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 private boolean checkMetaAnnotations; 132 133 /** 134 * Constructs an AnnotatedWith test for the specified annotation type. 135 */ 136 public AnnotatedWith(Class<? extends Annotation> annotation) { 137 this(annotation, false); 138 } 139 140 /** 141 * Constructs an AnnotatedWith test for the specified annotation type. 142 */ 143 public AnnotatedWith(Class<? extends Annotation> annotation, boolean checkMetaAnnotations) { 144 this.annotation = annotation; 145 this.checkMetaAnnotations = checkMetaAnnotations; 146 } 147 148 /** 149 * Returns true if the type is annotated with the class provided to the 150 * constructor. 151 */ 152 public boolean matches(Class type) { 153 return type != null && ObjectHelper.hasAnnotation(type, annotation, checkMetaAnnotations); 154 } 155 156 @Override 157 public String toString() { 158 return "annotated with @" + annotation.getSimpleName(); 159 } 160 } 161 162 /** 163 * The set of matches being accumulated. 164 */ 165 private Set<Class<? extends T>> matches = new HashSet<Class<? extends T>>(); 166 167 /** 168 * The ClassLoader to use when looking for classes. If null then the 169 * ClassLoader returned by Thread.currentThread().getContextClassLoader() 170 * will be used. 171 */ 172 private Set<ClassLoader> classLoaders; 173 174 /** 175 * Provides access to the classes discovered so far. If no calls have been 176 * made to any of the {@code find()} methods, this set will be empty. 177 * 178 * @return the set of classes that have been discovered. 179 */ 180 public Set<Class<? extends T>> getClasses() { 181 return matches; 182 } 183 184 185 /** 186 * Returns the classloaders that will be used for scanning for classes. If no 187 * explicit ClassLoader has been set by the calling, the context class 188 * loader will and the one that has loaded this class ResolverUtil be used. 189 * 190 * @return the ClassLoader instances that will be used to scan for classes 191 */ 192 public Set<ClassLoader> getClassLoaders() { 193 if (classLoaders == null) { 194 classLoaders = new HashSet<ClassLoader>(); 195 ClassLoader ccl = Thread.currentThread().getContextClassLoader(); 196 if (ccl != null) { 197 classLoaders.add(ccl); 198 } 199 classLoaders.add(ResolverUtil.class.getClassLoader()); 200 } 201 return classLoaders; 202 } 203 204 /** 205 * Sets the ClassLoader instances that should be used when scanning for 206 * classes. If none is set then the context classloader will be used. 207 * 208 * @param classLoaders a ClassLoader to use when scanning for classes 209 */ 210 public void setClassLoaders(Set<ClassLoader> classLoaders) { 211 this.classLoaders = classLoaders; 212 } 213 214 /** 215 * Attempts to discover classes that are assignable to the type provided. In 216 * the case that an interface is provided this method will collect 217 * implementations. In the case of a non-interface class, subclasses will be 218 * collected. Accumulated classes can be accessed by calling 219 * {@link #getClasses()}. 220 * 221 * @param parent the class of interface to find subclasses or 222 * implementations of 223 * @param packageNames one or more package names to scan (including 224 * subpackages) for classes 225 */ 226 public void findImplementations(Class parent, String... packageNames) { 227 if (packageNames == null) { 228 return; 229 } 230 231 if (LOG.isDebugEnabled()) { 232 LOG.debug("Searching for implementations of " + parent.getName() + " in packages: " + Arrays 233 .asList(packageNames)); 234 } 235 236 Test test = new IsA(parent); 237 for (String pkg : packageNames) { 238 find(test, pkg); 239 } 240 241 if (LOG.isDebugEnabled()) { 242 LOG.debug("Found: " + getClasses()); 243 } 244 } 245 246 /** 247 * Attempts to discover classes that are annotated with to the annotation. 248 * Accumulated classes can be accessed by calling {@link #getClasses()}. 249 * 250 * @param annotation the annotation that should be present on matching 251 * classes 252 * @param packageNames one or more package names to scan (including 253 * subpackages) for classes 254 */ 255 public void findAnnotated(Class<? extends Annotation> annotation, String... packageNames) { 256 if (packageNames == null) { 257 return; 258 } 259 260 if (LOG.isDebugEnabled()) { 261 LOG.debug("Searching for annotations of " + annotation.getName() + " in packages: " + Arrays 262 .asList(packageNames)); 263 } 264 265 Test test = new AnnotatedWith(annotation, true); 266 for (String pkg : packageNames) { 267 find(test, pkg); 268 } 269 270 if (LOG.isDebugEnabled()) { 271 LOG.debug("Found: " + getClasses()); 272 } 273 } 274 275 /** 276 * Scans for classes starting at the package provided and descending into 277 * subpackages. Each class is offered up to the Test as it is discovered, 278 * and if the Test returns true the class is retained. Accumulated classes 279 * can be fetched by calling {@link #getClasses()}. 280 * 281 * @param test an instance of {@link Test} that will be used to filter 282 * classes 283 * @param packageName the name of the package from which to start scanning 284 * for classes, e.g. {@code net.sourceforge.stripes} 285 */ 286 public void find(Test test, String packageName) { 287 packageName = packageName.replace('.', '/'); 288 289 Set<ClassLoader> set = getClassLoaders(); 290 291 LOG.debug("Using only regular classloaders"); 292 for (ClassLoader classLoader : set) { 293 find(test, packageName, classLoader); 294 } 295 } 296 297 298 299 /** 300 * Tries to find the reosurce in the package using the class loader. 301 * <p/> 302 * Will handle both plain URL based classloaders and OSGi bundle loaders. 303 * 304 * @param test what to find 305 * @param packageName the package to search in 306 * @param loader the class loader 307 */ 308 protected void find(Test test, String packageName, ClassLoader loader) { 309 if (LOG.isTraceEnabled()) { 310 LOG.trace("Searching for: " + test + " in package: " + packageName + " using classloader: " 311 + loader.getClass().getName()); 312 } 313 314 Enumeration<URL> urls; 315 try { 316 urls = getResources(loader, packageName); 317 if (!urls.hasMoreElements()) { 318 LOG.trace("No URLs returned by classloader"); 319 } 320 } catch (IOException ioe) { 321 LOG.warn("Could not read package: " + packageName, ioe); 322 return; 323 } 324 325 while (urls.hasMoreElements()) { 326 URL url = null; 327 try { 328 url = urls.nextElement(); 329 if (LOG.isTraceEnabled()) { 330 LOG.trace("URL from classloader: " + url); 331 } 332 333 String urlPath = url.getFile(); 334 urlPath = URLDecoder.decode(urlPath, "UTF-8"); 335 if (LOG.isTraceEnabled()) { 336 LOG.trace("Decoded urlPath: " + urlPath); 337 } 338 339 // If it's a file in a directory, trim the stupid file: spec 340 if (urlPath.startsWith("file:")) { 341 urlPath = urlPath.substring(5); 342 } 343 344 // osgi bundles should be skipped 345 if (url.toString().startsWith("bundle:") || urlPath.startsWith("bundle:")) { 346 LOG.trace("It's a virtual osgi bundle, skipping"); 347 continue; 348 } 349 350 // Else it's in a JAR, grab the path to the jar 351 if (urlPath.indexOf('!') > 0) { 352 urlPath = urlPath.substring(0, urlPath.indexOf('!')); 353 } 354 355 if (LOG.isTraceEnabled()) { 356 LOG.trace("Scanning for classes in [" + urlPath + "] matching criteria: " + test); 357 } 358 359 File file = new File(urlPath); 360 if (file.isDirectory()) { 361 if (LOG.isDebugEnabled()) { 362 LOG.debug("Loading from directory: " + file); 363 } 364 loadImplementationsInDirectory(test, packageName, file); 365 } else { 366 InputStream stream; 367 if (urlPath.startsWith("http:")) { 368 // load resources using http such as java webstart 369 LOG.debug("The current jar is accessed via http"); 370 URL urlStream = new URL(urlPath); 371 URLConnection con = urlStream.openConnection(); 372 // disable cache mainly to avoid jar file locking on Windows 373 con.setUseCaches(false); 374 stream = con.getInputStream(); 375 } else { 376 stream = new FileInputStream(file); 377 } 378 379 if (LOG.isDebugEnabled()) { 380 LOG.debug("Loading from jar: " + file); 381 } 382 loadImplementationsInJar(test, packageName, stream, urlPath); 383 } 384 } catch (IOException ioe) { 385 LOG.warn("Could not read entries in url: " + url, ioe); 386 } 387 } 388 } 389 390 /** 391 * Strategy to get the resources by the given classloader. 392 * <p/> 393 * Notice that in WebSphere platforms there is a {@link org.apache.camel.util.WebSphereResolverUtil} 394 * to take care of WebSphere's odditiy of resource loading. 395 * 396 * @param loader the classloader 397 * @param packageName the packagename for the package to load 398 * @return URL's for the given package 399 * @throws IOException is thrown by the classloader 400 */ 401 protected Enumeration<URL> getResources(ClassLoader loader, String packageName) throws IOException { 402 if (LOG.isTraceEnabled()) { 403 LOG.trace("Getting resource URL for package: " + packageName + " with classloader: " + loader); 404 } 405 return loader.getResources(packageName); 406 } 407 408 409 410 411 /** 412 * Finds matches in a physical directory on a filesystem. Examines all files 413 * within a directory - if the File object is not a directory, and ends with 414 * <i>.class</i> the file is loaded and tested to see if it is acceptable 415 * according to the Test. Operates recursively to find classes within a 416 * folder structure matching the package structure. 417 * 418 * @param test a Test used to filter the classes that are discovered 419 * @param parent the package name up to this directory in the package 420 * hierarchy. E.g. if /classes is in the classpath and we wish to 421 * examine files in /classes/org/apache then the values of 422 * <i>parent</i> would be <i>org/apache</i> 423 * @param location a File object representing a directory 424 */ 425 private void loadImplementationsInDirectory(Test test, String parent, File location) { 426 File[] files = location.listFiles(); 427 StringBuilder builder = null; 428 429 for (File file : files) { 430 builder = new StringBuilder(100); 431 String name = file.getName(); 432 if (name != null) { 433 name = name.trim(); 434 builder.append(parent).append("/").append(name); 435 String packageOrClass = parent == null ? name : builder.toString(); 436 437 if (file.isDirectory()) { 438 loadImplementationsInDirectory(test, packageOrClass, file); 439 } else if (name.endsWith(".class")) { 440 addIfMatching(test, packageOrClass); 441 } 442 } 443 } 444 } 445 446 /** 447 * Finds matching classes within a jar files that contains a folder 448 * structure matching the package structure. If the File is not a JarFile or 449 * does not exist a warning will be logged, but no error will be raised. 450 * 451 * @param test a Test used to filter the classes that are discovered 452 * @param parent the parent package under which classes must be in order to 453 * be considered 454 * @param jarfile the jar file to be examined for classes 455 * @param stream the inputstream of the jar file to be examined for classes 456 * @param urlPath the url of the jar file to be examined for classes 457 */ 458 private void loadImplementationsInJar(Test test, String parent, InputStream stream, String urlPath) { 459 JarInputStream jarStream = null; 460 try { 461 jarStream = new JarInputStream(stream); 462 463 JarEntry entry; 464 while ((entry = jarStream.getNextJarEntry()) != null) { 465 String name = entry.getName(); 466 if (name != null) { 467 name = name.trim(); 468 if (!entry.isDirectory() && name.startsWith(parent) && name.endsWith(".class")) { 469 addIfMatching(test, name); 470 } 471 } 472 } 473 } catch (IOException ioe) { 474 LOG.error("Could not search jar file '" + urlPath + "' for classes matching criteria: " + test 475 + " due to an IOException: " + ioe.getMessage(), ioe); 476 } finally { 477 ObjectHelper.close(jarStream, urlPath, LOG); 478 } 479 } 480 481 /** 482 * Add the class designated by the fully qualified class name provided to 483 * the set of resolved classes if and only if it is approved by the Test 484 * supplied. 485 * 486 * @param test the test used to determine if the class matches 487 * @param fqn the fully qualified name of a class 488 */ 489 protected void addIfMatching(Test test, String fqn) { 490 try { 491 String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.'); 492 Set<ClassLoader> set = getClassLoaders(); 493 boolean found = false; 494 for (ClassLoader classLoader : set) { 495 if (LOG.isTraceEnabled()) { 496 LOG.trace("Testing for class " + externalName + " matches criteria [" + test + "]"); 497 } 498 try { 499 Class type = classLoader.loadClass(externalName); 500 if (test.matches(type)) { 501 if (LOG.isTraceEnabled()) { 502 LOG.trace("Found class: " + type + " in classloader: " + classLoader); 503 } 504 matches.add((Class<T>)type); 505 } 506 found = true; 507 break; 508 } catch (ClassNotFoundException e) { 509 LOG.debug("Could not find class '" + fqn + "' in classloader: " + classLoader 510 + ". Reason: " + e, e); 511 } catch (NoClassDefFoundError e) { 512 LOG.debug("Could not find the class defintion '" + fqn + "' in classloader: " + classLoader 513 + ". Reason: " + e, e); 514 } 515 } 516 if (!found) { 517 LOG.warn("Could not find class '" + fqn + "' in any classloaders: " + set); 518 } 519 } catch (Throwable t) { 520 LOG.warn("Could not examine class '" + fqn + "' due to a " + t.getClass().getName() 521 + " with message: " + t.getMessage(), t); 522 } 523 } 524 525 }