package ajaxbook.chap4;import java.io.*;import java.text.ParseException;import java.text.SimpleDateFormat;import javax.servlet.*;import javax.servlet.http.*;public class ValidationServlet extends HttpServlet {            /** Handles the HTTP <code>GET</code> method.     * @param request servlet request     * @param response servlet response     */    protected void doGet(HttpServletRequest request, HttpServletResponse response)    throws ServletException, IOException {        PrintWriter out = response.getWriter();                boolean passed = validateDate(request.getParameter("birthDate"));        response.setContentType("text/xml");        response.setHeader("Cache-Control", "no-cache");        String message = "You have entered an invalid date.";                if (passed) {            message = "You have entered a valid date.";        }        out.println("<response>");        out.println("<passed>" + Boolean.toString(passed) + "</passed>");        out.println("<message>" + message + "</message>");        out.println("</response>");        out.close();     }        /**     * Checks to see whether the argument is a valid date.     * A null date is considered invalid. This method     * used the default data formatter and lenient     * parsing.     *     * @param date a String representing the date to check     * @return message a String represnting the outcome of the check     */    private boolean validateDate(String date) {                boolean isValid = true;        if(date != null) {            SimpleDateFormat formatter= new SimpleDateFormat("MM/dd/yyyy");            try {                formatter.parse(date);             } catch (ParseException pe) {                System.out.println(pe.toString());                isValid = false;            }        } else {            isValid = false;        }        return isValid;    }}