| /* |
| * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//jxpath/src/java/org/apache/commons/jxpath/JXPathContextFactory.java,v 1.3 2002/04/24 04:05:41 dmitri Exp $ |
| * $Revision: 1.3 $ |
| * $Date: 2002/04/24 04:05:41 $ |
| * |
| * ==================================================================== |
| * The Apache Software License, Version 1.1 |
| * |
| * |
| * Copyright (c) 1999-2001 The Apache Software Foundation. All rights |
| * reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * 3. The end-user documentation included with the redistribution, if |
| * any, must include the following acknowlegement: |
| * "This product includes software developed by the |
| * Apache Software Foundation (http://www.apache.org/)." |
| * Alternately, this acknowlegement may appear in the software itself, |
| * if and wherever such third-party acknowlegements normally appear. |
| * |
| * 4. The names "The Jakarta Project", "Commons", and "Apache Software |
| * Foundation" must not be used to endorse or promote products derived |
| * from this software without prior written permission. For written |
| * permission, please contact apache@apache.org. |
| * |
| * 5. Products derived from this software may not be called "Apache" |
| * nor may "Apache" appear in their names without prior written |
| * permission of the Apache Group. |
| * |
| * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR |
| * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
| * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * ==================================================================== |
| * |
| * This software consists of voluntary contributions made by many |
| * individuals on behalf of the Apache Software Foundation and was |
| * originally based on software copyright (c) 2001, Plotnix, Inc, |
| * <http://www.plotnix.com/>. |
| * For more information on the Apache Software Foundation, please see |
| * <http://www.apache.org/>. |
| */ |
| |
| package org.apache.commons.jxpath; |
| |
| import java.util.*; |
| import java.io.*; |
| |
| /** |
| * Defines a factory API that enables applications to obtain a |
| * JXPathContext instance. To acquire a JXPathContext, first call the |
| * static <code>newInstance()</code> method of JXPathContextFactory. |
| * This method returns a concrete JXPathContextFactory. |
| * Then call <code>newContext()</code> on that instance. You will rarely |
| * need to perform these steps explicitly: usually you can call one of the |
| * <code>JXPathContex.newContext</code> methods, which will perform these steps |
| * for you. |
| * |
| * @see JXPathContext#newContext(Object) |
| * @see JXPathContext#newContext(JXPathContext,Object) |
| * |
| * @author Dmitri Plotnikov |
| * @version $Revision: 1.3 $ $Date: 2002/04/24 04:05:41 $ |
| */ |
| public abstract class JXPathContextFactory { |
| |
| /** The default property */ |
| public static final String FACTORY_NAME_PROPERTY = |
| "org.apache.commons.jxpath.JXPathContextFactory"; |
| |
| /** The default factory class */ |
| private static final String defaultClassName = |
| "org.apache.commons.jxpath.ri.JXPathContextFactoryReferenceImpl"; |
| |
| protected JXPathContextFactory () { |
| |
| } |
| |
| /** |
| * Obtain a new instance of a <code>JXPathContextFactory</code>. |
| * This static method creates a new factory instance. |
| * This method uses the following ordered lookup procedure to determine |
| * the <code>JXPathContextFactory</code> implementation class to load: |
| * <ul> |
| * <li> |
| * Use the <code>org.apache.commons.jxpath.JXPathContextFactory</code> system |
| * property. |
| * </li> |
| * <li> |
| * Alternatively, use the JAVA_HOME (the parent directory where jdk is |
| * installed)/lib/jxpath.properties for a property file that contains the |
| * name of the implementation class keyed on |
| * <code>org.apache.commons.jxpath.JXPathContextFactory</code>. |
| * </li> |
| * <li> |
| * Use the Services API (as detailed in the JAR specification), if |
| * available, to determine the classname. The Services API will look |
| * for a classname in the file |
| * <code>META-INF/services/<i>org.apache.commons.jxpath.JXPathContextFactory</i></code> |
| * in jars available to the runtime. |
| * </li> |
| * <li> |
| * Platform default <code>JXPathContextFactory</code> instance. |
| * </li> |
| * </ul> |
| * |
| * Once an application has obtained a reference to a |
| * <code>JXPathContextFactory</code> it can use the factory to |
| * obtain JXPathContext instances. |
| * |
| * @exception JXPathFactoryConfigurationError if the implementation is not |
| * available or cannot be instantiated. |
| */ |
| |
| public static JXPathContextFactory newInstance() { |
| String factoryImplName = findFactory(FACTORY_NAME_PROPERTY, defaultClassName); |
| |
| if (factoryImplName == null) { |
| throw new JXPathContextFactoryConfigurationError( |
| "No default implementation found"); |
| } |
| |
| JXPathContextFactory factoryImpl; |
| try { |
| Class clazz = Class.forName(factoryImplName); |
| factoryImpl = (JXPathContextFactory)clazz.newInstance(); |
| } catch (ClassNotFoundException cnfe) { |
| throw new JXPathContextFactoryConfigurationError(cnfe); |
| } catch (IllegalAccessException iae) { |
| throw new JXPathContextFactoryConfigurationError(iae); |
| } catch (InstantiationException ie) { |
| throw new JXPathContextFactoryConfigurationError(ie); |
| } |
| return factoryImpl; |
| } |
| |
| /** |
| * Creates a new instance of a JXPathContext using the |
| * currently configured parameters. |
| * |
| * @exception JXPathContextFactoryConfigurationError if a JXPathContext |
| * cannot be created which satisfies the configuration requested |
| */ |
| |
| public abstract JXPathContext newContext(JXPathContext parentContext, Object contextBean) |
| throws JXPathContextFactoryConfigurationError; |
| |
| // -------------------- private methods -------------------- |
| // This code is duplicated in all factories. |
| // Keep it in sync or move it to a common place |
| // Because it's small probably it's easier to keep it here |
| /** Avoid reading all the files when the findFactory |
| method is called the second time ( cache the result of |
| finding the default impl ) |
| */ |
| private static String foundFactory = null; |
| |
| /** Temp debug code - this will be removed after we test everything |
| */ |
| private static boolean debug = false; |
| static { |
| try { |
| debug = System.getProperty("jxpath.debug") != null; |
| } |
| catch (SecurityException se) { |
| } |
| } |
| |
| /** Private implementation method - will find the implementation |
| class in the specified order. |
| @param property Property name |
| @param defaultFactory Default implementation, if nothing else is found |
| |
| @return class name of the JXPathContextFactory |
| */ |
| private static String findFactory(String property, String defaultFactory) { |
| // Use the system property first |
| try { |
| String systemProp = System.getProperty(property); |
| if (systemProp != null) { |
| if (debug){ |
| System.err.println("JXPath: found system property" + systemProp); |
| } |
| return systemProp; |
| } |
| |
| } |
| catch (SecurityException se) { |
| } |
| |
| if (foundFactory != null){ |
| return foundFactory; |
| } |
| |
| // Use the factory ID system property first |
| try { |
| String systemProp = System.getProperty(property); |
| if (systemProp != null) { |
| if (debug){ |
| System.err.println("JXPath: found system property" + systemProp); |
| } |
| return systemProp; |
| } |
| |
| } |
| catch (SecurityException se) { |
| } |
| |
| // try to read from $java.home/lib/xml.properties |
| try { |
| String javah = System.getProperty("java.home"); |
| String configFile = |
| javah + File.separator + "lib" + File.separator + "jxpath.properties"; |
| File f = new File(configFile); |
| if (f.exists()) { |
| Properties props = new Properties(); |
| props.load(new FileInputStream(f)); |
| foundFactory = props.getProperty(property); |
| if (debug){ |
| System.err.println("JXPath: found java.home property " + foundFactory); |
| } |
| if (foundFactory != null){ |
| return foundFactory; |
| } |
| } |
| } |
| catch (Exception ex) { |
| if (debug){ |
| ex.printStackTrace(); |
| } |
| } |
| |
| String serviceId = "META-INF/services/" + property; |
| // try to find services in CLASSPATH |
| try { |
| ClassLoader cl = JXPathContextFactory.class.getClassLoader(); |
| InputStream is = null; |
| if (cl == null) { |
| is = ClassLoader.getSystemResourceAsStream(serviceId); |
| } |
| else { |
| is = cl.getResourceAsStream(serviceId); |
| } |
| |
| if (is != null) { |
| if (debug){ |
| System.err.println("JXPath: found " + serviceId); |
| } |
| BufferedReader rd = new BufferedReader(new InputStreamReader(is)); |
| |
| foundFactory = rd.readLine(); |
| rd.close(); |
| |
| if (debug){ |
| System.err.println("JXPath: loaded from services: " + foundFactory); |
| } |
| if (foundFactory != null && !"".equals(foundFactory)) { |
| return foundFactory; |
| } |
| } |
| } |
| catch (Exception ex) { |
| if (debug){ |
| ex.printStackTrace(); |
| } |
| } |
| |
| return defaultFactory; |
| } |
| } |
