org.navimatrix.jaxen.function.BooleanFunction Maven / Gradle / Ivy
/*
* $Header: /cvs/jaxen/jaxen/src/java/main/org/jaxen/function/BooleanFunction.java,v 1.17 2006/02/05 21:47:41 elharo Exp $
* $Revision: 1.17 $
* $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 and
* James Strachan . For more information on the
* Jaxen Project, please see
* 4.3 boolean boolean(object)
*
*
*
*
* The boolean
* function converts its argument to a boolean as follows:
*
*
*
*
* -
*
* a number is true if and only if it is neither positive or negative
* zero nor NaN
*
*
*
* -
*
* a node-set is true if and only if it is non-empty
*
*
*
* -
*
* a string is true if and only if its length is non-zero
*
*
*
* -
*
*
* an object of a type other than the four basic types is converted to a
* boolean in a way that is dependent on that type
*
*
*
* @author bob mcwhirter (bob @ werken.com)
* @see Section 4.3 of the XPath Specification
*/
public class BooleanFunction implements Function
{
/**
* Create a new BooleanFunction object.
*/
public BooleanFunction() {}
/** Convert the argument to a Boolean
*
* @param context the context at the point in the
* expression when the function is called
* @param args a list with exactly one item which will be converted to a
* Boolean
*
* @return the result of evaluating the function;
* Boolean.TRUE or Boolean.FALSE
*
* @throws FunctionCallException if args has more or less than one item
*/
public Object call(Context context,
List args) throws FunctionCallException
{
if ( args.size() == 1 )
{
return evaluate( args.get(0), context.getNavigator() );
}
throw new FunctionCallException("boolean() requires one argument");
}
/**
* Convert the argument obj to a Boolean
* according to the following rules:
*
*
* - Lists are false if they're empty; true if they're not.
* - Booleans are false if they're false; true if they're true.
* - Strings are false if they're empty; true if they're not.
* - Numbers are false if they're 0 or NaN; true if they're not.
* - All other objects are true.
*
*
* @param obj the object to convert to a boolean
* @param nav ignored
*
* @return Boolean.TRUE or Boolean.FALSE
*/
public static Boolean evaluate(Object obj, Navigator nav)
{
if ( obj instanceof List )
{
List list = (List) obj;
// if it's an empty list, then we have a null node-set -> false
if (list.size() == 0)
{
return Boolean.FALSE;
}
// otherwise, unwrap the list and check the primitive
obj = list.get(0);
}
// now check for primitive types
// otherwise a non-empty node-set is true
// if it's a Boolean, let it decide
if ( obj instanceof Boolean )
{
return (Boolean) obj;
}
// if it's a Number, != 0 -> true
else if ( obj instanceof Number )
{
double d = ((Number) obj).doubleValue();
if ( d == 0 || Double.isNaN(d) )
{
return Boolean.FALSE;
}
return Boolean.TRUE;
}
// if it's a String, "" -> false
else if ( obj instanceof String )
{
return ( ((String)obj).length() > 0
? Boolean.TRUE
: Boolean.FALSE );
}
else
{
// assume it's a node so that this node-set is non-empty
// and so it's true
return ( obj != null ) ? Boolean.TRUE : Boolean.FALSE;
}
}
}
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