org.apache.xpath.functions

Class Function

java.lang.Object

org.apache.xpath.Expression

org.apache.xpath.functions.Function

All Implemented Interfaces:

Serializable, SourceLocator, ExpressionNode, XPathVisitable

Direct Known 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

Constructor Summary

Constructors

Constructor and Description
Function()

Method Summary

Methods

Modifier and Type	Method and Description
void	callArgVisitors(XPathVisitor visitor) Call the visitors for the function arguments.
void	callVisitors(ExpressionOwner owner, XPathVisitor visitor) This will traverse the heararchy, calling the visitor for each member.
void	checkNumberArgs(int argNum) Check that the number of arguments passed to this function is correct.
boolean	deepEquals(Expression expr) Compare this object with another object and see if they are equal, include the sub heararchy.
XObject	execute(XPathContext xctxt) Execute an XPath function object.
void	postCompileStep(Compiler compiler) This function is currently only being used by Position() and Last().
protected void	reportWrongNumberArgs() Constructs and throws a WrongNumberArgException with the appropriate message for this function object.
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, error, execute, execute, execute, executeCharsToContentHandler, exprAddChild, exprGetChild, exprGetNumChildren, exprGetParent, exprSetParent, fixupVariables, getColumnNumber, getExpressionOwner, getLineNumber, getPublicId, getSystemId, isNodesetExpr, isSameClass, isStableNumber, num, warn, xstr

Methods inherited from class java.lang.Object

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

Constructor Detail

Function

public Function()

Method 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.

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.

Throws:

WrongNumberArgsException

reportWrongNumberArgs

protected void reportWrongNumberArgs()
                              throws WrongNumberArgsException

Constructs and throws a WrongNumberArgException with the appropriate message for this function object. This method is meant to be overloaded by derived classes so that the message will be as specific as possible.

Throws:

WrongNumberArgsException

execute

public XObject execute(XPathContext xctxt)
                throws TransformerException

Execute an XPath function object. The function must return a valid object.

Specified by:

execute in class Expression

Parameters:

xctxt - The execution current context.

Returns:

A valid XObject.

Throws:

TransformerException

callArgVisitors

public void callArgVisitors(XPathVisitor visitor)

Call the visitors for the function arguments.

callVisitors

public void callVisitors(ExpressionOwner owner,
                XPathVisitor visitor)

Description copied from interface: XPathVisitable

This will traverse the heararchy, calling the visitor for each member. If the called visitor method returns false, the subtree should not be called.

Parameters:

owner - The owner of the visitor, where that path may be rewritten if needed.

visitor - The visitor whose appropriate method will be called.

See Also:

XPathVisitable.callVisitors(ExpressionOwner, XPathVisitor)

deepEquals

public boolean deepEquals(Expression expr)

Description copied from class: Expression

Compare this object with another object and see if they are equal, include the sub heararchy.

Specified by:

deepEquals in class Expression

Parameters:

expr - Another expression object.

Returns:

true if this objects class and the expr object's class are the same, and the data contained within both objects are considered equal.

See Also:

Expression.deepEquals(Expression)

postCompileStep

public void postCompileStep(Compiler compiler)

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