Converting JSON string to object returns "Expected BEGIN_ARRAY but was STRING"

Question

I have a JSON response coming back from my server in the format:

[
    {
        "id": "one",
        "values": {
            "name": "John",
        }
    },
    {
        "id": "two",
        "values": {
            "name": "Bob",
        }
    }
]

Here is the class I've set up:

public class TestClass implements Serializable {

    @SerializedName("id")
    private String id;

    @SerializedName("values")
    private List<String> values;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public List<String> getValues() {
        return values;
    }

    public void setValues(List<String> values) {
        this.values = values;
    }
}

Here is my code to parse the JSON into a list of objects:

String response = serverResponseHere;
Gson gson = new Gson();
String json = gson.toJson(response);

Type collectionType = new TypeToken<List<TestClass>>(){}.getType();
List<TestClass> values = gson.fromJson(json, collectionType);

However, I get the following error:

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING

What's going on here?

using the object as a list has caused the error . this is the right: = Type collectionType = new TypeToken(){}.getType(); . also your son is wrong — Bayar Şahintekin, Sep 28 '18 at 14:36

Sotirios Delimanolis · Answer 1 · 2018-09-28T14:40:09.277

You're taking your JSON response content

String response = serverResponseHere;

and converting it to JSON

Gson gson = new Gson();
String json = gson.toJson(response);

This produces a JSON string containing your content. That looks like

"[\n    {\n        \"id\": \"one\",\n        \"values\": {\n            \"name\": \"John\",\n        }\n    },\n    {\n        \"id\": \"two\",\n        \"values\": {\n            \"name\": \"Bob\",\n        }\n    }\n]\n"

When you try to deserialize that as a List<TestClass>, it obviously fails because it's a JSON String instead of a JSON Array.

Don't serialize your content to JSON before deserializing it, it's already JSON.

Others have mentioned this, your values field doesn't match what your JSON content. See here for how to fix that:

Why does Gson fromJson throw a JsonSyntaxException: Expected BEGIN_OBJECT but was BEGIN_ARRAY?

This should be the accepted answer. – Paul Benn Sep 28 '18 at 14:34 — Paul Benn, Sep 28 '18 at 14:34

score -2 · Answer 2 · answered Sep 28 '18 at 14:09

-2

Change your server response json from :

[
    {
        "id": "one",
        "values": {
            "name": "John",
        }
    },
    {
        "id": "two",
        "values": {
            "name": "Bob",
        }
    }
]

To :

[
    {
        "id": "one",
        "values": [
            {"name": "John"}
        ]
    },
    {
        "id": "two",
        "values": [
            {"name": "Bob"}
        ]
    }
]

answered Sep 28 '18 at 14:09

Koustuv Ganguly

897
7
21

Still won't work, as `{"name": "John"}` is not a string – Ayush Gupta Sep 28 '18 at 14:09
That should not be also cause it need to be a json object inside json array. Error is it's getting string where array is expected. – Koustuv Ganguly Sep 28 '18 at 14:11
`List` expects something like `["John", "Bob"]` – Ayush Gupta Sep 28 '18 at 14:12

Converting JSON string to object returns "Expected BEGIN_ARRAY but was STRING"

2 Answers2