org.apache.xpath.operations

Class VariableSafeAbsRef

java.lang.Object

org.apache.xpath.Expression

org.apache.xpath.operations.Variable

org.apache.xpath.operations.VariableSafeAbsRef

All Implemented Interfaces:

Serializable, SourceLocator, PathComponent, ExpressionNode, XPathVisitable

public class VariableSafeAbsRef
extends Variable

This is a "smart" variable reference that is used in situations where an absolute path is optimized into a variable reference, but may be used in some situations where the document context may have changed. For instance, in select="document(doc/@href)//name[//salary > 7250]", the root in the predicate will be different for each node in the set. While this is easy to detect statically in this case, in other cases static detection would be very hard or impossible. So, this class does a dynamic check to make sure the document context of the referenced variable is the same as the current document context, and, if it is not, execute the referenced variable's expression with the current context instead.

See Also:

Serialized Form

Field Summary

Fields inherited from class org.apache.xpath.operations.Variable

m_index, m_isGlobal, m_qname

Constructor Summary

Constructors

Constructor and Description
VariableSafeAbsRef()

Method Summary

Modifier and Type	Method and Description
XObject	execute(XPathContext xctxt, boolean destructiveOK) Dereference the variable, and return the reference value.

Methods inherited from class org.apache.xpath.operations.Variable

callVisitors, deepEquals, execute, fixupVariables, getAnalysisBits, getElemVariable, getGlobal, getIndex, getQName, isPsuedoVarRef, isStableNumber, setIndex, setIsGlobal, setQName

Methods inherited from class org.apache.xpath.Expression

asIterator, asIteratorRaw, asNode, assertion, bool, canTraverseOutsideSubtree, error, execute, execute, executeCharsToContentHandler, exprAddChild, exprGetChild, exprGetNumChildren, exprGetParent, exprSetParent, getColumnNumber, getExpressionOwner, getLineNumber, getPublicId, getSystemId, isNodesetExpr, isSameClass, num, warn, xstr

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

VariableSafeAbsRef

public VariableSafeAbsRef()

Method Detail

execute

public XObject execute(XPathContext xctxt,
                       boolean destructiveOK)
                throws TransformerException

Dereference the variable, and return the reference value. Note that lazy evaluation will occur. If a variable within scope is not found, a warning will be sent to the error listener, and an empty nodeset will be returned.

Overrides:

execute in class Variable

Parameters:

xctxt - The runtime execution context.

destructiveOK - true if a "safe" object doesn't need to be returned.

Returns:

The evaluated variable, or an empty nodeset if not found.

Throws:

TransformerException