Database Connection from mobile not happening

[garudadwajan]

Hi Everybody,

I'm very new to J2ME, and I'm writing a sample code to retrieve the values from the database and display it on my mobile screen. I'm able to extract the data from the DB in an emulator. But when I try in the mobile I'm neither getting any error nor am I able to create in to the database. I have tried various mobiles which supports MIDP 2.0, but was not successful.
This is my midlet code:

package hello;

import java.io.*;
import java.util.*;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;

public class HelloMIDlet extends MIDlet implements CommandListener {
private StreamConnection streamConnection = null;
private InputStream inputStream = null;


private String url =
"http://192.168.39.19:8084/ServletforTest/getConnection";

private Display display;
private Command exit = new Command("EXIT", Command.EXIT, 1);;
private Command connect = new Command("Connect", Command.SCREEN, 1);
private TextField tb;
private Form menu;
private TextField tb1;
private TextField tb2;
DB db;

private Command exitCommand;
private Form form;
private StringItem stringItem;

public HelloMIDlet() {
display = Display.getDisplay(this);
}

private void initialize() {
}

public void startMIDlet() {
// write pre-action user code here
switchDisplayable(null, getForm());
// write post-action user code here
}

public void resumeMIDlet() {
}

public void switchDisplayable(Alert alert, Displayable nextDisplayable) {

Display display = getDisplay();
if (alert == null) {
display.setCurrent(nextDisplayable);
} else {
display.setCurrent(alert, nextDisplayable);
}

}

public void commandAction(Command command, Displayable displayable) {

if (displayable == form) {
if (command == exitCommand) {
exitMIDlet();
}
}

if (command == exit) {
destroyApp(false);
notifyDestroyed();
} else if (command == connect) {
db = new DB(this);
db.start();
}
}

public Command getExitCommand() {
if (exitCommand == null) {
exitCommand = new Command("Exit", Command.EXIT, 0);
}
return exitCommand;
}

public Form getForm() {
if (form == null) {
form = new Form("Welcome", new Item[] { getStringItem() });
form.addCommand(getExitCommand());
form.setCommandListener(this);
}
return form;
}

public StringItem getStringItem() {
if (stringItem == null) {
stringItem = new StringItem("Hello", "Hello, World!");
}
return stringItem;
}

public Display getDisplay () {
return Display.getDisplay(this);
}


public void exitMIDlet() {
switchDisplayable (null, null);
destroyApp(true);
notifyDestroyed();
}


public void startApp() {
displayMenu();
}

public void displayMenu() {
menu = new Form("Connect");

menu.addCommand(exit);
menu.addCommand(connect);
menu.setCommandListener(this);
display.setCurrent(menu);
}

public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}

public class DB implements Runnable {
HelloMIDlet midlet;
private Display display;
String db;
String user;
String pwd;
public DB( HelloMIDlet midlet) {
this.midlet = midlet;
display = Display.getDisplay(midlet);
}

public void start() {
Thread t = new Thread(this);
t.start();
}

public void run() {

StringBuffer sb = new StringBuffer();
try {
HttpConnection c = (HttpConnection)Connector.open(url);
c.setRequestProperty("User-Agent","Profile/MIDP-2.0, Configuration/CLDC-1.0");
c.setRequestProperty("Content-Language","en-US");
c.setRequestMethod(HttpConnection.POST);


DataOutputStream os = (DataOutputStream)c.openDataOutputStream();
os.flush();
os.close();

InputStream is =c.openInputStream();
int len = (int)c.getLength();
int ch;
sb = new StringBuffer();
while ((ch = is.read()) != -1) {
sb.append((char)ch);
}
showAlert(sb.toString());
is.close();
c.close();
} catch (Exception e) {
showAlert(e.getMessage());
}
}

private void showAlert(String err) {
Alert a = new Alert("");
a.setString(err);
a.setTimeout(Alert.FOREVER);
display.setCurrent(a);
}
};
}


This is my servlet code:

package servlet;

import java.io.*;
import java.text.*;
import java.util.*;
import javax.servlet.*;
import java.sql.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class getConnection extends HttpServlet {
private Connection conn;

public void init() {
}


// @Override
public void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException,
IOException {

doPost(request,response);
}


//@Override
public void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException,
IOException {
PrintWriter out = response.getWriter();
System.out.println("This is inside ");


DataInputStream in = new DataInputStream(
(InputStream)request.getInputStream());

String db ="system";
String user ="Stridus_demo";
String pwd = "Stridus_demo";
Statement stmt=null;
ResultSet rs=null;
String ur = "";



String message ="jdbcracle:thin:@122.166.39.27:1521:"+db+","+user+","+pwd;
try {

connect(db.toLowerCase().trim(),user.toLowerCase().trim(),
pwd.toLowerCase().trim());

stmt= conn.createStatement();

rs=stmt.executeQuery("select name from MOBILETESTGARUDA");

while(rs.next()){
ur = rs.getString(1)+" & " + ur;
}

response.setContentType("text/html");
response.setContentLength(ur.length());
out.println(ur);


} catch (Throwable t) {
message += "200 " + t.toString();
}
finally
{
try {

out.close();
out.flush();
rs.close();
stmt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}


private void connect(String db, String user,String pwd) throws Exception {

Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
conn = DriverManager.getConnection("jdbcracle:thin:@122.166.39.27:1521:"+db,user,pwd);
}
}

As i have said this is working absolutely fine in the emulator, but not in the actual device.
Is there a problem in the code itself or I'm not having a proper mobile to execute this code or is there any particular settings that has to be changed in mobile to execute this particular code.

Thanks and Regards
Garudadwajan.R

[grahamhughes]

192.168.39.19 looks like the address on your local network. Do you use a different address when you put this on a phone?

Cheers,
Graham.

[garudadwajan]

Oh ya..sorry about that...I didn't change the IP while uploading the code now...

I'm using external IP when I'm uploading the .jad file.

[grahamhughes]

OK. Do you have any other Java application that connects to the network? Are you sure the device's network settings are correct? Try downloading http://mini.opera.com, see if that application works. See if you can access your server's URL using Opera Mini.

[garudadwajan]

Yes!! I have done that too!!!! In the browser's url I typed the address specified in the midlet with external IP and I'm able to output the value of the DB in my screen!!!!!

The problem comes when I try to connect to the servlet from my midlet.

Another info I'd like to share is...

I'm using netbeans for my project. Both my servlet and my midlet are in seperate "projects". So before I send my jar and jad files to the mobile, I'm also deploying the servlet.

That has to be done everytime or once done is good enough?

[grahamhughes]

Which browser? Install Opera Mini and try that, not the device's internal browser. The browser may use different settings to Java apps.

What happens? Does the application lock, or is there an exception?

Cheers,
Graham.

[garudadwajan]

Hi Graham,

I'm not at all using any browser here. Only for cross checking the code I typed the url in the browser and it is working absolutely fine.

I'm installing the app directly and as soon as I run my app, it should display me the value directly from the DB. I'm not using any browser as a medium. The output I'm trying to portray is just a normal display type.

[grahamhughes]

I realize that. But, please do install Opera Mini and try the URL in that. You need to find out if the phone is configured correctly.

Graham.

[garudadwajan]

Hi Graham,

I tried with opera mini...itz working in that browser too..

[grahamhughes]

OK. So, when you run your application, what happens?

Also: why do you POST, and open and close an OutputStream, when you don't appear to write any data?

[garudadwajan]

Absolutely nothing!!!!

First it asks for sending of HTTP information. Den it'll just be blank.
Nothing happens.

But if I try to connect it while it is happening I get some info like TCP open.

[grahamhughes]

OK. Next, try this:

import java.io.*;
import javax.microedition.io.*;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class HttpReader extends MIDlet implements CommandListener, Runnable {

    private static final Command cmdGET  = new Command("GET", Command.SCREEN, 1);
    private static final Command cmdEXIT = new Command("Exit", Command.EXIT, 1);

    /// PUT YOUR URL HERE
    private static final String DOCUMENT_URL = "http://";

    private Form form;
    private StringItem status;
    
    public void startApp() {
        Display disp = Display.getDisplay(this);

        form = new Form("HttpReader");
        form.addCommand(cmdEXIT);
        form.addCommand(cmdGET);
        form.setCommandListener(this);

        status = new StringItem(null, "Ready");
        form.append(status);

        disp.setCurrent(form);
    }

    public void pauseApp() {
    }

    public void destroyApp(boolean bUnconditional) {
    }

    private void setStatus(String s) {
        status.setText(s);
    }

    // implementation: CommandListener
    
    public void commandAction(Command cmd, Displayable disp) {
        if (cmd == cmdEXIT) {
            destroyApp(false);
            notifyDestroyed();
        } else if (cmd == cmdGET) {
            form.removeCommand(cmdGET);
            form.removeCommand(cmdEXIT);
            
            (new Thread(this)).start();
        }
    }

    // implementation: Runnable

    public void run() {
        try {
            setStatus("Connecting...");
            HttpConnection con =(HttpConnection) Connector.open(DOCUMENT_URL);

            try {
                con.setRequestMethod(HttpConnection.GET);
                int len = (int) con.getLength();

                if (len >= 0) {
                    byte[] ao = new byte[len];
                    DataInputStream din = con.openDataInputStream();
                    try {
                        din.readFully(ao);
                    } finally {
                        din.close();
                    }

                    form.append(new String(ao));
                } else {
                    setStatus("no length");
                }
            } finally {
                con.close();
            }
        } catch (Exception e) {
            setStatus("Error: " + e);
        } finally {
            form.addCommand(cmdEXIT);
        }
        setStatus("Complete.");
    }
} 

[garudadwajan]

Now I'm getting a null pointer exception with this code...
It says there is some error in startApp..

This is what he error says:

startApp threw an Exception
java.lang.NullPointerException
java.lang.NullPointerException
at javax.microedition.lcdui.Displayable.addCommand(Displayable.java:300)
at hello.HelloMIDlet.startApp(+29)
at javax.microedition.midlet.MIDletProxy.startApp(MIDletProxy.java:43)
at com.sun.midp.midlet.Scheduler.schedule(Scheduler.java:374)
at com.sun.midp.main.Main.runLocalClass(Main.java:466)
at com.sun.midp.main.Main.main(Main.java:120)

[grahamhughes]

That's because you've mixed bits of my code with bits of yours.

[raj_J2ME]

Hi,
I guess you have mixed the commands..and either of the command is null,
please check the same,