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Demo

GenericServlet.java

package edu.virtualschool.jwaa;

import java.io.IOException;
import java.util.HashMap;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Logger;

public abstract class GenericServlet extends HttpServlet
{
  final HashMap dispatchTable = new HashMap();
  static Logger logger = Logger.getLogger(GenericServlet .class.getName());

  public GenericServlet(MetaPage[] metaPages)
  {
    BasicConfigurator.configure();
    for (int i = 0; i < metaPages.length; i++)
    {
      MetaPage metaPage = metaPages[i];
      String url = metaPage.link.getText();

      MetaPage prior = (MetaPage)dispatchTable.get(url);
      if (prior != null)
        logger.error("Non-unique url: " + url + ". See \n" +
            " page "+metaPage+" and \n" +
            " page "+prior + "\n");

      dispatchTable.put(url, metaPage);
    }
  }
  public void doGet(HttpServletRequest req, HttpServletResponse rsp)
    throws ServletException, IOException
  {
    doRequest(req, rsp);
  }
  public void doPost(HttpServletRequest req, HttpServletResponse rsp)
    throws ServletException, IOException
  {
    doRequest(req, rsp);
  }
  public final void  doRequest(HttpServletRequest req, HttpServletResponse rsp)
    throws IOException, ServletException
  {
    AccountAbstraction person = getAccountOrNull(req);
    String uri = req.getRequestURI();
    MetaPage meta = findMetaPage(uri);
    logRequest(meta, req, rsp);
    if (!meta.allowsAccessBy(person))
        meta = getRefusePage();
    try
    {
      GenericPage page = (GenericPage)meta.pageClass.newInstance();
      page.init(meta, this, req, rsp);
      page.run();
    }
    catch (IgnorableFault e)
    {
    }
    catch (IOFault e)
    {
      doFault(meta, req, rsp, e);
      throw (IOException)e.getChainedException();
    }
    catch (IOException e)
    {
      doFault(meta, req, rsp, e);
      throw e;
    }
    catch (ServletException e)
    {
      doFault(meta, req, rsp, e);
      throw e;
    }
    catch (Throwable e)
    {
      doFault(meta, req, rsp, e);
    }
  }
  public AccountAbstraction getAccountOrNull(HttpServletRequest req)
  {
    HttpSession session = req.getSession();
    if (session == null)
      return null;
    AccountAbstraction person = (AccountAbstraction) session.getAttribute(GenericPage.SESSION_ATTRIBUTE_NAME);
    if (person == null)
      return null;
    else
      return person;
  }
  public void  logRequest(MetaPage meta, HttpServletRequest req, HttpServletResponse rsp)
  {
    if (logger.isDebugEnabled())
    {
      logger.debug("request: "+req.getClass().getName());
      logger.debug("  contextPath:    "+req.getContextPath());
      logger.debug("  servletPath:    "+req.getServletPath());
      logger.debug("  pathInfo:       "+req.getPathInfo());
      logger.debug("  queryString:    "+req.getQueryString());
      logger.debug("  requestURI:     "+req.getRequestURI());
      logger.debug("  page:           "+meta);
    }
  }
  public MetaPage findMetaPage(String key)
  {
    Object o = dispatchTable.get(key);
    MetaPage meta = (MetaPage)o;
    if (meta == null)
      meta = getDefaultPage(); 
    return meta;
  }
  public abstract void doFault(MetaPage meta, HttpServletRequest req, HttpServletResponse rsp, Throwable e);
  public abstract AccountAbstraction getNullAccount();
  public abstract MetaPage getDefaultPage();
  public abstract MetaPage getRefusePage();
  public abstract MetaPage getRootPage();
//  /**
//   * Get the servlet name from ServletConfig
//   * 
//   * @return String
//   */
//  public final String getServletNameX()
//  {
//    ServletConfig config = getServletConfig();
//    if (config == null)
//      return "ServletConfig not initialized";
//    else
//      return config.getServletName();
//  }
//  public final String getContextNameX()
//  {
//    ServletConfig config = getServletConfig();
//    ServletContext context = config.getServletContext();
//    return context.getServletContextName();
//  }
//  public final String toString()
//  {
//    return getServletName();
//  }

  public final RequestDispatcher getRequestDispatcher(String path) throws IOFault
  {
    if (!path.startsWith("/"))
      throw new IOFault("" + path + " does not begin with \"/\"");
    else
    {
      int i = path.indexOf("/", 1);
      if (i < 0)
        throw new IOFault("" + path + " does not begin with \"/contextName/\"");

      String pathInContext = path.substring(i);
      ServletContext servletContext = getServletContext();
      RequestDispatcher dispatcher =
        servletContext.getRequestDispatcher(pathInContext);

      if (dispatcher == null)
        throw new IOFault(
          "" + this +".getRequestDispatcher: " + path + " failed");
      return dispatcher;
    }
  }
}