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

All Implemented Interfaces:

Cloneable, DTMIterator, ExpressionNode, PathComponent, Serializable, javax.xml.transform.SourceLocator, XPathVisitable

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

Field Summary

Fields inherited from class org.apache.xpath.objects.XNodeSet

S_EQ, S_GT, S_GTE, S_LT, S_LTE, S_NEQ

Fields inherited from class org.apache.xpath.axes.NodeSequence

m_dtmMgr, m_iter, m_last, m_next

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, m_obj

Fields inherited from class org.apache.xpath.Expression

Fields inherited from interface org.apache.xml.dtm.DTMIterator

FILTER_ACCEPT, FILTER_REJECT, FILTER_SKIP

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.
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.
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

addNodeInDocOrder, allowDetachToRelease, clone, cloneWithReset, detach, fixupVariables, getAnalysisBits, getAxis, getContainedIter, getCurrentNode, getCurrentPos, getDTM, getDTMManager, getExpandEntityReferences, getLength, getRoot, getVector, getWhatToShow, hasCache, isDocOrdered, isFresh, isMutable, item, nextNode, previousNode, reset, runTo, setCurrentPos, setItem, setIter, setRoot, setShouldCacheNodes, SetVector

Methods inherited from class org.apache.xpath.objects.XObject

callVisitors, castToType, create, create, deepEquals, destruct, error, error, 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, isSameClass, isStableNumber, num, warn, xstr

Methods inherited from class java.lang.Object

equals, finalize, 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.

Overrides:

getType in class XNodeSet

Returns:

type CLASS_NULL

getTypeString

public String getTypeString()

Given a request type, return the equivalent string. For diagnostic purposes.

Overrides:

getTypeString in class XNodeSet

Returns:

type string "#CLASS_NULL"

num

public double num()

Cast result object to a number.

Overrides:

num in class XNodeSet

Returns:

0.0

bool

public boolean bool()

Cast result object to a boolean.

Overrides:

bool in class XNodeSet

Returns:

false

str

public String str()

Cast result object to a string.

Overrides:

str in class XNodeSet

Returns:

empty string ""

rtf

public int rtf(XPathContext support)

Cast result object to a result tree fragment.

Overrides:

rtf in class XObject

Parameters:

support - XPath context to use for the conversion

Returns:

The object as a result tree fragment.

equals

public boolean equals(XObject obj2)

Tell if two objects are functionally equal.

Overrides:

equals in class XNodeSet

Parameters:

obj2 - Object to compare this to

Returns:

True if the given object is of type CLASS_NULL