Struts example source code file (SubsetIteratorFilter.java)

This example Struts source code file (SubsetIteratorFilter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Struts tags/keywords

arraylist, arraylist, decider, illegalargumentexception, iterator, iterator, iteratorfiltersupport, list, logger, object, object, source, source, string, util

The Struts SubsetIteratorFilter.java source code

/*
 * $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;
    }
}