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/*
 * 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: XPathVisitor.java 468655 2006-10-28 07:12:06Z minchau $
 */
package org.apache.xpath;

import org.apache.xpath.axes.LocPathIterator;
import org.apache.xpath.axes.UnionPathIterator;
import org.apache.xpath.functions.Function;
import org.apache.xpath.objects.XNumber;
import org.apache.xpath.objects.XString;
import org.apache.xpath.operations.Operation;
import org.apache.xpath.operations.UnaryOperation;
import org.apache.xpath.operations.Variable;
import org.apache.xpath.patterns.NodeTest;
import org.apache.xpath.patterns.StepPattern;
import org.apache.xpath.patterns.UnionPattern;

/**
 * A derivation from this class can be passed to a class that implements 
 * the XPathVisitable interface, to have the appropriate method called 
 * for each component of the XPath.  Aside from possible other uses, the 
 * main intention is to provide a reasonable means to perform expression 
 * rewriting.
 * 
 * 

Each method has the form * boolean visitComponentType(ExpressionOwner owner, ComponentType compType). * The ExpressionOwner argument is the owner of the component, and can * be used to reset the expression for rewriting. If a method returns * false, the sub hierarchy will not be traversed.

* *

This class is meant to be a base class that will be derived by concrete classes, * and doesn't much except return true for each method.

*/ public class XPathVisitor { /** * Visit a LocationPath. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param path The LocationPath object. * @return true if the sub expressions should be traversed. */ public boolean visitLocationPath(ExpressionOwner owner, LocPathIterator path) { return true; } /** * Visit a UnionPath. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param path The UnionPath object. * @return true if the sub expressions should be traversed. */ public boolean visitUnionPath(ExpressionOwner owner, UnionPathIterator path) { return true; } /** * Visit a step within a location path. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param step The Step object. * @return true if the sub expressions should be traversed. */ public boolean visitStep(ExpressionOwner owner, NodeTest step) { return true; } /** * Visit a predicate within a location path. Note that there isn't a * proper unique component for predicates, and that the expression will * be called also for whatever type Expression is. * * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param pred The predicate object. * @return true if the sub expressions should be traversed. */ public boolean visitPredicate(ExpressionOwner owner, Expression pred) { return true; } /** * Visit a binary operation. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param op The operation object. * @return true if the sub expressions should be traversed. */ public boolean visitBinaryOperation(ExpressionOwner owner, Operation op) { return true; } /** * Visit a unary operation. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param op The operation object. * @return true if the sub expressions should be traversed. */ public boolean visitUnaryOperation(ExpressionOwner owner, UnaryOperation op) { return true; } /** * Visit a variable reference. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param var The variable reference object. * @return true if the sub expressions should be traversed. */ public boolean visitVariableRef(ExpressionOwner owner, Variable var) { return true; } /** * Visit a function. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param func The function reference object. * @return true if the sub expressions should be traversed. */ public boolean visitFunction(ExpressionOwner owner, Function func) { return true; } /** * Visit a match pattern. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param pattern The match pattern object. * @return true if the sub expressions should be traversed. */ public boolean visitMatchPattern(ExpressionOwner owner, StepPattern pattern) { return true; } /** * Visit a union pattern. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param pattern The union pattern object. * @return true if the sub expressions should be traversed. */ public boolean visitUnionPattern(ExpressionOwner owner, UnionPattern pattern) { return true; } /** * Visit a string literal. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param str The string literal object. * @return true if the sub expressions should be traversed. */ public boolean visitStringLiteral(ExpressionOwner owner, XString str) { return true; } /** * Visit a number literal. * @param owner The owner of the expression, to which the expression can * be reset if rewriting takes place. * @param num The number literal object. * @return true if the sub expressions should be traversed. */ public boolean visitNumberLiteral(ExpressionOwner owner, XNumber num) { return true; } }




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