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Demo

PagesElement.java

package edu.virtualschool.jwaa.xml;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.log4j.Logger;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;

import edu.virtualschool.jwaa.Fault;
import edu.virtualschool.jwaa.GenericIdentifiable;
import edu.virtualschool.jwaa.IOFault;
import edu.virtualschool.jwaa.field.*;
import edu.virtualschool.jwaa.field.FieldUtil;
import edu.virtualschool.jwaa.field.Validatable;

public class PagesElement extends GenericIdentifiable
{
  final ApplicationElement app;
  final FileField fileMonitor;
  final ArrayList pageList = new ArrayList();
  boolean needsCommit = false;
  
  final static Logger logger = Logger.getLogger(PagesElement.class.getName());
  
  PagesElement(ApplicationElement parent, Element element)  throws Fault
  {
    super(element.getAttributeValue("id"));
    this.app = parent;
    String path = element.getAttributeValue("path");
    this.fileMonitor = new FileField(parent.getDirectory().toString(), path);
    FieldUtil.validateFields(new Validatable[] { fileMonitor});
    logger.info("Constructing pages "+fileMonitor);
  }
  void update() throws Fault
  {
    if (!fileMonitor.isUpToDate())
    {
      logger.info("Updating pages "+fileMonitor);
      try
      {
        FileInputStream fis = new FileInputStream(fileMonitor.file);
        BufferedInputStream bis = new BufferedInputStream(fis);
        SAXBuilder builder = new SAXBuilder();
        
        Document dom = builder.build(fis);
        Element rootElement = dom.getRootElement();
        if (!rootElement.getName().equals("pages"))
          throw new ValidationFault("requires pages as root element, got "+rootElement);

        pageList.clear();
        List list = rootElement.getChildren("page", rootElement.getNamespace());
        for (Iterator iterator = list.iterator(); iterator.hasNext(); )
        {
          Element element = (Element)iterator.next();
          PageElement page = new PageElement(this, element);
          if (findPage(page.id) != null)
            throw new ValidationFault(fileMonitor+" contains a multiply defined page id: "+page.id);
          pageList.add(page);
          iterator.remove(); // detach element from parent
        }
        fis.close();
      }
      catch (IOException e)
      {
        throw new IOFault("IOFault loading " + fileMonitor, e);
      }
      catch (JDOMException e)
      {
        throw new ValidationFault
          ("Validation fault in "+fileMonitor+"\n"+e.getMessage());
      }
      fileMonitor.update();
      needsCommit = true;
    }
  }
  public void commit() throws ValidationFault
  {
    if (needsCommit)
    {
      for (Iterator iterator = pageList.iterator(); iterator.hasNext(); )
      {
        PageElement page = (PageElement)iterator.next();
        page.commit();
      }
    }
  }

  public final PageElement getFirstPage()
  {
    if (pageList.size() < 1)
      return null;
    else 
      return (PageElement)pageList.get(0);
  }
  public final PageElement findPage(String id)
  {
    for (Iterator iterator = pageList.iterator(); iterator.hasNext(); )
    {
      PageElement page = (PageElement)iterator.next();
      if (page.id.equals(id))
        return page;
    }
    return null;
  }
  public final ApplicationElement getApplication() 
  {
    return app;
  }
  public final ArrayList getPages() 
  {
    return pageList;
  }
  public String getFilePath()
  {
    return fileMonitor.file.toString();
  }
}