Servlet chaining problem..

Question

import java.io.*;
    import javax.servlet.*;
    import javax.servlet.http.*;
    public class Deblink extends HttpServlet {
      public void doGet(HttpServletRequest req, HttpServletResponse res)
                                   throws ServletException, IOException {
        String contentType = req.getContentType();  // get the incoming type
        if (contentType == null) return;  // nothing incoming, nothing to do
        res.setContentType(contentType);  // set outgoing type to be incoming type
        PrintWriter out = res.getWriter();
        BufferedReader in = req.getReader();
        String line = null;
        while ((line = in.readLine()) != null) {
          line = replace(line, "<BLINK>", "");
          line = replace(line, "</BLINK>", "");
          out.println(line);
      public void doPost(HttpServletRequest req, HttpServletResponse res)
                                    throws ServletException, IOException {
        doGet(req, res);
      private String replace(String line, String oldString, String newString) {
        int index = 0;
        while ((index = line.indexOf(oldString, index)) >= 0) {
          // Replace the old string with the new string (inefficiently)
          line = line.substring(0, index) +
                 newString +
                 line.substring(index + oldString.length());
          index += newString.length();
        return line;
What is pre request fo above code to work.
I had tried this many time but it is not working, what will be calling servlet look like

Answer 1

And can you explain why your title is "Servlet chaining problem"?