org.apache.xpath.functions.Function Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* $Id: Function.java 468655 2006-10-28 07:12:06Z minchau $
*/
package org.apache.xpath.functions;
import org.apache.xalan.res.XSLMessages;
import org.apache.xpath.Expression;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.XPathContext;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.compiler.Compiler;
import org.apache.xpath.objects.XObject;
/**
* 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.
* @xsl.usage advanced
*/
public abstract class Function extends Expression
{
static final long serialVersionUID = 6927661240854599768L;
/**
* Set an argument expression for a function. This method is called by the
* XPath compiler.
*
* @param arg non-null expression that represents the argument.
* @param argNum The argument number index.
*
* @throws WrongNumberArgsException If the argNum parameter is beyond what
* is specified for this function.
*/
public void setArg(Expression arg, int argNum)
throws WrongNumberArgsException
{
// throw new WrongNumberArgsException(XSLMessages.createXPATHMessage("zero", null));
reportWrongNumberArgs();
}
/**
* 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.
*
* @param argNum The number of arguments that is being passed to the function.
*
* @throws WrongNumberArgsException
*/
public void checkNumberArgs(int argNum) throws WrongNumberArgsException
{
if (argNum != 0)
reportWrongNumberArgs();
}
/**
* 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
*/
protected void reportWrongNumberArgs() throws WrongNumberArgsException {
throw new WrongNumberArgsException(XSLMessages.createXPATHMessage("zero", null));
}
/**
* Execute an XPath function object. The function must return
* a valid object.
* @param xctxt The execution current context.
* @return A valid XObject.
*
* @throws javax.xml.transform.TransformerException
*/
public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException
{
// Programmer's assert. (And, no, I don't want the method to be abstract).
System.out.println("Error! Function.execute should not be called!");
return null;
}
/**
* Call the visitors for the function arguments.
*/
public void callArgVisitors(XPathVisitor visitor)
{
}
/**
* @see org.apache.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
*/
public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
{
if(visitor.visitFunction(owner, this))
{
callArgVisitors(visitor);
}
}
/**
* @see Expression#deepEquals(Expression)
*/
public boolean deepEquals(Expression expr)
{
if(!isSameClass(expr))
return false;
return true;
}
/**
* This function is currently only being used by Position()
* and Last(). See respective functions for more detail.
*/
public void postCompileStep(Compiler compiler)
{
// no default action
}
}