Get JSON string from Android JSONException

Question

My Volley request can come back as either JSONArray (valid) or JSONObject (error message) and in order to correctly display the error response, I want to parse the failed JSONArray string as JSONObject. It appears that JSONException objects wrap the original text. Is it possible to get just the failed text in order to parse it differently?

Example:

org.json.JSONException: Value {"error":"User has not signed up to be a customer"} of type org.json.JSONObject cannot be converted to JSONArray

and I want to get just the JSON string component because it's a valid JSONObject.

Does your error comes with HTTP 200 or do you get an specific status code? — Androiderson
– Androiderson, Commented Dec 8, 2015 at 0:28

BNK · Accepted Answer · 2015-12-08 02:13:59Z

1

Because your response is either JSONArray (valid) or JSONObject (error message), so you can refer to the following code:

// Check the response if it is JSONObject or JSONArray
Object json = new JSONTokener(response).nextValue();
if (json instanceof JSONObject) {
    // do something...
} else if (json instanceof JSONArray) {
    // do something...
}

Hope it helps!

answered Dec 8, 2015 at 2:13

BNK

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1 Comment

MechEngineer Over a year ago

This pointed me in the right direction, thanks! I've added an answer to see what I did.

MechEngineer · Accepted Answer · 2015-12-08 14:22:01Z

I don't think it's actually possible to retrieve just the JSON string from inside a JSONException so in the end I took the answer from BNK and did what is probably the easiest solution in this situation.

The trick seems to be to receive a StringRequest and do the JSON processing once you know there's a valid string response. Here's how that looks in my project.

StringRequest request = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            activity.hideProgress();

            try {
                Object json = new JSONTokener(response).nextValue();
                if (json instanceof JSONArray) {
                    // an array is a valid result
                    dataModel.loadData((JSONArray)json);
                } else if (json instanceof JSONObject) {
                    // this is an error
                    showErrorMessageIfFound((JSONObject)json);
                }
            } catch (JSONException error) {
                error.printStackTrace();
            }

            refreshTable();
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            activity.hideProgress();
            showVolleyError(error);
            // check for a JSONObject parse error
        }
    });

First there's a StringRequest to retrieve the response. The error response displays the error with my custom error processor. The success response parses the JSON and uses the end result to display the correct thing to the end user.

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