subsetiteratorfilter.java

webwork source

/*
 * WebWork, Web Application Framework
 *
 * Distributable under Apache license.
 * See terms of license at opensource.org
 */
package webwork.util;

import org.apache.commons.logging.*;

import java.util.ArrayList;
import java.util.Iterator;

/**
 *	A bean that takes an iterator and outputs a subset of it.
 *
 *	@author Rickard 謆erg ([e-mail])
 *	@version $Revision: 1.9 $
 */
public class SubsetIteratorFilter
   extends IteratorFilterSupport
   implements java.util.Iterator, webwork.action.Action
{
   // Attributes ----------------------------------------------------
   int start = 0;
   int count = -1;
   int currentCount = 0;
   Object source;
   Iterator iterator;

   // Public --------------------------------------------------------
   public void setSource(Object anIterator)
   {
      source = anIterator;
   }

   public void setStart(int aStart)
   {
      this.start = aStart;
   }

   public void setCount(int aCount)
   {
      this.count = aCount;
   }

   // Action implementation -----------------------------------------
   public String execute()
   {
      if (source==null) {
         LogFactory.getLog(SubsetIteratorFilter.class.getName()).warn("Source is null returning empty set.");
         return ERROR;
      }

      // Make source transformations
      source = getIterator(source);

      // Calculate iterator filter
      if (source instanceof Iterator)
      {
         iterator = (Iterator)source;

         // Read away <start> items
         for (int i = 0; i < start && iterator.hasNext(); i++)
            iterator.next();
      } else if(source.getClass().isArray())
      {
         ArrayList list = new ArrayList(((Object[])source).length);
         Object[] objects = (Object[])source;
         int len = objects.length;
         if (count != -1)
            len -= count;
         for(int j = start; j < len; j++)
            list.add(objects[j]);
         count = -1; // Don't have to check this in the iterator code
         iterator = list.iterator();
      }

      if (iterator == null)
         throw new IllegalArgumentException("Source is not an iterator:"+source);

      return SUCCESS;
   }

   // Iterator implementation ---------------------------------------
   public boolean hasNext()
   {
      return (iterator==null) ? false: iterator.hasNext() && (count == -1 || currentCount < count);
   }

   public Object next()
   {
      currentCount++;
      return iterator.next();
   }

   public void remove()
   {
      iterator.remove();
   }
}