package commercials;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.util.*;/** * Commercials class randomizes a commercial from a given list. * Initialization-parameters: "commercialsfile" is where you store the * commercials *  * The number before the commercial is the "priority number", the higher, the * bigger the chance is that this commercial appears. *  * @version 1.0 * @since 1.0 * @see HttpServlet */public final class Commercials extends HttpServlet {	private static final String XML_VERSION = "<?xml version=\"1.0\"?>";	private static final String CONTENT_TYPE = "text/vnd.wap.wml";	private static final String DOC_TYPE = "<!DOCTYPE wml PUBLIC \"-//WAPFORUM//DTD WML 1.1//EN\"\n"			+ "  \"http://www.wapforum.org/DTD/wml_1.1.xml\">";	private static final Vector commercials = new Vector();	private static int[] priorities = null;	private static int prioritiesTogether = 0;	/**	 * This is the initialization code that runs only once. The servlet is being	 * placed into service.	 * 	 * @exception ServletException	 *                if an error occurs	 */	public void init() throws ServletException {		String commercialsFile = getInitParameter("commercialsfile");		commercialsFile = getServletContext().getRealPath(commercialsFile);		try {			BufferedReader reader = new BufferedReader(new FileReader(					commercialsFile));			String line;			while ((line = reader.readLine()) != null) {				if (line.trim().equals(""))					break;				commercials.add(line);			}		} catch (java.io.IOException e) {			System.err.println(e);			throw new ServletException(e);		}		priorities = new int[commercials.size()];		for (int i = 0; i < commercials.size(); ++i) {			String commercial = (String) commercials.get(i);			StringTokenizer st = new StringTokenizer(commercial, ";");			int number = Integer.parseInt(st.nextToken());			priorities[i] = number;			prioritiesTogether += number;		}	}	/**	 * "doGet" is called when we want a commercial to appear.	 * 	 * @param request	 *            a <code>HttpServletRequest</code> value	 * @param response	 *            a <code>HttpServletResponse</code> value	 * @exception ServletException	 *                if an error occurs	 * @exception IOException	 *                if an error occurs	 */	public void doGet(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		HttpSession session = request.getSession();		boolean cookieCompatible = false;		String chosenCommercial = getRandomCommercial();		response.setContentType(CONTENT_TYPE);		// prevent caching of the response		response.setHeader("cache-control", "no-cache");		PrintWriter out = response.getWriter();		out.println(XML_VERSION);		out.println(DOC_TYPE);		out.println("<wml>");		out.println("<template>");		out.println("<do type=\"prev\">");		out.println("<prev/>");		out.println("</do>");		out.println("</template>");		out.println("<card id=\"ads\" title=\"Ads\">");		out.println("<p align=\"center\">***<br/>");		out.println(chosenCommercial);		out.println("<br/>***</p>");		out.println("</card>");		out.println("</wml>");	}	/**	 * Selects randomly a commercial to be shown according to set priorities for	 * the commercials	 * 	 * @return a <code>String</code> value	 */	public static String getRandomCommercial() {		try {			if (priorities == null || priorities.length == 0)				return "";			int rnd = (int) (Math.random() * prioritiesTogether);			int commercialToBeChosen = 0;			int x = priorities[commercialToBeChosen];			while (x <= rnd)				x += priorities[++commercialToBeChosen];			StringTokenizer st = new StringTokenizer((String) commercials					.get(commercialToBeChosen), ";");			System.out.println("commercial: "					+ (String) commercials.get(commercialToBeChosen));			st.nextToken();			String chosenCommercial = st.nextToken();			return chosenCommercial == null ? "" : chosenCommercial;		} catch (Exception e) {			System.err.println(e);			return "";		}	}}