src/main/java/freemarker/template/utility/Constants.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,
 * 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.utility;

import freemarker.template.SimpleNumber;
import freemarker.template.TemplateBooleanModel;
import freemarker.template.TemplateCollectionModel;
import freemarker.template.TemplateHashModelEx;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;
import freemarker.template.TemplateModelIterator;
import freemarker.template.TemplateNumberModel;
import freemarker.template.TemplateScalarModel;
import freemarker.template.TemplateSequenceModel;

/**
 * Frequently used constant {@link TemplateModel} values.
 * 
 * <p>These constants should be stored in the {@link TemplateModel}
 * sub-interfaces, but for bacward compatibility they are stored here instead.
 * Starting from FreeMarker 2.4 they should be copyed (not moved!) into the
 * {@link TemplateModel} sub-interfaces, and this class should be marked as
 * deprecated.</p>
 */
public class Constants {

    public static final TemplateBooleanModel TRUE = TemplateBooleanModel.TRUE;

    public static final TemplateBooleanModel FALSE = TemplateBooleanModel.FALSE;
    
    public static final TemplateScalarModel EMPTY_STRING = (TemplateScalarModel) TemplateScalarModel.EMPTY_STRING;

    public static final TemplateNumberModel ZERO = new SimpleNumber(0);
    
    public static final TemplateNumberModel ONE = new SimpleNumber(1);
    
    public static final TemplateNumberModel MINUS_ONE = new SimpleNumber(-1);
    
    public static final TemplateModelIterator EMPTY_ITERATOR = new TemplateModelIterator() {

        public TemplateModel next() throws TemplateModelException {
            throw new TemplateModelException("The collection has no more elements.");
        }

        public boolean hasNext() throws TemplateModelException {
            return false;
        }
        
    };

    public static final TemplateCollectionModel EMPTY_COLLECTION = new TemplateCollectionModel() {

        public TemplateModelIterator iterator() throws TemplateModelException {
            return EMPTY_ITERATOR;
        }
        
    };
    
    public static final TemplateSequenceModel EMPTY_SEQUENCE
            = new TemplateSequenceModel() {
    
        public TemplateModel get(int index) throws TemplateModelException {
            return null;
        }
    
        public int size() throws TemplateModelException {
            return 0;
        }
        
    };
    
    public static final TemplateHashModelEx EMPTY_HASH = new TemplateHashModelEx() {

        public int size() throws TemplateModelException {
            return 0;
        }

        public TemplateCollectionModel keys() throws TemplateModelException {
            return EMPTY_COLLECTION;
        }

        public TemplateCollectionModel values() throws TemplateModelException {
            return EMPTY_COLLECTION;
        }

        public TemplateModel get(String key) throws TemplateModelException {
            return null;
        }

        public boolean isEmpty() throws TemplateModelException {
            return true;
        }
        
    };
    
}