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Problem in receiving data in servlet from android client?

seraj ela

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posted 11 years ago

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am developing a android application which need to exchange data with mysql database via local server.
In this coding when tried to pass the data through sql query it shows null.

servlet coding

public class ClassDetails extends HttpServlet {
	Connection conn = null;            
        PreparedStatement stmt = null;     
       String sql = null;
       ArrayList<Classdata> stundList = new ArrayList<Classdata>();
  	private static final long serialVersionUID = 1L;
  	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
       }
  	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

PrintWriter out = response.getWriter();
		String title = "Database Result";
		String docType =  "<!doctype html public \"-//w3c//dtd html 4.0 " +"transitional//en\">\n";
		out.println(docType + "<html>\n" + "<head><title>" + title + "</title></head>\n" + "<body bgcolor=\"#f0f0f0\">\n" +  "<h1 align=\"center\">" + title + "</h1>\n");
		
       String sldept = request.getParameter("sldept");
       String sldegree = request.getParameter("sldegree");
       out.printf("dept=",sldept);
       try {      
           Context ctx = (Context) new InitialContext().lookup("java:comp/env");
           conn = ((DataSource) ctx.lookup("jdbc/mysql")).getConnection();

sql = "Select * from "+sldept+";"; 
          
           stmt = conn.prepareStatement(sql);
           ResultSet rs = stmt.executeQuery(); 
          
           while(rs.next()){ 
               Classdata classdata = new Classdata(); 
               classdata.setname(rs.getString("name").trim());
               classdata.setregno(rs.getString("regno")== null ? 0 : Integer.parseInt(rs.getString("regno").trim()));;
               stundList.add(classdata);
           }

rs.close();                                                               
           stmt.close();                                                             
           stmt = null;

conn.close();                                                             
           conn = null;

}                                                               
       catch(Exception e){System.out.println(e);}

finally {                                                       
           /*                                                             
            * close any jdbc instances here that weren't                  
            * explicitly closed during normal code path, so               
            * that we don't 'leak' resources...                           
            */

if (stmt != null) {                                            
               try {                                                         
                   stmt.close();                                                
               } catch (SQLException sqlex) {                                
                   // ignore -- as we can't do anything about it here           
               }

stmt = null;                                            
           }

if (conn != null) {                                      
               try {                                                   
                   conn.close();                                          
               } catch (SQLException sqlex) {                          
                   // ignore -- as we can't do anything about it here     
               }

conn = null;                                            
           }                                                        
       }

return;

}  
   
    	}

Android Coding

public class Parshingdata extends Activity {
	
	public void onCreate(Bundle savedInstanceState) {
		
		 super.onCreate(savedInstanceState);
        setContentView(R.layout.studdetails);

TextView tv = (TextView) findViewById(R.id.textView1);
    String url = "http://10.0.2.2:8080/SpinnerJson/ClassDetails";
    grabURL(url); 
		}
	public void grabURL(String url) {
        Log.v("Android Spinner JSON Data Activity", url);
        new GrabURL().execute(url);
    }
	private class GrabURL extends  AsyncTask<String, Void, String> {
        private static final int REGISTRATION_TIMEOUT = 3 * 1000;
        private static final int WAIT_TIMEOUT = 30 * 1000;
        private final HttpClient httpclient = new DefaultHttpClient();
        final HttpParams params = httpclient.getParams();
        HttpResponse response;
        private String content =  null;
        private boolean error = false;
        private ProgressDialog dialog = new ProgressDialog(Parshingdata.this);

protected void onPreExecute() {
            dialog.setMessage("Getting your data... Please wait...");
            dialog.show();
        }
        protected String doInBackground(String... urls) {

String URL = null;

try {
            	
    	
    	String sldept = getIntent().getExtras().getString("sldept");
        String sldegree = getIntent().getExtras().getString("sldegree");
        String slyear = getIntent().getExtras().getString("slyear");
        String slsubjname = getIntent().getExtras().getString("slsubjname");
        String slperiod = getIntent().getExtras().getString("slperiod");
        String sldate = getIntent().getExtras().getString("sldate");
    	// creating default Client 
    	HttpClient mClient = new DefaultHttpClient();
    	// Connect URL 
    	StringBuilder sb=new StringBuilder(URL);
    	// Establishing post connection to Specified URL 
    	HttpPost httpPost = new HttpPost(sb.toString());
    	// NameValuePair : A simple class encapsulating an attribute/value pair.
    	// List Size is 8 atributes
    	List<BasicNameValuePair> nameValuepairs = new ArrayList<BasicNameValuePair>(4);
    	// adding attributes to List 
    	nameValuepairs.add(new BasicNameValuePair("sldept",sldept));
    	nameValuepairs.add(new BasicNameValuePair("sldegree",sldegree));
    	nameValuepairs.add(new BasicNameValuePair("slyear",slyear));
    	nameValuepairs.add(new BasicNameValuePair("slsubjname",slsubjname));
    	// UrlEncodedFormEntity :An entity composed of a list of url-encoded pairs. This is typically 
    	// useful while sending an HTTP POST request.
    	 	// excute request and get response 
    	response = httpclient.execute(httpPost);

StatusLine statusLine = response.getStatusLine();
        if(statusLine.getStatusCode() == HttpStatus.SC_OK){
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            response.getEntity().writeTo(out);
            out.close();
            content = out.toString();
        } else{
            //Closes the connection.
            Log.w("HTTP1:",statusLine.getReasonPhrase());
            response.getEntity().getContent().close();
            throw new IOException(statusLine.getReasonPhrase());
        }
    } catch (ClientProtocolException e) {
        Log.w("HTTP2:",e );
        content = e.getMessage();
        error = true;
        cancel(true);
    } catch (IOException e) {
        Log.w("HTTP3:",e );
        content = e.getMessage();
        error = true;
        cancel(true);
    }catch (Exception e) {
        Log.w("HTTP4:",e );
        content = e.getMessage();
        error = true;
        cancel(true);
    }

return content;
}

protected void onCancelled() {
    dialog.dismiss();
    Toast toast = Toast.makeText(Parshingdata.this, "Error connecting to Server", Toast.LENGTH_LONG);
    toast.setGravity(Gravity.TOP, 25, 400);
    toast.show();

}

protected void onPostExecute(String content) {
    dialog.dismiss();
    Toast toast;
    if (error) {
        toast = Toast.makeText(Parshingdata.this, content, Toast.LENGTH_LONG);
        toast.setGravity(Gravity.TOP, 25, 400);
        toast.show();
    } else {
        
    }
}
	}
}

Tim Moores

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posted 11 years ago

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What is null? Is this an an Android problem, an HTTP or servlet problem, or a JDBC problem?

seraj ela

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posted 11 years ago

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connection is working fine..JDBC also fine.I think it is a servlet problem.Client returns the value before passing.

Tim Moores

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posted 11 years ago

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So at which spot in the code is everything still OK, and where does it start to go wrong? What have you done for debugging so far?

seraj ela

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posted 11 years ago

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tried to print the data. but still returns null. i don't know where the problem was.

Tim Moores

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posted 11 years ago

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What returns null?

Also:

So at which spot in the code is everything still OK, and where does it start to go wrong? What have you done for debugging so far?

seraj ela

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posted 11 years ago

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Tim Moores

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Tim Moores wrote:What returns null?

Posting just the code explains nothing.

seraj ela

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URL is not initialized..
it works by adding URL = urls[0];
in line 36 in client coding.

Tim Moores

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posted 11 years ago

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So all is good now?

Moises Kline

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posted 10 years ago

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All is good now I think .