how to deserialize Gson with empty list of custom object

Question

Recently, I got an issue with Gson deserialization. This is my object:

class Foo{
    public List<Donation> donations;
    class Donation{
         // SerializedName here.
    }
}

This is my json:

{
   "donations": [] // sometimes, this array is empty.
}
// this is none empty one.
{
"donations": [
        {
          "doner_id": 4,
          "name": "abc",
          "donate": "103"
        }
    ]
}

When parsing this JSON with the above object, I always got the error: Expected a com.google.gson.JsonObject but was com.google.gson.JsonArray. If the donations above is not empty, everything works well. How can I do to resolve it?

just check the condition if donation list size or length is >0 then apply your code else do nothing. — Dileep Patel, Nov 18 '17 at 06:48
check jsonarray.length() > 0 then pass through inside to get json. — Mohamed Mohaideen AH, Nov 18 '17 at 07:38

vikas kumar · Answer 1 · 2017-11-18T07:09:14.567

Here I compiled your json and it works fine for empty as well as non empty donations, check if it what you are looking for.

String json  = "{\n" +
            "\"donations\": [\n" +
            "        {\n" +
            "          \"doner_id\": 4,\n" +
            "          \"name\": \"abc\",\n" +
            "          \"donate\": \"103\"\n" +
            "        }\n" +
            "    ]\n" +
            "}";
    JsonParser jsonParser = new JsonParser();
    JsonObject object = jsonParser.parse(json).getAsJsonObject();
    Gson gson = new Gson();
    SampleModel sampleModels1 =  gson.fromJson(object, SampleModel.class);
    assertNotNull(sampleModels1);

SampleModel.java

   public class SampleModel {
    @SerializedName("donations")
    @Expose
    private List<Donations> mDonationsList;

    public List<Donations> getDonationsList() {
        return mDonationsList;
    }

    public void setDonationsList(final List<Donations> donationsList) {
        mDonationsList = donationsList;
    }

    public class Donations {
        @SerializedName("doner_id")
        @Expose
        private String doner_id;
        @SerializedName("name")
        @Expose
        private String name;
        @SerializedName("donate")
        @Expose
        private String donate;

        public String getDoner_id() {
            return doner_id;
        }

        public void setDoner_id(final String doner_id) {
            this.doner_id = doner_id;
        }

        public String getName() {
            return name;
        }

        public void setName(final String name) {
            this.name = name;
        }

        public String getDonate() {
            return donate;
        }

        public void setDonate(final String donate) {
            this.donate = donate;
        }

    }
}

score 0 · Answer 2 · answered Nov 18 '17 at 08:14

Check this out if it's is json array:

import java.lang.reflect.Type;
import com.google.gson.reflect.TypeToken;

...

Type listType = new TypeToken<ArrayList<YourClass>>(){}.getType();
List<YourClass> yourClassList = new Gson().fromJson(jsonArray, listType);

Google Gson - deserialize list object? (generic type)

how to deserialize Gson with empty list of custom object

2 Answers2