problem using ObjectOutputStream in multithreading

[sanjeevbindroo]

hi...
m developing a chatting software using sockets..
in that i want to use ObjectOutputStream and ObjectInputStream to send and recieve object...
the main problem is that i m using multithreading in server..when it is single server and single client application then it works well..but when i m using multithreading at serverside it is giving "NullPointerException"
and the thing is that when i m using DataOutput and DataInput Streams its working well with the same server supporting multithreading...plz help me...as i need ObjectOutputStream and ObjectInputStream to send and recieve files and other objects.

the clientside code is:
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class site1 extends JFrame implements ActionListener
{
JButton B;
JTextField tf;
TextArea ta;
JLabel l;
Socket skt;
ServerSocket servskt;
ObjectInputStream in;
ObjectOutputStream out;
JMenuBar mbar;
JMenu file,edit,view;
JMenuItem i1,i2,i3,i4,i5,i6,i7,i8,sconv;
//StatusBar s;
public site1()
{
.....
......
try
{
skt=new Socket("127.0.0.1",4444);
in=new ObjectInputStream(skt.getInputStream());
out=new ObjectOutputStream(skt.getOutputStream());
while(true)
{
Object s2=in.readObject();
ta.append("\nSENDER::\t"+s2.toString()+"\n");
System.out.println(s2);
}
}catch(Exception e9){JOptionPane.showMessageDialog(null,"The other System is offline");}

}

public void actionPerformed(ActionEvent ae)
{
String st=ta.getSelectedText();
if(ae.getSource()==B || ae.getSource()==tf)//if i click button
{ String s1=tf.getText();

try
{
//out.writeObject("hhh");

if(s1.equals(""))
JOptionPane.showMessageDialog(null,"enter valid text");
else
{
ta.append("\nME:\t"+s1);
System.out.println(s1);
tf.setText("");
System.out.println(s1);
out.writeObject(s1);
//out.flush();
}
}catch(Exception e3)
{
JOptionPane.showMessageDialog(null,"The other System is not reachable.\n Try later");
System.out.println("33"+e3); }
/*catch(IOException e3){
JOptionPane.showMessageDialog(null,"io ex.\n Try later");
System.out.println("33"+e3); }*/
}

if(ae.getSource()==i4)
{
JOptionPane.showMessageDialog(null,"Thanks for using Synergy Talk");
System.exit(1);
}
if(ae.getSource()==sconv)
{
try
{
String s5=ta.getText();
String sr=JOptionPane.showInputDialog("Enter the name of file");
byte[] b=s5.getBytes();
//System.out.println(conv);
FileOutputStream fout=new FileOutputStream(sr+".txt");
fout.write(b);
}catch(Exception E8){ System.out.println("ttt"+E8); }
}
if(ae.getSource()==i6)
{
//String st=ta.getSelectedText();
System.out.println("copied"+st);
}

if(ae.getSource()==i7)
{
System.out.println("test1");
// String st=ta.getSelectedText();
String sr=tf.getText()+st;
tf.setText(sr);
System.out.println("pasted"+st);
}
}

public static void main(String args[])
{
site1 s1=new site1();

s1.show();
//s1.setVisible(true);
s1.setSize(200,200);
}


}//end class


and


the server code is:
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JOptionPane.*;

public class synergyserver
{
private ServerSocket server;
private int port = 4444;


public synergyserver()
{
try {
server = new ServerSocket(port,14);
} catch (IOException e)
{
e.printStackTrace();
}
}

public static void main(String[] args)
{
synergyserver example = new synergyserver();
example.handleConnection();
}

public void handleConnection()
{
System.out.println("Waiting for client message...");

//
// The server do a loop here to accept all connection initiated by the
// client application.
//
while (true)
{
try {
Socket socket = server.accept();
new ConnectionHandler(socket);
} catch (IOException e)
{
e.printStackTrace();
}
}
}
}

class ConnectionHandler implements Runnable
{
private Socket socket;
ObjectInputStream din;
ObjectOutputStream dout;
//DataOutputStream dout;
//DataInputStream din;

public ConnectionHandler(Socket socket)
{
this.socket = socket;

Thread t = new Thread(this);
t.start();
}

public void run() {
try
{
//
// Read a message sent by client application
//
// ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
din=new ObjectInputStream(socket.getInputStream());
// String message1 = (String) din.readUTF();
//System.out.println("Message Received: " + message1);

while(true)
{

String message = (String) din.readObject();
System.out.println("Message Received: " + message);

//
// Send a response to the client application
// ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
dout=new ObjectOutputStream(socket.getOutputStream());

//dout.writeUTF("Hi...");

//din.close();
//dout.close();
//socket.close();
}

//System.out.println("Waiting for client message...");
} catch (Exception e54545)
{
System.out.println("kjhkjhkjhkjhkjh"+e54545);
//e.printStackTrace();
}
//catch (ClassNotFoundException e)
//{
//e.printStackTrace();
//}
}
}


well this was just the demo program i was trying if it works well i can move further..plz help me...

[mrmatt1111]

Hard to read your code without code tags [ c o d e ] [ / c o d e] (no spaces)

Can you give more info on exactly where you are getting the null exception?

[sanjeevbindroo]

well i m having problem with the ObjectOutputStream,when i use writeObject..well here is where i get the problem
i have a button "send" and when i click on that the program should send the message from textfield to server..
m storing the text from textfield to String and then i m sending it via ObjectOutputStream


and the exact problem is here:
if(ae.getSource()==B || ae.getSource()==tf)//if i click button B or press enter
{ String s1=tf.getText();

try
{
//out.writeObject("hhh");

if(s1.equals(""))
JOptionPane.showMessageDialog(null,"enter valid text");
else
{
ta.append("\nME:\t"+s1);
System.out.println(s1);
tf.setText("");
System.out.println(s1);
out.writeObject(s1);//here is where i get exception
//out.flush();
}
}catch(Exception e3)
{
JOptionPane.showMessageDialog(null,"The other System is not reachable.\n Try later");
System.out.println("33"+e3); }


now can u suggest anything..
waiting for ur reply..

[sanjeevbindroo]

hey i wrote a different code and its working fine for that but the problem still persists with multithreaded server.....