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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// $Id: FactoryFinder.java 670431 2008-06-23 01:40:03Z mrglavas $

package javax.xml.parsers;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Properties;

/**
 * This class is duplicated for each JAXP subpackage so keep it in
 * sync.  It is package private.
 *
 * This code is designed to implement the JAXP 1.1 spec pluggability
 * feature and is designed to run on JDK version 1.1 and later including
 * JVMs that perform early linking like the Microsoft JVM in IE 5.  Note
 * however that it must be compiled on a JDK version 1.2 or later system
 * since it calls Thread#getContextClassLoader().  The code also runs both
 * as part of an unbundled jar file and when bundled as part of the JDK.
 */
final class FactoryFinder {
    
    /**
     * 

Debug flag to trace loading process.

*/ private static boolean debug = false; /** *

Cache properties for performance.

*/ private static Properties cacheProps = new Properties(); /** *

First time requires initialization overhead.

*/ private static boolean firstTime = true; /** * Default columns per line. */ private static final int DEFAULT_LINE_LENGTH = 80; // Define system property "jaxp.debug" to get output static { // Use try/catch block to support applets, which throws // SecurityException out of this code. try { String val = SecuritySupport.getSystemProperty("jaxp.debug"); // Allow simply setting the prop to turn on debug debug = val != null && (! "false".equals(val)); } catch (SecurityException se) { debug = false; } } private FactoryFinder() {} private static void dPrint(String msg) { if (debug) { System.err.println("JAXP: " + msg); } } /** * Create an instance of a class using the specified ClassLoader and * optionally fall back to the current ClassLoader if not found. * * @param className Name of the concrete class corresponding to the * service provider * * @param cl ClassLoader to use to load the class, null means to use * the bootstrap ClassLoader * * @param doFallback true if the current ClassLoader should be tried as * a fallback if the class is not found using cl */ static Object newInstance(String className, ClassLoader cl, boolean doFallback) throws ConfigurationError { // assert(className != null); try { Class providerClass; if (cl == null) { // If classloader is null Use the bootstrap ClassLoader. // Thus Class.forName(String) will use the current // ClassLoader which will be the bootstrap ClassLoader. providerClass = Class.forName(className); } else { try { providerClass = cl.loadClass(className); } catch (ClassNotFoundException x) { if (doFallback) { // Fall back to current classloader cl = FactoryFinder.class.getClassLoader(); if (cl != null) { providerClass = cl.loadClass(className); } else { providerClass = Class.forName(className); } } else { throw x; } } } Object instance = providerClass.newInstance(); if (debug) dPrint("created new instance of " + providerClass + " using ClassLoader: " + cl); return instance; } catch (ClassNotFoundException x) { throw new ConfigurationError( "Provider " + className + " not found", x); } catch (Exception x) { throw new ConfigurationError( "Provider " + className + " could not be instantiated: " + x, x); } } /** * Finds the implementation Class object in the specified order. Main * entry point. * @return Class object of factory, never null * * @param factoryId Name of the factory to find, same as * a property name * @param fallbackClassName Implementation class name, if nothing else * is found. Use null to mean no fallback. * * Package private so this code can be shared. */ static Object find(String factoryId, String fallbackClassName) throws ConfigurationError { // Figure out which ClassLoader to use for loading the provider // class. If there is a Context ClassLoader then use it. ClassLoader classLoader = SecuritySupport.getContextClassLoader(); if (classLoader == null) { // if we have no Context ClassLoader // so use the current ClassLoader classLoader = FactoryFinder.class.getClassLoader(); } if (debug) dPrint("find factoryId =" + factoryId); // Use the system property first try { String systemProp = SecuritySupport.getSystemProperty(factoryId); if (systemProp != null && systemProp.length() > 0) { if (debug) dPrint("found system property, value=" + systemProp); return newInstance(systemProp, classLoader, true); } } catch (SecurityException se) { //if first option fails due to any reason we should try next option in the //look up algorithm. } // try to read from $java.home/lib/jaxp.properties try { String javah = SecuritySupport.getSystemProperty("java.home"); String configFile = javah + File.separator + "lib" + File.separator + "jaxp.properties"; String factoryClassName = null; if(firstTime){ synchronized(cacheProps){ if(firstTime){ File f=new File( configFile ); firstTime = false; if(SecuritySupport.doesFileExist(f)){ if (debug) dPrint("Read properties file "+f); //cacheProps.load( new FileInputStream(f)); cacheProps.load(SecuritySupport.getFileInputStream(f)); } } } } factoryClassName = cacheProps.getProperty(factoryId); if(factoryClassName != null){ if (debug) dPrint("found in $java.home/jaxp.properties, value=" + factoryClassName); return newInstance(factoryClassName, classLoader, true); } } catch(Exception ex ) { if( debug ) ex.printStackTrace(); } // Try Jar Service Provider Mechanism Object provider = findJarServiceProvider(factoryId); if (provider != null) { return provider; } if (fallbackClassName == null) { throw new ConfigurationError( "Provider for " + factoryId + " cannot be found", null); } if (debug) dPrint("loaded from fallback value: " + fallbackClassName); return newInstance(fallbackClassName, classLoader, true); } /* * Try to find provider using Jar Service Provider Mechanism * * @return instance of provider class if found or null */ private static Object findJarServiceProvider(String factoryId) throws ConfigurationError { String serviceId = "META-INF/services/" + factoryId; InputStream is = null; // First try the Context ClassLoader ClassLoader cl = SecuritySupport.getContextClassLoader(); if (cl != null) { is = SecuritySupport.getResourceAsStream(cl, serviceId); // If no provider found then try the current ClassLoader if (is == null) { cl = FactoryFinder.class.getClassLoader(); is = SecuritySupport.getResourceAsStream(cl, serviceId); } } else { // No Context ClassLoader, try the current // ClassLoader cl = FactoryFinder.class.getClassLoader(); is = SecuritySupport.getResourceAsStream(cl, serviceId); } if (is == null) { // No provider found return null; } if (debug) dPrint("found jar resource=" + serviceId + " using ClassLoader: " + cl); // Read the service provider name in UTF-8 as specified in // the jar spec. Unfortunately this fails in Microsoft // VJ++, which does not implement the UTF-8 // encoding. Theoretically, we should simply let it fail in // that case, since the JVM is obviously broken if it // doesn't support such a basic standard. But since there // are still some users attempting to use VJ++ for // development, we have dropped in a fallback which makes a // second attempt using the platform's default encoding. In // VJ++ this is apparently ASCII, which is a subset of // UTF-8... and since the strings we'll be reading here are // also primarily limited to the 7-bit ASCII range (at // least, in English versions), this should work well // enough to keep us on the air until we're ready to // officially decommit from VJ++. [Edited comment from // jkesselm] BufferedReader rd; try { rd = new BufferedReader(new InputStreamReader(is, "UTF-8"), DEFAULT_LINE_LENGTH); } catch (java.io.UnsupportedEncodingException e) { rd = new BufferedReader(new InputStreamReader(is), DEFAULT_LINE_LENGTH); } String factoryClassName = null; try { // XXX Does not handle all possible input as specified by the // Jar Service Provider specification factoryClassName = rd.readLine(); } catch (IOException x) { // No provider found return null; } finally { try { // try to close the reader. rd.close(); } // Ignore the exception. catch (IOException exc) {} } if (factoryClassName != null && ! "".equals(factoryClassName)) { if (debug) dPrint("found in resource, value=" + factoryClassName); // Note: here we do not want to fall back to the current // ClassLoader because we want to avoid the case where the // resource file was found using one ClassLoader and the // provider class was instantiated using a different one. return newInstance(factoryClassName, cl, false); } // No provider found return null; } static class ConfigurationError extends Error { private Exception exception; /** * Construct a new instance with the specified detail string and * exception. */ ConfigurationError(String msg, Exception x) { super(msg); this.exception = x; } Exception getException() { return exception; } } }




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