commercials.java

Java的wap push

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 "";
		}
	}

}