001    /*
002            Copyright (c) 2009 Olivier Chafik, All Rights Reserved
003            
004            This file is part of JNAerator (http://jnaerator.googlecode.com/).
005            
006            JNAerator is free software: you can redistribute it and/or modify
007            it under the terms of the GNU General Public License as published by
008            the Free Software Foundation, either version 3 of the License, or
009            (at your option) any later version.
010            
011            JNAerator is distributed in the hope that it will be useful,
012            but WITHOUT ANY WARRANTY; without even the implied warranty of
013            MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
014            GNU General Public License for more details.
015            
016            You should have received a copy of the GNU General Public License
017            along with JNAerator.  If not, see <http://www.gnu.org/licenses/>.
018    */
019    package com.ochafik.xml;
020    
021    import java.lang.ref.SoftReference;
022    import java.util.HashMap;
023    import java.util.List;
024    import java.util.Map;
025    
026    import javax.xml.xpath.XPath;
027    import javax.xml.xpath.XPathConstants;
028    import javax.xml.xpath.XPathExpression;
029    import javax.xml.xpath.XPathExpressionException;
030    import javax.xml.xpath.XPathFactory;
031    
032    import org.w3c.dom.Node;
033    import org.w3c.dom.NodeList;
034    
035    import com.ochafik.lang.SyntaxUtils;
036    
037    public class XPathUtils {
038            public static Map<String, SoftReference<XPathExpression>> xPathExpressionsCache = new HashMap<String, SoftReference<XPathExpression>>();
039            private static SoftReference<XPath> sharedXPath; 
040            public static XPath getSharedXPath() {
041                    XPath xPath = null;
042                    if (sharedXPath != null)
043                            xPath = sharedXPath.get();
044                    if (xPath == null) {
045                            XPathFactory xPathFactory = XPathFactory.newInstance();
046                            sharedXPath = new SoftReference<XPath>(xPath = xPathFactory.newXPath()); 
047                    }
048                    return xPath;
049            }
050            public static List<Node> findNodesByXPath(String xPathString, Object source) throws XPathExpressionException {
051                    return XMLUtils.list((NodeList)getXPathExpression(xPathString).evaluate(source, XPathConstants.NODESET));
052            }
053            public static Iterable<Node> findNodesIterableByXPath(String xPathString, Object source) throws XPathExpressionException {
054                    return SyntaxUtils.iterable((NodeList)getXPathExpression(xPathString).evaluate(source, XPathConstants.NODESET));
055            }
056            public static Node findNodeByXPath(String xPathString, Object source) throws XPathExpressionException {
057                    NodeList list = (NodeList)getXPathExpression(xPathString).evaluate(source, XPathConstants.NODESET);
058                    int len = list.getLength();
059                    return len == 0 ? null : list.item(0); 
060            }
061            public static String findStringByXPath(String xPathString, Object source) throws XPathExpressionException {
062                    return (String)getXPathExpression(xPathString).evaluate(source, XPathConstants.STRING);
063            }
064            public static XPathExpression getXPathExpression(String xPathString) throws XPathExpressionException {
065                    SoftReference<XPathExpression> ref = xPathExpressionsCache.get(xPathString);
066                    XPathExpression expression = ref == null ? null : ref.get();
067                    if (expression == null)
068                            xPathExpressionsCache.put(xPathString, new SoftReference<XPathExpression>(expression = getSharedXPath().compile(xPathString)));
069                                    
070                    return expression;
071            }
072    
073    }