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.lang.annotation.Annotation; 023 import java.net.URL; 024 import java.net.URLDecoder; 025 import java.util.Arrays; 026 import java.util.Enumeration; 027 import java.util.HashSet; 028 import java.util.Set; 029 import java.util.jar.JarEntry; 030 import java.util.jar.JarInputStream; 031 032 import org.apache.commons.logging.Log; 033 import org.apache.commons.logging.LogFactory; 034 035 /** 036 * <p> 037 * ResolverUtil is used to locate classes that are available in the/a class path 038 * and meet arbitrary conditions. The two most common conditions are that a 039 * class implements/extends another class, or that is it annotated with a 040 * specific annotation. However, through the use of the {@link Test} class it is 041 * possible to search using arbitrary conditions. 042 * </p> 043 * 044 * <p> 045 * A ClassLoader is used to locate all locations (directories and jar files) in 046 * the class path that contain classes within certain packages, and then to load 047 * those classes and check them. By default the ClassLoader returned by 048 * {@code Thread.currentThread().getContextClassLoader()} is used, but this can 049 * be overridden by calling {@link #setClassLoaders(Set)} prior to 050 * invoking any of the {@code find()} methods. 051 * </p> 052 * 053 * <p> 054 * General searches are initiated by calling the 055 * {@link #find(ResolverUtil.Test, String)} ()} method and supplying a package 056 * name and a Test instance. This will cause the named package <b>and all 057 * sub-packages</b> to be scanned for classes that meet the test. There are 058 * also utility methods for the common use cases of scanning multiple packages 059 * for extensions of particular classes, or classes annotated with a specific 060 * annotation. 061 * </p> 062 * 063 * <p> 064 * The standard usage pattern for the ResolverUtil class is as follows: 065 * </p> 066 * 067 * <pre> 068 * esolverUtil<ActionBean> resolver = new ResolverUtil<ActionBean>(); 069 * esolver.findImplementation(ActionBean.class, pkg1, pkg2); 070 * esolver.find(new CustomTest(), pkg1); 071 * esolver.find(new CustomTest(), pkg2); 072 * ollection<ActionBean> beans = resolver.getClasses(); 073 * </pre> 074 * 075 * @author Tim Fennell 076 */ 077 public class ResolverUtil<T> { 078 private static final transient Log LOG = LogFactory.getLog(ResolverUtil.class); 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; 128 129 /** 130 * Constructs an AnnotatedWith test for the specified annotation type. 131 */ 132 public AnnotatedWith(Class<? extends Annotation> annotation) { 133 this.annotation = annotation; 134 } 135 136 /** 137 * Returns true if the type is annotated with the class provided to the 138 * constructor. 139 */ 140 public boolean matches(Class type) { 141 return type != null && type.isAnnotationPresent(annotation); 142 } 143 144 @Override 145 public String toString() { 146 return "annotated with @" + annotation.getSimpleName(); 147 } 148 } 149 150 /** The set of matches being accumulated. */ 151 private Set<Class<? extends T>> matches = new HashSet<Class<? extends T>>(); 152 153 /** 154 * The ClassLoader to use when looking for classes. If null then the 155 * ClassLoader returned by Thread.currentThread().getContextClassLoader() 156 * will be used. 157 */ 158 private Set<ClassLoader> classLoaders; 159 160 /** 161 * Provides access to the classes discovered so far. If no calls have been 162 * made to any of the {@code find()} methods, this set will be empty. 163 * 164 * @return the set of classes that have been discovered. 165 */ 166 public Set<Class<? extends T>> getClasses() { 167 return matches; 168 } 169 170 171 /** 172 * Returns the classloaders that will be used for scanning for classes. If no 173 * explicit ClassLoader has been set by the calling, the context class 174 * loader will be used. 175 * 176 * @return the ClassLoader instances that will be used to scan for classes 177 */ 178 public Set<ClassLoader> getClassLoaders() { 179 if (classLoaders == null) { 180 classLoaders = new HashSet<ClassLoader>(); 181 classLoaders.add(Thread.currentThread().getContextClassLoader()); 182 } 183 return classLoaders; 184 } 185 186 /** 187 * Sets the ClassLoader instances that should be used when scanning for 188 * classes. If none is set then the context classloader will be used. 189 * 190 * @param classLoaders a ClassLoader to use when scanning for classes 191 */ 192 public void setClassLoaders(Set<ClassLoader> classLoaders) { 193 this.classLoaders = classLoaders; 194 } 195 196 /** 197 * Attempts to discover classes that are assignable to the type provided. In 198 * the case that an interface is provided this method will collect 199 * implementations. In the case of a non-interface class, subclasses will be 200 * collected. Accumulated classes can be accessed by calling 201 * {@link #getClasses()}. 202 * 203 * @param parent the class of interface to find subclasses or 204 * implementations of 205 * @param packageNames one or more package names to scan (including 206 * subpackages) for classes 207 */ 208 public void findImplementations(Class parent, String... packageNames) { 209 if (packageNames == null) { 210 return; 211 } 212 213 LOG.debug("Searching for implementations of " + parent.getName() + " in packages: " + Arrays.asList(packageNames)); 214 215 Test test = new IsA(parent); 216 for (String pkg : packageNames) { 217 find(test, pkg); 218 } 219 220 LOG.debug("Found: " + getClasses()); 221 } 222 223 /** 224 * Attempts to discover classes that are annotated with to the annotation. 225 * Accumulated classes can be accessed by calling {@link #getClasses()}. 226 * 227 * @param annotation the annotation that should be present on matching 228 * classes 229 * @param packageNames one or more package names to scan (including 230 * subpackages) for classes 231 */ 232 public void findAnnotated(Class<? extends Annotation> annotation, String... packageNames) { 233 if (packageNames == null) { 234 return; 235 } 236 237 Test test = new AnnotatedWith(annotation); 238 for (String pkg : packageNames) { 239 find(test, pkg); 240 } 241 } 242 243 /** 244 * Scans for classes starting at the package provided and descending into 245 * subpackages. Each class is offered up to the Test as it is discovered, 246 * and if the Test returns true the class is retained. Accumulated classes 247 * can be fetched by calling {@link #getClasses()}. 248 * 249 * @param test an instance of {@link Test} that will be used to filter 250 * classes 251 * @param packageName the name of the package from which to start scanning 252 * for classes, e.g. {@code net.sourceforge.stripes} 253 */ 254 public void find(Test test, String packageName) { 255 packageName = packageName.replace('.', '/'); 256 257 Set<ClassLoader> set = getClassLoaders(); 258 for (ClassLoader classLoader : set) { 259 LOG.trace("Searching: " + classLoader); 260 261 find(test, packageName, classLoader); 262 } 263 } 264 265 protected void find(Test test, String packageName, ClassLoader loader) { 266 Enumeration<URL> urls; 267 268 try { 269 urls = loader.getResources(packageName); 270 } catch (IOException ioe) { 271 LOG.warn("Could not read package: " + packageName, ioe); 272 return; 273 } 274 275 while (urls.hasMoreElements()) { 276 try { 277 URL url = urls.nextElement(); 278 279 String urlPath = url.getFile(); 280 urlPath = URLDecoder.decode(urlPath, "UTF-8"); 281 282 // If it's a file in a directory, trim the stupid file: spec 283 if (urlPath.startsWith("file:")) { 284 urlPath = urlPath.substring(5); 285 } 286 287 // Else it's in a JAR, grab the path to the jar 288 if (urlPath.indexOf('!') > 0) { 289 urlPath = urlPath.substring(0, urlPath.indexOf('!')); 290 } 291 292 LOG.debug("Scanning for classes in [" + urlPath + "] matching criteria: " + test); 293 File file = new File(urlPath); 294 if (file.isDirectory()) { 295 loadImplementationsInDirectory(test, packageName, file); 296 } else { 297 loadImplementationsInJar(test, packageName, file); 298 } 299 } catch (IOException ioe) { 300 LOG.warn("could not read entries", ioe); 301 } 302 } 303 } 304 305 /** 306 * Finds matches in a physical directory on a filesystem. Examines all files 307 * within a directory - if the File object is not a directory, and ends with 308 * <i>.class</i> the file is loaded and tested to see if it is acceptable 309 * according to the Test. Operates recursively to find classes within a 310 * folder structure matching the package structure. 311 * 312 * @param test a Test used to filter the classes that are discovered 313 * @param parent the package name up to this directory in the package 314 * hierarchy. E.g. if /classes is in the classpath and we 315 * wish to examine files in /classes/org/apache then the 316 * values of <i>parent</i> would be <i>org/apache</i> 317 * @param location a File object representing a directory 318 */ 319 private void loadImplementationsInDirectory(Test test, String parent, File location) { 320 File[] files = location.listFiles(); 321 StringBuilder builder = null; 322 323 for (File file : files) { 324 builder = new StringBuilder(100); 325 String name = file.getName(); 326 if (name != null) { 327 name = name.trim(); 328 329 builder.append(parent).append("/").append(name); 330 String packageOrClass = parent == null ? name : builder.toString(); 331 332 if (file.isDirectory()) { 333 loadImplementationsInDirectory(test, packageOrClass, file); 334 } else if (name.endsWith(".class")) { 335 addIfMatching(test, packageOrClass); 336 } 337 } 338 } 339 } 340 341 /** 342 * Finds matching classes within a jar files that contains a folder 343 * structure matching the package structure. If the File is not a JarFile or 344 * does not exist a warning will be logged, but no error will be raised. 345 * 346 * @param test a Test used to filter the classes that are discovered 347 * @param parent the parent package under which classes must be in order to 348 * be considered 349 * @param jarfile the jar file to be examined for classes 350 */ 351 private void loadImplementationsInJar(Test test, String parent, File jarfile) { 352 353 try { 354 JarEntry entry; 355 JarInputStream jarStream = new JarInputStream(new FileInputStream(jarfile)); 356 357 while ((entry = jarStream.getNextJarEntry()) != null) { 358 String name = entry.getName(); 359 if (name != null) { 360 name = name.trim(); 361 if (!entry.isDirectory() && name.startsWith(parent) && name.endsWith(".class")) { 362 addIfMatching(test, name); 363 } 364 } 365 } 366 } catch (IOException ioe) { 367 LOG.error("Could not search jar file '" + jarfile + "' for classes matching criteria: " + test 368 + "due to an IOException: " + ioe.getMessage()); 369 } 370 } 371 372 /** 373 * Add the class designated by the fully qualified class name provided to 374 * the set of resolved classes if and only if it is approved by the Test 375 * supplied. 376 * 377 * @param test the test used to determine if the class matches 378 * @param fqn the fully qualified name of a class 379 */ 380 protected void addIfMatching(Test test, String fqn) { 381 try { 382 String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.'); 383 Set<ClassLoader> set = getClassLoaders(); 384 boolean found = false; 385 for (ClassLoader classLoader : set) { 386 LOG.trace("Checking to see if class " + externalName + " matches criteria [" + test + "]"); 387 388 try { 389 Class type = classLoader.loadClass(externalName); 390 if (test.matches(type)) { 391 matches.add((Class<T>)type); 392 } 393 found = true; 394 break; 395 } catch (ClassNotFoundException e) { 396 LOG.debug("Could not find class '" + fqn + "' in class loader: " + classLoader 397 + ". Reason: " + e, e); 398 } 399 } 400 if (!found) { 401 LOG.warn("Could not find class '" + fqn + "' in any class loaders: " + set); 402 } 403 } catch (Throwable t) { 404 LOG.warn("Could not examine class '" + fqn + "' due to a " + t.getClass().getName() 405 + " with message: " + t.getMessage()); 406 } 407 } 408 }