Servlet Context problem.

Question

have two classes, one is a servletcontextlistner implementation and another one is the actual servlet that will call the first class.
I am trying to have a counter in a servlet that keeps track of how many users have used the servlet. I like to store that in a servletcontextlistener and then call the counters value in the servlet. and also update that counters value.
how can I do this ? are there any good examples that you know ? please help, as i have been stuck on this for manny hours.
ServletContextListner implementation.
public class counterContextListener implements ServletContextListener{
String initialValue = "0";
public counterContextListener(){}
public void contextDestroyed(ServletContextEvent event){}
public void contextInitialized(ServletContextEvent event){
ServletContext context = event.getServletContext();
context.setAttribute("countername", initialValue);
public static String getCounterValue(ServletContext context) {
String value = (String)context.getAttribute("countername");
if (value == null) {
value ="0";
return(value);
}//getCounterValue
} // end of class
Servlet
public void doPost(HttpServletRequest req, HttpServletResponse res) throws
ServletException, IOException{
con = null;
res.setContentType("text/plain");
ServletInputStream sis = req.getInputStream();
DataInputStream dis = new DataInputStream(sis);
String username = dis.readUTF();
dis.close();
PrintWriter out = res.getWriter();
System.out.println("The user has come:"+username+" " +count_users);
//Using servlet context to get the current counter
ServletContext context = getServletContext();
String counter = getCounterValue(context); // passing context object.
Error
C:\Program Files\Apache Group\Tomcat 4.1\webapps\mudServlet>javac mudServletTTT.java
mudServletTTT.java:36: cannot resolve symbol
symbol : method getCounterValue (javax.servlet.ServletContext)
location: class mudServletTTT
String counter = getCounterValue(context);
^

Answer 1

Why would you make the Context Listener also responsible for keeping track of the counts?
1st of all, you are doing this inside the Servlet:
String counter = getCounterValue(context); // passing context object.
But the servlet does not have a mehtod called getCounterValue. You need to call the CounterContextListener's method, which means you have to create one:
  CounterContextListener ccl = new CounterContextListener();
  String counter = ccl.getCounterValue(context);Second, why give the counter context listener two jobs that it doesn't need? You should make a new object - a Counter class:
public class Counter {
  private int count;
  public Counter() { this(0); }
  public Counter(String initialValue) {
    this(Integer.parseInt(initialValue);
  public Counter(Integer initialValue) {
    this(initialValue.intValue());
  public Counter (int initialValue) {
    count = initialValue;
  public Integer getCount() { return new Integer(count); }
  public void increment() { addCount(1); }
  public void decriment() { addCount(-1); }
  public void addCount(int amountToAdd) {
    count = count + amountToAdd;
}Then in your context listener, all you do is add one of these to the context:
public class CounterContextListener implement ServletContextListener {
    public void contextInitialized(ServletContextEvent sce) {
        ServletContext context = sce.getServletContext();
        Counter counter = new Counter();
        context.setAttribute("counter", counter);
    public void contextDestroyed(ServletContextEvenet sce) {
    }In your servlet, you get the counter from the context, get the count, and increment it if you want to:
public void MyServlet exctends HttpServlet {
    public void doPost( ... ) ... {
        ServletContext context = this.getServletContext();
        Counter counter = context.getCounter();
        int count = counter.getCount();
        counter.increment();
}