JSON error Caused by: java.lang.NullPointerException

Question

im trying to make a register page on android using JSON. everytime i press register button on avd, i get an error "unfortunately database has stopped". i have a error on my logcat that i cannot understand. this my code. please someone help me.

this my register.java

import android.util.Log;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }


    public JSONObject getJSONFromUrl(final String url) {

        // Making HTTP request
        try {
            // Construct the client and the HTTP request.
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            // Execute the POST request and store the response locally.
            HttpResponse httpResponse = httpClient.execute(httpPost);
            // Extract data from the response.
            HttpEntity httpEntity = httpResponse.getEntity();
            // Open an inputStream with the data content.
            is = httpEntity.getContent();

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            // Create a BufferedReader to parse through the inputStream.
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            // Declare a string builder to help with the parsing.
            StringBuilder sb = new StringBuilder();
            // Declare a string to store the JSON object data in string form.
            String line = null;

            // Build the string until null.
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }

            // Close the input stream.
            is.close();
            // Convert the string builder data to an actual string.
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // Try to parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // Return the JSON Object.
        return jObj;

    }


    // function get json from url
// by making HTTP POST or GET mehtod
    public JSONObject makeHttpRequest(String url, String method,
                                      List<NameValuePair> params) {

        // Making HTTP request
        try {

            // check for request method
            if (method.equalsIgnoreCase("POST")) {
                // request method is POST
                // defaultHttpClient
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params));

                HttpResponse httpResponse = httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();

            } else if (method.equalsIgnoreCase("GET")) {
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
                HttpGet httpGet = new HttpGet(url);

                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();
            }

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        if (is != null) {
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(
                        is, "iso-8859-1"), 8);
                StringBuilder sb = new StringBuilder();
                String line = null;
                while ((line = reader.readLine()) != null) {
                    sb.append(line + "\n");
                }
                is.close();
                json = sb.toString();
            } catch (Exception e) {
                Log.e("Buffer Error", "Error converting result " + e.toString());
            }
        }
        // try parse the string to a JSON object
        if (json != null) {
            try {
                jObj = new JSONObject(json);
            } catch (JSONException e) {
                Log.e("JSON Parser", "Error parsing data " + e.toString());
            }
        }

        // return JSON String
        return jObj;

    }
}

this is JSONparser.java

import android.util.Log;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }


    public JSONObject getJSONFromUrl(final String url) {

        // Making HTTP request
        try {
            // Construct the client and the HTTP request.
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            // Execute the POST request and store the response locally.
            HttpResponse httpResponse = httpClient.execute(httpPost);
            // Extract data from the response.
            HttpEntity httpEntity = httpResponse.getEntity();
            // Open an inputStream with the data content.
            is = httpEntity.getContent();

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            // Create a BufferedReader to parse through the inputStream.
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            // Declare a string builder to help with the parsing.
            StringBuilder sb = new StringBuilder();
            // Declare a string to store the JSON object data in string form.
            String line = null;

            // Build the string until null.
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }

            // Close the input stream.
            is.close();
            // Convert the string builder data to an actual string.
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // Try to parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // Return the JSON Object.
        return jObj;

    }


    // function get json from url
    // by making HTTP POST or GET mehtod
    public JSONObject makeHttpRequest(String url, String method,
                                      List<NameValuePair> params) {

        // Making HTTP request
        try {

            // check for request method
            if(method == "POST"){
                // request method is POST
                // defaultHttpClient
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params));

                HttpResponse httpResponse = httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();

            }else if(method == "GET"){
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
                HttpGet httpGet = new HttpGet(url);

                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();
            }

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

and this my error

08-19 00:46:55.832    2369-2388/com.example.blackcustomzier.database E/JSON Parser﹕ Error parsing data org.json.JSONException: End of input at character 0 of
08-19 00:46:55.882    2369-2388/com.example.blackcustomzier.database W/dalvikvm﹕ threadid=15: thread exiting with uncaught exception (group=0xb0f37648)
08-19 00:46:55.882    2369-2388/com.example.blackcustomzier.database E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #5
    java.lang.RuntimeException: An error occured while executing doInBackground()
            at android.os.AsyncTask$3.done(AsyncTask.java:299)
            at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
            at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
            at java.util.concurrent.FutureTask.run(FutureTask.java:239)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
            at java.lang.Thread.run(Thread.java:841)
     Caused by: java.lang.NullPointerException
            at com.example.blackcustomzier.database.Register$CreateUser.doInBackground(Register.java:108)
            at com.example.blackcustomzier.database.Register$CreateUser.doInBackground(Register.java:74)
            at android.os.AsyncTask$2.call(AsyncTask.java:287)
            at java.util.concurrent.FutureTask.run(FutureTask.java:234)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
            at java.lang.Thread.run(Thread.java:841)
08-19 00:46:55.912    2369-2369/com.example.blackcustomzier.database W/EGL_emulation﹕ eglSurfaceAttrib not implemented
08-19 00:46:56.272    2369-2369/com.example.blackcustomzier.database W/EGL_emulation﹕ eglSurfaceAttrib not implemented
08-19 00:46:56.662    2369-2369/com.example.blackcustomzier.database E/WindowManager﹕ Activity com.example.blackcustomzier.database.Register has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{b1341960 V.E..... R......D 0,0-1026,288} that was originally added here
    android.view.WindowLeaked: Activity com.example.blackcustomzier.database.Register has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{b1341960 V.E..... R......D 0,0-1026,288} that was originally added here
            at android.view.ViewRootImpl.<init>(ViewRootImpl.java:345)
            at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:239)
            at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
            at android.app.Dialog.show(Dialog.java:281)
            at com.example.blackcustomzier.database.Register$CreateUser.onPreExecute(Register.java:85)
            at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
            at android.os.AsyncTask.execute(AsyncTask.java:534)
            at com.example.blackcustomzier.database.Register.onClick(Register.java:70)
            at android.view.View.performClick(View.java:4240)
            at android.view.View$PerformClick.run(View.java:17721)
            at android.os.Handler.handleCallback(Handler.java:730)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5103)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
            at dalvik.system.NativeStart.main(Native Method)

please help me to solve this thx

Please don't make me count up to 108. I don't have that many fingers and toes. Please let us know which line in Register.java is line 108. — ajb
– ajb, Commented Aug 19, 2014 at 3:55
do not compare String using == sign instead of == sign use .equalsIgnoreCase in jsonParsor at line if(method == "POST") so ur code will be if(method.equalsIgnoreCase("POST")) same for "GET" — Rohan Pawar
– Rohan Pawar, Commented Aug 19, 2014 at 4:06
You are passing something null to your JSON , Please check for are you getting correct data from DB or not — Kirtikumar A.
– Kirtikumar A., Commented Aug 19, 2014 at 4:08
@ajb line 108 in register.java is Log.d("Registering attempt", json.toString()); — user3821853
– user3821853, Commented Aug 19, 2014 at 4:25
Add if (json != null) before this Log.d. You don't want your log lines throwing exceptions. As for why your makeHttpRequest is returning null, it starts with the Error converting result message I see in the log, and that leads to the Error parsing data message, which leads to the null result. So you'll need to track that down. Eran gave you some ideas, and maybe not using == to compare strings will fix everything. — ajb
– ajb, Commented Aug 19, 2014 at 4:58

Eran · Accepted Answer · 2014-08-19 04:28:11Z

As mentioned in a comment, your String comparisons in makeHttpRequest (for example, if(method == "POST")) are wrong.

Since they would always return false, is won't be initialized, so later passing it to InputStreamReader is the probable cause of your NullPointerException :

BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);

If that's not the cause of the NullPointerException, the cause is probably calling :

is.close();

when is is not initialized.

Use if (method.equalsIgnoreCase("POST")) to fix your problem.

In addition, I would add some null checks, just to be safe :

// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
                                  List<NameValuePair> params) {

    // Making HTTP request
    try {

        // check for request method
        if (method.equalsIgnoreCase("POST")) {
            // request method is POST
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        } else if (method.equalsIgnoreCase("GET")) {
            // request method is GET
            DefaultHttpClient httpClient = new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            HttpGet httpGet = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();
        }

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    if (is != null) {
      try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
      } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
      }
    }
    // try parse the string to a JSON object
    if (json != null) {
      try {
        jObj = new JSONObject(json);
      } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
      }
    }

    // return JSON String
    return jObj;

}

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