Java Tutorial/Servlet/Counter

Servlet Simple Counter

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class MyServlet extends HttpServlet {
  int count = 0;
  public void doGet(HttpServletRequest req, HttpServletResponse res)
                               throws ServletException, IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();
    count++;
    out.println("Since loading, this servlet has been accessed " +
                count + " times.");
  }
}

Servlet Static Field As Counter

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
public class MyServlet extends HttpServlet {
  static int classCount = 0;  // shared by all instances
  int count = 0;              // separate for each servlet
  static Hashtable instances = new Hashtable();  // also shared
  public void doGet(HttpServletRequest req, HttpServletResponse res)
                               throws ServletException, IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();
    count++;
    out.println("Since loading, this servlet instance has been accessed " + count + " times.");
    // Keep track of the instance count by putting a reference to this
    // instance in a Hashtable. Duplicate entries are ignored.
    // The size() method returns the number of unique instances stored.
    instances.put(this, this);
    out.println("There are currently " +instances.size() + " instances.");
    classCount++;
    out.println("Across all instances, this servlet class has been " +
                "accessed " + classCount + " times.");
  }
}