Non-static variable in multithreaded servlet

I have a multithreaded servlet and a counter variable to keep count of when each thread finishes executing.
I have set the variable to be a static integer.
The problem is that the counter variable persists across requests whereas I want it to reset with each request. What should I do?

Thanks a lot. It works.
I set the counter =1 in the variable passed to the thread and set it as a static variable in the thread definition.
Thanks once more.

Similar Messages

  • Help me please~ non-static variable rs cannot be referenced ...

    i make counter
    but this error occurrence
    only i doing resultset make and closed
    why non-static variable rs ....
    i am sorry i don't speak English ...
    help me please..
    error message
    non-static variable rs cannot be referenced from a static context
    source
    ===============================================
    package jjaekim;
    import java.sql.*;
    import java.util.*;
    import javax.servlet.*;
    import javax.servlet.http.*;
    public class Count{
              Statement stmt;
              ResultSet rs;
              ResultSet rs2;
              Connection conn;
              //DBPoolManager dbpm;
         public static String add(HttpServletRequest request){
              try{
                        int year =0;
                        int month=0;
                        int date =0;
                        int hour =0;
                        int min     =0;
                        int week =0;
                        String str_date=new String();
                        String str_time=new String();
                        String referer_url     =request.getHeader("Referer");
                        String infomation     =request.getHeader("User-Agent");
                        String ip               =request.getRemoteAddr();
                        int access_date=0;
                        int access_time=0;
                        Calendar cal     =Calendar.getInstance();
                        year               =cal.get(cal.YEAR);
                        month               =cal.get(cal.MONTH) + 1;
                        date               =cal.get(cal.DATE);
                        hour               =cal.get(cal.HOUR_OF_DAY);
                        min                    =cal.get(cal.MINUTE);
                        week               =cal.get(cal.DAY_OF_WEEK);
                        access_date          =(month*100)+date;
                        access_time          =(hour*100)+min;
                        if(access_date<1000)
                             str_date="0"+new Integer(access_date).toString();
                        else
                             str_date=new Integer(access_date).toString();
                        if(access_time<100)
                             str_time="0"+new Integer(access_time).toString();
                        else
                             str_time="0"+new Integer(access_time).toString();
                   }catch(Exception e){
                        //System.out.print("Exc"+e.getMessage());
                        //return false;
                   finally{
                             if(rs!=null){
                                  try{     rs.close();}catch(Exception e){}
                             if(rs2!=null){
                                  try{     rs2.close();}catch(Exception e){}
                             if (stmt!=null){
                                  try{     stmt.close();}catch(Exception e){}
                             //if (conn!=null){
                                  try{     conn.close(); }catch(Exception e){}
                        //return back;
    /*     public static void main(String[] args)
              System.out.println("Hello World!");

    Hello jjaekim,
    if rs is a class variable (the same value for all objects),
    try this (more likely to be the right solution) :
    static ResultSet rs;
    instead of :
    ResultSet rs;
    if rs has a different values in different objects,
    then you should add the object name when using it like this :
    myObject.rs or this.rs

  • Static and non-static variables and methods

    Hi all,
    There's an excellent thread that outlines very clearly the differences between static and non-static:
    http://forum.java.sun.com/thread.jsp?forum=54&thread=374018
    But I have to admit, that it still hasn't helped me solve my problem. There's obviously something I haven't yet grasped and if anyone could make it clear to me I would be most grateful.
    Bascially, I've got a servlet that instatiates a message system (ie starts it running), or, according to the action passed to it from the form, stops the message system, queries its status (ie finds out if its actually running or not) and, from time to time, writes the message system's progress to the browser.
    My skeleton code then looks like this:
    public class IMS extends HttpServlet
        public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
            doPost(request, response);
       public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
          //get the various parameters...
             if (user.equalsIgnoreCase(username) && pass.equalsIgnoreCase(password))
                if(action.equalsIgnoreCase("start"))
                    try
                        IMSRequest imsRequest = new IMSRequest();
                        imsRequest.startIMS(response);
                    catch(IOException ex)
                    catch(ClassNotFoundException ex)
                else if(action.equalsIgnoreCase("stop"))
                    try
                        StopIMS stopIMS = new StopIMS();
                        stopIMS.stop(response);
                    catch(IOException ex)
                 else if(action.equalsIgnoreCase("status"))
                    try
                        ViewStatus status = new ViewStatus();
                        status.view(response);
                    catch(IOException ex)
             else
                response.sendRedirect ("/IMS/wrongPassword.html");
    public class IMSRequest
    //a whole load of other variables   
      public  PrintWriter    out;
        public  int                 messageNumber;
        public  int                 n;
        public  boolean         status = false;  //surely this is a static variable?
        public  String            messageData = ""; // and perhaps this too?
        public IMSRequest()
        public void startIMS(HttpServletResponse response) throws IOException, ClassNotFoundException
            try
                response.setContentType("text/html");
                out = response.getWriter();
                for(n = 1 ; ; n++ )
                    getMessageInstance();
                    File file = new File("/Users/damian/Desktop/Test/stop_IMS");
                    if (n == 1 && file.exists())
                        file.delete();
                    else if (file.exists())
                        throw new ServletException();
                    try
                        databaseConnect();
                   catch (ClassNotFoundException e)
    //here I start to get compile problems, saying I can't access non-static methods from inside a static method               
                   out.println(FrontPage.displayHeader()); 
                    out.println("</BODY>\n</HTML>");
                    out.close();
                    Thread.sleep(1000);
            catch (Exception e)
        }OK, so, specifially, my problem is this:
    Do I assume that when I instantiate the object imsRequest thus;
    IMSRequest imsRequest = new IMSRequest();
    imsRequest.startIMS(response); I am no longer in a static method? That's what I thought. But the problem is that, in the class, IMSRequest I start to get compile problems saying that I can't access non-static variables from a static method, and so on and so on.
    I know I can cheat by changing these to static variables, but there are some specific variables that just shouldn't be static. It seems that something has escaped me. Can anyone point out what it is?
    Many thanks for your time and I will gladly post more code/explain my problem in more detail, if it helps you to explain it to me.
    Damian

    Can I just ask you one more question though?Okay, but I warn you: it's 1:00 a.m., I've been doing almost nothing but Java for about 18 hours, and I don't do servlets, so don't take any of this as gospel.
    If, however, from another class (FrontPage for
    example), I call ((new.IMSRequest().writeHTML) or
    something like that, then I'm creating a new instance
    of IMSRequest (right?)That's what new does, yes.
    and therefore I am never going
    to see the information I need from my original
    IMSRequest instance. Am I right on this?I don't know. That's up to you. What do you do with the existing IMS request when you create the new FrontPage? Is there another reference to it somewhere? I don't know enough about your design or the goal of your software to really answer.
    On the other hand, IMSRequest is designed to run
    continuously (prehaps for hours), so I don't really
    want to just print out a continuous stream of stuff to
    the browser. How can I though, every so often, call
    the status of this instance of this servlet?One possibility is to pass the existing IMSRequest to the FrontPage and have it use that one, rather than creating its own. Or is that not what you're asking? Again, I don't have enough details (or maybe just not enough functioning brain cells) to see how it all fits together.
    One thing that puzzles me here: It seems to me that FP uses IMSReq, but IMSReq also uses FP. Is that the case? Those two way dependencies can make things ugly in a hurry, and are often a sign of bad design. It may be perfectly valid for what you're doing, but you may want to look at it closely and see if there's a better way.

  • Error on compile - non-static variable can not be referencedfrom static con

    Error on compile happening with addButton?
    Thanks
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.JButton;
    import javax.swing.JLabel;
    import javax.swing.JTextField;
    import javax.swing.JFrame;
    public class Log implements ActionListener {
    JButton addButton;
    public static void addComponentsToPane(Container pane) {
    pane.setLayout(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
         c.gridy = 3;
    c.gridx = 0;
         JLabel callsignLabel= new JLabel("Callsign");
    pane.add(callsignLabel, c);
         c.gridy = 3;
    c.gridx = 1;
         JLabel nameLabel= new JLabel("Name");
    pane.add(nameLabel, c);
         c.gridy = 3;
    c.gridx = 2;
         JLabel timeLabel= new JLabel("Time");
    pane.add(timeLabel, c);
         c.gridy = 3;
    c.gridx = 3;
         JLabel dateLabel= new JLabel("Date");
    pane.add(dateLabel, c);
         c.gridy = 3;
    c.gridx = 4;
         JLabel frequencyLabel= new JLabel("Freq ");
    pane.add(frequencyLabel, c);
         c.gridy = 3;
    c.gridx = 5;
         JLabel locationLabel = new JLabel("Country/State");
    pane.add(locationLabel, c);
    c.gridy = 5;
    c.gridx = 0;
         addButton = new JButton("Add");
    pane.add(addButton, c);
         addButton.addActionListener(this);

    Thank you for the reply
    I am new to Java
    What is wrong with the way it is coded?The error message tells you what's wrong: You're trying to reference a non-static variable from a static context.
    If you don't know what that means, then click the link I provided and look at the results from that google search. You might have to go through a few before you find a satisfactory explanation. And after you've done that, if you have specific questions about things you didn't understand there, please post again.

  • Non-static variable Help needed

    Hi, I am creating a multi threaded web server but get the following error
    non-static variable this cannot be referenced from a static context
    HttpRequest request = new HttpRequest(connectionSocket);
    Please could someone help.
    Many Thanks
    import java.io.* ;
    import java.net.* ;
    import java.util.* ;
    public final class MultiWebServer
    public static void main(String argv[]) throws Exception
         // Set the port number.
         int port = 6789;
    // Establish the listen socket.
                   String fileName;
                   ServerSocket listenSocket = new ServerSocket(port);
    // Process HTTP service requests in an infinite loop.
    while (true) {
         // Listen for a TCP connection request.
         Socket connectionSocket = listenSocket.accept();
    // Construct an object to process the HTTP request message.
    HttpRequest request = new HttpRequest(connectionSocket);
    // Create a new thread to process the request.
    Thread thread = new Thread(request);
    // Start the thread.
    thread.start();
    final class HttpRequest implements Runnable
         final static String CRLF = "\r\n";
         Socket socket;
    String requestMessageLine;
    String fileName;
    Date todaysDate;
         // Constructor
         public HttpRequest(Socket socket) throws Exception
              this.socket = socket;
              socket = null;
    // Implement the run() method of the Runnable interface.
    public void run()
         try {
              processRequest();
         } catch (Exception e) {
              System.out.println(e);
    private void processRequest() throws Exception
         // Get a reference to the socket's input and output streams.
         //InputStream is = new InputStream(socket.getInputStream());
         //DataOutputStream os = new DataOutputStream(socket.getOutputStream());
    BufferedReader inFromClient =
                        new BufferedReader(new InputStreamReader(
                             socket.getInputStream()));
                   DataOutputStream outToClient =
                        new DataOutputStream(
                             socket.getOutputStream());
         // Set up input stream filters.
         requestMessageLine = inFromClient.readLine();
         //BufferedReader br = null;
         // Get the request line of the HTTP request message.
    String requestLine = null;
    // Display the request line.
    System.out.println();
    System.out.println(requestLine);
    StringTokenizer tokenizedLine =
                             new StringTokenizer(requestMessageLine);
                   if (tokenizedLine.nextToken().equals("GET"))
                        fileName = tokenizedLine.nextToken();
                        if ( fileName.startsWith("/")==true )
                             fileName = fileName.substring(1);
    File file = new File(fileName);
                        int numOfBytes = (int)file.length();
                        FileInputStream inFile = new FileInputStream(fileName);
                        byte[] fileInBytes = new byte[numOfBytes];
                        inFile.read(fileInBytes);
                        /* Send the HTTP header */
                        outToClient.writeBytes("HTTP/1.1 200 Document Follows\r\n");
                        if (fileName.endsWith(".jpg"))
                             outToClient.writeBytes("Content-Type: image/jpeg\r\n");
                        if (fileName.endsWith(".jpeg"))
                             outToClient.writeBytes("Content-Type: image/jpeg\r\n");
                        if (fileName.endsWith(".gif"))
                             outToClient.writeBytes("Content-Type: image/gif\r\n");
                        if (fileName.endsWith(".html"))
                             outToClient.writeBytes("Content-Type: text/html\r\n");
                        if (fileName.endsWith(".htm"))
                             outToClient.writeBytes("Content-Type: text/html\r\n");
                        outToClient.writeBytes("Content-Length: " + numOfBytes + "\r\n");
                        outToClient.writeBytes("\r\n");
                        /* Now send the actual data */
                        outToClient.write(fileInBytes, 0, numOfBytes);
                        socket.close();
                   else
                   System.out.println("Bad Request Message");
                   todaysDate = new Date();          
                   try {
                        FileInputStream inlog = new FileInputStream("log.txt");
                        System.out.println(requestMessageLine + " " + todaysDate );
                        FileOutputStream log = new FileOutputStream("log.txt", true);
                        PrintStream myOutput = new PrintStream(log);
                        myOutput.println("FILE -> " + requestMessageLine + " DATE/TIME -> " + todaysDate);
                   catch (IOException e) {
                   System.out.println("Error -> " + e);
                   System.exit(1);
    socket.close();

    import java.io.* ;
    import java.net.* ;
    import java.util.* ;
    public final class MultiWebServer
    public MultiWebServer(){
    try{
    // Set the port number.
    int port=6789;
    // Establish the listen socket.
    String fileName;
    ServerSocket listenSocket=new ServerSocket(port);
    // Process HTTP service requests in an infinite loop.
    while(true){
    // Listen for a TCP connection request.
    Socket connectionSocket=listenSocket.accept();
    // Construct an object to process the HTTP request message.
    HttpRequest request=new HttpRequest(connectionSocket);
    // Create a new thread to process the request.
    Thread thread=new Thread(request);
    // Start the thread.
    thread.start();
    }catch(IOException ioe){
    }catch(Exception e){
    public static void main(String argv[]) throws Exception
    new MultiWebServer();
    final class HttpRequest implements Runnable
    final static String CRLF = "\r\n";
    Socket socket;
    String requestMessageLine;
    String fileName;
    Date todaysDate;
    // Constructor
    public HttpRequest(Socket socket) throws Exception
    this.socket = socket;
    socket = null;
    // Implement the run() method of the Runnable interface.
    public void run()
    try {
    processRequest();
    } catch (Exception e) {
    System.out.println(e);
    private void processRequest() throws Exception
    // Get a reference to the socket's input and output streams.
    //InputStream is = new InputStream(socket.getInputStream());
    //DataOutputStream os = new DataOutputStream(socket.getOutputStream());
    BufferedReader inFromClient =
    new BufferedReader(new InputStreamReader(
    socket.getInputStream()));
    DataOutputStream outToClient =
    new DataOutputStream(
    socket.getOutputStream());
    // Set up input stream filters.
    requestMessageLine = inFromClient.readLine();
    //BufferedReader br = null;
    // Get the request line of the HTTP request message.
    String requestLine = null;
    // Display the request line.
    System.out.println();
    System.out.println(requestLine);
    StringTokenizer tokenizedLine =
    new StringTokenizer(requestMessageLine);
    if (tokenizedLine.nextToken().equals("GET"))
    fileName = tokenizedLine.nextToken();
    if ( fileName.startsWith("/")==true )
    fileName = fileName.substring(1);
    File file = new File(fileName);
    int numOfBytes = (int)file.length();
    FileInputStream inFile = new FileInputStream(fileName);
    byte[] fileInBytes = new byte[numOfBytes];
    inFile.read(fileInBytes);
    /* Send the HTTP header */
    outToClient.writeBytes("HTTP/1.1 200 Document Follows\r\n");
    if (fileName.endsWith(".jpg"))
    outToClient.writeBytes("Content-Type: image/jpeg\r\n");
    if (fileName.endsWith(".jpeg"))
    outToClient.writeBytes("Content-Type: image/jpeg\r\n");
    if (fileName.endsWith(".gif"))
    outToClient.writeBytes("Content-Type: image/gif\r\n");
    if (fileName.endsWith(".html"))
    outToClient.writeBytes("Content-Type: text/html\r\n");
    if (fileName.endsWith(".htm"))
    outToClient.writeBytes("Content-Type: text/html\r\n");
    outToClient.writeBytes("Content-Length: " + numOfBytes + "\r\n");
    outToClient.writeBytes("\r\n");
    /* Now send the actual data */
    outToClient.write(fileInBytes, 0, numOfBytes);
    socket.close();
    else
    System.out.println("Bad Request Message");
    todaysDate = new Date();
    try {
    FileInputStream inlog = new FileInputStream("log.txt");
    System.out.println(requestMessageLine + " " + todaysDate );
    FileOutputStream log = new FileOutputStream("log.txt", true);
    PrintStream myOutput = new PrintStream(log);
    myOutput.println("FILE -> " + requestMessageLine + " DATE/TIME -> " + todaysDate);
    catch (IOException e) {
    System.out.println("Error -> " + e);
    System.exit(1);
    socket.close();

  • Non-static variable being used in static context

    I am currently attempting to write a basic user login system using basic applets. I have two JTextFields named "userText" and "passText".
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    However when i try to compare the string in the file with the one in the text field using the following code:
    if ((line.compareTo(username)) == 0)
    i get the following error...
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    Any ideas?

    The static method doesn't know about instances of the class instead you pass the instance to the method:
    static public void myMethod(MyClass instance, String var) {
      if(instance.line.compareTo(var))
    And then the call would be:
    MyClass.myMethod(anInstance, userName);

  • Non-static variable cant accessed from the static context..your suggestion

    Once again stuck in my own thinking, As per my knowledge there is a general error in java.
    i.e. 'Non-static variable cant accessed from static context....'
    Now the thing is that, When we are declaring any variables(non-static) and trying to access it within the same method, Its working perfectly fine.
    i.e.
    public class trial{
    ���������� public static void main(String ar[]){      ////static context
    ������������ int counter=0; ///Non static variable
    ������������ for(;counter<10;) {
    �������������� counter++;
    �������������� System.out.println("Value of counter = " + counter) ; ///working fine
    �������������� }
    ���������� }
    Now the question is that if we are trying to declare a variable out-side the method (Non-static) , Then we defenately face the error' Non-static varialble can't accessed from the static context', BUT here within the static context we declared the non-static variable and accessed it perfectly.
    Please give your valuable suggestions.
    Thanks,
    Jeff

    Once again stuck in my own thinking, As per my
    knowledge there is a general error in java.
    i.e. 'Non-static variable cant accessed from static
    context....'
    Now the thing is that, When we are declaring any
    variables(non-static) and trying to access it within
    the same method, Its working perfectly fine.
    i.e.
    public class trial{
    ���������� public static void
    main(String ar[]){      ////static context
    ������������ int counter=0; ///Non
    static variable
    ������������ for(;counter<10;) {
    �������������� counter++;
    ��������������
    System.out.println("Value
    of counter = " + counter) ; ///working fine
    �������������� }
    ���������� }
    w the question is that if we are trying to declare a
    variable out-side the method (Non-static) , Then we
    defenately face the error' Non-static varialble can't
    accessed from the static context', BUT here within
    the static context we declared the non-static
    variable and accessed it perfectly.
    Please give your valuable suggestions.
    Thanks,
    JeffHi,
    You are declaring a variable inside a static method,
    that means you are opening a static scope... i.e. static block internally...
    whatever the variable you declare inside a static block... will be static by default, even if you didn't add static while declaring...
    But if you put ... it will be considered as redundant by compiler.
    More over, static context does not get "this" pointer...
    that's the reason we refer to any non-static variables declared outside of any methods... by creating an object... this gives "this" pointer to static method controller.

  • Non-static variable from a static context

    This is the error i get . If i understand the error correctly it says im using a static variable when i shouldnt be? Or is it the other way round? below the error is the actual code....
    The error...
    Googler.java:27: non-static variable this cannot be referenced from a static context
              submitButton.addActionListener(new ButtonHandler());The code...
              JButton submitButton = new JButton("Submit Query");
              submitButton.addActionListener(new ButtonHandler());

    thanks for the response.
    I have already tried what you said but I tried it again anyway and i get the same error more less...
    Googler.java:28: non-static variable this cannot be referenced from a static context
              ButtonHandler buttonHandler = new ButtonHandler();here is part of my code
    public class Googler
      static JTextField input1, input2;
         public static void main(String[] args)
              JFrame myFrame = new JFrame("Googler v1.0");
              Container c = myFrame.getContentPane();
              JLabel lab1 = new JLabel("Enter Google Query:");
              JLabel lab2 = new JLabel("Enter Unique API Key:");
              input1 = new JTextField(15);
              input2 = new JTextField(15);
              JRadioButton radSearch = new JRadioButton("Search Query");
              JRadioButton radCached = new JRadioButton("Cached Query");
              JButton submitButton = new JButton("Submit Query");
              ButtonHandler buttonHandler = new ButtonHandler();
              submitButton.addActionListener(buttonHandler);
              ButtonGroup group = new ButtonGroup();
              group.add(radSearch);
              group.add(radCached);Ive tried declaring buttonHandler as a static variable and this dosn't work either. I've never had this problem before it must be something silly im missing...?
    Thanks
    Lee

  • Non-static variable from static context?

    Hi,
    I've created a program using swing components
    and I've set up a addActionListener to a button,
    button.addActionListener(this);
    when try and compile I get the following error:
    non-static variable this cannot be referenced from a
    static context
    button.addActionListener(this);
    I've checked site and my notes I don't seem to have
    done anything different from programs that have compiled
    in the past.
    I'm currently doing a programming course so I'm fairly
    new to Java, try not to get to advanced on me :)
    Thx in advance for any help.
    Chris

    Well what is declared static? If I remeber right this error means that you have a static method that is trying to access data it does not have access to. Static methods cannot access data that is intance data because they do not exist in the instance (not 100% sure about this but I believe it is true, at the very least I know they do not have access to any non-static data). Post some more of your code like where you declare this (like class def) and where you set up the button.

  • Non static  variable in static context

    import java.util.Scanner;
    public class project4_5 {
         int die1, die2;
         int comptotal = 0, playertotal = 0, turntotal = 0;
         int turn, comprun = 0;
         String playername;
         String action = ("R");
         Scanner scan = new Scanner(System.in);
            public static void main (String[] args)
            PairOfDice mydie = new PairOfDice();
         System.out.println("!!!!!!PIG!!!!!!");
         System.out.println();
         System.out.println("Enter your name! ");
         playername = scan.nextLine();
         while(playertotal>100 && comptotal>100){
         while(action.equalsIgnoreCase("R")){
                   System.out.println(playername+" roll or pass the die (R/P) ");
                   action = scan.nextLine();
                   if(action.equalsIgnoreCase("P"))
                        break;
                   mydie.roll();
                   die1 = mydie.getFace1();
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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

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