1 /* 2 * Copyright 2005-2010 the original author or authors. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package org.springframework.xml.xpath; 18 19 import java.util.List; 20 21 import org.w3c.dom.Node; 22 23 /** 24 * Defines the contract for a precompiled XPath expression. Concrete instances can be obtained through the {@link 25 * XPathExpressionFactory}. 26 * <p/> 27 * Implementations of this interface are precompiled, and thus faster, but less flexible, than the XPath expressions 28 * used by {@link XPathOperations} implementations. 29 * 30 * @author Arjen Poutsma 31 * @since 1.0.0 32 */ 33 public interface XPathExpression { 34 35 /** 36 * Evaluates the given expression as a <code>boolean</code>. Returns the boolean evaluation of the expression, or 37 * <code>false</code> if it is invalid. 38 * <p/> 39 * The return value is determined per the {@code boolean()} function defined in the XPath specification. 40 * This means that an expression that selects zero nodes will return {@code false}, while an expression that 41 * selects one or more nodes will return {@code true}. 42 * An expression that returns a string returns {@code false} for empty strings and {@code true} for all other 43 * strings. 44 * An expression that returns a number returns {@code false} for zero and {@code true} for non-zero numbers. 45 * 46 * @param node the starting point 47 * @return the result of the evaluation 48 * @throws XPathException in case of XPath errors 49 * @see <a href="http://www.w3.org/TR/xpath/#function-boolean">XPath specification - boolean() function</a> 50 */ 51 boolean evaluateAsBoolean(Node node) throws XPathException; 52 53 /** 54 * Evaluates the given expression as a {@link Node}. Returns the evaluation of the expression, or <code>null</code> 55 * if it is invalid. 56 * 57 * @param node the starting point 58 * @return the result of the evaluation 59 * @throws XPathException in case of XPath errors 60 * @see <a href="http://www.w3.org/TR/xpath#node-sets">XPath specification</a> 61 */ 62 Node evaluateAsNode(Node node) throws XPathException; 63 64 /** 65 * Evaluates the given expression, and returns all {@link Node} objects that conform to it. Returns an empty list if 66 * no result could be found. 67 * 68 * @param node the starting point 69 * @return a list of <code>Node</code>s that are selected by the expression 70 * @throws XPathException in case of XPath errors 71 * @see <a href="http://www.w3.org/TR/xpath#node-sets">XPath specification</a> 72 */ 73 List<Node> evaluateAsNodeList(Node node) throws XPathException; 74 75 /** 76 * Evaluates the given expression as a number (<code>double</code>). Returns the numeric evaluation of the 77 * expression, or {@link Double#NaN} if it is invalid. 78 * <p/> 79 * The return value is determined per the {@code number()} function as defined in the XPath specification. 80 * This means that if the expression selects multiple nodes, it will return the number value of the first node. 81 * 82 * @param node the starting point 83 * @return the result of the evaluation 84 * @throws XPathException in case of XPath errors 85 * @see <a href="http://www.w3.org/TR/xpath/#function-number">XPath specification - number() function</a> 86 */ 87 double evaluateAsNumber(Node node) throws XPathException; 88 89 /** 90 * Evaluates the given expression as a String. Returns <code>null</code> if no result could be found. 91 * <p/> 92 * The return value is determined per the {@code string()} function as defined in the XPath specification. 93 * This means that if the expression selects multiple nodes, it will return the string value of the first node. 94 * 95 * @param node the starting point 96 * @return the result of the evaluation 97 * @throws XPathException in case of XPath errors 98 * @see <a href="http://www.w3.org/TR/xpath/#function-string">XPath specification - string() function</a> 99 */ 100 String evaluateAsString(Node node) throws XPathException; 101 102 /** 103 * Evaluates the given expression, mapping a single {@link Node} result to a Java object via a {@link NodeMapper}. 104 * 105 * @param node the starting point 106 * @param nodeMapper object that will map one object per node 107 * @return the single mapped object 108 * @throws XPathException in case of XPath errors 109 * @see <a href="http://www.w3.org/TR/xpath#node-sets">XPath specification</a> 110 */ 111 <T> T evaluateAsObject(Node node, NodeMapper<T> nodeMapper) throws XPathException; 112 113 /** 114 * Evaluates the given expression, mapping each result {@link Node} objects to a Java object via a {@link 115 * NodeMapper}. 116 * 117 * @param node the starting point 118 * @param nodeMapper object that will map one object per node 119 * @return the result list, containing mapped objects 120 * @throws XPathException in case of XPath errors 121 * @see <a href="http://www.w3.org/TR/xpath#node-sets">XPath specification</a> 122 */ 123 <T> List<T> evaluate(Node node, NodeMapper<T> nodeMapper) throws XPathException; 124 }