Java tutorial
//package com.java2s; /* Copyright (c) 2009-2011 Olivier Chafik, All Rights Reserved This file is part of JNAerator (http://jnaerator.googlecode.com/). JNAerator is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. JNAerator is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with JNAerator. If not, see <http://www.gnu.org/licenses/>. */ import java.lang.ref.SoftReference; import java.util.LinkedHashMap; import java.util.Map; import javax.xml.xpath.XPath; import javax.xml.xpath.XPathConstants; import javax.xml.xpath.XPathExpression; import javax.xml.xpath.XPathExpressionException; import javax.xml.xpath.XPathFactory; public class Main { public static Map<String, SoftReference<XPathExpression>> xPathExpressionsCache = new LinkedHashMap<String, SoftReference<XPathExpression>>(); private static SoftReference<XPath> sharedXPath; public static String findStringByXPath(String xPathString, Object source) throws XPathExpressionException { return (String) getXPathExpression(xPathString).evaluate(source, XPathConstants.STRING); } public static XPathExpression getXPathExpression(String xPathString) throws XPathExpressionException { SoftReference<XPathExpression> ref = xPathExpressionsCache.get(xPathString); XPathExpression expression = ref == null ? null : ref.get(); if (expression == null) xPathExpressionsCache.put(xPathString, new SoftReference<XPathExpression>(expression = getSharedXPath().compile(xPathString))); return expression; } public static XPath getSharedXPath() { XPath xPath = null; if (sharedXPath != null) xPath = sharedXPath.get(); if (xPath == null) { XPathFactory xPathFactory = XPathFactory.newInstance(); sharedXPath = new SoftReference<XPath>(xPath = xPathFactory.newXPath()); } return xPath; } }