1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 /* 19 * $Id: Function.java 468655 2006-10-28 07:12:06Z minchau $ 20 */ 21 package org.apache.xpath.functions; 22 23 import org.apache.xalan.res.XSLMessages; 24 import org.apache.xpath.Expression; 25 import org.apache.xpath.ExpressionOwner; 26 import org.apache.xpath.XPathContext; 27 import org.apache.xpath.XPathVisitor; 28 import org.apache.xpath.compiler.Compiler; 29 import org.apache.xpath.objects.XObject; 30 31 /** 32 * This is a superclass of all XPath functions. This allows two 33 * ways for the class to be called. One method is that the 34 * super class processes the arguments and hands the results to 35 * the derived class, the other method is that the derived 36 * class may process it's own arguments, which is faster since 37 * the arguments don't have to be added to an array, but causes 38 * a larger code footprint. 39 * @xsl.usage advanced 40 */ 41 public abstract class Function extends Expression 42 { 43 static final long serialVersionUID = 6927661240854599768L; 44 45 /** 46 * Set an argument expression for a function. This method is called by the 47 * XPath compiler. 48 * 49 * @param arg non-null expression that represents the argument. 50 * @param argNum The argument number index. 51 * 52 * @throws WrongNumberArgsException If the argNum parameter is beyond what 53 * is specified for this function. 54 */ setArg(Expression arg, int argNum)55 public void setArg(Expression arg, int argNum) 56 throws WrongNumberArgsException 57 { 58 // throw new WrongNumberArgsException(XSLMessages.createXPATHMessage("zero", null)); 59 reportWrongNumberArgs(); 60 } 61 62 /** 63 * Check that the number of arguments passed to this function is correct. 64 * This method is meant to be overloaded by derived classes, to check for 65 * the number of arguments for a specific function type. This method is 66 * called by the compiler for static number of arguments checking. 67 * 68 * @param argNum The number of arguments that is being passed to the function. 69 * 70 * @throws WrongNumberArgsException 71 */ checkNumberArgs(int argNum)72 public void checkNumberArgs(int argNum) throws WrongNumberArgsException 73 { 74 if (argNum != 0) 75 reportWrongNumberArgs(); 76 } 77 78 /** 79 * Constructs and throws a WrongNumberArgException with the appropriate 80 * message for this function object. This method is meant to be overloaded 81 * by derived classes so that the message will be as specific as possible. 82 * 83 * @throws WrongNumberArgsException 84 */ reportWrongNumberArgs()85 protected void reportWrongNumberArgs() throws WrongNumberArgsException { 86 throw new WrongNumberArgsException(XSLMessages.createXPATHMessage("zero", null)); 87 } 88 89 /** 90 * Execute an XPath function object. The function must return 91 * a valid object. 92 * @param xctxt The execution current context. 93 * @return A valid XObject. 94 * 95 * @throws javax.xml.transform.TransformerException 96 */ execute(XPathContext xctxt)97 public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException 98 { 99 100 // Programmer's assert. (And, no, I don't want the method to be abstract). 101 System.out.println("Error! Function.execute should not be called!"); 102 103 return null; 104 } 105 106 /** 107 * Call the visitors for the function arguments. 108 */ callArgVisitors(XPathVisitor visitor)109 public void callArgVisitors(XPathVisitor visitor) 110 { 111 } 112 113 114 /** 115 * @see org.apache.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor) 116 */ callVisitors(ExpressionOwner owner, XPathVisitor visitor)117 public void callVisitors(ExpressionOwner owner, XPathVisitor visitor) 118 { 119 if(visitor.visitFunction(owner, this)) 120 { 121 callArgVisitors(visitor); 122 } 123 } 124 125 /** 126 * @see Expression#deepEquals(Expression) 127 */ deepEquals(Expression expr)128 public boolean deepEquals(Expression expr) 129 { 130 if(!isSameClass(expr)) 131 return false; 132 133 return true; 134 } 135 136 /** 137 * This function is currently only being used by Position() 138 * and Last(). See respective functions for more detail. 139 */ postCompileStep(Compiler compiler)140 public void postCompileStep(Compiler compiler) 141 { 142 // no default action 143 } 144 } 145