La classe UnsafeServlet | Servlet e Multithreading

La classe UnsafeServlet

package unsafeweb;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletConfig;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;

public class UnsafeServlet extends javax.servlet.http.HttpServlet
 implements javax.servlet.Servlet
{
 private String userID;
 private String password;

 public UnsafeServlet() { super(); }

 public void init(ServletConfig config) throws ServletException
 {
 super.init(config);
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException
 {
 String userID = request.getParameter("userID");
 String password = request.getParameter("password");

 this.userID = userID;
 this.password = password;

 try
 {
 String sleeptime = getInitParameter("sleep");
 int sleep = Integer.parseInt(sleeptime);
 Thread.sleep(sleep);
 }
 catch(Exception exc)
 {
 log("",exc);
 }

 try
 {
 response.setContentType("text/html");
 PrintWriter writer = response.getWriter();
 writer.println("<html><body>");
 writer.println("Valori delle variabili locali al metodo" + " doPost() ");
 writer.println("userID=" + userID + " ");
 writer.println("password=" + password + "");
 writer.println("Valori degli attributi della Servlet ");
 writer.println("userID=" + this.userID +" ");
 writer.println("password=" + this.password + "");
 writer.println("</body></html>");
 writer.close();
 }
 catch (Exception exc)
 {
 exc.printStackTrace();
 }
 }
}