1 /*
2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package com.sun.xml.internal.ws.util;
27
28 import com.sun.istack.internal.NotNull;
29 import com.sun.istack.internal.Nullable;
30 import com.sun.xml.internal.ws.api.Component;
31 import com.sun.xml.internal.ws.api.ComponentEx;
32 import com.sun.xml.internal.ws.api.server.ContainerResolver;
33
34 import java.io.BufferedReader;
35 import java.io.IOException;
36 import java.io.InputStream;
37 import java.io.InputStreamReader;
38 import java.lang.reflect.Array;
39 import java.net.URL;
40 import java.util.ArrayList;
41 import java.util.Arrays;
42 import java.util.Collection;
43 import java.util.Collections;
44 import java.util.Enumeration;
45 import java.util.Iterator;
46 import java.util.List;
47 import java.util.NoSuchElementException;
48 import java.util.Set;
49 import java.util.TreeSet;
50 import java.util.WeakHashMap;
51 import java.util.concurrent.ConcurrentHashMap;
52
53
54 /**
55 * A simple service-provider lookup mechanism. A <i>service</i> is a
56 * well-known set of interfaces and (usually abstract) classes. A <i>service
57 * provider</i> is a specific implementation of a service. The classes in a
58 * provider typically implement the interfaces and subclass the classes defined
59 * in the service itself. Service providers may be installed in an
60 * implementation of the Java platform in the form of extensions, that is, jar
61 * files placed into any of the usual extension directories. Providers may
62 * also be made available by adding them to the applet or application class
63 * path or by some other platform-specific means.
64 * <p/>
65 * <p> In this lookup mechanism a service is represented by an interface or an
66 * abstract class. (A concrete class may be used, but this is not
67 * recommended.) A provider of a given service contains one or more concrete
68 * classes that extend this <i>service class</i> with data and code specific to
69 * the provider. This <i>provider class</i> will typically not be the entire
70 * provider itself but rather a proxy that contains enough information to
71 * decide whether the provider is able to satisfy a particular request together
72 * with code that can create the actual provider on demand. The details of
73 * provider classes tend to be highly service-specific; no single class or
74 * interface could possibly unify them, so no such class has been defined. The
75 * only requirement enforced here is that provider classes must have a
76 * zero-argument constructor so that they may be instantiated during lookup.
77 * <p/>
78 * <p> A service provider identifies itself by placing a provider-configuration
79 * file in the resource directory {@code META-INF/services}. The file's name
80 * should consist of the fully-qualified name of the abstract service class.
81 * The file should contain a list of fully-qualified concrete provider-class
82 * names, one per line. Space and tab characters surrounding each name, as
83 * well as blank lines, are ignored. The comment character is {@code '#'}
84 * ({@code 0x23}); on each line all characters following the first comment
85 * character are ignored. The file must be encoded in UTF-8.
86 * <p/>
87 * <p> If a particular concrete provider class is named in more than one
88 * configuration file, or is named in the same configuration file more than
89 * once, then the duplicates will be ignored. The configuration file naming a
90 * particular provider need not be in the same jar file or other distribution
91 * unit as the provider itself. The provider must be accessible from the same
92 * class loader that was initially queried to locate the configuration file;
93 * note that this is not necessarily the class loader that found the file.
94 * <p/>
95 * <p> <b>Example:</b> Suppose we have a service class named
96 * {@code java.io.spi.CharCodec}. It has two abstract methods:
97 * <p/>
98 * <pre>
99 * public abstract CharEncoder getEncoder(String encodingName);
100 * public abstract CharDecoder getDecoder(String encodingName);
101 * </pre>
102 * <p/>
103 * Each method returns an appropriate object or {@code null} if it cannot
104 * translate the given encoding. Typical {@code CharCodec} providers will
105 * support more than one encoding.
106 * <p/>
107 * <p> If {@code sun.io.StandardCodec} is a provider of the {@code CharCodec}
108 * service then its jar file would contain the file
109 * {@code META-INF/services/java.io.spi.CharCodec}. This file would contain
110 * the single line:
111 * <p/>
112 * <pre>
113 * sun.io.StandardCodec # Standard codecs for the platform
114 * </pre>
115 * <p/>
116 * To locate an codec for a given encoding name, the internal I/O code would
117 * do something like this:
118 * <p/>
119 * <pre>
120 * CharEncoder getEncoder(String encodingName) {
121 * for( CharCodec cc : ServiceFinder.find(CharCodec.class) ) {
122 * CharEncoder ce = cc.getEncoder(encodingName);
123 * if (ce != null)
124 * return ce;
125 * }
126 * return null;
127 * }
128 * </pre>
129 * <p/>
130 * The provider-lookup mechanism always executes in the security context of the
131 * caller. Trusted system code should typically invoke the methods in this
132 * class from within a privileged security context.
133 *
134 * @author Mark Reinhold
135 * @version 1.11, 03/12/19
136 * @since 1.3
137 */
138 public final class ServiceFinder<T> implements Iterable<T> {
139
140 private static final String prefix = "META-INF/services/";
141
142 private static WeakHashMap<ClassLoader, ConcurrentHashMap<String, ServiceName[]>> serviceNameCache
143 = new WeakHashMap<ClassLoader, ConcurrentHashMap<String, ServiceName[]>>();
144
145 private final Class<T> serviceClass;
146 private final @Nullable ClassLoader classLoader;
147 private final @Nullable ComponentEx component;
148
149 private static class ServiceName {
150 final String className;
151 final URL config;
152 public ServiceName(String className, URL config) {
153 this.className = className;
154 this.config = config;
155 }
156 }
157
158 public static <T> ServiceFinder<T> find(@NotNull Class<T> service, @Nullable ClassLoader loader, Component component) {
159 return new ServiceFinder<T>(service, loader, component);
160 }
161
162 public static <T> ServiceFinder<T> find(@NotNull Class<T> service, Component component) {
163 return find(service,Thread.currentThread().getContextClassLoader(),component);
164 }
165
166 /**
167 * Locates and incrementally instantiates the available providers of a
168 * given service using the given class loader.
169 * <p/>
170 * <p> This method transforms the name of the given service class into a
171 * provider-configuration filename as described above and then uses the
172 * {@code getResources} method of the given class loader to find all
173 * available files with that name. These files are then read and parsed to
174 * produce a list of provider-class names. The iterator that is returned
175 * uses the given class loader to lookup and then instantiate each element
176 * of the list.
177 * <p/>
178 * <p> Because it is possible for extensions to be installed into a running
179 * Java virtual machine, this method may return different results each time
180 * it is invoked. <p>
181 *
182 * @param service The service's abstract service class
183 * @param loader The class loader to be used to load provider-configuration files
184 * and instantiate provider classes, or {@code null} if the system
185 * class loader (or, failing that the bootstrap class loader) is to
186 * be used
187 * @throws ServiceConfigurationError If a provider-configuration file violates the specified format
188 * or names a provider class that cannot be found and instantiated
189 * @see #find(Class)
190 */
191 public static <T> ServiceFinder<T> find(@NotNull Class<T> service, @Nullable ClassLoader loader) {
192 return find(service, loader, ContainerResolver.getInstance().getContainer());
193 }
194
195 /**
196 * Locates and incrementally instantiates the available providers of a
197 * given service using the context class loader. This convenience method
198 * is equivalent to
199 * <p/>
200 * <pre>
201 * ClassLoader cl = Thread.currentThread().getContextClassLoader();
202 * return Service.providers(service, cl);
203 * </pre>
204 *
205 * @param service The service's abstract service class
206 *
207 * @throws ServiceConfigurationError If a provider-configuration file violates the specified format
208 * or names a provider class that cannot be found and instantiated
209 * @see #find(Class, ClassLoader)
210 */
211 public static <T> ServiceFinder<T> find(Class<T> service) {
212 return find(service,Thread.currentThread().getContextClassLoader());
213 }
214
215 private ServiceFinder(Class<T> service, ClassLoader loader, Component component) {
216 this.serviceClass = service;
217 this.classLoader = loader;
218 this.component = getComponentEx(component);
219 }
220
221 private static ServiceName[] serviceClassNames(Class serviceClass, ClassLoader classLoader) {
222 ArrayList<ServiceName> l = new ArrayList<ServiceName>();
223 for (Iterator<ServiceName> it = new ServiceNameIterator(serviceClass,classLoader);it.hasNext();) l.add(it.next());
224 return l.toArray(new ServiceName[l.size()]);
225 }
226
227 /**
228 * Returns discovered objects incrementally.
229 *
230 * @return An {@code Iterator} that yields provider objects for the given
231 * service, in some arbitrary order. The iterator will throw a
232 * {@code ServiceConfigurationError} if a provider-configuration
233 * file violates the specified format or if a provider class cannot
234 * be found and instantiated.
235 */
236 @SuppressWarnings("unchecked")
237 public Iterator<T> iterator() {
238 Iterator<T> it = new LazyIterator<T>(serviceClass,classLoader);
239 return component != null ?
240 new CompositeIterator<T>(
241 component.getIterableSPI(serviceClass).iterator(),it) :
242 it;
243 }
244
245 /**
246 * Returns discovered objects all at once.
247 *
248 * @return
249 * can be empty but never null.
250 *
251 * @throws ServiceConfigurationError
252 */
253 public T[] toArray() {
254 List<T> result = new ArrayList<T>();
255 for (T t : this) {
256 result.add(t);
257 }
258 return result.toArray((T[])Array.newInstance(serviceClass,result.size()));
259 }
260
261 private static void fail(Class service, String msg, Throwable cause)
262 throws ServiceConfigurationError {
263 ServiceConfigurationError sce
264 = new ServiceConfigurationError(service.getName() + ": " + msg);
265 sce.initCause(cause);
266 throw sce;
267 }
268
269 private static void fail(Class service, String msg)
270 throws ServiceConfigurationError {
271 throw new ServiceConfigurationError(service.getName() + ": " + msg);
272 }
273
274 private static void fail(Class service, URL u, int line, String msg)
275 throws ServiceConfigurationError {
276 fail(service, u + ":" + line + ": " + msg);
277 }
278
279 /**
280 * Parse a single line from the given configuration file, adding the name
281 * on the line to both the names list and the returned set iff the name is
282 * not already a member of the returned set.
283 */
284 private static int parseLine(Class service, URL u, BufferedReader r, int lc,
285 List<String> names, Set<String> returned)
286 throws IOException, ServiceConfigurationError {
287 String ln = r.readLine();
288 if (ln == null) {
289 return -1;
290 }
291 int ci = ln.indexOf('#');
292 if (ci >= 0) ln = ln.substring(0, ci);
293 ln = ln.trim();
294 int n = ln.length();
295 if (n != 0) {
296 if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0))
297 fail(service, u, lc, "Illegal configuration-file syntax");
298 int cp = ln.codePointAt(0);
299 if (!Character.isJavaIdentifierStart(cp))
300 fail(service, u, lc, "Illegal provider-class name: " + ln);
301 for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) {
302 cp = ln.codePointAt(i);
303 if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))
304 fail(service, u, lc, "Illegal provider-class name: " + ln);
305 }
306 if (!returned.contains(ln)) {
307 names.add(ln);
308 returned.add(ln);
309 }
310 }
311 return lc + 1;
312 }
313
314 /**
315 * Parse the content of the given URL as a provider-configuration file.
316 *
317 * @param service The service class for which providers are being sought;
318 * used to construct error detail strings
319 * @param u The URL naming the configuration file to be parsed
320 * @param returned A Set containing the names of provider classes that have already
321 * been returned. This set will be updated to contain the names
322 * that will be yielded from the returned {@code Iterator}.
323 * @return A (possibly empty) {@code Iterator} that will yield the
324 * provider-class names in the given configuration file that are
325 * not yet members of the returned set
326 * @throws ServiceConfigurationError If an I/O error occurs while reading from the given URL, or
327 * if a configuration-file format error is detected
328 */
329 @SuppressWarnings({"StatementWithEmptyBody"})
330 private static Iterator<String> parse(Class service, URL u, Set<String> returned)
331 throws ServiceConfigurationError {
332 InputStream in = null;
333 BufferedReader r = null;
334 ArrayList<String> names = new ArrayList<String>();
335 try {
336 in = u.openStream();
337 r = new BufferedReader(new InputStreamReader(in, "utf-8"));
338 int lc = 1;
339 while ((lc = parseLine(service, u, r, lc, names, returned)) >= 0) ;
340 } catch (IOException x) {
341 fail(service, ": " + x);
342 } finally {
343 try {
344 if (r != null) r.close();
345 if (in != null) in.close();
346 } catch (IOException y) {
347 fail(service, ": " + y);
348 }
349 }
350 return names.iterator();
351 }
352
353 private static ComponentEx getComponentEx(Component component) {
354 if (component instanceof ComponentEx)
355 return (ComponentEx) component;
356
357 return component != null ? new ComponentExWrapper(component) : null;
358 }
359
360 private static class ComponentExWrapper implements ComponentEx {
361 private final Component component;
362
363 public ComponentExWrapper(Component component) {
364 this.component = component;
365 }
366
367 public <S> S getSPI(Class<S> spiType) {
368 return component.getSPI(spiType);
369 }
370
371 public <S> Iterable<S> getIterableSPI(Class<S> spiType) {
372 S item = getSPI(spiType);
373 if (item != null) {
374 Collection<S> c = Collections.singletonList(item);
375 return c;
376 }
377 return Collections.emptySet();
378 }
379 }
380
381 private static class CompositeIterator<T> implements Iterator<T> {
382 private final Iterator<Iterator<T>> it;
383 private Iterator<T> current = null;
384
385 public CompositeIterator(Iterator<T>... iterators) {
386 it = Arrays.asList(iterators).iterator();
387 }
388
389 public boolean hasNext() {
390 if (current != null && current.hasNext())
391 return true;
392
393 while (it.hasNext()) {
394 current = it.next();
395 if (current.hasNext())
396 return true;
397
398 }
399
400 return false;
401 }
402
403 public T next() {
404 if (!hasNext())
405 throw new NoSuchElementException();
406
407 return current.next();
408 }
409
410 public void remove() {
411 throw new UnsupportedOperationException();
412 }
413 }
414
415 /**
416 * Private inner class implementing fully-lazy provider lookup
417 */
418 private static class ServiceNameIterator implements Iterator<ServiceName> {
419 Class service;
420 @Nullable ClassLoader loader;
421 Enumeration<URL> configs = null;
422 Iterator<String> pending = null;
423 Set<String> returned = new TreeSet<String>();
424 String nextName = null;
425 URL currentConfig = null;
426
427 private ServiceNameIterator(Class service, ClassLoader loader) {
428 this.service = service;
429 this.loader = loader;
430 }
431
432 public boolean hasNext() throws ServiceConfigurationError {
433 if (nextName != null) {
434 return true;
435 }
436 if (configs == null) {
437 try {
438 String fullName = prefix + service.getName();
439 if (loader == null)
440 configs = ClassLoader.getSystemResources(fullName);
441 else
442 configs = loader.getResources(fullName);
443 } catch (IOException x) {
444 fail(service, ": " + x);
445 }
446 }
447 while ((pending == null) || !pending.hasNext()) {
448 if (!configs.hasMoreElements()) {
449 return false;
450 }
451 currentConfig = configs.nextElement();
452 pending = parse(service, currentConfig, returned);
453 }
454 nextName = pending.next();
455 return true;
456 }
457
458 public ServiceName next() throws ServiceConfigurationError {
459 if (!hasNext()) {
460 throw new NoSuchElementException();
461 }
462 String cn = nextName;
463 nextName = null;
464 return new ServiceName(cn, currentConfig);
465 }
466
467 public void remove() {
468 throw new UnsupportedOperationException();
469 }
470 }
471
472 private static class LazyIterator<T> implements Iterator<T> {
473 Class<T> service;
474 @Nullable ClassLoader loader;
475 ServiceName[] names;
476 int index;
477
478 private LazyIterator(Class<T> service, ClassLoader loader) {
479 this.service = service;
480 this.loader = loader;
481 this.names = null;
482 index = 0;
483 }
484
485 @Override
486 public boolean hasNext() {
487 if (names == null) {
488 ConcurrentHashMap<String, ServiceName[]> nameMap = null;
489 synchronized(serviceNameCache){ nameMap = serviceNameCache.get(loader); }
490 names = (nameMap != null)? nameMap.get(service.getName()) : null;
491 if (names == null) {
492 names = serviceClassNames(service, loader);
493 if (nameMap == null) nameMap = new ConcurrentHashMap<String, ServiceName[]>();
494 nameMap.put(service.getName(), names);
495 synchronized(serviceNameCache){ serviceNameCache.put(loader,nameMap); }
496 }
497 }
498 return (index < names.length);
499 }
500
501 @Override
502 public T next() {
503 if (!hasNext()) throw new NoSuchElementException();
504 ServiceName sn = names[index++];
505 String cn = sn.className;
506 URL currentConfig = sn.config;
507 try {
508 return service.cast(Class.forName(cn, true, loader).newInstance());
509 } catch (ClassNotFoundException x) {
510 fail(service, "Provider " + cn + " is specified in "+currentConfig+" but not found");
511 } catch (Exception x) {
512 fail(service, "Provider " + cn + " is specified in "+currentConfig+"but could not be instantiated: " + x, x);
513 }
514 return null; /* This cannot happen */
515 }
516
517 @Override
518 public void remove() {
519 throw new UnsupportedOperationException();
520 }
521
522 }
523 }