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/*
 * ====================================================================
 * This software is subject to the terms of the Common Public License
 * Agreement, available at the following URL:
 *   http://www.opensource.org/licenses/cpl.html .
 * Copyright (C) 2003-2004 TONBELLER AG.
 * All Rights Reserved.
 * You must accept the terms of that agreement to use this software.
 * ====================================================================
 *
 * 
 */
package net.sf.wcfart.wcf.controller;

import java.util.List;

import javax.servlet.http.HttpSession;

/**
 * provides access to the dispatcher and next view
 */
public abstract class Controller implements RequestListener {
  private static final Controller NULL_CONTROLLER = new Controller() {
    public void addRequestListener(RequestListener l) {
    }

    public String getNextView() {
      return null;
    }

    public List getRootListeners() {
      return null;
    }

    public void removeRequestListener(RequestListener l) {
    }

    public void setNextView(String uri) {
    }

    public void request(RequestContext context) throws Exception {
    }
  };
  public static Controller instance(HttpSession session) {
    try {
      return WcfController.instance(session);
    } catch (IllegalStateException e) {
      // session already invalidated
      return NULL_CONTROLLER;
      
    }
  }
  
  public abstract void addRequestListener(RequestListener l);
  public abstract void removeRequestListener(RequestListener l);
  public abstract void setNextView(String uri);
  public abstract String getNextView();

  /**
   * returns all registered RequestListeners
   */
  public abstract List getRootListeners();
}