Android HttpClient, DefaultHttpClient, HttpPost

Question

How would I send a string data (JSONObject.toString()) to a url. I want to write a static method in a util class to do this. I want the method signature to be as follows

public static String postData (String url, String postData) throws SomeCustomException

What should be the format of the string url

The return String is the response from the server in as a string representation of json data.

EDIT

Present connection util

package my.package;
import my.package.exceptions.CustomException;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URLDecoder;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;


 public class ConnectionUtil {

 public static String postData(String url, String postData)
        throws CustomException {

    // Create a new HttpClient and Post Header
    InputStream is = null;
    StringBuilder sb = null;
    String result = "";
    HttpClient httpclient = new DefaultHttpClient();

HttpPost httppost = new HttpPost();
    httppost.setHeader("host", url);

    Log.v("ConnectionUtil", "Opening POST connection to URI = " + httppost.getURI() + " url = " + URLDecoder.decode(url));

    try {
        httppost.setEntity(new StringEntity(postData));

        // Execute HTTP Post Request
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();

    } catch (Exception e) {
        Log.e("log_tag", "Error in http connection " + e.toString());
        e.printStackTrace();
        throw new CustomException("Could not establish network connection");
    }
    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "utf-8"), 8);
        sb = new StringBuilder();
        sb.append(reader.readLine() + "\n");
        String line = "0";

        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }

        is.close();
        result = sb.toString();

    } catch (Exception e) {
        Log.e("log_tag", "Error converting result " + e.toString());
        throw new CustomException("Error parsing the response");
    }
    Log.v("ConnectionUtil", "Sent: "+postData);
    Log.v("ConnectionUtil", "Got result "+result);
    return result;

}

}

Logcat output

10-16 11:27:27.287: E/log_tag(4935): Error in http connection java.lang.NullPointerException 10-16 11:27:27.287: W/System.err(4935): java.lang.NullPointerException 10-16 11:27:27.287: W/System.err(4935): at org.apache.http.impl.client.AbstractHttpClient.determineTarget(AbstractHttpClient.java:496) 10-16 11:27:27.307: W/System.err(4935): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 10-16 11:27:27.327: W/System.err(4935): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) 10-16 11:27:27.327: W/System.err(4935): at in.gharpay.zap.integration.ConnectionUtil.postData(ConnectionUtil.java:92) 10-16 11:27:27.327: W/System.err(4935): at in.gharpay.zap.integration.ZapTransaction$1.doInBackground(ZapTransaction.java:54) 10-16 11:27:27.327: W/System.err(4935): at in.gharpay.zap.integration.ZapTransaction$1.doInBackground(ZapTransaction.java:1) 10-16 11:27:27.327: W/System.err(4935): at android.os.AsyncTask$2.call(AsyncTask.java:185) 10-16 11:27:27.327: W/System.err(4935): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306) 10-16 11:27:27.327: W/System.err(4935): at java.util.concurrent.FutureTask.run(FutureTask.java:138) 10-16 11:27:27.327: W/System.err(4935): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088) 10-16 11:27:27.327: W/System.err(4935): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581) 10-16 11:27:27.327: W/System.err(4935): at java.lang.Thread.run(Thread.java:1019) 10-16 11:27:27.327: V/log_tag(4935): Could not establish network connection

Answer 1

Well, here are my thoughts on your question:-

1. First, you should simply send the data to the server by using POST method. Its easy and absolutely possible in Android also. A simple code snippet for sending POST data can be like:

   HttpClient httpclient = new DefaultHttpClient();
   HttpPost httppost = new HttpPost(
           "http://yourserverIP/postdata.php");
   String serverResponse = null;
   try {
       List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
       nameValuePairs.add(new BasicNameValuePair("datakey1", dataValue1));
       nameValuePairs.add(new BasicNameValuePair("datakey2",
               dataValue2));
   
       httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
       HttpResponse response = httpclient.execute(httppost);
   
       serverResponse = response.getStatusLine().toString();
       Log.e("response", serverResponse);
   } catch (ClientProtocolException e) {
       e.printStackTrace();
   } catch (IOException e) {
       e.printStackTrace();
   }
   

   The above code sends data to a PHP script postdata on your server.

2. Next, for parsing the JSON data sent by the server, you can use a JSONParser and then easily utilize it as per your needs. You can get the response returned from the server by using the following code:

   String jsonData = EntityUtils.toString(serverResponse.getEntity());
   

Hope this helps. Thanks.

Answer 2

try using this method where strJsonRequest is the json string you want to post and the strUrl is the url to which you want to post the strJsonRequest

   public String urlPost(String strJsonRequest, String strURL) throws Exception 
{
    try
    {
        URL objURL = new URL(strURL);
        connection = (HttpURLConnection)objURL.openConnection();
        connection.setDoInput(true);
        connection.setDoOutput(true);
        connection.setAllowUserInteraction(false);
        connection.setUseCaches(false);
        connection.setConnectTimeout(TIMEOUT_CONNECT_MILLIS);
        connection.setReadTimeout(TIMEOUT_READ_MILLIS);
        connection.setRequestMethod("POST");
        connection.setRequestProperty("Accept-Charset", "utf-8");
        connection.setRequestProperty("Content-Type", "application/json; charset=utf-8");
        connection.setRequestProperty("Content-Length", ""+strJsonRequest.toString().getBytes("UTF8").length);

        DataOutputStream outputStream = new DataOutputStream(connection.getOutputStream());

        byte [] b = strJsonRequest.getBytes("UTF-8");

        outputStream.write(b);
        outputStream.flush();

        inputstreamObj = (InputStream) connection.getContent();//getInputStream();

        if(inputstreamObj != null)
            strResponse = convertStreamToString(inputstreamObj);

    }
    catch(Exception e)
    {
        throw e;
    }
    return strResponse;
}

and the method convertStreamToString() is as below

private static String convertStreamToString(InputStream is)
{
    /*
     * To convert the InputStream to String we use the BufferedReader.readLine()
     * method. We iterate until the BufferedReader return null which means
     * there's no more data to read. Each line will appended to a StringBuilder
     * and returned as String.
     */
    BufferedReader reader = null;
        try {
            reader = new BufferedReader(new InputStreamReader(is));
        } catch (Exception e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    StringBuilder sb = new StringBuilder();

    String line = null;
    try
    {
        while ((line = reader.readLine()) != null) 
        {
            sb.append(line + "\n");
        }
    } 
    catch (IOException e) 
    {
        e.printStackTrace();
    }
    finally 
    {
        try 
        {
            is.close();
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }
    }
    return sb.toString();
}