001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.camel.util; 018 019 import java.io.File; 020 import java.io.FileInputStream; 021 import java.io.IOException; 022 import java.io.InputStream; 023 import java.lang.annotation.Annotation; 024 import java.lang.reflect.Method; 025 import java.net.URL; 026 import java.net.URLConnection; 027 import java.net.URLDecoder; 028 import java.util.Arrays; 029 import java.util.Enumeration; 030 import java.util.HashSet; 031 import java.util.Set; 032 import java.util.jar.JarEntry; 033 import java.util.jar.JarInputStream; 034 035 import org.apache.commons.logging.Log; 036 import org.apache.commons.logging.LogFactory; 037 038 /** 039 * <p> 040 * ResolverUtil is used to locate classes that are available in the/a class path 041 * and meet arbitrary conditions. The two most common conditions are that a 042 * class implements/extends another class, or that is it annotated with a 043 * specific annotation. However, through the use of the {@link Test} class it is 044 * possible to search using arbitrary conditions. 045 * </p> 046 * <p/> 047 * <p> 048 * A ClassLoader is used to locate all locations (directories and jar files) in 049 * the class path that contain classes within certain packages, and then to load 050 * those classes and check them. By default the ClassLoader returned by 051 * {@code Thread.currentThread().getContextClassLoader()} is used, but this can 052 * be overridden by calling {@link #setClassLoaders(Set)} prior to 053 * invoking any of the {@code find()} methods. 054 * </p> 055 * <p/> 056 * <p> 057 * General searches are initiated by calling the 058 * {@link #find(ResolverUtil.Test, String)} ()} method and supplying a package 059 * name and a Test instance. This will cause the named package <b>and all 060 * sub-packages</b> to be scanned for classes that meet the test. There are 061 * also utility methods for the common use cases of scanning multiple packages 062 * for extensions of particular classes, or classes annotated with a specific 063 * annotation. 064 * </p> 065 * <p/> 066 * <p> 067 * The standard usage pattern for the ResolverUtil class is as follows: 068 * </p> 069 * <p/> 070 * <pre> 071 * resolverUtil<ActionBean> resolver = new ResolverUtil<ActionBean>(); 072 * resolver.findImplementation(ActionBean.class, pkg1, pkg2); 073 * resolver.find(new CustomTest(), pkg1); 074 * resolver.find(new CustomTest(), pkg2); 075 * collection<ActionBean> beans = resolver.getClasses(); 076 * </pre> 077 * 078 * @author Tim Fennell 079 */ 080 public class ResolverUtil<T> { 081 protected static final transient Log LOG = LogFactory.getLog(ResolverUtil.class); 082 083 /** 084 * A simple interface that specifies how to test classes to determine if 085 * they are to be included in the results produced by the ResolverUtil. 086 */ 087 public static interface Test { 088 /** 089 * Will be called repeatedly with candidate classes. Must return True if 090 * a class is to be included in the results, false otherwise. 091 */ 092 boolean matches(Class type); 093 } 094 095 /** 096 * A Test that checks to see if each class is assignable to the provided 097 * class. Note that this test will match the parent type itself if it is 098 * presented for matching. 099 */ 100 public static class IsA implements Test { 101 private Class parent; 102 103 /** 104 * Constructs an IsA test using the supplied Class as the parent 105 * class/interface. 106 */ 107 public IsA(Class parentType) { 108 this.parent = parentType; 109 } 110 111 /** 112 * Returns true if type is assignable to the parent type supplied in the 113 * constructor. 114 */ 115 public boolean matches(Class type) { 116 return type != null && parent.isAssignableFrom(type); 117 } 118 119 @Override 120 public String toString() { 121 return "is assignable to " + parent.getSimpleName(); 122 } 123 } 124 125 /** 126 * A Test that checks to see if each class is annotated with a specific 127 * annotation. If it is, then the test returns true, otherwise false. 128 */ 129 public static class AnnotatedWith implements Test { 130 private Class<? extends Annotation> annotation; 131 132 /** 133 * Constructs an AnnotatedWith test for the specified annotation type. 134 */ 135 public AnnotatedWith(Class<? extends Annotation> annotation) { 136 this.annotation = annotation; 137 } 138 139 /** 140 * Returns true if the type is annotated with the class provided to the 141 * constructor. 142 */ 143 public boolean matches(Class type) { 144 return type != null && type.isAnnotationPresent(annotation); 145 } 146 147 @Override 148 public String toString() { 149 return "annotated with @" + annotation.getSimpleName(); 150 } 151 } 152 153 /** 154 * The set of matches being accumulated. 155 */ 156 private Set<Class<? extends T>> matches = new HashSet<Class<? extends T>>(); 157 158 /** 159 * The ClassLoader to use when looking for classes. If null then the 160 * ClassLoader returned by Thread.currentThread().getContextClassLoader() 161 * will be used. 162 */ 163 private Set<ClassLoader> classLoaders; 164 165 /** 166 * Provides access to the classes discovered so far. If no calls have been 167 * made to any of the {@code find()} methods, this set will be empty. 168 * 169 * @return the set of classes that have been discovered. 170 */ 171 public Set<Class<? extends T>> getClasses() { 172 return matches; 173 } 174 175 176 /** 177 * Returns the classloaders that will be used for scanning for classes. If no 178 * explicit ClassLoader has been set by the calling, the context class 179 * loader will and the one that has loaded this class ResolverUtil be used. 180 * 181 * @return the ClassLoader instances that will be used to scan for classes 182 */ 183 public Set<ClassLoader> getClassLoaders() { 184 if (classLoaders == null) { 185 classLoaders = new HashSet<ClassLoader>(); 186 classLoaders.add(Thread.currentThread().getContextClassLoader()); 187 classLoaders.add(ResolverUtil.class.getClassLoader()); 188 } 189 return classLoaders; 190 } 191 192 /** 193 * Sets the ClassLoader instances that should be used when scanning for 194 * classes. If none is set then the context classloader will be used. 195 * 196 * @param classLoaders a ClassLoader to use when scanning for classes 197 */ 198 public void setClassLoaders(Set<ClassLoader> classLoaders) { 199 this.classLoaders = classLoaders; 200 } 201 202 /** 203 * Attempts to discover classes that are assignable to the type provided. In 204 * the case that an interface is provided this method will collect 205 * implementations. In the case of a non-interface class, subclasses will be 206 * collected. Accumulated classes can be accessed by calling 207 * {@link #getClasses()}. 208 * 209 * @param parent the class of interface to find subclasses or 210 * implementations of 211 * @param packageNames one or more package names to scan (including 212 * subpackages) for classes 213 */ 214 public void findImplementations(Class parent, String... packageNames) { 215 if (packageNames == null) { 216 return; 217 } 218 219 if (LOG.isDebugEnabled()) { 220 LOG.debug("Searching for implementations of " + parent.getName() + " in packages: " + Arrays 221 .asList(packageNames)); 222 } 223 224 Test test = new IsA(parent); 225 for (String pkg : packageNames) { 226 find(test, pkg); 227 } 228 229 if (LOG.isDebugEnabled()) { 230 LOG.debug("Found: " + getClasses()); 231 } 232 } 233 234 /** 235 * Attempts to discover classes that are annotated with to the annotation. 236 * Accumulated classes can be accessed by calling {@link #getClasses()}. 237 * 238 * @param annotation the annotation that should be present on matching 239 * classes 240 * @param packageNames one or more package names to scan (including 241 * subpackages) for classes 242 */ 243 public void findAnnotated(Class<? extends Annotation> annotation, String... packageNames) { 244 if (packageNames == null) { 245 return; 246 } 247 248 if (LOG.isDebugEnabled()) { 249 LOG.debug("Searching for annotations of " + annotation.getName() + " in packages: " + Arrays 250 .asList(packageNames)); 251 } 252 253 Test test = new AnnotatedWith(annotation); 254 for (String pkg : packageNames) { 255 find(test, pkg); 256 } 257 258 if (LOG.isDebugEnabled()) { 259 LOG.debug("Found: " + getClasses()); 260 } 261 } 262 263 /** 264 * Scans for classes starting at the package provided and descending into 265 * subpackages. Each class is offered up to the Test as it is discovered, 266 * and if the Test returns true the class is retained. Accumulated classes 267 * can be fetched by calling {@link #getClasses()}. 268 * 269 * @param test an instance of {@link Test} that will be used to filter 270 * classes 271 * @param packageName the name of the package from which to start scanning 272 * for classes, e.g. {@code net.sourceforge.stripes} 273 */ 274 public void find(Test test, String packageName) { 275 packageName = packageName.replace('.', '/'); 276 277 Set<ClassLoader> set = getClassLoaders(); 278 279 ClassLoader osgiClassLoader = getOsgiClassLoader(set); 280 281 if (osgiClassLoader != null) { 282 // if we have an osgi bundle loader use this one only 283 LOG.debug("Using only osgi bundle classloader"); 284 find(test, packageName, osgiClassLoader, true); 285 } else { 286 LOG.debug("Using only regular classloaders"); 287 for (ClassLoader classLoader : set) { 288 if (!isOsgiClassloader(classLoader)) { 289 find(test, packageName, classLoader, false); 290 } 291 } 292 } 293 } 294 295 /** 296 * Gets the osgi classloader if any in the given set 297 */ 298 private static ClassLoader getOsgiClassLoader(Set<ClassLoader> set) { 299 for (ClassLoader loader : set) { 300 if (isOsgiClassloader(loader)) { 301 return loader; 302 } 303 } 304 return null; 305 } 306 307 /** 308 * Is it an osgi classloader 309 */ 310 private static boolean isOsgiClassloader(ClassLoader loader) { 311 try { 312 Method mth = loader.getClass().getMethod("getBundle", new Class[]{}); 313 if (mth != null) { 314 return true; 315 } 316 } catch (NoSuchMethodException e) { 317 // ignore its not an osgi loader 318 } 319 return false; 320 } 321 322 /** 323 * Tries to find the reosurce in the package using the class loader. 324 * <p/> 325 * Will handle both plain URL based classloaders and OSGi bundle loaders. 326 * 327 * @param test what to find 328 * @param packageName the package to search in 329 * @param loader the class loader 330 * @param osgi true if its a osgi bundle loader, false if regular classloader 331 */ 332 protected void find(Test test, String packageName, ClassLoader loader, boolean osgi) { 333 if (LOG.isTraceEnabled()) { 334 LOG.trace("Searching for: " + test + " in package: " + packageName + " using classloader: " 335 + loader.getClass().getName() + " osgi bundle classloader: " + osgi); 336 } 337 338 if (osgi) { 339 try { 340 Method mth = loader.getClass().getMethod("getBundle", new Class[]{}); 341 if (mth != null) { 342 if (LOG.isDebugEnabled()) { 343 LOG.debug("Loading from osgi buindle using classloader: " + loader); 344 } 345 loadImplementationsInBundle(test, packageName, loader, mth); 346 return; 347 } 348 } catch (NoSuchMethodException e) { 349 LOG.warn("It's not an osgi bundle classloader: " + loader); 350 return; 351 } 352 } 353 354 Enumeration<URL> urls; 355 try { 356 urls = getResources(loader, packageName); 357 if (!urls.hasMoreElements()) { 358 LOG.trace("No URLs returned by classloader"); 359 } 360 } catch (IOException ioe) { 361 LOG.warn("Could not read package: " + packageName, ioe); 362 return; 363 } 364 365 while (urls.hasMoreElements()) { 366 URL url = null; 367 try { 368 url = urls.nextElement(); 369 if (LOG.isTraceEnabled()) { 370 LOG.trace("URL from classloader: " + url); 371 } 372 373 String urlPath = url.getFile(); 374 urlPath = URLDecoder.decode(urlPath, "UTF-8"); 375 if (LOG.isTraceEnabled()) { 376 LOG.trace("Decoded urlPath: " + urlPath); 377 } 378 379 // If it's a file in a directory, trim the stupid file: spec 380 if (urlPath.startsWith("file:")) { 381 urlPath = urlPath.substring(5); 382 } 383 384 // osgi bundles should be skipped 385 if (urlPath.startsWith("bundle:")) { 386 LOG.trace("It's a virtual osgi bundle, skipping"); 387 continue; 388 } 389 390 // Else it's in a JAR, grab the path to the jar 391 if (urlPath.indexOf('!') > 0) { 392 urlPath = urlPath.substring(0, urlPath.indexOf('!')); 393 } 394 395 if (LOG.isTraceEnabled()) { 396 LOG.trace("Scanning for classes in [" + urlPath + "] matching criteria: " + test); 397 } 398 399 File file = new File(urlPath); 400 if (file.isDirectory()) { 401 if (LOG.isDebugEnabled()) { 402 LOG.debug("Loading from directory: " + file); 403 } 404 loadImplementationsInDirectory(test, packageName, file); 405 } else { 406 InputStream stream; 407 if (urlPath.startsWith("http:")) { 408 // load resources using http such as java webstart 409 LOG.debug("The current jar is accessed via http"); 410 URL urlStream = new URL(urlPath); 411 URLConnection con = urlStream.openConnection(); 412 // disable cache mainly to avoid jar file locking on Windows 413 con.setUseCaches(false); 414 stream = con.getInputStream(); 415 } else { 416 stream = new FileInputStream(file); 417 } 418 419 if (LOG.isDebugEnabled()) { 420 LOG.debug("Loading from jar: " + file); 421 } 422 loadImplementationsInJar(test, packageName, stream, urlPath); 423 } 424 } catch (IOException ioe) { 425 LOG.warn("Could not read entries in url: " + url, ioe); 426 } 427 } 428 } 429 430 /** 431 * Strategy to get the resources by the given classloader. 432 * <p/> 433 * Notice that in WebSphere platforms there is a {@link org.apache.camel.util.WebSphereResolverUtil} 434 * to take care of WebSphere's odditiy of resource loading. 435 * 436 * @param loader the classloader 437 * @param packageName the packagename for the package to load 438 * @return URL's for the given package 439 * @throws IOException is thrown by the classloader 440 */ 441 protected Enumeration<URL> getResources(ClassLoader loader, String packageName) throws IOException { 442 if (LOG.isTraceEnabled()) { 443 LOG.trace("Getting resource URL for package: " + packageName + " with classloader: " + loader); 444 } 445 return loader.getResources(packageName); 446 } 447 448 private void loadImplementationsInBundle(Test test, String packageName, ClassLoader loader, Method mth) { 449 // Use an inner class to avoid a NoClassDefFoundError when used in a non-osgi env 450 Set<String> urls = OsgiUtil.getImplementationsInBundle(test, packageName, loader, mth); 451 if (urls != null) { 452 for (String url : urls) { 453 // substring to avoid leading slashes 454 addIfMatching(test, url); 455 } 456 } 457 } 458 459 private static final class OsgiUtil { 460 private OsgiUtil() { 461 // Helper class 462 } 463 static Set<String> getImplementationsInBundle(Test test, String packageName, ClassLoader loader, Method mth) { 464 try { 465 org.osgi.framework.Bundle bundle = (org.osgi.framework.Bundle) mth.invoke(loader); 466 org.osgi.framework.Bundle[] bundles = bundle.getBundleContext().getBundles(); 467 Set<String> urls = new HashSet<String>(); 468 for (org.osgi.framework.Bundle bd : bundles) { 469 if (LOG.isTraceEnabled()) { 470 LOG.trace("Searching in bundle:" + bd); 471 } 472 Enumeration<URL> paths = bd.findEntries("/" + packageName, "*.class", true); 473 while (paths != null && paths.hasMoreElements()) { 474 URL path = paths.nextElement(); 475 urls.add(path.getPath().substring(1)); 476 } 477 } 478 return urls; 479 } catch (Throwable t) { 480 LOG.error("Could not search osgi bundles for classes matching criteria: " + test 481 + "due to an Exception: " + t.getMessage()); 482 return null; 483 } 484 } 485 } 486 487 488 /** 489 * Finds matches in a physical directory on a filesystem. Examines all files 490 * within a directory - if the File object is not a directory, and ends with 491 * <i>.class</i> the file is loaded and tested to see if it is acceptable 492 * according to the Test. Operates recursively to find classes within a 493 * folder structure matching the package structure. 494 * 495 * @param test a Test used to filter the classes that are discovered 496 * @param parent the package name up to this directory in the package 497 * hierarchy. E.g. if /classes is in the classpath and we wish to 498 * examine files in /classes/org/apache then the values of 499 * <i>parent</i> would be <i>org/apache</i> 500 * @param location a File object representing a directory 501 */ 502 private void loadImplementationsInDirectory(Test test, String parent, File location) { 503 File[] files = location.listFiles(); 504 StringBuilder builder = null; 505 506 for (File file : files) { 507 builder = new StringBuilder(100); 508 String name = file.getName(); 509 if (name != null) { 510 name = name.trim(); 511 builder.append(parent).append("/").append(name); 512 String packageOrClass = parent == null ? name : builder.toString(); 513 514 if (file.isDirectory()) { 515 loadImplementationsInDirectory(test, packageOrClass, file); 516 } else if (name.endsWith(".class")) { 517 addIfMatching(test, packageOrClass); 518 } 519 } 520 } 521 } 522 523 /** 524 * Finds matching classes within a jar files that contains a folder 525 * structure matching the package structure. If the File is not a JarFile or 526 * does not exist a warning will be logged, but no error will be raised. 527 * 528 * @param test a Test used to filter the classes that are discovered 529 * @param parent the parent package under which classes must be in order to 530 * be considered 531 * @param jarfile the jar file to be examined for classes 532 * @param stream the inputstream of the jar file to be examined for classes 533 * @param urlPath the url of the jar file to be examined for classes 534 */ 535 private void loadImplementationsInJar(Test test, String parent, InputStream stream, String urlPath) { 536 JarInputStream jarStream = null; 537 try { 538 jarStream = new JarInputStream(stream); 539 540 JarEntry entry; 541 while ((entry = jarStream.getNextJarEntry()) != null) { 542 String name = entry.getName(); 543 if (name != null) { 544 name = name.trim(); 545 if (!entry.isDirectory() && name.startsWith(parent) && name.endsWith(".class")) { 546 addIfMatching(test, name); 547 } 548 } 549 } 550 } catch (IOException ioe) { 551 LOG.error("Could not search jar file '" + urlPath + "' for classes matching criteria: " + test 552 + " due to an IOException: " + ioe.getMessage(), ioe); 553 } finally { 554 ObjectHelper.close(jarStream, urlPath, LOG); 555 } 556 } 557 558 /** 559 * Add the class designated by the fully qualified class name provided to 560 * the set of resolved classes if and only if it is approved by the Test 561 * supplied. 562 * 563 * @param test the test used to determine if the class matches 564 * @param fqn the fully qualified name of a class 565 */ 566 protected void addIfMatching(Test test, String fqn) { 567 try { 568 String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.'); 569 Set<ClassLoader> set = getClassLoaders(); 570 boolean found = false; 571 for (ClassLoader classLoader : set) { 572 if (LOG.isTraceEnabled()) { 573 LOG.trace("Testing for class " + externalName + " matches criteria [" + test + "]"); 574 } 575 try { 576 Class type = classLoader.loadClass(externalName); 577 if (test.matches(type)) { 578 if (LOG.isTraceEnabled()) { 579 LOG.trace("Found class: " + type + " in classloader: " + classLoader); 580 } 581 matches.add((Class<T>)type); 582 } 583 found = true; 584 break; 585 } catch (ClassNotFoundException e) { 586 LOG.debug("Could not find class '" + fqn + "' in classloader: " + classLoader 587 + ". Reason: " + e, e); 588 } catch (NoClassDefFoundError e) { 589 LOG.debug("Could not find the class defintion '" + fqn + "' in classloader: " + classLoader 590 + ". Reason: " + e, e); 591 } 592 } 593 if (!found) { 594 LOG.warn("Could not find class '" + fqn + "' in any classloaders: " + set); 595 } 596 } catch (Throwable t) { 597 LOG.warn("Could not examine class '" + fqn + "' due to a " + t.getClass().getName() 598 + " with message: " + t.getMessage(), t); 599 } 600 } 601 602 }