src/main/java/freemarker/template/SimpleSequence.java

/*
 * 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,
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 * 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.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import freemarker.ext.beans.BeansWrapper;

/**
 * <p>A convenient implementation of a list. This
 * object implements {@link TemplateSequenceModel}, using an underlying 
 * <tt>java.util.List</tt> implementation.</p>
 *
 * <p>A <tt>SimpleSequence</tt> can act as a cache for a
 * <tt>TemplateCollectionModel</tt>, e.g. one that gets data from a
 * database.  When passed a <tt>TemplateCollectionModel</tt> as an
 * argument to its constructor, the <tt>SimpleSequence</tt> immediately 
 * copies all the elements and discards the <tt>TemplateCollectionModel</tt>.</p>
 *
 * <p>This class is thread-safe if you don't call the <tt>add</tt> method after you
 * have made the object available for multiple threads.
 *
 * <p><b>Note:</b><br />
 * As of 2.0, this class is unsynchronized by default.
 * To obtain a synchronized wrapper, call the {@link #synchronizedWrapper} method.</p>
 *
 * @see SimpleHash
 * @see SimpleScalar
 */
public class SimpleSequence extends WrappingTemplateModel
implements TemplateSequenceModel, Serializable {

    /**
     * @serial The <tt>List</tt> that this <tt>SimpleSequence</tt> wraps.
     */
    protected final List list;
    private List unwrappedList;

    /**
     * Constructs an empty simple sequence that will use the the default object 
     * wrapper set in 
     * {@link WrappingTemplateModel#setDefaultObjectWrapper(ObjectWrapper)}.
     */
    public SimpleSequence() {
        this((ObjectWrapper) null);
    }

    /**
     * Constructs an empty simple sequence with preallocated capacity and using
     * the default object wrapper set in 
     * {@link WrappingTemplateModel#setDefaultObjectWrapper(ObjectWrapper)}.
     */
    public SimpleSequence(int capacity) {
        list = new ArrayList(capacity);
    }

    /**
     * Constructs a simple sequence that will contain the elements
     * from the specified {@link Collection} and will use the the default 
     * object wrapper set in 
     * {@link WrappingTemplateModel#setDefaultObjectWrapper(ObjectWrapper)}.
     * @param collection the collection containing initial values. Note that a
     * copy of the collection is made for internal use.
     */
    public SimpleSequence(Collection collection) {
        this(collection, null);
    }
    
    /**
     * Constructs a simple sequence from the passed collection model using the
     * default object wrapper set in 
     * {@link WrappingTemplateModel#setDefaultObjectWrapper(ObjectWrapper)}.
     */
    public SimpleSequence(TemplateCollectionModel tcm) throws TemplateModelException {
        ArrayList alist = new ArrayList();
        for (TemplateModelIterator it = tcm.iterator(); it.hasNext();) {
            alist.add(it.next());
        }
        alist.trimToSize();
        list = alist;
    }

    /**
     * Constructs an empty simple sequence using the specified object wrapper.
     * @param wrapper The object wrapper to use to wrap objects into
     * {@link TemplateModel} instances. If null, the default wrapper set in 
     * {@link WrappingTemplateModel#setDefaultObjectWrapper(ObjectWrapper)} is
     * used.
     */
    public SimpleSequence(ObjectWrapper wrapper) {
        super(wrapper);
        list = new ArrayList();
    }
    
    /**
     * Constructs a simple sequence that will contain the elements
     * from the specified {@link Collection} and will use the specified object
     * wrapper.
     * @param collection the collection containing initial values. Note that a
     * copy of the collection is made for internal use.
     * @param wrapper The object wrapper to use to wrap objects into
     * {@link TemplateModel} instances. If null, the default wrapper set in 
     * {@link WrappingTemplateModel#setDefaultObjectWrapper(ObjectWrapper)} is
     * used.
     */
    public SimpleSequence(Collection collection, ObjectWrapper wrapper) {
        super(wrapper);
        list = new ArrayList(collection);
    }

    /**
     * Adds an arbitrary object to the end of this <tt>SimpleSequence</tt>.
     * If the object itself does not implement the {@link TemplateModel} 
     * interface, it will be wrapped into an appropriate adapter on the first 
     * call to {@link #get(int)}.
     *
     * @param obj the boolean to be added.
     */
    public void add(Object obj) {
        list.add(obj);
        unwrappedList = null;
    }

    /**
     * Adds a boolean to the end of this <tt>SimpleSequence</tt>, by 
     * coercing the boolean into {@link TemplateBooleanModel#TRUE} or 
     * {@link TemplateBooleanModel#FALSE}.
     *
     * @param b the boolean to be added.
     */
    public void add(boolean b) {
        if (b) {
            add(TemplateBooleanModel.TRUE);
        } 
        else {
            add(TemplateBooleanModel.FALSE);
        }
    }
    
    /**
     * Note that this method creates and returns a deep-copy of the underlying list used
     * internally. This could be a gotcha for some people
     * at some point who want to alter something in the data model,
     * but we should maintain our immutability semantics (at least using default SimpleXXX wrappers) 
     * for the data model. It will recursively unwrap the stuff in the underlying container. 
     */
    public List toList() throws TemplateModelException {
        if (unwrappedList == null) {
            Class listClass = list.getClass();
            List result = null;
            try {
                result = (List) listClass.newInstance();
            } catch (Exception e) {
                throw new TemplateModelException("Error instantiating an object of type " + listClass.getName() + "\n" + e.getMessage());
            }
            BeansWrapper bw = BeansWrapper.getDefaultInstance();
            for (int i=0; i<list.size(); i++) {
                Object elem = list.get(i);
                if (elem instanceof TemplateModel) {
                    elem = bw.unwrap((TemplateModel) elem);
                }
                result.add(elem);
            }
            unwrappedList = result;
        }
        return unwrappedList;
    }
    
    /**
     * @return the specified index in the list
     */
    public TemplateModel get(int i) throws TemplateModelException {
        try {
            Object value = list.get(i);
            if (value instanceof TemplateModel) {
                return (TemplateModel) value;
            }
            TemplateModel tm = wrap(value);
            list.set(i, tm);
            return tm;
        }
        catch(IndexOutOfBoundsException e) {
            return null;
//            throw new TemplateModelException(i + " out of bounds [0, " + list.size() + ")");
        }
    }

    public int size() {
        return list.size();
    }

    /**
     * @return a synchronized wrapper for list.
     */
    public SimpleSequence synchronizedWrapper() {
        return new SynchronizedSequence();
    }
    
    public String toString() {
        return list.toString();
    }

    private class SynchronizedSequence extends SimpleSequence {

        public void add(Object obj) {
            synchronized (SimpleSequence.this) {
                SimpleSequence.this.add(obj);
            }
        }

        public TemplateModel get(int i) throws TemplateModelException {
            synchronized (SimpleSequence.this) {
                return SimpleSequence.this.get(i);
            }
        }
        
        public int size() {
            synchronized (SimpleSequence.this) {
                return SimpleSequence.this.size();
            }
        }
        public List toList() throws TemplateModelException {
            synchronized (SimpleSequence.this) {
                return SimpleSequence.this.toList();
            }
        }
    }
}