/*
* $Header: /home/cvs/jakarta-commons-sandbox/jelly/src/java/org/apache/commons/jelly/expression/ExpressionSupport.java,v 1.6 2002/07/13 01:03:27 plynch Exp $
* $Revision: 1.6 $
* $Date: 2002/07/13 01:03:27 $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999-2002 The Apache Software Foundation. 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 acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* 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 APACHE SOFTWARE FOUNDATION 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 Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
* $Id: ExpressionSupport.java,v 1.6 2002/07/13 01:03:27 plynch Exp $
*/
package org.apache.commons.jelly.expression;
import java.util.Collections;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.apache.commons.collections.ArrayIterator;
import org.apache.commons.collections.EnumerationIterator;
import org.apache.commons.collections.SingletonIterator;
import org.apache.commons.jelly.JellyContext;
/** <p><code>ExpressionSupport</code>
* an abstract base class for Expression implementations
* which provides default implementations of some of the
* typesafe evaluation methods.</p>
*
* @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
* @version $Revision: 1.6 $
*/
public abstract class ExpressionSupport implements Expression {
protected static final Iterator EMPTY_ITERATOR = Collections.EMPTY_LIST.iterator();
// inherit javadoc from interface
public String evaluateAsString(JellyContext context) {
Object value = evaluate(context);
if ( value != null ) {
return value.toString();
}
return null;
}
// inherit javadoc from interface
public boolean evaluateAsBoolean(JellyContext context) {
Object value = evaluate(context);
if ( value instanceof Boolean ) {
Boolean b = (Boolean) value;
return b.booleanValue();
}
else if ( value instanceof String ) {
// return Boolean.getBoolean( (String) value );
String str = (String) value;
if ( str.equals( "on" )
||
str.equals( "yes" )
||
str.equals( "1" )
||
str.equals( "true" ) )
{
return true;
}
else
{
return false;
}
}
return false;
}
// inherit javadoc from interface
public Iterator evaluateAsIterator(JellyContext context) {
Object value = evaluate(context);
if ( value == null ) {
return EMPTY_ITERATOR;
}
else
if ( value instanceof Iterator ) {
return (Iterator) value;
}
else if ( value instanceof List ) {
List list = (List) value;
return list.iterator();
}
else if ( value instanceof Map ) {
Map map = (Map) value;
return map.entrySet().iterator();
}
else if ( value.getClass().isArray() ) {
return new ArrayIterator( value );
}
else if ( value instanceof Enumeration ) {
return new EnumerationIterator((Enumeration ) value);
}
else if ( value instanceof Collection ) {
Collection collection = (Collection) value;
return collection.iterator();
}
else {
// XXX: should we return single iterator?
return new SingletonIterator( value );
}
}
}