JSON parsing with Java - how to handle different values?

Question

I have a server call that returns JSON which I try to parse with Java. If there is an error on the server, then it returns JSON with error:error_name

But if there is not error, the server returns data inside the JSON.

The way I have the parsing set up currently is crashing when I check if there was an error. Here is what I have:

try
{
    JSONArray obj = new JSONArray(result);
    if ( obj != null )
    {
        discussion.clear();
        if ( obj.length() == 0 )
        {
            DiscussionMessage message = new DiscussionMessage ( );                            
            discussion.add( message );
        }
        else
        {
            JSONObject ob = obj.getJSONObject(0);
            String error = ob.getString("error");
            if (error != null && 
                ( error.equals("no_problem_id") || 
                  error.equals("error_adding_suggested_solution_comment") || 
                  error.equals("no_recent_topic_id") ||
                  error.equals("no_comment") ||
                  error.equals("no_member_id") ||
                  error.equals("no_plan_id") ||
                  error.equals("error_duplicate_topic_comment") ) 
               )
            {
                {                
                    Toast.makeText(getApplicationContext(), "Could not get the current discussion.", Toast.LENGTH_LONG).show();                                 
                    sendEmail("Add business comment error response" , "Error response from server. Response: " + result);   
                }
            }
            else if ( error != null &&  error.equals("no_email_in_public_plan"))
            {
                Toast.makeText(getApplicationContext(),"Unexpected error. Please let us know about this" , Toast.LENGTH_LONG).show();    
                sendEmail("Error adding fundraising comment" , "Empty email adding fundraising plan comment");
            }
            else
            {
                try
                {
                    for ( int i = 0; i < obj.length(); i++ )
                    {
                        JSONObject o = obj.getJSONObject(i);
                        //String suggested_solution_id = o.getString("suggested_solution_id");
                        String comment = o.getString("comment");
                        String commenter_id = o.getString("commenter_id");
                        String comment_id = o.getString("comment_id");
                        String first_name = o.getString("first_name");
                        String is_private = o.getString("privacy");
                    }
                }
                catch ( Exception e )
                {
                }
            }
        }
    }
}
catch ( Exception e )
{
}

Is there something fundamentally incorrect about the way I am trying to send and parse this JSON? It feels so :)

Please help me understand what is the correct way of doing this Thanks.

Here is a crash error:

Exception: No value for error , and result was: [{\"comment_id\":\"24\",\"plan_id\":\"20\",\"commenter_id\":\"1\",\"comment\":\"test\",\"solution_part\":\"1\",\"date\":\"2013-03-13\",\"first_name\":\"Alex\",\"privacy\":\"0\"},{\"comment_id\":\"25\",\"plan_id\":\"20\",\"commenter_id\":\"55018\",\"comment\":\"hi\",\"solution_part\":\"1\",\"date\":\"2013-03-13\",\"first_name\":\"Sddggh\",\"privacy\":\"0\"}]

Answer 1

In the case where you do not have an error, the call to ob.getString("error") is throwing the exception that you are experiencing because there is no "error" key in the object. Either use the JSONObject#has method to test whether the key exists prior to trying to get it, or follow an approach like Premal laid out in the other answer.

Answer 2

Can you please paste your json in both cases ?

typically you should always enclose your response json in one json object so when you are looking at response you always know what to look for. so for e.g.

{"result":"ok", data :[{"data1":"value1", "data2":"value2"}]}

or

{"result":"error"}

so your code is very simplified

JSONObject responseObj = new JSONObject(responseString);
String result = responseObject.get("result");
if(result.equalsIgnoreCase("ok") 
{ /* handle good case */ 
    JSONArray list = (JSONArray)responseObj.get("data");
    for(...) {}
}
else { /* handle error case*/ }

-Premal