org.apache.xpath.objects
Class XNull

java.lang.Object
  |
  +--org.apache.xpath.Expression
        |
        +--org.apache.xpath.objects.XObject
              |
              +--org.apache.xpath.axes.NodeSequence
                    |
                    +--org.apache.xpath.objects.XNodeSet
                          |
                          +--org.apache.xpath.objects.XNull

public class XNull
extends XNodeSet

This class represents an XPath null object, and is capable of converting the null to other types, such as a string.

See Also:
Serialized Form
Usage:

Fields inherited from class org.apache.xpath.objects.XObject
CLASS_BOOLEAN, CLASS_NODESET, CLASS_NULL, CLASS_NUMBER, CLASS_RTREEFRAG, CLASS_STRING, CLASS_UNKNOWN, CLASS_UNRESOLVEDVARIABLE
 
Constructor Summary
XNull()
          Create an XObject.
 
Method Summary
 boolean bool()
          Cast result object to a boolean.
 boolean equals(XObject obj2)
          Tell if two objects are functionally equal.
 int getType()
          Tell what kind of class this is.
 java.lang.String getTypeString()
          Given a request type, return the equivalent string.
 double num()
          Cast result object to a number.
 int rtf(XPathContext support)
          Cast result object to a result tree fragment.
 java.lang.String str()
          Cast result object to a string.
 
Methods inherited from class org.apache.xpath.objects.XNodeSet
appendToFsb, boolWithSideEffects, compare, dispatchCharactersEvents, getFresh, getNumberFromNode, getStringFromNode, greaterThan, greaterThanOrEqual, iter, iterRaw, lessThan, lessThanOrEqual, mutableNodeset, nodelist, nodeset, notEquals, numWithSideEffects, object, release, xstr
 
Methods inherited from class org.apache.xpath.axes.NodeSequence
allowDetachToRelease, clone, cloneWithReset, detach, fixupVariables, getAnalysisBits, getAxis, getContainedIter, getCurrentNode, getCurrentPos, getDTM, getDTMManager, getExpandEntityReferences, getLength, getRoot, getWhatToShow, hasCache, isDocOrdered, isFresh, isMutable, item, nextNode, previousNode, reset, runTo, setCurrentPos, setItem, setIter, setRoot, setShouldCacheNodes
 
Methods inherited from class org.apache.xpath.objects.XObject
callVisitors, castToType, create, create, deepEquals, destruct, execute, rtf, rtree, rtree, toString
 
Methods inherited from class org.apache.xpath.Expression
asIterator, asIteratorRaw, asNode, assertion, bool, canTraverseOutsideSubtree, error, execute, execute, execute, executeCharsToContentHandler, exprAddChild, exprGetChild, exprGetNumChildren, exprGetParent, exprSetParent, getColumnNumber, getExpressionOwner, getLineNumber, getPublicId, getSystemId, isNodesetExpr, isStableNumber, num, warn, xstr
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

XNull

public XNull()
Create an XObject.
Method Detail

getType

public int getType()
Tell what kind of class this is.
Returns:
type CLASS_NULL
Overrides:
getType in class XNodeSet

getTypeString

public java.lang.String getTypeString()
Given a request type, return the equivalent string. For diagnostic purposes.
Returns:
type string "#CLASS_NULL"
Overrides:
getTypeString in class XNodeSet

num

public double num()
Cast result object to a number.
Returns:
0.0
Overrides:
num in class XNodeSet

bool

public boolean bool()
Cast result object to a boolean.
Returns:
false
Overrides:
bool in class XNodeSet

str

public java.lang.String str()
Cast result object to a string.
Returns:
empty string ""
Overrides:
str in class XNodeSet

rtf

public int rtf(XPathContext support)
Cast result object to a result tree fragment.
Parameters:
support - XPath context to use for the conversion
Returns:
The object as a result tree fragment.
Overrides:
rtf in class XObject

equals

public boolean equals(XObject obj2)
Tell if two objects are functionally equal.
Parameters:
obj2 - Object to compare this to
Returns:
True if the given object is of type CLASS_NULL
Overrides:
equals in class XNodeSet


Copyright 2006 Apache XML Project. All Rights Reserved.