org.apache.xpath.functions

Class Function

Implemented Interfaces:
java.io.Serializable, ExpressionNode, SourceLocator, XPathVisitable
Known Direct Subclasses:
FuncCurrent, FuncExtFunction, FuncFalse, FuncLast, FuncPosition, FunctionOneArg, FuncTrue

public abstract class Function
extends Expression

This is a superclass of all XPath functions. This allows two ways for the class to be called. One method is that the super class processes the arguments and hands the results to the derived class, the other method is that the derived class may process it's own arguments, which is faster since the arguments don't have to be added to an array, but causes a larger code footprint.
See Also:
Serialized Form

Method Summary

void
callArgVisitors(XPathVisitor visitor)
Call the visitors for the function arguments.
void
callVisitors(ExpressionOwner owner, XPathVisitor visitor)
void
checkNumberArgs(int argNum)
Check that the number of arguments passed to this function is correct.
boolean
deepEquals(Expression expr)
XObject
execute(XPathContext xctxt)
Execute an XPath function object.
void
postCompileStep(Compiler compiler)
This function is currently only being used by Position() and Last().
void
setArg(Expression arg, int argNum)
Set an argument expression for a function.

Methods inherited from class org.apache.xpath.Expression

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

Method Details

callArgVisitors

public void callArgVisitors(XPathVisitor visitor)
Call the visitors for the function arguments.

callVisitors

public void callVisitors(ExpressionOwner owner,
                         XPathVisitor visitor)
Specified by:
callVisitors in interface XPathVisitable

checkNumberArgs

public void checkNumberArgs(int argNum)
            throws WrongNumberArgsException
Check that the number of arguments passed to this function is correct. This method is meant to be overloaded by derived classes, to check for the number of arguments for a specific function type. This method is called by the compiler for static number of arguments checking.
Parameters:
argNum - The number of arguments that is being passed to the function.

deepEquals

public boolean deepEquals(Expression expr)
Overrides:
deepEquals in interface Expression

execute

public XObject execute(XPathContext xctxt)
            throws javax.xml.transform.TransformerException
Execute an XPath function object. The function must return a valid object.
Overrides:
execute in interface Expression
Parameters:
xctxt - The execution current context.
Returns:
A valid XObject.

postCompileStep

public void postCompileStep(Compiler compiler)
This function is currently only being used by Position() and Last(). See respective functions for more detail.

setArg

public void setArg(Expression arg,
                   int argNum)
            throws WrongNumberArgsException
Set an argument expression for a function. This method is called by the XPath compiler.
Parameters:
arg - non-null expression that represents the argument.
argNum - The argument number index.
Throws:
WrongNumberArgsException - If the argNum parameter is beyond what is specified for this function.

Copyright B) 2006 Apache XML Project. All Rights Reserved.