Fetch json from url giving NullPointerException

Question

I am fetching URL from below URL but i got following error

 url = "http://qrpromenad.azurewebsites.net/api/question?id=1&imei=35404304";


    public JSONObject getJSONFromUrl(String url) {
    System.out.println(url);
    try {
        // defaultHttpClient
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);

        HttpResponse httpResponse = httpClient.execute(httpPost);
        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();  // here i got null value

    } catch (Exception e) {
        e.printStackTrace();
    }

The following is logcat error

       04-17 16:00:12.739: W/System.err(4579): java.lang.NullPointerException
       04-17 16:00:12.739: W/System.err(4579):  at         com.qrcodetest.JSONParser.getJSONFromUrl(JSONParser.java:40)
       04-17 16:00:12.739: W/System.err(4579):  at com.qrcodetest.Result$FetchURL.doInBackground(Result.java:50)
       04-17 16:00:12.739: W/System.err(4579):  at com.qrcodetest.Result$FetchURL.doInBackground(Result.java:1)
       04-17 16:00:12.739: W/System.err(4579):  at android.os.AsyncTask$2.call(AsyncTask.java:185)
       04-17 16:00:12.739: W/System.err(4579):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
       04-17 16:00:12.739: W/System.err(4579):  at java.util.concurrent.FutureTask.run(FutureTask.java:138)
       04-17 16:00:12.739: W/System.err(4579):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
       04-17 16:00:12.739: W/System.err(4579):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
       04-17 16:00:12.739: W/System.err(4579):  at java.lang.Thread.run(Thread.java:1019)

but if i use another url like http://api.androidhive.info/contacts/ it is working fine

i have used POST method but still NULL is returning

     DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(Const.POST_URL);
        // Add your data
        List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
        nameValuePairs.add(new BasicNameValuePair("id", "1"));
        nameValuePairs.add(new BasicNameValuePair("imei", "123456"));
        httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));


        HttpResponse httpResponse = httpClient.execute(httpPost);
        HttpEntity httpEntity = httpResponse.getEntity();
        System.out.println("httpEntity "+httpEntity); // here is null
        if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {// false
            is = httpEntity.getContent();
        }

What's the line giving the NPE? (i.e. line 40 of your JSONParser class) — Matt Taylor
– Matt Taylor, Commented Apr 17, 2013 at 10:42
Have you modified anything in the PHP script. check whether it is properly returning the json response you need. — SKK
– SKK, Commented Apr 17, 2013 at 10:43
Why do you use getJSONFromURL() when the next moment you contact the server yourself? If you really need to POST, the getJSONFromUrl() may not get a reasonable answer. — class stacker
– class stacker, Commented Apr 17, 2013 at 10:43
Always check the HTTP response status (with httpResponse.getStatusLine().getStatusCode()) before trying to read it's data. You may very well be bombing on is = httpEntity.getContent(), assuming you've shown all your code. — Perception
– Perception, Commented Apr 17, 2013 at 10:45

Perception · Accepted Answer · 2013-04-17 11:32:42Z

1

The URL in question does not support posts (you can test that yourself with any kind of REST client). But, as you yourself have indicated, it does work with GET's. So switch up your code to something like as shown below and problem solved:

final String url = "http://qrpromenad.azurewebsites.net/api/question?id=1&imei=35404304";

DefaultHttpClient httpClient = new DefaultHttpClient();
HttpGet get = new HttpGet(url);

HttpResponse httpResponse = httpClient.execute(get);

String responseData = null;
final int status = httpResponse.getStatusLine().getStatusCode();
if (status == HttpStatus.SC_OK) {
    responseData = EntityUtils.toString(httpResponse.getEntity());
} else {
    System.err.println("HTTP request failed with status " + status);
}

System.out.println(responseData);

You need to add back in (of course) some more advanced error handling

answered Apr 17, 2013 at 11:32

Perception

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1 Comment

Siddhpura Amit Over a year ago

Thank you soooo much Perception :)

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