commercials.java

wap push功能程序 WAP开发网 : http://www.wapkf.com

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 ""; }
    }

}