org.apache.xpath.operations
Class VariableSafeAbsRef

java.lang.Object
  |
  +--org.apache.xpath.Expression
        |
        +--org.apache.xpath.operations.Variable
              |
              +--org.apache.xpath.operations.VariableSafeAbsRef

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

Constructor Summary
VariableSafeAbsRef()
           
 
Method Summary
 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, num, warn, xstr
 
Methods inherited from class java.lang.Object
equals, 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.
Parameters:
xctxt - The runtime execution context.
Returns:
The evaluated variable, or an empty nodeset if not found.
Throws:
TransformerException -  
Overrides:
execute in class Variable


Copyright 2006 Apache XML Project. All Rights Reserved.