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 classLoaders.add(Thread.currentThread().getContextClassLoader());
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 jarfile the jar file to be examined for classes
452 * @param stream the inputstream of the jar file to be examined for classes
453 * @param urlPath the url of the jar file to be examined for classes
454 */
455 private void loadImplementationsInJar(Test test, String parent, InputStream stream, String urlPath) {
456 JarInputStream jarStream = null;
457 try {
458 jarStream = new JarInputStream(stream);
459
460 JarEntry entry;
461 while ((entry = jarStream.getNextJarEntry()) != null) {
462 String name = entry.getName();
463 if (name != null) {
464 name = name.trim();
465 if (!entry.isDirectory() && name.startsWith(parent) && name.endsWith(".class")) {
466 addIfMatching(test, name);
467 }
468 }
469 }
470 } catch (IOException ioe) {
471 LOG.error("Could not search jar file '" + urlPath + "' for classes matching criteria: " + test
472 + " due to an IOException: " + ioe.getMessage(), ioe);
473 } finally {
474 ObjectHelper.close(jarStream, urlPath, LOG);
475 }
476 }
477
478 /**
479 * Add the class designated by the fully qualified class name provided to
480 * the set of resolved classes if and only if it is approved by the Test
481 * supplied.
482 *
483 * @param test the test used to determine if the class matches
484 * @param fqn the fully qualified name of a class
485 */
486 protected void addIfMatching(Test test, String fqn) {
487 try {
488 String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.');
489 Set<ClassLoader> set = getClassLoaders();
490 boolean found = false;
491 for (ClassLoader classLoader : set) {
492 if (LOG.isTraceEnabled()) {
493 LOG.trace("Testing for class " + externalName + " matches criteria [" + test + "]");
494 }
495 try {
496 Class type = classLoader.loadClass(externalName);
497 if (test.matches(type)) {
498 if (LOG.isTraceEnabled()) {
499 LOG.trace("Found class: " + type + " in classloader: " + classLoader);
500 }
501 matches.add((Class<T>)type);
502 }
503 found = true;
504 break;
505 } catch (ClassNotFoundException e) {
506 LOG.debug("Could not find class '" + fqn + "' in classloader: " + classLoader
507 + ". Reason: " + e, e);
508 } catch (NoClassDefFoundError e) {
509 LOG.debug("Could not find the class defintion '" + fqn + "' in classloader: " + classLoader
510 + ". Reason: " + e, e);
511 }
512 }
513 if (!found) {
514 LOG.warn("Could not find class '" + fqn + "' in any classloaders: " + set);
515 }
516 } catch (Throwable t) {
517 LOG.warn("Could not examine class '" + fqn + "' due to a " + t.getClass().getName()
518 + " with message: " + t.getMessage(), t);
519 }
520 }
521
522 }