAdapter = moshi.adapter(MyModel.class).toJson(model);

However, the code crashes at this point:

Response response = api.getString().execute();

The exception is:

com.squareup.moshi.JsonDataException: Expected a string but was BEGIN_OBJECT at path $

What did I do wrong?

score 17 · Accepted Answer · edited Nov 10 '21 at 14:02

17

I found the solution: My api interface needed to have

@GET("/") Call<JsonObject> getString();

NOT

@GET("/") Call<String> getString();

The reason is that I am mocking a JSON response, not a plain String.

edited Nov 10 '21 at 14:02

Salvatore Testa

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answered May 03 '16 at 18:54

IgorGanapolsky

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score 6 · Answer 2 · answered Mar 22 '21 at 13:37

6

In my case, when my codes are as the following, i get the same error mentioned in the question.

com.squareup.moshi.JsonDataException: Expected BEGIN_OBJECT but was STRING at path $.elections[0].ocdDivisionId

private val moshi = Moshi.Builder()
    .add(KotlinJsonAdapterFactory())
    .add(DateAdapter())
    .add(ElectionAdapter())
    .build()

The problem is related to ElectionAdapter.

After changing the order of adding adapters, namely putting .add(ElectionAdapter()) at the top as show below, the problem is solved :

private val moshi = Moshi.Builder()
    .add(ElectionAdapter())
    .add(KotlinJsonAdapterFactory())
    .add(DateAdapter())
    .build()

answered Mar 22 '21 at 13:37

oiyio

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What is **ElectionAdapter**? – IgorGanapolsky Mar 22 '21 at 20:34
1

@IgorGanapolsky this relates to a custom adapter on a project we are doing at Udacity Online Course. – Tonnie May 26 '21 at 16:30
Yes it is a custom adapter :) – oiyio May 27 '21 at 05:57
Coming from Udacity too, this helps. But can you explain why? – Sam Chen Aug 06 '21 at 23:01

score 6 · Answer 3 · answered May 26 '21 at 17:16

For my case I omitted the ScalarsConverterFactory for parsing the JSONString

You see my API Call was supposed to return a JSON String

` @GET("neo/rest/v1/feed")
     suspend fun getNearEarthObjects(@Query("api_key") apiKey: String): String`

When building the Retrofit Object I had the Moshi for parsing Kotlin Objects but I forgot the ScalarsConverter

//Build Retrofit Object
val retrofit =
    Retrofit.Builder()
        .addConverterFactory(ScalarsConverterFactory.create())
        .addConverterFactory(MoshiConverterFactory.create(moshi))
        .baseUrl(BASE_URL)
        .build()

The sufficient part is that `ScalarsConverterFactory` should go before `MoshiConverterFactory`. — Alexander Skvortsov, Oct 28 '21 at 10:43

Moshi Retrofit error: "Expected a string but was BEGIN_OBJECT"

3 Answers3