How to handle JSON objects wrapped into one JSON object with retrofit2?

Julian Eggers :

I want to receive items using retrofit and parse them into a Java list. However, the server response is not a JSON array but a JSON object containing the items. That is why retrofit cannot just convert the response into a java list.

The response looks something like this:

{
    "4": {
        "key": "value",
        ...
    },
    "5": {
        ...
    }, 
    ...
}

Usually, I would try to receive the items like this:

@GET("items")
Call<List<Item>> getItems();

But this obviously does not work and Retrofit responds: Expected BEGIN_ARRAY but was BEGIN_OBJECT

What is my best option to convert this object into a java list using retrofit?

Fred :

I'd personally do this in 2 steps to avoid having to write a custom adapter for the deserialization.

I'd write the interface like:

@GET("items")
Call<Map<String, Item>> getItems();

And once you'd call the API on the response I'd just call values().

Things to take into consideration is that because the API returns a map and not a list, there's no guarantee that the order of any list you'd produce would be consistent. The json standard doesn't define any order for objects unless they're in a json array.

How to handle JSON objects wrapped into one JSON object with retrofit2?

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