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 }