Oracle8i Application Developer's Guide - XML
Release 3 (8.1.7)

Part Number A86030-01


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Customizing Content with XML: Dynamic News Application, 12 of 16

1 Get End-User Preferences

Logic for processing preferences is distributed throughout the application, which stores the data both in the database and in client-side cookies. The application reads preference data from a cookie whenever possible to improve performance. If it can't get the data from a cookie (for example, because the end-user is visiting the site for the first time, or the end-user's browser does not accept cookies), the application reads preference data from the database.

From a Client-Side Cookie

The two methods below show how the application processes preference data stored in a cookie. Both methods come from xmlnews.common.UserPreference. Here's a sample cookie:


The cookie uses dollar signs to separate preference values, pound signs to separate categories, and three asterisks as a token to separate user ID and preference data. The sample cookie above shows that user 242 wants items from categories 3 and 4. In category 3, the user wants items of all types in all subcategories (a value of 0 selects all items). In category 4, the user wants items from subcategory 2 only, and within that subcategory, only items of type 1.

The sample app processes such cookies in two steps:

  1. First, getNewsCookie gets the "DynamicServlet" cookie from the browser that issued the HTTP request.

  2. Then loadPreferenceFromCookie parses it to get a String that contains that user's ID and preferences.

    public Cookie getNewsCookie(HttpServletRequest request)
                      throws Exception {
              Cookie c[] = request.getCookies();
              Cookie l_returnCookie = null;
                      for (int i = 0; (c!= null) && (i < c.length); i++) {
                      if (c[i].getName().equals("DynamicServlet")) {
                          l_returnCookie = c[i];
                        return l_returnCookie;
        public Vector loadPreferenceFromCookie(Cookie p_cookie) throws Exception {
              Vector l_prefId = new Vector(2);    
              String l_Preferences = p_cookie.getValue();
              StringTokenizer l_stToken = new StringTokenizer(l_Preferences, "***");
              String l_userId = "";
              while (l_stToken.hasMoreTokens()) {
                 // First Token is User Preference.
                 l_Preferences = l_stToken.nextToken();
                 // Second Token is User ID.
                 l_userId = l_stToken.nextToken();
              return l_prefId;

Querying the Database

If it can't read preferences from a cookie, the application queries the database. The class xmlnews.common.GenUtility implements methods that connect to the database and fetch news categories, sub-categories, and types.

The semi-dynamic servlet and the dynamic servlet both call these methods and the methods loadInitalPreference and constructUserPreference . These are both implemented in xmlnews/common/

Method loadInitalPreference calls getSubCategories, then loops through the result set, combining category values with separator characters to build a preference string.

public String loadInitialPreference(Vector p_category, Vector p_subcategory,
        Vector p_types, Connection p_con)
throws Exception {
GenUtility m_general = new GenUtility();
for (int i = 0; i < p_category.size(); i++) {
        String l_cat[] = (String []) p_category.elementAt(i);
        l_category = l_cat[0];
        Vector l_subcategory = m_general.getSubCategories(p_con,l_cat[0]);

        for(int l_j = 0, l_k = 0; l_j < l_subcategory.size(); l_j++, l_k++)
// Append the next preferences to the constructed string
   l_userPref = l_userPref+"#"+l_category+"$"+l_subCat+"$"+l_typeStr;
    return l_userPref;

public static Vector getSubCategories(Connection p_conn, String p_categoryId)
    throws Exception {
    Vector l_subCats = new Vector();

PreparedStatement l_pstmt = p_conn.prepareStatement(
   "Select id, name from sub_categories where category_id = ? ");
    l_pstmt.setString(1, p_categoryId);
    ResultSet l_rset = l_pstmt.executeQuery();

while ( {
     String[] l_subCat = new String[2];
     l_subCat[0] = new String(l_rset.getString(1));
     l_subCat[1] = new String(l_rset.getString(2));
return l_subCats; 

For example, the following code comes from xmlnews.dynamic.DynamicServlet.service.

It calls these methods to read end-user preferences from the database, then uses the preferences to build an HTML page.

public void service(HttpServletRequest p_request, 
      HttpServletResponse p_  response)
      throws ServletException {

   // The following are declared elsewhere as class variables 
   // and initialized in the servlet's init method.
   // GenUtility m_general = null; 

   // m_general = new GenUtility();
   // UserPreference m_userPreference = null;
   // m_userPreference = new UserPreference();

   // If the database connection has been closed, reopen it.
      if (m_connection == null || m_connection.isClosed())
          m_connection = m_general.dbConnection();
      String l_preference = m_userPreference.loadInitialPreference(
      null, m_general.getTypes(m_connection),

m_userPreference = m_userPreference.constructUserPreference
   ( l_preference,m_status);

   // Display the Dynamic Page
      this.sendDynamicPage(l_browserType, p_response, 
      l_userName, m_userPreference,
      m_servletPath + "?REQUEST_TYPE=LOGIN_REQUEST",
      m_servletPath + "?REQUEST_TYPE=LOG_OUT_REQUEST",

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