/*
* $Id: SubsetIteratorFilter.java 651946 2008-04-27 13:41:38Z apetrelli $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.struts2.util;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
/**
* A bean that takes an iterator and outputs a subset of it.
*
*/
public class SubsetIteratorFilter extends IteratorFilterSupport implements Iterator, Action {
private static final Logger LOG = LoggerFactory.getLogger(SubsetIteratorFilter.class);
Iterator iterator;
Object source;
int count = -1;
int currentCount = 0;
Decider decider;
// Attributes ----------------------------------------------------
int start = 0;
public void setCount(int aCount) {
this.count = aCount;
}
// Public --------------------------------------------------------
public void setSource(Object anIterator) {
source = anIterator;
}
public void setStart(int aStart) {
this.start = aStart;
}
public void setDecider(Decider aDecider) {
this.decider = aDecider;
}
// Action implementation -----------------------------------------
public String execute() {
if (source == null) {
LoggerFactory.getLogger(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();
}
// now let Decider decide if element should be added (if a decider exist)
if (decider != null) {
List list = new ArrayList();
while(iterator.hasNext()) {
Object currentElement = iterator.next();
if (decide(currentElement)) {
list.add(currentElement);
}
}
iterator = list.iterator();
}
} else if (source.getClass().isArray()) {
ArrayList list = new ArrayList(((Object[]) source).length);
Object[] objects = (Object[]) source;
int len = objects.length;
if (count >= 0) {
len = start + count;
if (len > objects.length) {
len = objects.length;
}
}
for (int j = start; j < len; j++) {
if (decide(objects[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 < 0) || (currentCount < count)));
}
public Object next() {
currentCount++;
return iterator.next();
}
public void remove() {
iterator.remove();
}
// inner class ---------------------------------------------------
/**
* A decider determines if the given element should be added to the list or not.
*/
public static interface Decider {
/**
* Should the object be added to the list?
* @param element the object
* @return true to add.
* @throws Exception can be thrown.
*/
boolean decide(Object element) throws Exception;
}
// protected -----------------------------------------------------
protected boolean decide(Object element) {
if (decider != null) {
try {
boolean okToAdd = decider.decide(element);
return okToAdd;
}
catch(Exception e) {
LOG.warn("decider ["+decider+"] encountered an error while decide adding element ["+element+"], element will be ignored, it will not appeared in subseted iterator", e);
return false;
}
}
return true;
}
}
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