How to handle null response for json object

Question

I get a JSON response as

{
"edges": [],
"nodes": []
}

how to check if the objects has null values and handle the case??

JSONObject jobj = new JSONObject(line);
JSONArray jArray = jobj.getJSONArray("edges");
if(jArray.length()!=0)
{    
  for(int i=0;i<jArray.length();i++){
  JSONObject json_data = jArray.getJSONObject(i);
  x.add((float) json_data.getInt("x"));
  y.add((float) json_data.getInt("y"));
end

This retrurns me : org.json.JSONException: end of input at character 0 of

Does that exception throw at this line, by any chance? JSONObject jobj = new JSONObject(line); I suspect you aren't parsing the response you think you are, since the exception message indicates you tried to parse an empty string. The parsing happens on your first line; the rest is fluff. — dokkaebi
– dokkaebi, Commented Dec 5, 2012 at 20:42

fgeorgiew · Accepted Answer · 2012-12-05 21:03:40Z

3

try this one:

String jsonString = "{ "edges": [], "nodes": [] }";

JSONObject jsonObject = new JSONObject(jsonString);

if( jsonObject.isNull("edges") == false) {
//do sth
}

if( jsonObject.isNull("nodes") == false) {
//do sth
}

you can also check if you have some particular key in your json by jsonObject.has("edges")

you are passing some \line\ variable to the JSONObject constructor. make sure that this variable contains your whole json string like this one in my example and not something like "{" or ' "edges": [] ' maybe the problem is in your json source like dokkaebi suggested in comment

answered Dec 5, 2012 at 21:03

fgeorgiew

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2 Comments

ρяσѕρєя K Over a year ago

are u sure this will work because isNull just check key is exist in JsonObject or not

fgeorgiew Over a year ago

isNull check if key exist or if it have null value has() method checks only some key existence this is what documentation says "Determine if the value associated with the key is null or if there is no value."

ρяσѕρєя K · Accepted Answer · 2012-12-05 21:01:01Z

2

you can check as:

JSONObject jobj = new JSONObject(line);
if (jobj.getJSONArray("edges").length() == 0) {

    System.out.println("JSONArray is null");      
 }
 else{
      System.out.println("JSONArray is not null");
      //parse your string here         
     }

edited Dec 5, 2012 at 21:01

answered Dec 5, 2012 at 19:55

ρяσѕρєя K

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6 Comments

ρяσѕρєя K Over a year ago

what error it's showing? because you have two json Array inside JSONObject so JSONObject is not null. now you only need to check JSONArray is empty or not

ChanChow Over a year ago

org.json.JSONException: end of input at character 0 of

ρяσѕρєя K Over a year ago

@user1494754 : if still facing same issue then check jArray.length() > -1 because if it's empty then it contain less then zero element . as you known also indexing start from 0

ChanChow Over a year ago

Nope.No luck.It did the same

ρяσѕρєя K Over a year ago

@user1494754 : you have tried jArray.length() > -1 condition ?

|

sachin003 · Accepted Answer · 2012-12-06 11:02:17Z

try this on. I am showing example only for only one array depending on flag value you can show proper error message or on success you can bind parsed data to UI component.

String impuStr = "{\"edges\": [],\"nodes\": []}";

String flag = serverResponse(impuStr);

private String serverResponse(String jsonStr) { String flag = "success";

    JSONObject jobj;
    try {
        jobj = new JSONObject(jsonStr);

        JSONArray jArrayEdges = jobj.getJSONArray("edges");
        if(jArrayEdges != null && jArrayEdges.length() > 0)
        {    
          for(int i=0;i<jArrayEdges.length();i++)
          {
              JSONObject json_data = jArrayEdges.getJSONObject(i);
              // process data here
          }
         }else
             flag = "edges_list_empty";

    } catch (JSONException e) 
    {
        // TODO Auto-generated catch block
        e.printStackTrace();
        flag = "failure";
    }

    return flag;
}

jtt · Accepted Answer · 2012-12-05 19:52:27Z

0

Using simple java rules. Check if the array is empty, if the array does not exist and you try to get it, it just returns null. Just handle it. Don't continue parsing if you know its going to fail. Just exist gracefully.

if (myObj != null)
{
  ... process
}

answered Dec 5, 2012 at 19:52

jtt

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