wicket.extensions.markup.html.repeater.refreshing.ReuseIfModelsEqualStrategy Maven / Gradle / Ivy
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/*
* $Id: ReuseIfModelsEqualStrategy.java 462569 2006-10-10 21:15:40Z dashorst $
* $Revision: 462569 $
* $Date: 2006-10-10 23:15:40 +0200 (Tue, 10 Oct 2006) $
*
* ====================================================================
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package wicket.extensions.markup.html.repeater.refreshing;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import wicket.model.IModel;
/**
* Reuse strategy that will reuse an old item if its model is equal to a model
* inside the newModels iterator. Useful when state needs to be kept across
* requests for as long as the item is visible within the view.
*
* Notice that the model and not the model object needs to
* implement the equals method. Most of the time it is a good idea to forward
* the equals call to the object, however if a detachable model is used it is
* often enough to compare object ids models point to ( this saves the model
* from loading the object).
*
* @author Igor Vaynberg (ivaynberg)
*
*/
public class ReuseIfModelsEqualStrategy implements IItemReuseStrategy
{
private static final long serialVersionUID = 1L;
private static IItemReuseStrategy instance = new ReuseIfModelsEqualStrategy();
/**
* @return static instance
*/
public static IItemReuseStrategy getInstance()
{
return instance;
}
/**
* @see wicket.extensions.markup.html.repeater.refreshing.IItemReuseStrategy#getItems(wicket.extensions.markup.html.repeater.refreshing.IItemFactory,
* java.util.Iterator, java.util.Iterator)
*/
public Iterator getItems(final IItemFactory factory, final Iterator newModels,
Iterator existingItems)
{
final Map modelToItem = new HashMap();
while (existingItems.hasNext())
{
final Item item = (Item)existingItems.next();
modelToItem.put(item.getModel(), item);
}
return new Iterator()
{
private int index = 0;
public boolean hasNext()
{
return newModels.hasNext();
}
public Object next()
{
final IModel model = (IModel)newModels.next();
final Item oldItem = (Item)modelToItem.get(model);
final Item item;
if (oldItem == null)
{
item = factory.newItem(index, model);
}
else
{
oldItem.setIndex(index);
item = oldItem;
}
index++;
return item;
}
public void remove()
{
throw new UnsupportedOperationException();
}
};
}
}