/*
* $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/StringFunction.java,v 1.33 2006/02/05 21:47:41 elharo Exp $
* $Revision: 1.33 $
* $Date: 2006/02/05 21:47:41 $
*
* ====================================================================
*
* Copyright 2000-2002 bob mcwhirter & James Strachan.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * 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.
*
* * Neither the name of the Jaxen Project nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS 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 COPYRIGHT OWNER
* OR 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 Jaxen Project and was originally
* created by bob mcwhirter <bob@werken.com> and
* James Strachan <jstrachan@apache.org>. For more information on the
* Jaxen Project, please see <http://www.jaxen.org/>.
*
* $Id: StringFunction.java,v 1.33 2006/02/05 21:47:41 elharo Exp $
*/
package org.jaxen.function;
import org.jaxen.Context;
import org.jaxen.Function;
import org.jaxen.FunctionCallException;
import org.jaxen.Navigator;
import org.jaxen.UnsupportedAxisException;
import org.jaxen.JaxenRuntimeException;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.DecimalFormatSymbols;
import java.util.List;
import java.util.Iterator;
import java.util.Locale;
/**
* <p>
* <b>4.2</b> <code><i>string</i> string(<i>object</i>)</code>
* </p>
*
*
* <blockquote src="http://www.w3.org/TR/xpath">
* <p>
* The <b>string</b> function converts
* an object to a string as follows:
* </p>
*
* <ul>
*
* <li>
* <p>
* A node-set is converted to a string by returning the <a
* href="http://www.w3.org/TR/xpath#dt-string-value" target="_top">string-value</a> of the node in the node-set
* that is first in <a href="http://www.w3.org/TR/xpath#dt-document-order" target="_top">document order</a>. If
* the node-set is empty, an empty string is returned.
* </p>
* </li>
*
* <li>
* <p>
* A number is converted to a string as follows
* </p>
*
* <ul>
*
* <li>
* <p>
* NaN is converted to the string <code>NaN</code>
* </p>
* </li>
*
* <li>
* <p>
* positive zero is converted to the string <code>0</code>
* </p>
* </li>
*
* <li>
*
* <p>
* negative zero is converted to the string <code>0</code>
* </p>
* </li>
*
* <li>
* <p>
* positive infinity is converted to the string <code>Infinity</code>
* </p>
* </li>
*
* <li>
* <p>
* negative infinity is converted to the string <code>-Infinity</code>
*
* </p>
* </li>
*
* <li>
* <p>
* if the number is an integer, the number is represented in decimal
* form as a <a href="http://www.w3.org/TR/xpath#NT-Number" target="_top">Number</a> with no decimal point and
* no leading zeros, preceded by a minus sign (<code>-</code>) if
* the number is negative
* </p>
* </li>
*
* <li>
* <p>
* otherwise, the number is represented in decimal form as a Number including a decimal point with at least
* one digit before the decimal point and at least one digit after the
* decimal point, preceded by a minus sign (<code>-</code>) if the
* number is negative; there must be no leading zeros before the decimal
* point apart possibly from the one required digit immediately before
* the decimal point; beyond the one required digit after the decimal
* point there must be as many, but only as many, more digits as are
* needed to uniquely distinguish the number from all other IEEE 754
* numeric values.
* </p>
*
* </li>
*
* </ul>
*
* </li>
*
* <li>
* <p>
* The boolean false value is converted to the string <code>false</code>.
* The boolean true value is converted to the string <code>true</code>.
* </p>
* </li>
*
* <li>
* <p>
* An object of a type other than the four basic types is converted to a
* string in a way that is dependent on that type.
* </p>
*
* </li>
*
* </ul>
*
* <p>
* If the argument is omitted, it defaults to a node-set with the
* context node as its only member.
* </p>
*
* </blockquote>
*
* @author bob mcwhirter (bob @ werken.com)
* @see <a href="http://www.w3.org/TR/xpath#function-string"
* target="_top">Section 4.2 of the XPath Specification</a>
*/
public class StringFunction implements Function
{
private static DecimalFormat format = (DecimalFormat) NumberFormat.getInstance(Locale.ENGLISH);
static {
DecimalFormatSymbols symbols = new DecimalFormatSymbols(Locale.ENGLISH);
symbols.setNaN("NaN");
symbols.setInfinity("Infinity");
format.setGroupingUsed(false);
format.setMaximumFractionDigits(32);
format.setDecimalFormatSymbols(symbols);
}
/**
* Create a new <code>StringFunction</code> object.
*/
public StringFunction() {}
/**
* Returns the string-value of <code>args.get(0)</code>
* or of the context node if <code>args</code> is empty.
*
* @param context the context at the point in the
* expression where the function is called
* @param args list with zero or one element
*
* @return a <code>String</code>
*
* @throws FunctionCallException if <code>args</code> has more than one item
*/
public Object call(Context context,
List args) throws FunctionCallException
{
int size = args.size();
if ( size == 0 )
{
return evaluate( context.getNodeSet(),
context.getNavigator() );
}
else if ( size == 1 )
{
return evaluate( args.get(0),
context.getNavigator() );
}
throw new FunctionCallException( "string() takes at most argument." );
}
/**
* Returns the XPath string-value of <code>obj</code>.
* This operation is only defined if obj is a node, node-set,
* <code>String</code>, <code>Number</code>, or
* <code>Boolean</code>. For other types this function
* returns the empty string.
*
* @param obj the node, node-set, string, number, or boolean
* whose string-value is calculated
* @param nav the navigator used to calculate the string-value
*
* @return a <code>String</code>. May be empty but is never null.
*/
public static String evaluate(Object obj,
Navigator nav)
{
try
{
// Workaround because XOM uses lists for Text nodes
// so we need to check for that first
if (nav != null && nav.isText(obj))
{
return nav.getTextStringValue(obj);
}
if (obj instanceof List)
{
List list = (List) obj;
if (list.isEmpty())
{
return "";
}
// do not recurse: only first list should unwrap
obj = list.get(0);
}
if (nav != null) {
// This stack of instanceof really suggests there's
// a failure to take advantage of polymorphism here
if (nav.isElement(obj))
{
return nav.getElementStringValue(obj);
}
else if (nav.isAttribute(obj))
{
return nav.getAttributeStringValue(obj);
}
else if (nav.isDocument(obj))
{
Iterator childAxisIterator = nav.getChildAxisIterator(obj);
while (childAxisIterator.hasNext())
{
Object descendant = childAxisIterator.next();
if (nav.isElement(descendant))
{
return nav.getElementStringValue(descendant);
}
}
}
else if (nav.isProcessingInstruction(obj))
{
return nav.getProcessingInstructionData(obj);
}
else if (nav.isComment(obj))
{
return nav.getCommentStringValue(obj);
}
else if (nav.isText(obj))
{
return nav.getTextStringValue(obj);
}
else if (nav.isNamespace(obj))
{
return nav.getNamespaceStringValue(obj);
}
}
if (obj instanceof String)
{
return (String) obj;
}
else if (obj instanceof Boolean)
{
return stringValue(((Boolean) obj).booleanValue());
}
else if (obj instanceof Number)
{
return stringValue(((Number) obj).doubleValue());
}
}
catch (UnsupportedAxisException e)
{
throw new JaxenRuntimeException(e);
}
return "";
}
private static String stringValue(double value)
{
// DecimalFormat formats negative zero as "-0".
// Therefore we need to test for zero explicitly here.
if (value == 0) return "0";
// need to synchronize object for thread-safety
String result = null;
synchronized (format) {
result = format.format(value);
}
return result;
}
private static String stringValue(boolean value)
{
return value ? "true" : "false";
}
}