1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 // $Id: XPathFactoryFinder.java 670432 2008-06-23 02:02:08Z mrglavas $ 18 19 package javax.xml.xpath; 20 21 import java.io.BufferedReader; 22 import java.io.File; 23 import java.io.IOException; 24 import java.io.InputStream; 25 import java.io.InputStreamReader; 26 import java.net.URL; 27 import java.util.ArrayList; 28 import java.util.Enumeration; 29 import java.util.Iterator; 30 import java.util.NoSuchElementException; 31 import java.util.Properties; 32 import javax.xml.validation.SchemaFactory; 33 34 /** 35 * Implementation of {@link XPathFactory#newInstance(String)}. 36 * 37 * @author <a href="Kohsuke.Kawaguchi (at) Sun.com">Kohsuke Kawaguchi</a> 38 * @version $Revision: 670432 $, $Date: 2008-06-22 19:02:08 -0700 (Sun, 22 Jun 2008) $ 39 * @since 1.5 40 */ 41 final class XPathFactoryFinder { 42 43 /** debug support code. */ 44 private static boolean debug = false; 45 46 /** 47 * Default columns per line. 48 */ 49 private static final int DEFAULT_LINE_LENGTH = 80; 50 51 static { 52 // Use try/catch block to support applets 53 try { 54 String val = SecuritySupport.getSystemProperty("jaxp.debug"); 55 // Allow simply setting the prop to turn on debug 56 debug = val != null && (! "false".equals(val)); 57 } catch (Exception _) { 58 debug = false; 59 } 60 } 61 62 /** 63 * <p>Cache properties for performance.</p> 64 */ 65 private static Properties cacheProps = new Properties(); 66 67 /** 68 * <p>First time requires initialization overhead.</p> 69 */ 70 private static boolean firstTime = true; 71 72 /** 73 * <p>Conditional debug printing.</p> 74 * 75 * @param msg to print 76 */ 77 private static void debugPrintln(String msg) { 78 if (debug) { 79 System.err.println("JAXP: " + msg); 80 } 81 } 82 83 /** 84 * <p><code>ClassLoader</code> to use to find <code>SchemaFactory</code>.</p> 85 */ 86 private final ClassLoader classLoader; 87 88 /** 89 * <p>Constructor that specifies <code>ClassLoader</code> to use 90 * to find <code>SchemaFactory</code>.</p> 91 * 92 * @param loader 93 * to be used to load resource, {@link SchemaFactory}, and 94 * {@link SchemaFactoryLoader} implementations during 95 * the resolution process. 96 * If this parameter is null, the default system class loader 97 * will be used. 98 */ 99 public XPathFactoryFinder(ClassLoader loader) { 100 this.classLoader = loader; 101 if( debug ) { 102 debugDisplayClassLoader(); 103 } 104 } 105 106 private void debugDisplayClassLoader() { 107 try { 108 if( classLoader == SecuritySupport.getContextClassLoader() ) { 109 debugPrintln("using thread context class loader ("+classLoader+") for search"); 110 return; 111 } 112 } 113 // The VM ran out of memory or there was some other serious problem. Re-throw. 114 catch (VirtualMachineError vme) { 115 throw vme; 116 } 117 // ThreadDeath should always be re-thrown 118 catch (ThreadDeath td) { 119 throw td; 120 } 121 catch (Throwable _) { 122 ; // getContextClassLoader() undefined in JDK1.1 123 } 124 125 if( classLoader==ClassLoader.getSystemClassLoader() ) { 126 debugPrintln("using system class loader ("+classLoader+") for search"); 127 return; 128 } 129 130 debugPrintln("using class loader ("+classLoader+") for search"); 131 } 132 133 /** 134 * <p>Creates a new {@link XPathFactory} object for the specified 135 * schema language.</p> 136 * 137 * @param uri 138 * Identifies the underlying object model. 139 * 140 * @return <code>null</code> if the callee fails to create one. 141 * 142 * @throws NullPointerException 143 * If the parameter is null. 144 */ 145 public XPathFactory newFactory(String uri) { 146 if(uri==null) throw new NullPointerException(); 147 XPathFactory f = _newFactory(uri); 148 if (debug) { 149 if (f != null) { 150 debugPrintln("factory '" + f.getClass().getName() + "' was found for " + uri); 151 } else { 152 debugPrintln("unable to find a factory for " + uri); 153 } 154 } 155 return f; 156 } 157 158 /** 159 * <p>Lookup a {@link XPathFactory} for the given object model.</p> 160 * 161 * @param uri identifies the object model. 162 * 163 * @return {@link XPathFactory} for the given object model. 164 */ 165 private XPathFactory _newFactory(String uri) { 166 XPathFactory xpf; 167 168 String propertyName = SERVICE_CLASS.getName() + ":" + uri; 169 170 // system property look up 171 try { 172 if (debug) debugPrintln("Looking up system property '"+propertyName+"'" ); 173 String r = SecuritySupport.getSystemProperty(propertyName); 174 if (r != null && r.length() > 0) { 175 if (debug) debugPrintln("The value is '"+r+"'"); 176 xpf = createInstance(r); 177 if(xpf!=null) return xpf; 178 } 179 else if (debug) { 180 debugPrintln("The property is undefined."); 181 } 182 } 183 // The VM ran out of memory or there was some other serious problem. Re-throw. 184 catch (VirtualMachineError vme) { 185 throw vme; 186 } 187 // ThreadDeath should always be re-thrown 188 catch (ThreadDeath td) { 189 throw td; 190 } 191 catch (Throwable t) { 192 if( debug ) { 193 debugPrintln("failed to look up system property '"+propertyName+"'" ); 194 t.printStackTrace(); 195 } 196 } 197 198 String javah = SecuritySupport.getSystemProperty( "java.home" ); 199 String configFile = javah + File.separator + 200 "lib" + File.separator + "jaxp.properties"; 201 202 String factoryClassName = null ; 203 204 // try to read from $java.home/lib/jaxp.properties 205 try { 206 if(firstTime){ 207 synchronized(cacheProps){ 208 if(firstTime){ 209 File f=new File( configFile ); 210 firstTime = false; 211 if(SecuritySupport.doesFileExist(f)){ 212 if (debug) debugPrintln("Read properties file " + f); 213 cacheProps.load(SecuritySupport.getFileInputStream(f)); 214 } 215 } 216 } 217 } 218 factoryClassName = cacheProps.getProperty(propertyName); 219 if (debug) debugPrintln("found " + factoryClassName + " in $java.home/jaxp.properties"); 220 221 if (factoryClassName != null) { 222 xpf = createInstance(factoryClassName); 223 if(xpf != null){ 224 return xpf; 225 } 226 } 227 } catch (Exception ex) { 228 if (debug) { 229 ex.printStackTrace(); 230 } 231 } 232 233 // try META-INF/services files 234 Iterator sitr = createServiceFileIterator(); 235 while(sitr.hasNext()) { 236 URL resource = (URL)sitr.next(); 237 if (debug) debugPrintln("looking into " + resource); 238 try { 239 xpf = loadFromServicesFile(uri, resource.toExternalForm(), SecuritySupport.getURLInputStream(resource)); 240 if(xpf!=null) return xpf; 241 } catch(IOException e) { 242 if( debug ) { 243 debugPrintln("failed to read "+resource); 244 e.printStackTrace(); 245 } 246 } 247 } 248 249 // platform default 250 if(uri.equals(XPathFactory.DEFAULT_OBJECT_MODEL_URI)) { 251 if (debug) debugPrintln("attempting to use the platform default W3C DOM XPath lib"); 252 return createInstance("org.apache.xpath.jaxp.XPathFactoryImpl"); 253 } 254 255 if (debug) debugPrintln("all things were tried, but none was found. bailing out."); 256 return null; 257 } 258 259 /** 260 * <p>Creates an instance of the specified and returns it.</p> 261 * 262 * @param className 263 * fully qualified class name to be instanciated. 264 * 265 * @return null 266 * if it fails. Error messages will be printed by this method. 267 */ 268 XPathFactory createInstance( String className ) { 269 try { 270 if (debug) debugPrintln("instanciating "+className); 271 Class clazz; 272 if( classLoader!=null ) 273 clazz = classLoader.loadClass(className); 274 else 275 clazz = Class.forName(className); 276 if(debug) debugPrintln("loaded it from "+which(clazz)); 277 Object o = clazz.newInstance(); 278 279 if( o instanceof XPathFactory ) 280 return (XPathFactory)o; 281 282 if (debug) debugPrintln(className+" is not assignable to "+SERVICE_CLASS.getName()); 283 } 284 // The VM ran out of memory or there was some other serious problem. Re-throw. 285 catch (VirtualMachineError vme) { 286 throw vme; 287 } 288 // ThreadDeath should always be re-thrown 289 catch (ThreadDeath td) { 290 throw td; 291 } 292 catch (Throwable t) { 293 if (debug) { 294 debugPrintln("failed to instanciate "+className); 295 t.printStackTrace(); 296 } 297 } 298 return null; 299 } 300 301 /** Iterator that lazily computes one value and returns it. */ 302 private static abstract class SingleIterator implements Iterator { 303 private boolean seen = false; 304 305 public final void remove() { throw new UnsupportedOperationException(); } 306 public final boolean hasNext() { return !seen; } 307 public final Object next() { 308 if(seen) throw new NoSuchElementException(); 309 seen = true; 310 return value(); 311 } 312 313 protected abstract Object value(); 314 } 315 316 /** Searches for a XPathFactory for a given uri in a META-INF/services file. */ 317 private XPathFactory loadFromServicesFile(String uri, String resourceName, InputStream in) { 318 319 if (debug) debugPrintln("Reading " + resourceName ); 320 321 BufferedReader rd; 322 try { 323 rd = new BufferedReader(new InputStreamReader(in, "UTF-8"), DEFAULT_LINE_LENGTH); 324 } catch (java.io.UnsupportedEncodingException e) { 325 rd = new BufferedReader(new InputStreamReader(in), DEFAULT_LINE_LENGTH); 326 } 327 328 String factoryClassName = null; 329 XPathFactory resultFactory = null; 330 // See spec for provider-configuration files: http://java.sun.com/j2se/1.5.0/docs/guide/jar/jar.html#Provider%20Configuration%20File 331 while (true) { 332 try { 333 factoryClassName = rd.readLine(); 334 } catch (IOException x) { 335 // No provider found 336 break; 337 } 338 if (factoryClassName != null) { 339 // Ignore comments in the provider-configuration file 340 int hashIndex = factoryClassName.indexOf('#'); 341 if (hashIndex != -1) { 342 factoryClassName = factoryClassName.substring(0, hashIndex); 343 } 344 345 // Ignore leading and trailing whitespace 346 factoryClassName = factoryClassName.trim(); 347 348 // If there's no text left or if this was a blank line, go to the next one. 349 if (factoryClassName.length() == 0) { 350 continue; 351 } 352 353 try { 354 // Found the right XPathFactory if its isObjectModelSupported(String uri) method returns true. 355 XPathFactory foundFactory = (XPathFactory) createInstance(factoryClassName); 356 if (foundFactory.isObjectModelSupported(uri)) { 357 resultFactory = foundFactory; 358 break; 359 } 360 } 361 catch (Exception e) {} 362 } 363 else { 364 break; 365 } 366 } 367 368 try { 369 // try to close the reader. 370 rd.close(); 371 } 372 // Ignore the exception. 373 catch (IOException exc) {} 374 375 return resultFactory; 376 } 377 378 /** 379 * Returns an {@link Iterator} that enumerates all 380 * the META-INF/services files that we care. 381 */ 382 private Iterator createServiceFileIterator() { 383 if (classLoader == null) { 384 return new SingleIterator() { 385 protected Object value() { 386 ClassLoader classLoader = XPathFactoryFinder.class.getClassLoader(); 387 return SecuritySupport.getResourceAsURL(classLoader, SERVICE_ID); 388 //return (ClassLoader.getSystemResource( SERVICE_ID )); 389 } 390 }; 391 } else { 392 try { 393 //final Enumeration e = classLoader.getResources(SERVICE_ID); 394 final Enumeration e = SecuritySupport.getResources(classLoader, SERVICE_ID); 395 if (debug && !e.hasMoreElements()) { 396 debugPrintln("no "+SERVICE_ID+" file was found"); 397 } 398 399 // wrap it into an Iterator. 400 return new Iterator() { 401 public void remove() { 402 throw new UnsupportedOperationException(); 403 } 404 405 public boolean hasNext() { 406 return e.hasMoreElements(); 407 } 408 409 public Object next() { 410 return e.nextElement(); 411 } 412 }; 413 } catch (IOException e) { 414 if (debug) { 415 debugPrintln("failed to enumerate resources "+SERVICE_ID); 416 e.printStackTrace(); 417 } 418 return new ArrayList().iterator(); // empty iterator 419 } 420 } 421 } 422 423 private static final Class SERVICE_CLASS = XPathFactory.class; 424 private static final String SERVICE_ID = "META-INF/services/" + SERVICE_CLASS.getName(); 425 426 427 428 private static String which( Class clazz ) { 429 return which( clazz.getName(), clazz.getClassLoader() ); 430 } 431 432 /** 433 * <p>Search the specified classloader for the given classname.</p> 434 * 435 * @param classname the fully qualified name of the class to search for 436 * @param loader the classloader to search 437 * 438 * @return the source location of the resource, or null if it wasn't found 439 */ 440 private static String which(String classname, ClassLoader loader) { 441 442 String classnameAsResource = classname.replace('.', '/') + ".class"; 443 444 if( loader==null ) loader = ClassLoader.getSystemClassLoader(); 445 446 //URL it = loader.getResource(classnameAsResource); 447 URL it = SecuritySupport.getResourceAsURL(loader, classnameAsResource); 448 if (it != null) { 449 return it.toString(); 450 } else { 451 return null; 452 } 453 } 454 } 455
