Gson: Not a JSON Object

Question

I have the following String passed to server:

{
    "productId": "",
    "sellPrice": "",
    "buyPrice": "",
    "quantity": "",
    "bodies": [
        {
            "productId": "1",
            "sellPrice": "5",
            "buyPrice": "2",
            "quantity": "5"
        },
        {
            "productId": "2",
            "sellPrice": "3",
            "buyPrice": "1",
            "quantity": "1"
        }
    ]
}

which is a valid json for http://jsonlint.com/

I want to get the bodies array field.

That's how I'm doing it:

Gson gson = new Gson();
JsonObject object = gson.toJsonTree(value).getAsJsonObject();
JsonArray jsonBodies = object.get("bodies").getAsJsonArray();

But on the second line I'm getting exception listed below:

HTTP Status 500 - Not a JSON Object: "{\"productId\":\"\",\"sellPrice\":\"\",\"buyPrice\":\"\",\"quantity\":\"\",\"bodies\":[{\"productId\":\"1\",\"sellPrice\":\"5\",\"buyPrice\":\"2\",\"quantity\":\"5\"},{\"productId\":\"2\",\"sellPrice\":\"3\",\"buyPrice\":\"1\",\"quantity\":\"1\"}]}"

How to do it properly then ?

Answer 1

Gson#toJsonTree javadoc states

This method serializes the specified object into its equivalent representation as a tree of JsonElements.

That is, it basically does

String jsonRepresentation = gson.toJson(someString);
JsonElement object = gson.fromJson(jsonRepresentation, JsonElement.class);

A Java String is converted to a JSON String, ie. a JsonPrimitive, not a JsonObject. In other words, toJsonTree is interpreting the content of the String value you passed as a JSON string, not a JSON object.

You should use

JsonObject object = gson.fromJson(value, JsonObject.class);

directly, to convert your String to a JsonObject.