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