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Applet Hangs when submitting data to servlet

 
 
ILPTAB
Guest
Posts: n/a
 
      08-31-2007
I am currently supporting an interactive web site for a state agency.
Recently we started getting reports from SOME of the users that the
applet hangs when they attempt to submit data to the servlet running
on our web server. We have not made any changes to the java code so
the only thing I can figure is that it must be happening as a result
of an update to the java JRE or Windows. Note that I said it's
occurring with SOME of the users. Other people seem to be having no
problem at all with it.

To help illustrate the problem, I put together a small test server and
applet that demonstrates the problem. I have included the source code
for both parts below. On the applet side, it hangs when it comes to a
line that attempts to instantiate the ObjectInputStream class and
retrieve the input stream from the applet.

ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());

Since the applet locks up, I am unable to give you any error messages
in the java console. In fact the browser gets so locked up that it
requires the user to close the session from the Windows task manager.

On the Servlet side it hangs at the line that attempts to read the
data stream from the socket connection.

sSearchField_ = in.readLine();

The error messages generated at the server are as follows:

Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)

at ServerSide.run(ServerSide.java.9

at jave.lang.thread.run(Unkown Source)


Any help in resolving this problem would be greatly appricated.

Thank you.



Here is the source code for both the Servlet and the applet.


/* Class Name: AppletSide.java

Copyright 2007 Steve Rulison

Version 1.0.0

Purpose: This java applet will display relevent information
pertaining to
this examplet
*/

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.event.ListSelectionListener;
import javax.swing.event.ListSelectionEvent;
import javax.swing.table.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

import java.io.*;
import java.util.*;
import java.net.*;
import java.lang.*;

public class AppletSide extends JApplet
implements ActionListener, KeyListener, MouseListener, Serializable
{
private static final long serialVersionUID = 1;

private JButton theSubmitButton_, theClearButton_;
private Socket s;
private String host, ServerName_;
private TestData td;
private JPanel appletPanel, resultPanel, buttonPanel,
socketPanel, headingPanel;
private Font f1 = new Font("Sansserf", Font.BOLD, 2;

private JLabel socketConnectionLabel = new JLabel("");
private JTextField resultField1, resultField2, resultField3,
resultField4, resultField5;

private java.awt.List inquirylist;

//Constructor
public AppletSide()
{
headingPanel = new JPanel();
headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

//Initialize String variables for output.
searchSetup();
}//Constructor

public void init()
{
// Note: The getCodeBase().getHost() methods must be invoked from
the
// init() method.
ServerName_ = getCodeBase().getHost();
System.out.println(ServerName_);

System.out.println("Test Applet Version");
}//End of init.

//Establish a socket connection with the server.
private boolean createSocket(String pServerName)
{
boolean SocketConnectSuccessful = false;
try
{
int iPort = 554;
s = new Socket(pServerName, iPort);
SocketConnectSuccessful = true;
socketConnectionLabel.setText("Socket connection successfully
established with host " + pServerName + " on port " + iPort);
socketPanel.validate();
}
catch(Exception e)
{
e.printStackTrace(System.err);
System.out.println(e);
SocketConnectSuccessful = false;
socketConnectionRefused();
}//End of catch block.
return SocketConnectSuccessful;
}//End of method createSocket.

//This method is called when a socket connection could not be
established.
private void socketConnectionRefused()
{
socketConnectionLabel.setText("Unable to establish a connection with
host. Please contact you network administrator.");
socketPanel.validate();
}//End of method socketConnectionRefused.

//Setup search Inquiry labels.
private void searchSetup()
{
setLayout(new BorderLayout());

appletPanel = new JPanel();
appletPanel.setLayout(new GridLayout(0,1));


JLabel titleLabel = new JLabel("Test Page");
titleLabel.setFont(f1);
titleLabel.setForeground(Color.black);

headingPanel.add(titleLabel);
appletPanel.add(headingPanel);

JPanel inquiryPanel = new JPanel();
inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));

JLabel inquiryLabel = new JLabel("Make Selection: ");
inquiryPanel.add(inquiryLabel);

inquirylist = new java.awt.List();
inquirylist.add("Test 1");
inquirylist.add("Test 2");
inquirylist.add("Test 3");
inquirylist.select(0);

inquiryPanel.add(inquirylist);

appletPanel.add(inquiryPanel);

resultSetup();

socketPanel = new JPanel();
socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
socketPanel.add(socketConnectionLabel);
appletPanel.add(socketPanel);


buttonPanel = new JPanel();
buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

theSubmitButton_ = new JButton("Submit");
theSubmitButton_.addActionListener(this);
theSubmitButton_.addKeyListener(this);

buttonPanel.add(theSubmitButton_);
theClearButton_ = new JButton("Clear");
theClearButton_.addActionListener(this);
theClearButton_.addKeyListener(this);
buttonPanel.add(theClearButton_);
appletPanel.add(buttonPanel);

add(BorderLayout.CENTER, appletPanel);

}//End of method searchLabelSetup.

//Setup result labels.
private void resultSetup()
{
resultPanel = new JPanel();
resultPanel.setLayout(new GridLayout(5,2));

JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);

resultField1 = new JTextField("Default value 1", 5);
resultField1.setEditable(false);
resultField2 = new JTextField("Default value 2 ",5);
resultField2.setEditable(false);
resultField3 = new JTextField("Default value 3",5);
resultField3.setEditable(false);
resultField4 = new JTextField("Default value 4",5);
resultField4.setEditable(false);
resultField5 = new JTextField("Default value 5",5);
resultField5.setEditable(false);

resultPanel.add(resultLabel1);
resultPanel.add(resultField1);
resultPanel.add(resultLabel2);
resultPanel.add(resultField2);
resultPanel.add(resultLabel3);
resultPanel.add(resultField3);
resultPanel.add(resultLabel4);
resultPanel.add(resultField4);
resultPanel.add(resultLabel5);
resultPanel.add(resultField5);

appletPanel.add(resultPanel);

}//End of method resultLabelSetup.

// Display the fields that have been populated with data received
from the
// server application.
private void displayResults()
{
resultField1.setText(td.sField_1);
resultField2.setText(td.sField_2);
resultField3.setText(td.sField_3);
resultField4.setText(td.sField_4);
resultField5.setText(td.sField_5);
resultPanel.validate();
}//End of method displayResults.

//Clears fields of data
private void clearFields()
{
resultField1.setText("Default value 1");
resultField2.setText("Default value 2");
resultField3.setText("Default value 3");
resultField4.setText("Default value 4");
resultField5.setText("Default value 5");
resultPanel.validate();
inquirylist.select(0);
}//End of method clearFields.

//Reset the applet to allow the user to perform a new search.
private void resetSearch()
{
this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
clearFields();
createSocket(ServerName_);
this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
}//End of method resetSearch.

//Perform Input/Output operations with the server.
private void serverIO()
{
this.setCursor(new Cursor(Cursor.WAIT_CURSOR));

try
{
PrintWriter out =
new PrintWriter(
new BufferedWriter(
new OutputStreamWriter(
s.getOutputStream())),true);


System.out.println("Check point 1 @ serverIO method.");
out.println(inquirylist.getItem(inquirylist.getSel ectedIndex()));
// Thread.currentThread().sleep(5000);
System.out.println("Check point 2 @ serverIO method.");
//Read data back from server - Inputstream
ObjectInputStream inObj = new
ObjectInputStream(s.getInputStream());
System.out.println("Check point 3 @ serverIO method.");
out.flush();
System.out.println("Check point 4 @ serverIO method.");

td = (TestData) inObj.readObject();

s.close();
if(td.bRecFound)
displayResults();
else
resetSearch();
}
catch(Exception e)
{
System.out.println("Check point 1 - Exception: " + e);

}//End of try/catch block

this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
}//End of method ServerIO


//Event handling method.
public void actionPerformed(ActionEvent evt)
{
if(evt.getSource() == theClearButton_)
{
clearFields();
repaint();
}
else if(evt.getSource() == theSubmitButton_)
{
if(createSocket(ServerName_))
{
System.getSecurityManager();

// searchLabelSetup();
validate();
System.out.println(s.getInetAddress());
serverIO();
repaint();
}
else
socketConnectionRefused();
}
}//End of method actionPerformed


//Methodsfor handling for keyboard events
public void keyPressed(KeyEvent evt){}
public void keyReleased(KeyEvent evt){}
public void keyTyped(KeyEvent evt)
{
// System.out.println(" " + (int)evt.getKeyChar() );

if(evt.getSource() == theClearButton_)
{
clearFields();
repaint();
}
else if(evt.getSource() == theSubmitButton_)
{
serverIO();
repaint();
}
}//End of method keyTyped.

public void mouseClicked(MouseEvent evt)
{
if(evt.getClickCount() == 2)
{
}
}
public void mouseExited(MouseEvent event){}
public void mouseEntered(MouseEvent event){}
public void mouseReleased(MouseEvent event){}
public void mousePressed(MouseEvent event){}

}//End of class ApplSide.

class TestData implements Serializable
{
private static final long serialVersionUID = 1;

/* Test Data */
public String sField_1, sField_2, sField_3, sField_4, sField_5;
public boolean bRecFound;

//Constructor
TestData()
{}
}//End of class ServerTestData.

- - - - - - - - - - - - - - - - -
- - - -

/* Class name: ServerSide

Author: Steven Rulison

Purpose: Demonstrate the servlet side
*/

import java.io.*;
import java.util.*;
import java.net.*;

public class ServerSide extends Thread
{
private TestData td;
private Socket s;
private String sSearchField_;

public static void main(String[] Args)
{
try
{
ServerSocket ss = new ServerSocket(554);

int spawnCnt = 0;
while(true)
{
Socket s = ss.accept();

++spawnCnt;
System.out.println("Spawning " + spawnCnt);


Thread servSide = new Thread(new ServerSide(s), "serverside");
servSide.start();
}
}catch(IOException e)
{
e.printStackTrace(System.err);
}
}//End of main.


//Constructor.
public ServerSide(Socket s_)
{
s = s_;
}//End of Constructor.


private void testLookup(String sSearch)
{
td = new TestData();
td.bRecFound = true;
if(sSearch.trim().equals("Test 1"))
{
td.sField_1 = "Alpha";
td.sField_2 = "Beta";
td.sField_3 = "Gamma";
td.sField_4 = "Delta";
td.sField_5 = "Epsilon";
}
else if(sSearch.trim().equals("Test 2"))
{
td.sField_1 = "AAA";
td.sField_2 = "BBB";
td.sField_3 = "CCC";
td.sField_4 = "DDDD";
td.sField_5 = "EEEE";
}
else if(sSearch.trim().equals("Test 3"))
{
td.sField_1 = "111";
td.sField_2 = "222";
td.sField_3 = "333";
td.sField_4 = "444";
td.sField_5 = "555";
}
}// End of method testLookup.

public void run()
{
try
{
//Setup Input Stream.
BufferedReader in =
new BufferedReader( new InputStreamReader(s.getInputStream()));

// Setup output Stream.
ObjectOutputStream ObjOut = new
ObjectOutputStream(s.getOutputStream());

//Perform intial read...
sSearchField_ = in.readLine();

Thread.currentThread().sleep(5000);

System.out.println("The sSearchField_ variable = " + sSearchField_);

testLookup(sSearchField_);

ObjOut.writeObject(td);
ObjOut.flush();
ObjOut.close();

s.close();
}
catch(Exception e)
{
e.printStackTrace(System.err);
}
}//End of run method
}//End of ServerSide class...


/*
This is the class template that will be used to create the object
that will
be passed through to the ObjectInput/Output - stream to the lookup
applet.
*/
class TestData implements Serializable
{
private static final long serialVersionUID = 1;

/* Test Data */
public String sField_1, sField_2, sField_3, sField_4, sField_5;
public boolean bRecFound;

//Constructor
TestData()
{}

}//End of class ServerTestData.

 
Reply With Quote
 
 
 
 
Knute Johnson
Guest
Posts: n/a
 
      08-31-2007
ILPTAB wrote:
> I am currently supporting an interactive web site for a state agency.
> Recently we started getting reports from SOME of the users that the
> applet hangs when they attempt to submit data to the servlet running
> on our web server. We have not made any changes to the java code so
> the only thing I can figure is that it must be happening as a result
> of an update to the java JRE or Windows. Note that I said it's
> occurring with SOME of the users. Other people seem to be having no
> problem at all with it.
>
> To help illustrate the problem, I put together a small test server and
> applet that demonstrates the problem. I have included the source code
> for both parts below. On the applet side, it hangs when it comes to a
> line that attempts to instantiate the ObjectInputStream class and
> retrieve the input stream from the applet.
>
> ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());
>
> Since the applet locks up, I am unable to give you any error messages
> in the java console. In fact the browser gets so locked up that it
> requires the user to close the session from the Windows task manager.
>
> On the Servlet side it hangs at the line that attempts to read the
> data stream from the socket connection.
>
> sSearchField_ = in.readLine();
>
> The error messages generated at the server are as follows:
>
> Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)
>
> at ServerSide.run(ServerSide.java.9
>
> at jave.lang.thread.run(Unkown Source)
>
>
> Any help in resolving this problem would be greatly appricated.
>
> Thank you.
>
>
>
> Here is the source code for both the Servlet and the applet.
>
>
> /* Class Name: AppletSide.java
>
> Copyright 2007 Steve Rulison
>
> Version 1.0.0
>
> Purpose: This java applet will display relevent information
> pertaining to
> this examplet
> */
>
> import javax.swing.*;
> import javax.swing.event.*;
> import javax.swing.event.ListSelectionListener;
> import javax.swing.event.ListSelectionEvent;
> import javax.swing.table.*;
> import java.awt.*;
> import java.awt.event.*;
> import java.applet.*;
>
> import java.io.*;
> import java.util.*;
> import java.net.*;
> import java.lang.*;
>
> public class AppletSide extends JApplet
> implements ActionListener, KeyListener, MouseListener, Serializable
> {
> private static final long serialVersionUID = 1;
>
> private JButton theSubmitButton_, theClearButton_;
> private Socket s;
> private String host, ServerName_;
> private TestData td;
> private JPanel appletPanel, resultPanel, buttonPanel,
> socketPanel, headingPanel;
> private Font f1 = new Font("Sansserf", Font.BOLD, 2;
>
> private JLabel socketConnectionLabel = new JLabel("");
> private JTextField resultField1, resultField2, resultField3,
> resultField4, resultField5;
>
> private java.awt.List inquirylist;
>
> //Constructor
> public AppletSide()
> {
> headingPanel = new JPanel();
> headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
>
> //Initialize String variables for output.
> searchSetup();
> }//Constructor
>
> public void init()
> {
> // Note: The getCodeBase().getHost() methods must be invoked from
> the
> // init() method.
> ServerName_ = getCodeBase().getHost();
> System.out.println(ServerName_);
>
> System.out.println("Test Applet Version");
> }//End of init.
>
> //Establish a socket connection with the server.
> private boolean createSocket(String pServerName)
> {
> boolean SocketConnectSuccessful = false;
> try
> {
> int iPort = 554;
> s = new Socket(pServerName, iPort);
> SocketConnectSuccessful = true;
> socketConnectionLabel.setText("Socket connection successfully
> established with host " + pServerName + " on port " + iPort);
> socketPanel.validate();
> }
> catch(Exception e)
> {
> e.printStackTrace(System.err);
> System.out.println(e);
> SocketConnectSuccessful = false;
> socketConnectionRefused();
> }//End of catch block.
> return SocketConnectSuccessful;
> }//End of method createSocket.
>
> //This method is called when a socket connection could not be
> established.
> private void socketConnectionRefused()
> {
> socketConnectionLabel.setText("Unable to establish a connection with
> host. Please contact you network administrator.");
> socketPanel.validate();
> }//End of method socketConnectionRefused.
>
> //Setup search Inquiry labels.
> private void searchSetup()
> {
> setLayout(new BorderLayout());
>
> appletPanel = new JPanel();
> appletPanel.setLayout(new GridLayout(0,1));
>
>
> JLabel titleLabel = new JLabel("Test Page");
> titleLabel.setFont(f1);
> titleLabel.setForeground(Color.black);
>
> headingPanel.add(titleLabel);
> appletPanel.add(headingPanel);
>
> JPanel inquiryPanel = new JPanel();
> inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
>
> JLabel inquiryLabel = new JLabel("Make Selection: ");
> inquiryPanel.add(inquiryLabel);
>
> inquirylist = new java.awt.List();
> inquirylist.add("Test 1");
> inquirylist.add("Test 2");
> inquirylist.add("Test 3");
> inquirylist.select(0);
>
> inquiryPanel.add(inquirylist);
>
> appletPanel.add(inquiryPanel);
>
> resultSetup();
>
> socketPanel = new JPanel();
> socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
> socketPanel.add(socketConnectionLabel);
> appletPanel.add(socketPanel);
>
>
> buttonPanel = new JPanel();
> buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
>
> theSubmitButton_ = new JButton("Submit");
> theSubmitButton_.addActionListener(this);
> theSubmitButton_.addKeyListener(this);
>
> buttonPanel.add(theSubmitButton_);
> theClearButton_ = new JButton("Clear");
> theClearButton_.addActionListener(this);
> theClearButton_.addKeyListener(this);
> buttonPanel.add(theClearButton_);
> appletPanel.add(buttonPanel);
>
> add(BorderLayout.CENTER, appletPanel);
>
> }//End of method searchLabelSetup.
>
> //Setup result labels.
> private void resultSetup()
> {
> resultPanel = new JPanel();
> resultPanel.setLayout(new GridLayout(5,2));
>
> JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
> JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
> JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
> JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
> JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);
>
> resultField1 = new JTextField("Default value 1", 5);
> resultField1.setEditable(false);
> resultField2 = new JTextField("Default value 2 ",5);
> resultField2.setEditable(false);
> resultField3 = new JTextField("Default value 3",5);
> resultField3.setEditable(false);
> resultField4 = new JTextField("Default value 4",5);
> resultField4.setEditable(false);
> resultField5 = new JTextField("Default value 5",5);
> resultField5.setEditable(false);
>
> resultPanel.add(resultLabel1);
> resultPanel.add(resultField1);
> resultPanel.add(resultLabel2);
> resultPanel.add(resultField2);
> resultPanel.add(resultLabel3);
> resultPanel.add(resultField3);
> resultPanel.add(resultLabel4);
> resultPanel.add(resultField4);
> resultPanel.add(resultLabel5);
> resultPanel.add(resultField5);
>
> appletPanel.add(resultPanel);
>
> }//End of method resultLabelSetup.
>
> // Display the fields that have been populated with data received
> from the
> // server application.
> private void displayResults()
> {
> resultField1.setText(td.sField_1);
> resultField2.setText(td.sField_2);
> resultField3.setText(td.sField_3);
> resultField4.setText(td.sField_4);
> resultField5.setText(td.sField_5);
> resultPanel.validate();
> }//End of method displayResults.
>
> //Clears fields of data
> private void clearFields()
> {
> resultField1.setText("Default value 1");
> resultField2.setText("Default value 2");
> resultField3.setText("Default value 3");
> resultField4.setText("Default value 4");
> resultField5.setText("Default value 5");
> resultPanel.validate();
> inquirylist.select(0);
> }//End of method clearFields.
>
> //Reset the applet to allow the user to perform a new search.
> private void resetSearch()
> {
> this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
> clearFields();
> createSocket(ServerName_);
> this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
> }//End of method resetSearch.
>
> //Perform Input/Output operations with the server.
> private void serverIO()
> {
> this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
>
> try
> {
> PrintWriter out =
> new PrintWriter(
> new BufferedWriter(
> new OutputStreamWriter(
> s.getOutputStream())),true);
>
>
> System.out.println("Check point 1 @ serverIO method.");
> out.println(inquirylist.getItem(inquirylist.getSel ectedIndex()));
> // Thread.currentThread().sleep(5000);
> System.out.println("Check point 2 @ serverIO method.");
> //Read data back from server - Inputstream
> ObjectInputStream inObj = new
> ObjectInputStream(s.getInputStream());
> System.out.println("Check point 3 @ serverIO method.");
> out.flush();
> System.out.println("Check point 4 @ serverIO method.");
>
> td = (TestData) inObj.readObject();
>
> s.close();
> if(td.bRecFound)
> displayResults();
> else
> resetSearch();
> }
> catch(Exception e)
> {
> System.out.println("Check point 1 - Exception: " + e);
>
> }//End of try/catch block
>
> this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
> }//End of method ServerIO
>
>
> //Event handling method.
> public void actionPerformed(ActionEvent evt)
> {
> if(evt.getSource() == theClearButton_)
> {
> clearFields();
> repaint();
> }
> else if(evt.getSource() == theSubmitButton_)
> {
> if(createSocket(ServerName_))
> {
> System.getSecurityManager();
>
> // searchLabelSetup();
> validate();
> System.out.println(s.getInetAddress());
> serverIO();
> repaint();
> }
> else
> socketConnectionRefused();
> }
> }//End of method actionPerformed
>
>
> //Methodsfor handling for keyboard events
> public void keyPressed(KeyEvent evt){}
> public void keyReleased(KeyEvent evt){}
> public void keyTyped(KeyEvent evt)
> {
> // System.out.println(" " + (int)evt.getKeyChar() );
>
> if(evt.getSource() == theClearButton_)
> {
> clearFields();
> repaint();
> }
> else if(evt.getSource() == theSubmitButton_)
> {
> serverIO();
> repaint();
> }
> }//End of method keyTyped.
>
> public void mouseClicked(MouseEvent evt)
> {
> if(evt.getClickCount() == 2)
> {
> }
> }
> public void mouseExited(MouseEvent event){}
> public void mouseEntered(MouseEvent event){}
> public void mouseReleased(MouseEvent event){}
> public void mousePressed(MouseEvent event){}
>
> }//End of class ApplSide.
>
> class TestData implements Serializable
> {
> private static final long serialVersionUID = 1;
>
> /* Test Data */
> public String sField_1, sField_2, sField_3, sField_4, sField_5;
> public boolean bRecFound;
>
> //Constructor
> TestData()
> {}
> }//End of class ServerTestData.
>
> - - - - - - - - - - - - - - - - -
> - - - -
>
> /* Class name: ServerSide
>
> Author: Steven Rulison
>
> Purpose: Demonstrate the servlet side
> */
>
> import java.io.*;
> import java.util.*;
> import java.net.*;
>
> public class ServerSide extends Thread
> {
> private TestData td;
> private Socket s;
> private String sSearchField_;
>
> public static void main(String[] Args)
> {
> try
> {
> ServerSocket ss = new ServerSocket(554);
>
> int spawnCnt = 0;
> while(true)
> {
> Socket s = ss.accept();
>
> ++spawnCnt;
> System.out.println("Spawning " + spawnCnt);
>
>
> Thread servSide = new Thread(new ServerSide(s), "serverside");
> servSide.start();
> }
> }catch(IOException e)
> {
> e.printStackTrace(System.err);
> }
> }//End of main.
>
>
> //Constructor.
> public ServerSide(Socket s_)
> {
> s = s_;
> }//End of Constructor.
>
>
> private void testLookup(String sSearch)
> {
> td = new TestData();
> td.bRecFound = true;
> if(sSearch.trim().equals("Test 1"))
> {
> td.sField_1 = "Alpha";
> td.sField_2 = "Beta";
> td.sField_3 = "Gamma";
> td.sField_4 = "Delta";
> td.sField_5 = "Epsilon";
> }
> else if(sSearch.trim().equals("Test 2"))
> {
> td.sField_1 = "AAA";
> td.sField_2 = "BBB";
> td.sField_3 = "CCC";
> td.sField_4 = "DDDD";
> td.sField_5 = "EEEE";
> }
> else if(sSearch.trim().equals("Test 3"))
> {
> td.sField_1 = "111";
> td.sField_2 = "222";
> td.sField_3 = "333";
> td.sField_4 = "444";
> td.sField_5 = "555";
> }
> }// End of method testLookup.
>
> public void run()
> {
> try
> {
> //Setup Input Stream.
> BufferedReader in =
> new BufferedReader( new InputStreamReader(s.getInputStream()));
>
> // Setup output Stream.
> ObjectOutputStream ObjOut = new
> ObjectOutputStream(s.getOutputStream());
>
> //Perform intial read...
> sSearchField_ = in.readLine();
>
> Thread.currentThread().sleep(5000);
>
> System.out.println("The sSearchField_ variable = " + sSearchField_);
>
> testLookup(sSearchField_);
>
> ObjOut.writeObject(td);
> ObjOut.flush();
> ObjOut.close();
>
> s.close();
> }
> catch(Exception e)
> {
> e.printStackTrace(System.err);
> }
> }//End of run method
> }//End of ServerSide class...
>
>
> /*
> This is the class template that will be used to create the object
> that will
> be passed through to the ObjectInput/Output - stream to the lookup
> applet.
> */
> class TestData implements Serializable
> {
> private static final long serialVersionUID = 1;
>
> /* Test Data */
> public String sField_1, sField_2, sField_3, sField_4, sField_5;
> public boolean bRecFound;
>
> //Constructor
> TestData()
> {}
>
> }//End of class ServerTestData.
>


I have seen similar problems with applications. I cannot duplicate the
problem and it only happens once in a while. I'm getting socket I/O
hangs not just with ObjectOutputStream/InputStreams but with binary I/O
too. It started for me in May or June on an application that had been
running for over a year with no problems. It lasted several weeks and I
hadn't seen it again until about a week ago. That could be just
coincidence though. The computers I'm using are not being updated so I
don't think that is the problem.

The socket did not time out and I created another timer that closed the
socket if it was still open and that didn't work. I'm at a loss as to
what is happening and don't really know where to look. My client is not
very happy with me at the moment.

--

Knute Johnson
email s/nospam/knute/
 
Reply With Quote
 
 
 
 
Richard Maher
Guest
Posts: n/a
 
      09-01-2007
Hi,

I don't know what is causing the hang but FWIW I use the following Timeouts
to put a time limit on my socket connections and socket reads. At least then
you be able to identify which read isn't being satisfied and track down what
happened to the writer.

t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);

: : :

public void setTimeout(int msecs) throws UnknownHostException, IOException
{
t3Sock.setSoTimeout(msecs);
}

Cheers Richard Maher

"ILPTAB" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
I am currently supporting an interactive web site for a state agency.
Recently we started getting reports from SOME of the users that the
applet hangs when they attempt to submit data to the servlet running
on our web server. We have not made any changes to the java code so
the only thing I can figure is that it must be happening as a result
of an update to the java JRE or Windows. Note that I said it's
occurring with SOME of the users. Other people seem to be having no
problem at all with it.

To help illustrate the problem, I put together a small test server and
applet that demonstrates the problem. I have included the source code
for both parts below. On the applet side, it hangs when it comes to a
line that attempts to instantiate the ObjectInputStream class and
retrieve the input stream from the applet.

ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());

Since the applet locks up, I am unable to give you any error messages
in the java console. In fact the browser gets so locked up that it
requires the user to close the session from the Windows task manager.

On the Servlet side it hangs at the line that attempts to read the
data stream from the socket connection.

sSearchField_ = in.readLine();

The error messages generated at the server are as follows:

Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)

at ServerSide.run(ServerSide.java.9

at jave.lang.thread.run(Unkown Source)


Any help in resolving this problem would be greatly appricated.

Thank you.



Here is the source code for both the Servlet and the applet.


/* Class Name: AppletSide.java

Copyright 2007 Steve Rulison

Version 1.0.0

Purpose: This java applet will display relevent information
pertaining to
this examplet
*/

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.event.ListSelectionListener;
import javax.swing.event.ListSelectionEvent;
import javax.swing.table.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

import java.io.*;
import java.util.*;
import java.net.*;
import java.lang.*;

public class AppletSide extends JApplet
implements ActionListener, KeyListener, MouseListener, Serializable
{
private static final long serialVersionUID = 1;

private JButton theSubmitButton_, theClearButton_;
private Socket s;
private String host, ServerName_;
private TestData td;
private JPanel appletPanel, resultPanel, buttonPanel,
socketPanel, headingPanel;
private Font f1 = new Font("Sansserf", Font.BOLD, 2;

private JLabel socketConnectionLabel = new JLabel("");
private JTextField resultField1, resultField2, resultField3,
resultField4, resultField5;

private java.awt.List inquirylist;

//Constructor
public AppletSide()
{
headingPanel = new JPanel();
headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

//Initialize String variables for output.
searchSetup();
}//Constructor

public void init()
{
// Note: The getCodeBase().getHost() methods must be invoked from
the
// init() method.
ServerName_ = getCodeBase().getHost();
System.out.println(ServerName_);

System.out.println("Test Applet Version");
}//End of init.

//Establish a socket connection with the server.
private boolean createSocket(String pServerName)
{
boolean SocketConnectSuccessful = false;
try
{
int iPort = 554;
s = new Socket(pServerName, iPort);
SocketConnectSuccessful = true;
socketConnectionLabel.setText("Socket connection successfully
established with host " + pServerName + " on port " + iPort);
socketPanel.validate();
}
catch(Exception e)
{
e.printStackTrace(System.err);
System.out.println(e);
SocketConnectSuccessful = false;
socketConnectionRefused();
}//End of catch block.
return SocketConnectSuccessful;
}//End of method createSocket.

//This method is called when a socket connection could not be
established.
private void socketConnectionRefused()
{
socketConnectionLabel.setText("Unable to establish a connection with
host. Please contact you network administrator.");
socketPanel.validate();
}//End of method socketConnectionRefused.

//Setup search Inquiry labels.
private void searchSetup()
{
setLayout(new BorderLayout());

appletPanel = new JPanel();
appletPanel.setLayout(new GridLayout(0,1));


JLabel titleLabel = new JLabel("Test Page");
titleLabel.setFont(f1);
titleLabel.setForeground(Color.black);

headingPanel.add(titleLabel);
appletPanel.add(headingPanel);

JPanel inquiryPanel = new JPanel();
inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));

JLabel inquiryLabel = new JLabel("Make Selection: ");
inquiryPanel.add(inquiryLabel);

inquirylist = new java.awt.List();
inquirylist.add("Test 1");
inquirylist.add("Test 2");
inquirylist.add("Test 3");
inquirylist.select(0);

inquiryPanel.add(inquirylist);

appletPanel.add(inquiryPanel);

resultSetup();

socketPanel = new JPanel();
socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
socketPanel.add(socketConnectionLabel);
appletPanel.add(socketPanel);


buttonPanel = new JPanel();
buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

theSubmitButton_ = new JButton("Submit");
theSubmitButton_.addActionListener(this);
theSubmitButton_.addKeyListener(this);

buttonPanel.add(theSubmitButton_);
theClearButton_ = new JButton("Clear");
theClearButton_.addActionListener(this);
theClearButton_.addKeyListener(this);
buttonPanel.add(theClearButton_);
appletPanel.add(buttonPanel);

add(BorderLayout.CENTER, appletPanel);

}//End of method searchLabelSetup.

//Setup result labels.
private void resultSetup()
{
resultPanel = new JPanel();
resultPanel.setLayout(new GridLayout(5,2));

JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);

resultField1 = new JTextField("Default value 1", 5);
resultField1.setEditable(false);
resultField2 = new JTextField("Default value 2 ",5);
resultField2.setEditable(false);
resultField3 = new JTextField("Default value 3",5);
resultField3.setEditable(false);
resultField4 = new JTextField("Default value 4",5);
resultField4.setEditable(false);
resultField5 = new JTextField("Default value 5",5);
resultField5.setEditable(false);

resultPanel.add(resultLabel1);
resultPanel.add(resultField1);
resultPanel.add(resultLabel2);
resultPanel.add(resultField2);
resultPanel.add(resultLabel3);
resultPanel.add(resultField3);
resultPanel.add(resultLabel4);
resultPanel.add(resultField4);
resultPanel.add(resultLabel5);
resultPanel.add(resultField5);

appletPanel.add(resultPanel);

}//End of method resultLabelSetup.

// Display the fields that have been populated with data received
from the
// server application.
private void displayResults()
{
resultField1.setText(td.sField_1);
resultField2.setText(td.sField_2);
resultField3.setText(td.sField_3);
resultField4.setText(td.sField_4);
resultField5.setText(td.sField_5);
resultPanel.validate();
}//End of method displayResults.

//Clears fields of data
private void clearFields()
{
resultField1.setText("Default value 1");
resultField2.setText("Default value 2");
resultField3.setText("Default value 3");
resultField4.setText("Default value 4");
resultField5.setText("Default value 5");
resultPanel.validate();
inquirylist.select(0);
}//End of method clearFields.

//Reset the applet to allow the user to perform a new search.
private void resetSearch()
{
this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
clearFields();
createSocket(ServerName_);
this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
}//End of method resetSearch.

//Perform Input/Output operations with the server.
private void serverIO()
{
this.setCursor(new Cursor(Cursor.WAIT_CURSOR));

try
{
PrintWriter out =
new PrintWriter(
new BufferedWriter(
new OutputStreamWriter(
s.getOutputStream())),true);


System.out.println("Check point 1 @ serverIO method.");
out.println(inquirylist.getItem(inquirylist.getSel ectedIndex()));
// Thread.currentThread().sleep(5000);
System.out.println("Check point 2 @ serverIO method.");
//Read data back from server - Inputstream
ObjectInputStream inObj = new
ObjectInputStream(s.getInputStream());
System.out.println("Check point 3 @ serverIO method.");
out.flush();
System.out.println("Check point 4 @ serverIO method.");

td = (TestData) inObj.readObject();

s.close();
if(td.bRecFound)
displayResults();
else
resetSearch();
}
catch(Exception e)
{
System.out.println("Check point 1 - Exception: " + e);

}//End of try/catch block

this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
}//End of method ServerIO


//Event handling method.
public void actionPerformed(ActionEvent evt)
{
if(evt.getSource() == theClearButton_)
{
clearFields();
repaint();
}
else if(evt.getSource() == theSubmitButton_)
{
if(createSocket(ServerName_))
{
System.getSecurityManager();

// searchLabelSetup();
validate();
System.out.println(s.getInetAddress());
serverIO();
repaint();
}
else
socketConnectionRefused();
}
}//End of method actionPerformed


//Methodsfor handling for keyboard events
public void keyPressed(KeyEvent evt){}
public void keyReleased(KeyEvent evt){}
public void keyTyped(KeyEvent evt)
{
// System.out.println(" " + (int)evt.getKeyChar() );

if(evt.getSource() == theClearButton_)
{
clearFields();
repaint();
}
else if(evt.getSource() == theSubmitButton_)
{
serverIO();
repaint();
}
}//End of method keyTyped.

public void mouseClicked(MouseEvent evt)
{
if(evt.getClickCount() == 2)
{
}
}
public void mouseExited(MouseEvent event){}
public void mouseEntered(MouseEvent event){}
public void mouseReleased(MouseEvent event){}
public void mousePressed(MouseEvent event){}

}//End of class ApplSide.

class TestData implements Serializable
{
private static final long serialVersionUID = 1;

/* Test Data */
public String sField_1, sField_2, sField_3, sField_4, sField_5;
public boolean bRecFound;

//Constructor
TestData()
{}
}//End of class ServerTestData.

- - - - - - - - - - - - - - - - -
- - - -

/* Class name: ServerSide

Author: Steven Rulison

Purpose: Demonstrate the servlet side
*/

import java.io.*;
import java.util.*;
import java.net.*;

public class ServerSide extends Thread
{
private TestData td;
private Socket s;
private String sSearchField_;

public static void main(String[] Args)
{
try
{
ServerSocket ss = new ServerSocket(554);

int spawnCnt = 0;
while(true)
{
Socket s = ss.accept();

++spawnCnt;
System.out.println("Spawning " + spawnCnt);


Thread servSide = new Thread(new ServerSide(s), "serverside");
servSide.start();
}
}catch(IOException e)
{
e.printStackTrace(System.err);
}
}//End of main.


//Constructor.
public ServerSide(Socket s_)
{
s = s_;
}//End of Constructor.


private void testLookup(String sSearch)
{
td = new TestData();
td.bRecFound = true;
if(sSearch.trim().equals("Test 1"))
{
td.sField_1 = "Alpha";
td.sField_2 = "Beta";
td.sField_3 = "Gamma";
td.sField_4 = "Delta";
td.sField_5 = "Epsilon";
}
else if(sSearch.trim().equals("Test 2"))
{
td.sField_1 = "AAA";
td.sField_2 = "BBB";
td.sField_3 = "CCC";
td.sField_4 = "DDDD";
td.sField_5 = "EEEE";
}
else if(sSearch.trim().equals("Test 3"))
{
td.sField_1 = "111";
td.sField_2 = "222";
td.sField_3 = "333";
td.sField_4 = "444";
td.sField_5 = "555";
}
}// End of method testLookup.

public void run()
{
try
{
//Setup Input Stream.
BufferedReader in =
new BufferedReader( new InputStreamReader(s.getInputStream()));

// Setup output Stream.
ObjectOutputStream ObjOut = new
ObjectOutputStream(s.getOutputStream());

//Perform intial read...
sSearchField_ = in.readLine();

Thread.currentThread().sleep(5000);

System.out.println("The sSearchField_ variable = " + sSearchField_);

testLookup(sSearchField_);

ObjOut.writeObject(td);
ObjOut.flush();
ObjOut.close();

s.close();
}
catch(Exception e)
{
e.printStackTrace(System.err);
}
}//End of run method
}//End of ServerSide class...


/*
This is the class template that will be used to create the object
that will
be passed through to the ObjectInput/Output - stream to the lookup
applet.
*/
class TestData implements Serializable
{
private static final long serialVersionUID = 1;

/* Test Data */
public String sField_1, sField_2, sField_3, sField_4, sField_5;
public boolean bRecFound;

//Constructor
TestData()
{}

}//End of class ServerTestData.


 
Reply With Quote
 
Knute Johnson
Guest
Posts: n/a
 
      09-01-2007
Richard Maher wrote:
> Hi,
>
> I don't know what is causing the hang but FWIW I use the following Timeouts
> to put a time limit on my socket connections and socket reads. At least then
> you be able to identify which read isn't being satisfied and track down what
> happened to the writer.
>
> t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);
>
> : : :
>
> public void setTimeout(int msecs) throws UnknownHostException, IOException
> {
> t3Sock.setSoTimeout(msecs);
> }
>
> Cheers Richard Maher


At least in my case, socket timeout did not work when the hang occurred.

--

Knute Johnson
email s/nospam/knute/
 
Reply With Quote
 
ILPTAB
Guest
Posts: n/a
 
      09-01-2007
On Aug 31, 11:38 pm, Knute Johnson <(E-Mail Removed)>
wrote:
> Richard Maher wrote:
> > Hi,

>
> > I don't know what is causing the hang but FWIW I use the following Timeouts
> > to put a time limit on my socket connections and socket reads. At least then
> > you be able to identify which read isn't being satisfied and track down what
> > happened to the writer.

>
> > t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);

>
> > : : :

>
> > public void setTimeout(int msecs) throws UnknownHostException, IOException
> > {
> > t3Sock.setSoTimeout(msecs);
> > }

>
> > Cheers Richard Maher

>
> At least in my case, socket timeout did not work when the hang occurred.
>
> --
>
> Knute Johnson
> email s/nospam/knute/- Hide quoted text -
>
> - Show quoted text -


It's all back at the office so I haven't really had a chance to test
it. I wonder if there is a place to post this message on Sun
MicroSysten's site. I really need to get this fixed.

Steve Rulison


 
Reply With Quote
 
Knute Johnson
Guest
Posts: n/a
 
      09-01-2007
ILPTAB wrote:
> On Aug 31, 11:38 pm, Knute Johnson <(E-Mail Removed)>
> wrote:
>> Richard Maher wrote:
>>> Hi,
>>> I don't know what is causing the hang but FWIW I use the following Timeouts
>>> to put a time limit on my socket connections and socket reads. At least then
>>> you be able to identify which read isn't being satisfied and track down what
>>> happened to the writer.
>>> t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);
>>> : : :
>>> public void setTimeout(int msecs) throws UnknownHostException, IOException
>>> {
>>> t3Sock.setSoTimeout(msecs);
>>> }
>>> Cheers Richard Maher

>> At least in my case, socket timeout did not work when the hang occurred.
>>
>> --
>>
>> Knute Johnson
>> email s/nospam/knute/- Hide quoted text -
>>
>> - Show quoted text -

>
> It's all back at the office so I haven't really had a chance to test
> it. I wonder if there is a place to post this message on Sun
> MicroSysten's site. I really need to get this fixed.
>
> Steve Rulison
>


File a bug at bugs.sun.com. I'll vote for it if you post it.

--

Knute Johnson
email s/nospam/knute/
 
Reply With Quote
 
Knute Johnson
Guest
Posts: n/a
 
      09-03-2007
ILPTAB wrote:
> I am currently supporting an interactive web site for a state agency.
> Recently we started getting reports from SOME of the users that the
> applet hangs when they attempt to submit data to the servlet running
> on our web server. We have not made any changes to the java code so
> the only thing I can figure is that it must be happening as a result
> of an update to the java JRE or Windows. Note that I said it's
> occurring with SOME of the users. Other people seem to be having no
> problem at all with it.
>
> To help illustrate the problem, I put together a small test server and
> applet that demonstrates the problem. I have included the source code
> for both parts below. On the applet side, it hangs when it comes to a
> line that attempts to instantiate the ObjectInputStream class and
> retrieve the input stream from the applet.
>
> ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());
>
> Since the applet locks up, I am unable to give you any error messages
> in the java console. In fact the browser gets so locked up that it
> requires the user to close the session from the Windows task manager.
>
> On the Servlet side it hangs at the line that attempts to read the
> data stream from the socket connection.
>
> sSearchField_ = in.readLine();
>
> The error messages generated at the server are as follows:
>
> Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)
>
> at ServerSide.run(ServerSide.java.9
>
> at jave.lang.thread.run(Unkown Source)
>
>
> Any help in resolving this problem would be greatly appricated.
>
> Thank you.
>
>
>
> Here is the source code for both the Servlet and the applet.
>
>
> /* Class Name: AppletSide.java
>
> Copyright 2007 Steve Rulison
>
> Version 1.0.0
>
> Purpose: This java applet will display relevent information
> pertaining to
> this examplet
> */
>
> import javax.swing.*;
> import javax.swing.event.*;
> import javax.swing.event.ListSelectionListener;
> import javax.swing.event.ListSelectionEvent;
> import javax.swing.table.*;
> import java.awt.*;
> import java.awt.event.*;
> import java.applet.*;
>
> import java.io.*;
> import java.util.*;
> import java.net.*;
> import java.lang.*;
>
> public class AppletSide extends JApplet
> implements ActionListener, KeyListener, MouseListener, Serializable
> {
> private static final long serialVersionUID = 1;
>
> private JButton theSubmitButton_, theClearButton_;
> private Socket s;
> private String host, ServerName_;
> private TestData td;
> private JPanel appletPanel, resultPanel, buttonPanel,
> socketPanel, headingPanel;
> private Font f1 = new Font("Sansserf", Font.BOLD, 2;
>
> private JLabel socketConnectionLabel = new JLabel("");
> private JTextField resultField1, resultField2, resultField3,
> resultField4, resultField5;
>
> private java.awt.List inquirylist;
>
> //Constructor
> public AppletSide()
> {
> headingPanel = new JPanel();
> headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
>
> //Initialize String variables for output.
> searchSetup();
> }//Constructor
>
> public void init()
> {
> // Note: The getCodeBase().getHost() methods must be invoked from
> the
> // init() method.
> ServerName_ = getCodeBase().getHost();
> System.out.println(ServerName_);
>
> System.out.println("Test Applet Version");
> }//End of init.
>
> //Establish a socket connection with the server.
> private boolean createSocket(String pServerName)
> {
> boolean SocketConnectSuccessful = false;
> try
> {
> int iPort = 554;
> s = new Socket(pServerName, iPort);
> SocketConnectSuccessful = true;
> socketConnectionLabel.setText("Socket connection successfully
> established with host " + pServerName + " on port " + iPort);
> socketPanel.validate();
> }
> catch(Exception e)
> {
> e.printStackTrace(System.err);
> System.out.println(e);
> SocketConnectSuccessful = false;
> socketConnectionRefused();
> }//End of catch block.
> return SocketConnectSuccessful;
> }//End of method createSocket.
>
> //This method is called when a socket connection could not be
> established.
> private void socketConnectionRefused()
> {
> socketConnectionLabel.setText("Unable to establish a connection with
> host. Please contact you network administrator.");
> socketPanel.validate();
> }//End of method socketConnectionRefused.
>
> //Setup search Inquiry labels.
> private void searchSetup()
> {
> setLayout(new BorderLayout());
>
> appletPanel = new JPanel();
> appletPanel.setLayout(new GridLayout(0,1));
>
>
> JLabel titleLabel = new JLabel("Test Page");
> titleLabel.setFont(f1);
> titleLabel.setForeground(Color.black);
>
> headingPanel.add(titleLabel);
> appletPanel.add(headingPanel);
>
> JPanel inquiryPanel = new JPanel();
> inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
>
> JLabel inquiryLabel = new JLabel("Make Selection: ");
> inquiryPanel.add(inquiryLabel);
>
> inquirylist = new java.awt.List();
> inquirylist.add("Test 1");
> inquirylist.add("Test 2");
> inquirylist.add("Test 3");
> inquirylist.select(0);
>
> inquiryPanel.add(inquirylist);
>
> appletPanel.add(inquiryPanel);
>
> resultSetup();
>
> socketPanel = new JPanel();
> socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
> socketPanel.add(socketConnectionLabel);
> appletPanel.add(socketPanel);
>
>
> buttonPanel = new JPanel();
> buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
>
> theSubmitButton_ = new JButton("Submit");
> theSubmitButton_.addActionListener(this);
> theSubmitButton_.addKeyListener(this);
>
> buttonPanel.add(theSubmitButton_);
> theClearButton_ = new JButton("Clear");
> theClearButton_.addActionListener(this);
> theClearButton_.addKeyListener(this);
> buttonPanel.add(theClearButton_);
> appletPanel.add(buttonPanel);
>
> add(BorderLayout.CENTER, appletPanel);
>
> }//End of method searchLabelSetup.
>
> //Setup result labels.
> private void resultSetup()
> {
> resultPanel = new JPanel();
> resultPanel.setLayout(new GridLayout(5,2));
>
> JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
> JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
> JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
> JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
> JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);
>
> resultField1 = new JTextField("Default value 1", 5);
> resultField1.setEditable(false);
> resultField2 = new JTextField("Default value 2 ",5);
> resultField2.setEditable(false);
> resultField3 = new JTextField("Default value 3",5);
> resultField3.setEditable(false);
> resultField4 = new JTextField("Default value 4",5);
> resultField4.setEditable(false);
> resultField5 = new JTextField("Default value 5",5);
> resultField5.setEditable(false);
>
> resultPanel.add(resultLabel1);
> resultPanel.add(resultField1);
> resultPanel.add(resultLabel2);
> resultPanel.add(resultField2);
> resultPanel.add(resultLabel3);
> resultPanel.add(resultField3);
> resultPanel.add(resultLabel4);
> resultPanel.add(resultField4);
> resultPanel.add(resultLabel5);
> resultPanel.add(resultField5);
>
> appletPanel.add(resultPanel);
>
> }//End of method resultLabelSetup.
>
> // Display the fields that have been populated with data received
> from the
> // server application.
> private void displayResults()
> {
> resultField1.setText(td.sField_1);
> resultField2.setText(td.sField_2);
> resultField3.setText(td.sField_3);
> resultField4.setText(td.sField_4);
> resultField5.setText(td.sField_5);
> resultPanel.validate();
> }//End of method displayResults.
>
> //Clears fields of data
> private void clearFields()
> {
> resultField1.setText("Default value 1");
> resultField2.setText("Default value 2");
> resultField3.setText("Default value 3");
> resultField4.setText("Default value 4");
> resultField5.setText("Default value 5");
> resultPanel.validate();
> inquirylist.select(0);
> }//End of method clearFields.
>
> //Reset the applet to allow the user to perform a new search.
> private void resetSearch()
> {
> this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
> clearFields();
> createSocket(ServerName_);
> this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
> }//End of method resetSearch.
>
> //Perform Input/Output operations with the server.
> private void serverIO()
> {
> this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
>
> try
> {
> PrintWriter out =
> new PrintWriter(
> new BufferedWriter(
> new OutputStreamWriter(
> s.getOutputStream())),true);
>
>
> System.out.println("Check point 1 @ serverIO method.");
> out.println(inquirylist.getItem(inquirylist.getSel ectedIndex()));
> // Thread.currentThread().sleep(5000);
> System.out.println("Check point 2 @ serverIO method.");
> //Read data back from server - Inputstream
> ObjectInputStream inObj = new
> ObjectInputStream(s.getInputStream());
> System.out.println("Check point 3 @ serverIO method.");
> out.flush();
> System.out.println("Check point 4 @ serverIO method.");
>
> td = (TestData) inObj.readObject();
>
> s.close();
> if(td.bRecFound)
> displayResults();
> else
> resetSearch();
> }
> catch(Exception e)
> {
> System.out.println("Check point 1 - Exception: " + e);
>
> }//End of try/catch block
>
> this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
> }//End of method ServerIO
>
>
> //Event handling method.
> public void actionPerformed(ActionEvent evt)
> {
> if(evt.getSource() == theClearButton_)
> {
> clearFields();
> repaint();
> }
> else if(evt.getSource() == theSubmitButton_)
> {
> if(createSocket(ServerName_))
> {
> System.getSecurityManager();
>
> // searchLabelSetup();
> validate();
> System.out.println(s.getInetAddress());
> serverIO();
> repaint();
> }
> else
> socketConnectionRefused();
> }
> }//End of method actionPerformed
>
>
> //Methodsfor handling for keyboard events
> public void keyPressed(KeyEvent evt){}
> public void keyReleased(KeyEvent evt){}
> public void keyTyped(KeyEvent evt)
> {
> // System.out.println(" " + (int)evt.getKeyChar() );
>
> if(evt.getSource() == theClearButton_)
> {
> clearFields();
> repaint();
> }
> else if(evt.getSource() == theSubmitButton_)
> {
> serverIO();
> repaint();
> }
> }//End of method keyTyped.
>
> public void mouseClicked(MouseEvent evt)
> {
> if(evt.getClickCount() == 2)
> {
> }
> }
> public void mouseExited(MouseEvent event){}
> public void mouseEntered(MouseEvent event){}
> public void mouseReleased(MouseEvent event){}
> public void mousePressed(MouseEvent event){}
>
> }//End of class ApplSide.
>
> class TestData implements Serializable
> {
> private static final long serialVersionUID = 1;
>
> /* Test Data */
> public String sField_1, sField_2, sField_3, sField_4, sField_5;
> public boolean bRecFound;
>
> //Constructor
> TestData()
> {}
> }//End of class ServerTestData.
>
> - - - - - - - - - - - - - - - - -
> - - - -
>
> /* Class name: ServerSide
>
> Author: Steven Rulison
>
> Purpose: Demonstrate the servlet side
> */
>
> import java.io.*;
> import java.util.*;
> import java.net.*;
>
> public class ServerSide extends Thread
> {
> private TestData td;
> private Socket s;
> private String sSearchField_;
>
> public static void main(String[] Args)
> {
> try
> {
> ServerSocket ss = new ServerSocket(554);
>
> int spawnCnt = 0;
> while(true)
> {
> Socket s = ss.accept();
>
> ++spawnCnt;
> System.out.println("Spawning " + spawnCnt);
>
>
> Thread servSide = new Thread(new ServerSide(s), "serverside");
> servSide.start();
> }
> }catch(IOException e)
> {
> e.printStackTrace(System.err);
> }
> }//End of main.
>
>
> //Constructor.
> public ServerSide(Socket s_)
> {
> s = s_;
> }//End of Constructor.
>
>
> private void testLookup(String sSearch)
> {
> td = new TestData();
> td.bRecFound = true;
> if(sSearch.trim().equals("Test 1"))
> {
> td.sField_1 = "Alpha";
> td.sField_2 = "Beta";
> td.sField_3 = "Gamma";
> td.sField_4 = "Delta";
> td.sField_5 = "Epsilon";
> }
> else if(sSearch.trim().equals("Test 2"))
> {
> td.sField_1 = "AAA";
> td.sField_2 = "BBB";
> td.sField_3 = "CCC";
> td.sField_4 = "DDDD";
> td.sField_5 = "EEEE";
> }
> else if(sSearch.trim().equals("Test 3"))
> {
> td.sField_1 = "111";
> td.sField_2 = "222";
> td.sField_3 = "333";
> td.sField_4 = "444";
> td.sField_5 = "555";
> }
> }// End of method testLookup.
>
> public void run()
> {
> try
> {
> //Setup Input Stream.
> BufferedReader in =
> new BufferedReader( new InputStreamReader(s.getInputStream()));
>
> // Setup output Stream.
> ObjectOutputStream ObjOut = new
> ObjectOutputStream(s.get());
>
> //Perform intial read...
> sSearchField_ = in.readLine();
>
> Thread.currentThread().sleep(5000);
>
> System.out.println("The sSearchField_ variable = " + sSearchField_);
>
> testLookup(sSearchField_);
>
> ObjOut.writeObject(td);
> ObjOut.flush();
> ObjOut.close();
>
> s.close();
> }
> catch(Exception e)
> {
> e.printStackTrace(System.err);
> }
> }//End of run method
> }//End of ServerSide class...
>
>
> /*
> This is the class template that will be used to create the object
> that will
> be passed through to the ObjectInput/Output - stream to the lookup
> applet.
> */
> class TestData implements Serializable
> {
> private static final long serialVersionUID = 1;
>
> /* Test Data */
> public String sField_1, sField_2, sField_3, sField_4, sField_5;
> public boolean bRecFound;
>
> //Constructor
> TestData()
> {}
>
> }//End of class ServerTestData.
>


I may have done you a bad turn here. I think your problem is because
you aren't creating an ObjectOutputStream on the socket before you
create your ObjectInputStream. I think they have to be matched (at
least if you are going to do input) on the socket and the
ObjectOutputStream has to be created first. This is a known source of
hangs. I was too hasty reading your post the first time.

--

Knute Johnson
email s/nospam/knute/
 
Reply With Quote
 
ILPTAB
Guest
Posts: n/a
 
      09-03-2007
On Sep 2, 11:16 pm, Knute Johnson <(E-Mail Removed)>
wrote:
> ILPTAB wrote:
> > I am currently supporting an interactive web site for a state agency.
> > Recently we started getting reports from SOME of the users that the
> > applet hangs when they attempt to submit data to the servlet running
> > on our web server. We have not made any changes to the java code so
> > the only thing I can figure is that it must be happening as a result
> > of an update to the java JRE or Windows. Note that I said it's
> > occurring with SOME of the users. Other people seem to be having no
> > problem at all with it.

>
> > To help illustrate the problem, I put together a small test server and
> > applet that demonstrates the problem. I have included the source code
> > for both parts below. On the applet side, it hangs when it comes to a
> > line that attempts to instantiate the ObjectInputStream class and
> > retrieve the input stream from the applet.

>
> > ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());

>
> > Since the applet locks up, I am unable to give you any error messages
> > in the java console. In fact the browser gets so locked up that it
> > requires the user to close the session from the Windows task manager.

>
> > On the Servlet side it hangs at the line that attempts to read the
> > data stream from the socket connection.

>
> > sSearchField_ = in.readLine();

>
> > The error messages generated at the server are as follows:

>
> > Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)

>
> > at ServerSide.run(ServerSide.java.9

>
> > at jave.lang.thread.run(Unkown Source)

>
> > Any help in resolving this problem would be greatly appricated.

>
> > Thank you.

>
> > Here is the source code for both the Servlet and the applet.

>
> > /* Class Name: AppletSide.java

>
> > Copyright 2007 Steve Rulison

>
> > Version 1.0.0

>
> > Purpose: This java applet will display relevent information
> > pertaining to
> > this examplet
> > */

>
> > import javax.swing.*;
> > import javax.swing.event.*;
> > import javax.swing.event.ListSelectionListener;
> > import javax.swing.event.ListSelectionEvent;
> > import javax.swing.table.*;
> > import java.awt.*;
> > import java.awt.event.*;
> > import java.applet.*;

>
> > import java.io.*;
> > import java.util.*;
> > import java.net.*;
> > import java.lang.*;

>
> > public class AppletSide extends JApplet
> > implements ActionListener, KeyListener, MouseListener, Serializable
> > {
> > private static final long serialVersionUID = 1;

>
> > private JButton theSubmitButton_, theClearButton_;
> > private Socket s;
> > private String host, ServerName_;
> > private TestData td;
> > private JPanel appletPanel, resultPanel, buttonPanel,
> > socketPanel, headingPanel;
> > private Font f1 = new Font("Sansserf", Font.BOLD, 2;

>
> > private JLabel socketConnectionLabel = new JLabel("");
> > private JTextField resultField1, resultField2, resultField3,
> > resultField4, resultField5;

>
> > private java.awt.List inquirylist;

>
> > //Constructor
> > public AppletSide()
> > {
> > headingPanel = new JPanel();
> > headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

>
> > //Initialize String variables for output.
> > searchSetup();
> > }//Constructor

>
> > public void init()
> > {
> > // Note: The getCodeBase().getHost() methods must be invoked from
> > the
> > // init() method.
> > ServerName_ = getCodeBase().getHost();
> > System.out.println(ServerName_);

>
> > System.out.println("Test Applet Version");
> > }//End of init.

>
> > //Establish a socket connection with the server.
> > private boolean createSocket(String pServerName)
> > {
> > boolean SocketConnectSuccessful = false;
> > try
> > {
> > int iPort = 554;
> > s = new Socket(pServerName, iPort);
> > SocketConnectSuccessful = true;
> > socketConnectionLabel.setText("Socket connection successfully
> > established with host " + pServerName + " on port " + iPort);
> > socketPanel.validate();
> > }
> > catch(Exception e)
> > {
> > e.printStackTrace(System.err);
> > System.out.println(e);
> > SocketConnectSuccessful = false;
> > socketConnectionRefused();
> > }//End of catch block.
> > return SocketConnectSuccessful;
> > }//End of method createSocket.

>
> > //This method is called when a socket connection could not be
> > established.
> > private void socketConnectionRefused()
> > {
> > socketConnectionLabel.setText("Unable to establish a connection with
> > host. Please contact you network administrator.");
> > socketPanel.validate();
> > }//End of method socketConnectionRefused.

>
> > //Setup search Inquiry labels.
> > private void searchSetup()
> > {
> > setLayout(new BorderLayout());

>
> > appletPanel = new JPanel();
> > appletPanel.setLayout(new GridLayout(0,1));

>
> > JLabel titleLabel = new JLabel("Test Page");
> > titleLabel.setFont(f1);
> > titleLabel.setForeground(Color.black);

>
> > headingPanel.add(titleLabel);
> > appletPanel.add(headingPanel);

>
> > JPanel inquiryPanel = new JPanel();
> > inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));

>
> > JLabel inquiryLabel = new JLabel("Make Selection: ");
> > inquiryPanel.add(inquiryLabel);

>
> > inquirylist = new java.awt.List();
> > inquirylist.add("Test 1");
> > inquirylist.add("Test 2");
> > inquirylist.add("Test 3");
> > inquirylist.select(0);

>
> > inquiryPanel.add(inquirylist);

>
> > appletPanel.add(inquiryPanel);

>
> > resultSetup();

>
> > socketPanel = new JPanel();
> > socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
> > socketPanel.add(socketConnectionLabel);
> > appletPanel.add(socketPanel);

>
> > buttonPanel = new JPanel();
> > buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

>
> > theSubmitButton_ = new JButton("Submit");
> > theSubmitButton_.addActionListener(this);
> > theSubmitButton_.addKeyListener(this);

>
> > buttonPanel.add(theSubmitButton_);
> > theClearButton_ = new JButton("Clear");
> > theClearButton_.addActionListener(this);
> > theClearButton_.addKeyListener(this);
> > buttonPanel.add(theClearButton_);
> > appletPanel.add(buttonPanel);

>
> > add(BorderLayout.CENTER, appletPanel);

>
> > }//End of method searchLabelSetup.

>
> > //Setup result labels.
> > private void resultSetup()
> > {
> > resultPanel = new JPanel();
> > resultPanel.setLayout(new GridLayout(5,2));

>
> > JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
> > JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
> > JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
> > JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
> > JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);

>
> > resultField1 = new JTextField("Default value 1", 5);
> > resultField1.setEditable(false);
> > resultField2 = new JTextField("Default value 2 ",5);
> > resultField2.setEditable(false);
> > resultField3 = new JTextField("Default value 3",5);
> > resultField3.setEditable(false);
> > resultField4 = new JTextField("Default value 4",5);
> > resultField4.setEditable(false);
> > resultField5 = new JTextField("Default value 5",5);
> > resultField5.setEditable(false);

>
> > resultPanel.add(resultLabel1);
> > resultPanel.add(resultField1);
> > resultPanel.add(resultLabel2);
> > resultPanel.add(resultField2);
> > resultPanel.add(resultLabel3);
> > resultPanel.add(resultField3);
> > resultPanel.add(resultLabel4);
> > resultPanel.add(resultField4);
> > resultPanel.add(resultLabel5);
> > resultPanel.add(resultField5);

>
> > appletPanel.add(resultPanel);

>
> > }//End of method resultLabelSetup.

>
> > // Display the fields that have been populated with data received
> > from the
> > // server application.
> > private void displayResults()
> > {
> > resultField1.setText(td.sField_1);
> > resultField2.setText(td.sField_2);
> > resultField3.setText(td.sField_3);
> > resultField4.setText(td.sField_4);
> > resultField5.setText(td.sField_5);
> > resultPanel.validate();
> > }//End of method displayResults.

>
> > //Clears fields of data
> > private void clearFields()
> > {
> > resultField1.setText("Default value 1");
> > resultField2.setText("Default value 2");
> > resultField3.setText("Default value 3");
> > resultField4.setText("Default value 4");
> > resultField5.setText("Default value 5");
> > resultPanel.validate();
> > inquirylist.select(0);
> > }//End of method clearFields.

>
> > //Reset the applet to allow the user to perform a new search.
> > private void resetSearch()
> > {
> > this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
> > clearFields();
> > createSocket(ServerName_);
> > this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
> > }//End of method resetSearch.

>
> > //Perform Input/Output operations with the server.
> > private void serverIO()
> > {
> > this.setCursor(new Cursor(Cursor.WAIT_CURSOR));

>
> > try
> > {
> > PrintWriter out =
> > new PrintWriter(
> > new BufferedWriter(
> > new OutputStreamWriter(
> > s.getOutputStream())),true);

>
> > System.out.println("Check point 1 @ serverIO method.");
> > out.println(inquirylist.getItem(inquirylist.getSel ectedIndex()));
> > // Thread.currentThread().sleep(5000);
> > System.out.println("Check point 2 @ serverIO method.");
> > //Read data back from server - Inputstream
> > ObjectInputStream inObj = new
> > ObjectInputStream(s.getInputStream());
> > System.out.println("Check point 3 @ serverIO method.");
> > out.flush();
> > System.out.println("Check point 4 @ serverIO method.");

>
> > td = (TestData) inObj.readObject();

>
> > s.close();
> > if(td.bRecFound)
> > displayResults();
> > else
> > resetSearch();
> > }
> > catch(Exception e)
> > {
> > System.out.println("Check point 1 - Exception: " + e);

>
> > }//End of try/catch block

>
> > this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
> > }//End of method ServerIO

>
> > //Event handling method.
> > public void actionPerformed(ActionEvent evt)
> > {
> > if(evt.getSource() == theClearButton_)
> > {
> > clearFields();
> > repaint();
> > }
> > else if(evt.getSource() == theSubmitButton_)
> > {
> > if(createSocket(ServerName_))
> > {
> > System.getSecurityManager();

>
> > // searchLabelSetup();
> > validate();
> > System.out.println(s.getInetAddress());
> > serverIO();
> > repaint();
> > }
> > else
> > socketConnectionRefused();
> > }
> > }//End of method actionPerformed

>
> > //Methodsfor handling for keyboard events
> > public void keyPressed(KeyEvent evt){}
> > public void keyReleased(KeyEvent evt){}
> > public void keyTyped(KeyEvent evt)
> > {
> > // System.out.println(" " + (int)evt.getKeyChar() );

>
> > if(evt.getSource() == theClearButton_)
> > {
> > clearFields();
> > repaint();
> > }
> > else if(evt.getSource() == theSubmitButton_)
> > {
> > serverIO();
> > repaint();
> > }
> > }//End of method keyTyped.

>
> > public void mouseClicked(MouseEvent evt)
> > {
> > if(evt.getClickCount() == 2)
> > {
> > }
> > }
> > public void mouseExited(MouseEvent event){}
> > public void mouseEntered(MouseEvent event){}
> > public void mouseReleased(MouseEvent event){}
> > public void mousePressed(MouseEvent event){}

>
> > }//End of class ApplSide.

>
> > class TestData implements Serializable
> > {
> > private static final long serialVersionUID = 1;

>
> > /* Test Data */
> > public String sField_1, sField_2, sField_3, sField_4, sField_5;
> > public boolean bRecFound;

>
> > //Constructor
> > TestData()
> > {}
> > }//End of class ServerTestData.

>
> > - - - - - - - - - - - - - - - - -
> > - - - -

>
> > /* Class name: ServerSide

>
> > Author: Steven Rulison

>
> > Purpose: Demonstrate the servlet side
> > */

>
> > import java.io.*;
> > import java.util.*;
> > import java.net.*;

>
> > public class ServerSide extends Thread
> > {
> > private TestData td;
> > private Socket s;
> > private String sSearchField_;

>
> > public static void main(String[] Args)
> > {
> > try
> > {
> > ServerSocket ss = new ServerSocket(554);

>
> > int spawnCnt = 0;
> > while(true)
> > {
> > Socket s = ss.accept();

>
> > ++spawnCnt;
> > System.out.println("Spawning " + spawnCnt);

>
> > Thread servSide = new Thread(new ServerSide(s), "serverside");
> > servSide.start();
> > }
> > }catch(IOException e)
> > {
> > e.printStackTrace(System.err);
> > }
> > }//End of main.

>
> > //Constructor.
> > public ServerSide(Socket s_)
> > {
> > s = s_;
> > }//End of Constructor.

>
> > private void testLookup(String sSearch)
> > {
> > td = new TestData();
> > td.bRecFound = true;
> > if(sSearch.trim().equals("Test 1"))
> > {
> > td.sField_1 = "Alpha";
> > td.sField_2 = "Beta";
> > td.sField_3 = "Gamma";
> > td.sField_4 = "Delta";
> > td.sField_5 = "Epsilon";
> > }
> > else if(sSearch.trim().equals("Test 2"))
> > {
> > td.sField_1 = "AAA";
> > td.sField_2 = "BBB";
> > td.sField_3 = "CCC";
> > td.sField_4 = "DDDD";
> > td.sField_5 = "EEEE";
> > }
> > else if(sSearch.trim().equals("Test 3"))
> > {
> > td.sField_1 = "111";
> > td.sField_2 = "222";
> > td.sField_3 = "333";
> > td.sField_4 = "444";
> > td.sField_5 = "555";
> > }
> > }// End of method testLookup.

>
> > public void run()
> > {
> > try
> > {
> > //Setup Input Stream.
> > BufferedReader in =
> > new BufferedReader( new InputStreamReader(s.getInputStream()));

>
> > // Setup output Stream.
> > ObjectOutputStream ObjOut = new
> > ObjectOutputStream(s.get());

>
> > //Perform intial read...
> > sSearchField_ = in.readLine();

>
> > Thread.currentThread().sleep(5000);

>
> > System.out.println("The sSearchField_ variable = " + sSearchField_);

>
> > testLookup(sSearchField_);

>
> > ObjOut.writeObject(td);
> > ObjOut.flush();
> > ObjOut.close();

>
> > s.close();
> > }
> > catch(Exception e)
> > {
> > e.printStackTrace(System.err);
> > }
> > }//End of run method
> > }//End of ServerSide class...

>
> > /*
> > This is the class template that will be used to create the object
> > that will
> > be passed through to the ObjectInput/Output - stream to the lookup
> > applet.
> > */
> > class TestData implements Serializable
> > {
> > private static final long serialVersionUID = 1;

>
> > /* Test Data */
> > public String sField_1, sField_2, sField_3, sField_4, sField_5;
> > public boolean bRecFound;

>
> > //Constructor
> > TestData()
> > {}

>
> > }//End of class ServerTestData.

>
> I may have done you a bad turn here. I think your problem is because
> you aren't creating an ObjectOutputStream on the socket before you
> create your ObjectInputStream. I think they have to be matched (at
> least if you are going to do input) on the socket and the
> ObjectOutputStream has to be created first. This is a known source of
> hangs. I was too hasty reading your post the first time.
>
> --
>
> Knute Johnson
> email s/nospam/knute/


Interesting. I will look into it. The only thing is, it dosen't do
it consistanntly. The applet hangs for some people amd not on
others. Never the less, I will make the changes you suggested and see
how that works. Thanks for you imput.

Steve R.


 
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Knute Johnson
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Posts: n/a
 
      09-03-2007
ILPTAB wrote:
>> I may have done you a bad turn here. I think your problem is because
>> you aren't creating an ObjectOutputStream on the socket before you
>> create your ObjectInputStream. I think they have to be matched (at
>> least if you are going to do input) on the socket and the
>> ObjectOutputStream has to be created first. This is a known source of
>> hangs. I was too hasty reading your post the first time.
>>
>> --
>>
>> Knute Johnson
>> email s/nospam/knute/

>
> Interesting. I will look into it. The only thing is, it dosen't do
> it consistanntly. The applet hangs for some people amd not on
> others. Never the less, I will make the changes you suggested and see
> how that works. Thanks for you imput.
>
> Steve R.


Steve:

Sorry I didn't look at it more closely when you first posted. It
sounded just like the problem I'm having. Please post here if you get
it to work.

--

Knute Johnson
email s/nospam/knute/
 
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Roedy Green
Guest
Posts: n/a
 
      09-04-2007
On Fri, 31 Aug 2007 21:49:56 -0000, ILPTAB <(E-Mail Removed)> wrote,
quoted or indirectly quoted someone who said :

>
>Any help in resolving this problem would be greatly appricated.


I would put a version number in the Applet and SerialVersionUIDs on
all transported classes. Have the applet display its version number
first thing so you can be sure you are getting a fresh copy, not
something in cache.

Further I would put a Long as the first item in the stream; it is a
stream version number. It might just be a serialVersionUID of an
important class. Read and compare and if it does not match, bitch up
front rather than getting into some corner that hangs you.
--
Roedy Green Canadian Mind Products
The Java Glossary
http://mindprod.com
 
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