1 /*
   2  * Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package javax.xml.transform;
  27 
  28 import java.io.BufferedReader;
  29 import java.io.File;
  30 import java.io.IOException;
  31 import java.io.InputStream;
  32 import java.io.InputStreamReader;
  33 import java.lang.reflect.Method;
  34 import java.util.Properties;
  35 
  36 /**
  37  * <p>Implements pluggable Datatypes.</p>
  38  *
  39  * <p>This class is duplicated for each JAXP subpackage so keep it in
  40  * sync.  It is package private for secure class loading.</p>
  41  *
  42  * @author Santiago.PericasGeertsen@sun.com
  43  * @author Huizhe.Wang@oracle.com
  44  */
  45 class FactoryFinder {
  46 
  47     /**
  48      * Internal debug flag.
  49      */
  50     private static boolean debug = false;
  51 
  52     /**
  53      * Cache for properties in java.home/lib/jaxp.properties
  54      */
  55     static Properties cacheProps = new Properties();
  56 
  57     /**
  58      * Flag indicating if properties from java.home/lib/jaxp.properties
  59      * have been cached.
  60      */
  61     static volatile boolean firstTime = true;
  62 
  63     /**
  64      * Security support class use to check access control before
  65      * getting certain system resources.
  66      */
  67     static SecuritySupport ss = new SecuritySupport();
  68 
  69     // Define system property "jaxp.debug" to get output
  70     static {
  71         // Use try/catch block to support applets, which throws
  72         // SecurityException out of this code.
  73         try {
  74             String val = ss.getSystemProperty("jaxp.debug");
  75             // Allow simply setting the prop to turn on debug
  76             debug = val != null && !"false".equals(val);
  77         }
  78         catch (SecurityException se) {
  79             debug = false;
  80         }
  81     }
  82 
  83     private static void dPrint(String msg) {
  84         if (debug) {
  85             System.err.println("JAXP: " + msg);
  86         }
  87     }
  88 
  89     /**
  90      * Attempt to load a class using the class loader supplied. If that fails
  91      * and fall back is enabled, the current (i.e. bootstrap) class loader is
  92      * tried.
  93      *
  94      * If the class loader supplied is <code>null</code>, first try using the
  95      * context class loader followed by the current (i.e. bootstrap) class
  96      * loader.
  97      *
  98      * Use bootstrap classLoader if cl = null and useBSClsLoader is true
  99      */
 100     static private Class getProviderClass(String className, ClassLoader cl,
 101             boolean doFallback, boolean useBSClsLoader) throws ClassNotFoundException
 102     {
 103         try {
 104             if (cl == null) {
 105                 if (useBSClsLoader) {
 106                     return Class.forName(className, true, FactoryFinder.class.getClassLoader());
 107                 } else {
 108                     cl = ss.getContextClassLoader();
 109                     if (cl == null) {
 110                         throw new ClassNotFoundException();
 111                     }
 112                     else {
 113                         return cl.loadClass(className);
 114                     }
 115                 }
 116             }
 117             else {
 118                 return cl.loadClass(className);
 119             }
 120         }
 121         catch (ClassNotFoundException e1) {
 122             if (doFallback) {
 123                 // Use current class loader - should always be bootstrap CL
 124                 return Class.forName(className, true, FactoryFinder.class.getClassLoader());
 125             }
 126             else {
 127                 throw e1;
 128             }
 129         }
 130     }
 131 
 132     /**
 133      * Create an instance of a class. Delegates to method
 134      * <code>getProviderClass()</code> in order to load the class.
 135      *
 136      * @param className Name of the concrete class corresponding to the
 137      * service provider
 138      *
 139      * @param cl <code>ClassLoader</code> used to load the factory class. If <code>null</code>
 140      * current <code>Thread</code>'s context classLoader is used to load the factory class.
 141      *
 142      * @param doFallback True if the current ClassLoader should be tried as
 143      * a fallback if the class is not found using cl
 144      */
 145     static Object newInstance(String className, ClassLoader cl, boolean doFallback)
 146         throws ConfigurationError
 147     {
 148         return newInstance(className, cl, doFallback, false, false);
 149     }
 150 
 151     /**
 152      * Create an instance of a class. Delegates to method
 153      * <code>getProviderClass()</code> in order to load the class.
 154      *
 155      * @param className Name of the concrete class corresponding to the
 156      * service provider
 157      *
 158      * @param cl <code>ClassLoader</code> used to load the factory class. If <code>null</code>
 159      * current <code>Thread</code>'s context classLoader is used to load the factory class.
 160      *
 161      * @param doFallback True if the current ClassLoader should be tried as
 162      * a fallback if the class is not found using cl
 163      *
 164      * @param useBSClsLoader True if cl=null actually meant bootstrap classLoader. This parameter
 165      * is needed since DocumentBuilderFactory/SAXParserFactory defined null as context classLoader.
 166      *
 167      * @param useServicesMechanism True use services mechanism
 168      */
 169     static Object newInstance(String className, ClassLoader cl, boolean doFallback, boolean useBSClsLoader, boolean useServicesMechanism)
 170         throws ConfigurationError
 171     {
 172         try {
 173             Class providerClass = getProviderClass(className, cl, doFallback, useBSClsLoader);
 174             Object instance = null;
 175             if (!useServicesMechanism) {
 176                 instance = newInstanceNoServiceLoader(providerClass);
 177             }
 178             if (instance == null) {
 179                 instance = providerClass.newInstance();
 180             }
 181             if (debug) {    // Extra check to avoid computing cl strings
 182                 dPrint("created new instance of " + providerClass +
 183                        " using ClassLoader: " + cl);
 184             }
 185             return instance;
 186         }
 187         catch (ClassNotFoundException x) {
 188             throw new ConfigurationError(
 189                 "Provider " + className + " not found", x);
 190         }
 191         catch (Exception x) {
 192             throw new ConfigurationError(
 193                 "Provider " + className + " could not be instantiated: " + x,
 194                 x);
 195         }
 196     }
 197     /**
 198      * Try to construct using newTransformerFactoryNoServiceLoader
 199      *   method if available.
 200      */
 201     private static Object newInstanceNoServiceLoader(
 202          Class<?> providerClass
 203     ) {
 204         // Retain maximum compatibility if no security manager.
 205         if (System.getSecurityManager() == null) {
 206             return null;
 207         }
 208         try {
 209             Method creationMethod =
 210                 providerClass.getDeclaredMethod(
 211                     "newTransformerFactoryNoServiceLoader"
 212                 );
 213                 return creationMethod.invoke(null, null);
 214             } catch (NoSuchMethodException exc) {
 215                 return null;
 216             } catch (Exception exc) {
 217                 return null;
 218         }
 219     }
 220     /**
 221      * Finds the implementation Class object in the specified order.  Main
 222      * entry point.
 223      * @return Class object of factory, never null
 224      *
 225      * @param factoryId             Name of the factory to find, same as
 226      *                              a property name
 227      * @param fallbackClassName     Implementation class name, if nothing else
 228      *                              is found.  Use null to mean no fallback.
 229      *
 230      * Package private so this code can be shared.
 231      */
 232     static Object find(String factoryId, String fallbackClassName)
 233         throws ConfigurationError
 234     {
 235         dPrint("find factoryId =" + factoryId);
 236         // Use the system property first
 237         try {
 238             String systemProp = ss.getSystemProperty(factoryId);
 239             if (systemProp != null) {
 240                 dPrint("found system property, value=" + systemProp);
 241                 return newInstance(systemProp, null, true, false, true);
 242             }
 243         }
 244         catch (SecurityException se) {
 245             if (debug) se.printStackTrace();
 246         }
 247 
 248         // try to read from $java.home/lib/jaxp.properties
 249         try {
 250             String factoryClassName = null;
 251             if (firstTime) {
 252                 synchronized (cacheProps) {
 253                     if (firstTime) {
 254                         String configFile = ss.getSystemProperty("java.home") + File.separator +
 255                             "lib" + File.separator + "jaxp.properties";
 256                         File f = new File(configFile);
 257                         firstTime = false;
 258                         if (ss.doesFileExist(f)) {
 259                             dPrint("Read properties file "+f);
 260                             cacheProps.load(ss.getFileInputStream(f));
 261                         }
 262                     }
 263                 }
 264             }
 265             factoryClassName = cacheProps.getProperty(factoryId);
 266 
 267             if (factoryClassName != null) {
 268                 dPrint("found in $java.home/jaxp.properties, value=" + factoryClassName);
 269                 return newInstance(factoryClassName, null, true, false, true);
 270             }
 271         }
 272         catch (Exception ex) {
 273             if (debug) ex.printStackTrace();
 274         }
 275 
 276         // Try Jar Service Provider Mechanism
 277         Object provider = findJarServiceProvider(factoryId);
 278         if (provider != null) {
 279             return provider;
 280         }
 281         if (fallbackClassName == null) {
 282             throw new ConfigurationError(
 283                 "Provider for " + factoryId + " cannot be found", null);
 284         }
 285 
 286         dPrint("loaded from fallback value: " + fallbackClassName);
 287         return newInstance(fallbackClassName, null, true, false, true);
 288     }
 289 
 290     /*
 291      * Try to find provider using Jar Service Provider Mechanism
 292      *
 293      * @return instance of provider class if found or null
 294      */
 295     private static Object findJarServiceProvider(String factoryId)
 296         throws ConfigurationError
 297     {
 298         String serviceId = "META-INF/services/" + factoryId;
 299         InputStream is = null;
 300 
 301         // First try the Context ClassLoader
 302         ClassLoader cl = ss.getContextClassLoader();
 303         boolean useBSClsLoader = false;
 304         if (cl != null) {
 305             is = ss.getResourceAsStream(cl, serviceId);
 306 
 307             // If no provider found then try the current ClassLoader
 308             if (is == null) {
 309                 cl = FactoryFinder.class.getClassLoader();
 310                 is = ss.getResourceAsStream(cl, serviceId);
 311                 useBSClsLoader = true;
 312            }
 313         } else {
 314             // No Context ClassLoader, try the current ClassLoader
 315             cl = FactoryFinder.class.getClassLoader();
 316             is = ss.getResourceAsStream(cl, serviceId);
 317             useBSClsLoader = true;
 318         }
 319 
 320         if (is == null) {
 321             // No provider found
 322             return null;
 323         }
 324 
 325         if (debug) {    // Extra check to avoid computing cl strings
 326             dPrint("found jar resource=" + serviceId + " using ClassLoader: " + cl);
 327         }
 328 
 329         BufferedReader rd;
 330         try {
 331             rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));
 332         }
 333         catch (java.io.UnsupportedEncodingException e) {
 334             rd = new BufferedReader(new InputStreamReader(is));
 335         }
 336 
 337         String factoryClassName = null;
 338         try {
 339             // XXX Does not handle all possible input as specified by the
 340             // Jar Service Provider specification
 341             factoryClassName = rd.readLine();
 342             rd.close();
 343         } catch (IOException x) {
 344             // No provider found
 345             return null;
 346         }
 347 
 348         if (factoryClassName != null && !"".equals(factoryClassName)) {
 349             dPrint("found in resource, value=" + factoryClassName);
 350 
 351             // Note: here we do not want to fall back to the current
 352             // ClassLoader because we want to avoid the case where the
 353             // resource file was found using one ClassLoader and the
 354             // provider class was instantiated using a different one.
 355             return newInstance(factoryClassName, cl, false, useBSClsLoader, true);
 356         }
 357 
 358         // No provider found
 359         return null;
 360     }
 361 
 362     static class ConfigurationError extends Error {
 363         private Exception exception;
 364 
 365         /**
 366          * Construct a new instance with the specified detail string and
 367          * exception.
 368          */
 369         ConfigurationError(String msg, Exception x) {
 370             super(msg);
 371             this.exception = x;
 372         }
 373 
 374         Exception getException() {
 375             return exception;
 376         }
 377         /**
 378         * use the exception chaining mechanism of JDK1.4
 379         */
 380         @Override
 381         public Throwable getCause() {
 382             return exception;
 383         }
 384     }
 385 
 386 }