1 /*
2  * aTunes
3  * Copyright (C) Alex Aranda, Sylvain Gaudard and contributors
4  *
5  * See http://www.atunes.org/wiki/index.php?title=Contributing for information about contributors
6  *
7  * http://www.atunes.org
8  * http://sourceforge.net/projects/atunes
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public License
12  * as published by the Free Software Foundation; either version 2
13  * of the License, or (at your option) any later version.
14  *
15  * This program is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18  * GNU General Public License for more details.
19  */
20 
21 package net.sourceforge.atunes.utils;
22 
23 import javax.xml.xpath.XPath;
24 import javax.xml.xpath.XPathConstants;
25 import javax.xml.xpath.XPathExpressionException;
26 import javax.xml.xpath.XPathFactory;
27 
28 import org.w3c.dom.Node;
29 import org.w3c.dom.NodeList;
30 
31 /**
32  * Utility methods for XPath
33  * @author alex
34  *
35  */
36 public final class XPathUtils {
37 
XPathUtils()38 	private XPathUtils() {}
39 
40     private static volatile ThreadLocal<XPath> xPath;
41 
42     /**
43      * Evaluates a XPath expression from a XML node, returning a Node object.
44      *
45      * @param expression
46      *            A XPath expression
47      * @param node
48      *            The Node for which this expression should be evaluated
49      *
50      * @return The result of evaluating the XPath expression to the given Node
51      *         or <code>null</code> if an exception occured
52      */
evaluateXPathExpressionAndReturnNode(String expression, Node node)53     public static Node evaluateXPathExpressionAndReturnNode(String expression, Node node) {
54         try {
55             return (Node) getXPath().get().evaluate(expression, node, XPathConstants.NODE);
56         } catch (XPathExpressionException e) {
57             return null;
58         }
59     }
60 
61     /**
62      * Evaluates a XPath expression from a XML node, returning a NodeList.
63      *
64      * @param expression
65      *            A XPath expression
66      * @param node
67      *            The NodeList for which this expression should be evaluated
68      *
69      * @return The result of evaluating the XPath expression to the given or
70      *         <code>null</code> if an ecxception occured NodeList
71      */
evaluateXPathExpressionAndReturnNodeList(String expression, Node node)72     public static NodeList evaluateXPathExpressionAndReturnNodeList(String expression, Node node) {
73         try {
74             return (NodeList) getXPath().get().evaluate(expression, node, XPathConstants.NODESET);
75         } catch (XPathExpressionException e) {
76             return null;
77         }
78     }
79 
getXPath()80     private static ThreadLocal<XPath> getXPath() {
81         if (xPath == null) {
82             xPath = new ThreadLocal<XPath>() {
83                 @Override
84                 protected XPath initialValue() {
85                     return XPathFactory.newInstance().newXPath();
86                 }
87             };
88         }
89         return xPath;
90     }
91 }
92