ex6_44.txt

j2ee core design patterns

Example 6.44 	View Factory
public class ViewFactory {
  private static ViewFactory ourInstance;

  public synchronized static ViewFactory getInstance() {
    if (ourInstance == null) {
      ourInstance = new ViewFactory();
    }
    return ourInstance;
  }

  public String getViewTemplate(RequestContext requestContext, 
      String logicalViewName) {

    String viewHandle;
    Locale locale = requestContext.getUserLocale();
    String userAgent = requestContext.getUserAgent();

    // Identify ViewHandle from View Map
    viewHandle = getViewHandle(logicalViewName, userAgent, locale);
    return viewHandle;
  }

  private String getViewHandle(String logicalViewName, 
      String userAgent, Locale locale) {

    // select the View template to be displayed based on
    // logical view name, user locale, device type
    ViewMapKey viewKey = new ViewMapKey(
        logicalViewName, userAgent, locale);
    return (String) viewMap.get(viewKey);
  }

  private ViewFactory() {
    initializeViewMap();
  }

  private void initializeViewMap() {
    // initialization stub - This information would typically be
    // loaded from a ViewRegistry
    // viewMap.put ( logicalViewName, viewTemplateName);
  }

  private Map viewMap = new HashMap();
}