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  /*
   * Copyright (c) 2003 The Visigoth Software Society. All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in
  *    the documentation and/or other materials provided with the
  *    distribution.
  *
  * 3. The end-user documentation included with the redistribution, if
  *    any, must include the following acknowledgement:
  *       "This product includes software developed by the
  *        Visigoth Software Society (http://www.visigoths.org/)."
  *    Alternately, this acknowledgement may appear in the software itself,
  *    if and wherever such third-party acknowledgements normally appear.
  *
  * 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the 
  *    project contributors may be used to endorse or promote products derived
  *    from this software without prior written permission. For written
  *    permission, please contact visigoths@visigoths.org.
  *
  * 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
  *    nor may "FreeMarker" or "Visigoth" appear in their names
  *    without prior written permission of the Visigoth Software Society.
  *
  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED.  IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  * ====================================================================
  *
  * This software consists of voluntary contributions made by many
  * individuals on behalf of the Visigoth Software Society. For more
  * information on the Visigoth Software Society, please see
  * http://www.visigoths.org/
  */
 
 package freemarker.template;
 
 import java.util.*;

A simple implementation of TemplateCollectionModel. It's able to wrap java.util.Iterator-s and java.util.Collection-s. If you wrap an Iterator, the variable can be <list>-ed (<forach>-ed) only once!

Consider using SimpleSequence instead of this class if you want to wrap Iterators. SimpleSequence will read all elements of the Iterator, and store them in a List (this may cause too high resource consumption in some applications), so you can list the variable for unlimited times. Also, if you want to wrap Collections, and then list the resulting variable for many times, SimpleSequence may gives better performance, as the wrapping of non-TemplateModel objects happens only once.

This class is thread-safe. The returned TemplateModelIterator-s are not thread-safe.

Version:
$Id: SimpleCollection.java,v 1.13 2004/11/27 14:49:57 ddekany Exp $
 
 public class SimpleCollection extends WrappingTemplateModel
     
     private boolean iteratorDirty;
     private Iterator iterator;
     private Collection collection;
 
     public SimpleCollection(Iterator iterator) {
         this. = iterator;
     }
 
     public SimpleCollection(Collection collection) {
         this. = collection;
     }
 
     public SimpleCollection(Iterator iteratorObjectWrapper wrapper) {
         super(wrapper);
         this. = iterator;
     }
 
     public SimpleCollection(Collection collectionObjectWrapper wrapper) {
         super(wrapper);
         this. = collection;
     }

    
Retrieves a template model iterator that is used to iterate over the elements in this collection.

When you wrap an Iterator and you get TemplateModelIterator for multiple times, only on of the returned TemplateModelIterator instances can be really used. When you have called a method of a TemplateModelIterator instance, all other instance will throw a TemplateModelException when you try to call their methods, since the wrapped Iterator can't return the first element.

    public TemplateModelIterator iterator() {
        if ( != null) {
            return new SimpleTemplateModelIterator(true);
        } else {
            synchronized () {
                return new SimpleTemplateModelIterator(.iterator(), false);
            }
        }
    }
    
    /*
     * An instance of this class must be accessed only from a single thread.
     * The encapsulated Iterator may accessible from multiple threads (as multiple
     * SimpleTemplateModelIterator instance can wrap the same Iterator instance),
     * but the first thread which uses the shared Iterator will monopolize that.
     */
    private class SimpleTemplateModelIterator implements TemplateModelIterator {
        
        private Iterator iterator;
        private boolean iteratorShared;
            
        SimpleTemplateModelIterator(Iterator iteratorboolean iteratorShared) {
            this. = iterator;
            this. = iteratorShared;
        }
        public TemplateModel next() throws TemplateModelException {
            if (makeIteratorDirty();
            
            if (!.hasNext()) {
                throw new TemplateModelException("The collection has no more elements.");
            }
            
            Object value  = .next();
            if (value instanceof TemplateModel) {
                return (TemplateModelvalue;
            } else {
                return wrap(value);
            }
        }
        public boolean hasNext() throws TemplateModelException {
            /* 
             * Theorically this should not make the iterator dirty,
             * but I met sync. problems if I don't do it here. :(
             */
            if (makeIteratorDirty();
            return .hasNext();
        }
        
        private void makeIteratorDirty() throws TemplateModelException {
            synchronized (SimpleCollection.this) {
                if () {
                    throw new TemplateModelException(
                            "This collection variable wraps a java.util.Iterator, "
                            + "thus it can be <list>-ed or <foreach>-ed only once");
                } else {
                     = true;
                     = false;
                }
            }
        }
    }
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