Parse HashMap> with Gson throws java.lang.ClassCastException

Question

I have a Json like this:

{
    "a": [
        {"name": "a"}
    ],
    "b": [
        {"name": "b"}
    ]
}

And i use Retrofit for convert to java object like this:

public interface TheService {
    @GET("data")
    Call<HashMap<String, ArrayList<User>>> getUsers();
}

It's work fine. But when i cache my json string and parse it manually with Gson:

Gson gson = new Gson();
HashMap<String, ArrayList<User>> map = gson.fromJson(jsonString, HashMap.class);

It throws error: java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to xxx.User

So how can i covert jsonString to HashMap<String, ArrayList<User>> object with Gson?

Hope this one helps. https://stackoverflow.com/questions/2779251/how-can-i-convert-json-to-a-hashmap-using-gson — vinv, Apr 26 '20 at 00:07
I found solution here with TypeToken: https://stackoverflow.com/a/32494079/1472483 — MarsPeople, Apr 26 '20 at 19:17

score 0 · Accepted Answer · answered Apr 26 '20 at 19:20

With using TypeToken

Type type = new TypeToken<HashMap<String, ArrayList<User>>>() {}.getType();
HashMap<String, ArrayList<User>> map = gson.fromJson(jsonString, type);

1 Answers1