1 /*
2 * Copyright (c) 2013, 2020, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2019, Azul Systems, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation. Oracle designates this
9 * particular file as subject to the "Classpath" exception as provided
10 * by Oracle in the LICENSE file that accompanied this code.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
23 * or visit www.oracle.com if you need additional information or have any
24 * questions.
25 */
26
27 package java.lang;
28
29 import java.io.InputStream;
30 import java.io.IOException;
31 import java.io.UncheckedIOException;
32 import java.io.File;
33 import java.lang.reflect.Constructor;
34 import java.lang.reflect.InvocationTargetException;
35 import java.net.URL;
36 import java.security.AccessController;
37 import java.security.AccessControlContext;
38 import java.security.CodeSource;
39 import java.security.PrivilegedAction;
40 import java.security.ProtectionDomain;
41 import java.security.cert.Certificate;
42 import java.util.ArrayDeque;
43 import java.util.ArrayList;
44 import java.util.Arrays;
45 import java.util.Collections;
46 import java.util.Deque;
47 import java.util.Enumeration;
48 import java.util.HashMap;
49 import java.util.HashSet;
50 import java.util.Map;
51 import java.util.NoSuchElementException;
52 import java.util.Objects;
53 import java.util.Set;
54 import java.util.Spliterator;
55 import java.util.Spliterators;
56 import java.util.WeakHashMap;
57 import java.util.concurrent.ConcurrentHashMap;
58 import java.util.function.Supplier;
59 import java.util.stream.Stream;
60 import java.util.stream.StreamSupport;
61
62 import jdk.internal.loader.BuiltinClassLoader;
63 import jdk.internal.perf.PerfCounter;
64 import jdk.internal.loader.BootLoader;
65 import jdk.internal.loader.ClassLoaders;
66 import jdk.internal.misc.Unsafe;
67 import jdk.internal.misc.VM;
68 import jdk.internal.ref.CleanerFactory;
69 import jdk.internal.reflect.CallerSensitive;
70 import jdk.internal.reflect.Reflection;
71 import jdk.internal.util.StaticProperty;
72 import sun.reflect.misc.ReflectUtil;
73 import sun.security.util.SecurityConstants;
74
75 /**
76 * A class loader is an object that is responsible for loading classes. The
77 * class {@code ClassLoader} is an abstract class. Given the <a
78 * href="#binary-name">binary name</a> of a class, a class loader should attempt to
79 * locate or generate data that constitutes a definition for the class. A
80 * typical strategy is to transform the name into a file name and then read a
81 * "class file" of that name from a file system.
82 *
83 * <p> Every {@link java.lang.Class Class} object contains a {@link
84 * Class#getClassLoader() reference} to the {@code ClassLoader} that defined
85 * it.
86 *
87 * <p> {@code Class} objects for array classes are not created by class
88 * loaders, but are created automatically as required by the Java runtime.
89 * The class loader for an array class, as returned by {@link
90 * Class#getClassLoader()} is the same as the class loader for its element
91 * type; if the element type is a primitive type, then the array class has no
92 * class loader.
93 *
94 * <p> Applications implement subclasses of {@code ClassLoader} in order to
95 * extend the manner in which the Java virtual machine dynamically loads
96 * classes.
97 *
98 * <p> Class loaders may typically be used by security managers to indicate
99 * security domains.
100 *
101 * <p> In addition to loading classes, a class loader is also responsible for
102 * locating resources. A resource is some data (a "{@code .class}" file,
103 * configuration data, or an image for example) that is identified with an
104 * abstract '/'-separated path name. Resources are typically packaged with an
105 * application or library so that they can be located by code in the
106 * application or library. In some cases, the resources are included so that
107 * they can be located by other libraries.
108 *
109 * <p> The {@code ClassLoader} class uses a delegation model to search for
110 * classes and resources. Each instance of {@code ClassLoader} has an
111 * associated parent class loader. When requested to find a class or
112 * resource, a {@code ClassLoader} instance will usually delegate the search
113 * for the class or resource to its parent class loader before attempting to
114 * find the class or resource itself.
115 *
116 * <p> Class loaders that support concurrent loading of classes are known as
117 * <em>{@linkplain #isRegisteredAsParallelCapable() parallel capable}</em> class
118 * loaders and are required to register themselves at their class initialization
119 * time by invoking the {@link
120 * #registerAsParallelCapable ClassLoader.registerAsParallelCapable}
121 * method. Note that the {@code ClassLoader} class is registered as parallel
122 * capable by default. However, its subclasses still need to register themselves
123 * if they are parallel capable.
124 * In environments in which the delegation model is not strictly
125 * hierarchical, class loaders need to be parallel capable, otherwise class
126 * loading can lead to deadlocks because the loader lock is held for the
127 * duration of the class loading process (see {@link #loadClass
128 * loadClass} methods).
129 *
130 * <h2> <a id="builtinLoaders">Run-time Built-in Class Loaders</a></h2>
131 *
132 * The Java run-time has the following built-in class loaders:
133 *
134 * <ul>
135 * <li><p>Bootstrap class loader.
136 * It is the virtual machine's built-in class loader, typically represented
137 * as {@code null}, and does not have a parent.</li>
138 * <li><p>{@linkplain #getPlatformClassLoader() Platform class loader}.
139 * All <em>platform classes</em> are visible to the platform class loader
140 * that can be used as the parent of a {@code ClassLoader} instance.
141 * Platform classes include Java SE platform APIs, their implementation
142 * classes and JDK-specific run-time classes that are defined by the
143 * platform class loader or its ancestors.
144 * <p> To allow for upgrading/overriding of modules defined to the platform
145 * class loader, and where upgraded modules read modules defined to class
146 * loaders other than the platform class loader and its ancestors, then
147 * the platform class loader may have to delegate to other class loaders,
148 * the application class loader for example.
149 * In other words, classes in named modules defined to class loaders
150 * other than the platform class loader and its ancestors may be visible
151 * to the platform class loader. </li>
152 * <li><p>{@linkplain #getSystemClassLoader() System class loader}.
153 * It is also known as <em>application class loader</em> and is distinct
154 * from the platform class loader.
155 * The system class loader is typically used to define classes on the
156 * application class path, module path, and JDK-specific tools.
157 * The platform class loader is a parent or an ancestor of the system class
158 * loader that all platform classes are visible to it.</li>
159 * </ul>
160 *
161 * <p> Normally, the Java virtual machine loads classes from the local file
162 * system in a platform-dependent manner.
163 * However, some classes may not originate from a file; they may originate
164 * from other sources, such as the network, or they could be constructed by an
165 * application. The method {@link #defineClass(String, byte[], int, int)
166 * defineClass} converts an array of bytes into an instance of class
167 * {@code Class}. Instances of this newly defined class can be created using
168 * {@link Class#newInstance Class.newInstance}.
169 *
170 * <p> The methods and constructors of objects created by a class loader may
171 * reference other classes. To determine the class(es) referred to, the Java
172 * virtual machine invokes the {@link #loadClass loadClass} method of
173 * the class loader that originally created the class.
174 *
175 * <p> For example, an application could create a network class loader to
176 * download class files from a server. Sample code might look like:
177 *
178 * <blockquote><pre>
179 * ClassLoader loader = new NetworkClassLoader(host, port);
180 * Object main = loader.loadClass("Main", true).newInstance();
181 * . . .
182 * </pre></blockquote>
183 *
184 * <p> The network class loader subclass must define the methods {@link
185 * #findClass findClass} and {@code loadClassData} to load a class
186 * from the network. Once it has downloaded the bytes that make up the class,
187 * it should use the method {@link #defineClass defineClass} to
188 * create a class instance. A sample implementation is:
189 *
190 * <blockquote><pre>
191 * class NetworkClassLoader extends ClassLoader {
192 * String host;
193 * int port;
194 *
195 * public Class findClass(String name) {
196 * byte[] b = loadClassData(name);
197 * return defineClass(name, b, 0, b.length);
198 * }
199 *
200 * private byte[] loadClassData(String name) {
201 * // load the class data from the connection
202 * . . .
203 * }
204 * }
205 * </pre></blockquote>
206 *
207 * <h3> <a id="binary-name">Binary names</a> </h3>
208 *
209 * <p> Any class name provided as a {@code String} parameter to methods in
210 * {@code ClassLoader} must be a binary name as defined by
211 * <cite>The Java™ Language Specification</cite>.
212 *
213 * <p> Examples of valid class names include:
214 * <blockquote><pre>
215 * "java.lang.String"
216 * "javax.swing.JSpinner$DefaultEditor"
217 * "java.security.KeyStore$Builder$FileBuilder$1"
218 * "java.net.URLClassLoader$3$1"
219 * </pre></blockquote>
220 *
221 * <p> Any package name provided as a {@code String} parameter to methods in
222 * {@code ClassLoader} must be either the empty string (denoting an unnamed package)
223 * or a fully qualified name as defined by
224 * <cite>The Java™ Language Specification</cite>.
225 *
226 * @jls 6.7 Fully Qualified Names
227 * @jls 13.1 The Form of a Binary
228 * @see #resolveClass(Class)
229 * @since 1.0
230 * @revised 9
231 * @spec JPMS
232 */
233 public abstract class ClassLoader {
234
235 private static native void registerNatives();
236 static {
237 registerNatives();
238 }
239
240 // The parent class loader for delegation
241 // Note: VM hardcoded the offset of this field, thus all new fields
242 // must be added *after* it.
243 private final ClassLoader parent;
244
245 // class loader name
246 private final String name;
247
248 // the unnamed module for this ClassLoader
249 private final Module unnamedModule;
250
251 // a string for exception message printing
252 private final String nameAndId;
253
254 /**
255 * Encapsulates the set of parallel capable loader types.
256 */
257 private static class ParallelLoaders {
258 private ParallelLoaders() {}
259
260 // the set of parallel capable loader types
261 private static final Set<Class<? extends ClassLoader>> loaderTypes =
262 Collections.newSetFromMap(new WeakHashMap<>());
263 static {
264 synchronized (loaderTypes) { loaderTypes.add(ClassLoader.class); }
265 }
266
267 /**
268 * Registers the given class loader type as parallel capable.
269 * Returns {@code true} is successfully registered; {@code false} if
270 * loader's super class is not registered.
271 */
272 static boolean register(Class<? extends ClassLoader> c) {
273 synchronized (loaderTypes) {
274 if (loaderTypes.contains(c.getSuperclass())) {
275 // register the class loader as parallel capable
276 // if and only if all of its super classes are.
277 // Note: given current classloading sequence, if
278 // the immediate super class is parallel capable,
279 // all the super classes higher up must be too.
280 loaderTypes.add(c);
281 return true;
282 } else {
283 return false;
284 }
285 }
286 }
287
288 /**
289 * Returns {@code true} if the given class loader type is
290 * registered as parallel capable.
291 */
292 static boolean isRegistered(Class<? extends ClassLoader> c) {
293 synchronized (loaderTypes) {
294 return loaderTypes.contains(c);
295 }
296 }
297 }
298
299 // Maps class name to the corresponding lock object when the current
300 // class loader is parallel capable.
301 // Note: VM also uses this field to decide if the current class loader
302 // is parallel capable and the appropriate lock object for class loading.
303 private final ConcurrentHashMap<String, Object> parallelLockMap;
304
305 // Maps packages to certs
306 private final ConcurrentHashMap<String, Certificate[]> package2certs;
307
308 // Shared among all packages with unsigned classes
309 private static final Certificate[] nocerts = new Certificate[0];
310
311 // The classes loaded by this class loader. The only purpose of this table
312 // is to keep the classes from being GC'ed until the loader is GC'ed.
313 private final ArrayList<Class<?>> classes = new ArrayList<>();
314
315 // The "default" domain. Set as the default ProtectionDomain on newly
316 // created classes.
317 private final ProtectionDomain defaultDomain =
318 new ProtectionDomain(new CodeSource(null, (Certificate[]) null),
319 null, this, null);
320
321 // Invoked by the VM to record every loaded class with this loader.
322 void addClass(Class<?> c) {
323 synchronized (classes) {
324 classes.add(c);
325 }
326 }
327
328 // The packages defined in this class loader. Each package name is
329 // mapped to its corresponding NamedPackage object.
330 //
331 // The value is a Package object if ClassLoader::definePackage,
332 // Class::getPackage, ClassLoader::getDefinePackage(s) or
333 // Package::getPackage(s) method is called to define it.
334 // Otherwise, the value is a NamedPackage object.
335 private final ConcurrentHashMap<String, NamedPackage> packages
336 = new ConcurrentHashMap<>();
337
338 /*
339 * Returns a named package for the given module.
340 */
341 private NamedPackage getNamedPackage(String pn, Module m) {
342 NamedPackage p = packages.get(pn);
343 if (p == null) {
344 p = new NamedPackage(pn, m);
345
346 NamedPackage value = packages.putIfAbsent(pn, p);
347 if (value != null) {
348 // Package object already be defined for the named package
349 p = value;
350 // if definePackage is called by this class loader to define
351 // a package in a named module, this will return Package
352 // object of the same name. Package object may contain
353 // unexpected information but it does not impact the runtime.
354 // this assertion may be helpful for troubleshooting
355 assert value.module() == m;
356 }
357 }
358 return p;
359 }
360
361 private static Void checkCreateClassLoader() {
362 return checkCreateClassLoader(null);
363 }
364
365 private static Void checkCreateClassLoader(String name) {
366 if (name != null && name.isEmpty()) {
367 throw new IllegalArgumentException("name must be non-empty or null");
368 }
369
370 SecurityManager security = System.getSecurityManager();
371 if (security != null) {
372 security.checkCreateClassLoader();
373 }
374 return null;
375 }
376
377 private ClassLoader(Void unused, String name, ClassLoader parent) {
378 this.name = name;
379 this.parent = parent;
380 this.unnamedModule = new Module(this);
381 if (ParallelLoaders.isRegistered(this.getClass())) {
382 parallelLockMap = new ConcurrentHashMap<>();
383 assertionLock = new Object();
384 } else {
385 // no finer-grained lock; lock on the classloader instance
386 parallelLockMap = null;
387 assertionLock = this;
388 }
389 this.package2certs = new ConcurrentHashMap<>();
390 this.nameAndId = nameAndId(this);
391 }
392
393 /**
394 * If the defining loader has a name explicitly set then
395 * '<loader-name>' @<id>
396 * If the defining loader has no name then
397 * <qualified-class-name> @<id>
398 * If it's built-in loader then omit `@<id>` as there is only one instance.
399 */
400 private static String nameAndId(ClassLoader ld) {
401 String nid = ld.getName() != null ? "\'" + ld.getName() + "\'"
402 : ld.getClass().getName();
403 if (!(ld instanceof BuiltinClassLoader)) {
404 String id = Integer.toHexString(System.identityHashCode(ld));
405 nid = nid + " @" + id;
406 }
407 return nid;
408 }
409
410 /**
411 * Creates a new class loader of the specified name and using the
412 * specified parent class loader for delegation.
413 *
414 * @apiNote If the parent is specified as {@code null} (for the
415 * bootstrap class loader) then there is no guarantee that all platform
416 * classes are visible.
417 *
418 * @param name class loader name; or {@code null} if not named
419 * @param parent the parent class loader
420 *
421 * @throws IllegalArgumentException if the given name is empty.
422 *
423 * @throws SecurityException
424 * If a security manager exists and its
425 * {@link SecurityManager#checkCreateClassLoader()}
426 * method doesn't allow creation of a new class loader.
427 *
428 * @since 9
429 * @spec JPMS
430 */
431 protected ClassLoader(String name, ClassLoader parent) {
432 this(checkCreateClassLoader(name), name, parent);
433 }
434
435 /**
436 * Creates a new class loader using the specified parent class loader for
437 * delegation.
438 *
439 * <p> If there is a security manager, its {@link
440 * SecurityManager#checkCreateClassLoader() checkCreateClassLoader} method
441 * is invoked. This may result in a security exception. </p>
442 *
443 * @apiNote If the parent is specified as {@code null} (for the
444 * bootstrap class loader) then there is no guarantee that all platform
445 * classes are visible.
446 *
447 * @param parent
448 * The parent class loader
449 *
450 * @throws SecurityException
451 * If a security manager exists and its
452 * {@code checkCreateClassLoader} method doesn't allow creation
453 * of a new class loader.
454 *
455 * @since 1.2
456 */
457 protected ClassLoader(ClassLoader parent) {
458 this(checkCreateClassLoader(), null, parent);
459 }
460
461 /**
462 * Creates a new class loader using the {@code ClassLoader} returned by
463 * the method {@link #getSystemClassLoader()
464 * getSystemClassLoader()} as the parent class loader.
465 *
466 * <p> If there is a security manager, its {@link
467 * SecurityManager#checkCreateClassLoader()
468 * checkCreateClassLoader} method is invoked. This may result in
469 * a security exception. </p>
470 *
471 * @throws SecurityException
472 * If a security manager exists and its
473 * {@code checkCreateClassLoader} method doesn't allow creation
474 * of a new class loader.
475 */
476 protected ClassLoader() {
477 this(checkCreateClassLoader(), null, getSystemClassLoader());
478 }
479
480 /**
481 * Returns the name of this class loader or {@code null} if
482 * this class loader is not named.
483 *
484 * @apiNote This method is non-final for compatibility. If this
485 * method is overridden, this method must return the same name
486 * as specified when this class loader was instantiated.
487 *
488 * @return name of this class loader; or {@code null} if
489 * this class loader is not named.
490 *
491 * @since 9
492 * @spec JPMS
493 */
494 public String getName() {
495 return name;
496 }
497
498 // package-private used by StackTraceElement to avoid
499 // calling the overrideable getName method
500 final String name() {
501 return name;
502 }
503
504 // -- Class --
505
506 /**
507 * Loads the class with the specified <a href="#binary-name">binary name</a>.
508 * This method searches for classes in the same manner as the {@link
509 * #loadClass(String, boolean)} method. It is invoked by the Java virtual
510 * machine to resolve class references. Invoking this method is equivalent
511 * to invoking {@link #loadClass(String, boolean) loadClass(name,
512 * false)}.
513 *
514 * @param name
515 * The <a href="#binary-name">binary name</a> of the class
516 *
517 * @return The resulting {@code Class} object
518 *
519 * @throws ClassNotFoundException
520 * If the class was not found
521 */
522 public Class<?> loadClass(String name) throws ClassNotFoundException {
523 return loadClass(name, false);
524 }
525
526 /**
527 * Loads the class with the specified <a href="#binary-name">binary name</a>. The
528 * default implementation of this method searches for classes in the
529 * following order:
530 *
531 * <ol>
532 *
533 * <li><p> Invoke {@link #findLoadedClass(String)} to check if the class
534 * has already been loaded. </p></li>
535 *
536 * <li><p> Invoke the {@link #loadClass(String) loadClass} method
537 * on the parent class loader. If the parent is {@code null} the class
538 * loader built into the virtual machine is used, instead. </p></li>
539 *
540 * <li><p> Invoke the {@link #findClass(String)} method to find the
541 * class. </p></li>
542 *
543 * </ol>
544 *
545 * <p> If the class was found using the above steps, and the
546 * {@code resolve} flag is true, this method will then invoke the {@link
547 * #resolveClass(Class)} method on the resulting {@code Class} object.
548 *
549 * <p> Subclasses of {@code ClassLoader} are encouraged to override {@link
550 * #findClass(String)}, rather than this method. </p>
551 *
552 * <p> Unless overridden, this method synchronizes on the result of
553 * {@link #getClassLoadingLock getClassLoadingLock} method
554 * during the entire class loading process.
555 *
556 * @param name
557 * The <a href="#binary-name">binary name</a> of the class
558 *
559 * @param resolve
560 * If {@code true} then resolve the class
561 *
562 * @return The resulting {@code Class} object
563 *
564 * @throws ClassNotFoundException
565 * If the class could not be found
566 */
567 protected Class<?> loadClass(String name, boolean resolve)
568 throws ClassNotFoundException
569 {
570 synchronized (getClassLoadingLock(name)) {
571 // First, check if the class has already been loaded
572 Class<?> c = findLoadedClass(name);
573 if (c == null) {
574 long t0 = System.nanoTime();
575 try {
576 if (parent != null) {
577 c = parent.loadClass(name, false);
578 } else {
579 c = findBootstrapClassOrNull(name);
580 }
581 } catch (ClassNotFoundException e) {
582 // ClassNotFoundException thrown if class not found
583 // from the non-null parent class loader
584 }
585
586 if (c == null) {
587 // If still not found, then invoke findClass in order
588 // to find the class.
589 long t1 = System.nanoTime();
590 c = findClass(name);
591
592 // this is the defining class loader; record the stats
593 PerfCounter.getParentDelegationTime().addTime(t1 - t0);
594 PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
595 PerfCounter.getFindClasses().increment();
596 }
597 }
598 if (resolve) {
599 resolveClass(c);
600 }
601 return c;
602 }
603 }
604
605 /**
606 * Loads the class with the specified <a href="#binary-name">binary name</a>
607 * in a module defined to this class loader. This method returns {@code null}
608 * if the class could not be found.
609 *
610 * @apiNote This method does not delegate to the parent class loader.
611 *
612 * @implSpec The default implementation of this method searches for classes
613 * in the following order:
614 *
615 * <ol>
616 * <li>Invoke {@link #findLoadedClass(String)} to check if the class
617 * has already been loaded.</li>
618 * <li>Invoke the {@link #findClass(String, String)} method to find the
619 * class in the given module.</li>
620 * </ol>
621 *
622 * @param module
623 * The module
624 * @param name
625 * The <a href="#binary-name">binary name</a> of the class
626 *
627 * @return The resulting {@code Class} object in a module defined by
628 * this class loader, or {@code null} if the class could not be found.
629 */
630 final Class<?> loadClass(Module module, String name) {
631 synchronized (getClassLoadingLock(name)) {
632 // First, check if the class has already been loaded
633 Class<?> c = findLoadedClass(name);
634 if (c == null) {
635 c = findClass(module.getName(), name);
636 }
637 if (c != null && c.getModule() == module) {
638 return c;
639 } else {
640 return null;
641 }
642 }
643 }
644
645 /**
646 * Returns the lock object for class loading operations.
647 * For backward compatibility, the default implementation of this method
648 * behaves as follows. If this ClassLoader object is registered as
649 * parallel capable, the method returns a dedicated object associated
650 * with the specified class name. Otherwise, the method returns this
651 * ClassLoader object.
652 *
653 * @param className
654 * The name of the to-be-loaded class
655 *
656 * @return the lock for class loading operations
657 *
658 * @throws NullPointerException
659 * If registered as parallel capable and {@code className} is null
660 *
661 * @see #loadClass(String, boolean)
662 *
663 * @since 1.7
664 */
665 protected Object getClassLoadingLock(String className) {
666 Object lock = this;
667 if (parallelLockMap != null) {
668 Object newLock = new Object();
669 lock = parallelLockMap.putIfAbsent(className, newLock);
670 if (lock == null) {
671 lock = newLock;
672 }
673 }
674 return lock;
675 }
676
677 // Invoked by the VM after loading class with this loader.
678 private void checkPackageAccess(Class<?> cls, ProtectionDomain pd) {
679 final SecurityManager sm = System.getSecurityManager();
680 if (sm != null) {
681 if (ReflectUtil.isNonPublicProxyClass(cls)) {
682 for (Class<?> intf: cls.getInterfaces()) {
683 checkPackageAccess(intf, pd);
684 }
685 return;
686 }
687
688 final String packageName = cls.getPackageName();
689 if (!packageName.isEmpty()) {
690 AccessController.doPrivileged(new PrivilegedAction<>() {
691 public Void run() {
692 sm.checkPackageAccess(packageName);
693 return null;
694 }
695 }, new AccessControlContext(new ProtectionDomain[] {pd}));
696 }
697 }
698 }
699
700 /**
701 * Finds the class with the specified <a href="#binary-name">binary name</a>.
702 * This method should be overridden by class loader implementations that
703 * follow the delegation model for loading classes, and will be invoked by
704 * the {@link #loadClass loadClass} method after checking the
705 * parent class loader for the requested class.
706 *
707 * @implSpec The default implementation throws {@code ClassNotFoundException}.
708 *
709 * @param name
710 * The <a href="#binary-name">binary name</a> of the class
711 *
712 * @return The resulting {@code Class} object
713 *
714 * @throws ClassNotFoundException
715 * If the class could not be found
716 *
717 * @since 1.2
718 */
719 protected Class<?> findClass(String name) throws ClassNotFoundException {
720 throw new ClassNotFoundException(name);
721 }
722
723 /**
724 * Finds the class with the given <a href="#binary-name">binary name</a>
725 * in a module defined to this class loader.
726 * Class loader implementations that support loading from modules
727 * should override this method.
728 *
729 * @apiNote This method returns {@code null} rather than throwing
730 * {@code ClassNotFoundException} if the class could not be found.
731 *
732 * @implSpec The default implementation attempts to find the class by
733 * invoking {@link #findClass(String)} when the {@code moduleName} is
734 * {@code null}. It otherwise returns {@code null}.
735 *
736 * @param moduleName
737 * The module name; or {@code null} to find the class in the
738 * {@linkplain #getUnnamedModule() unnamed module} for this
739 * class loader
740
741 * @param name
742 * The <a href="#binary-name">binary name</a> of the class
743 *
744 * @return The resulting {@code Class} object, or {@code null}
745 * if the class could not be found.
746 *
747 * @since 9
748 * @spec JPMS
749 */
750 protected Class<?> findClass(String moduleName, String name) {
751 if (moduleName == null) {
752 try {
753 return findClass(name);
754 } catch (ClassNotFoundException ignore) { }
755 }
756 return null;
757 }
758
759
760 /**
761 * Converts an array of bytes into an instance of class {@code Class}.
762 * Before the {@code Class} can be used it must be resolved. This method
763 * is deprecated in favor of the version that takes a <a
764 * href="#binary-name">binary name</a> as its first argument, and is more secure.
765 *
766 * @param b
767 * The bytes that make up the class data. The bytes in positions
768 * {@code off} through {@code off+len-1} should have the format
769 * of a valid class file as defined by
770 * <cite>The Java™ Virtual Machine Specification</cite>.
771 *
772 * @param off
773 * The start offset in {@code b} of the class data
774 *
775 * @param len
776 * The length of the class data
777 *
778 * @return The {@code Class} object that was created from the specified
779 * class data
780 *
781 * @throws ClassFormatError
782 * If the data did not contain a valid class
783 *
784 * @throws IndexOutOfBoundsException
785 * If either {@code off} or {@code len} is negative, or if
786 * {@code off+len} is greater than {@code b.length}.
787 *
788 * @throws SecurityException
789 * If an attempt is made to add this class to a package that
790 * contains classes that were signed by a different set of
791 * certificates than this class, or if an attempt is made
792 * to define a class in a package with a fully-qualified name
793 * that starts with "{@code java.}".
794 *
795 * @see #loadClass(String, boolean)
796 * @see #resolveClass(Class)
797 *
798 * @deprecated Replaced by {@link #defineClass(String, byte[], int, int)
799 * defineClass(String, byte[], int, int)}
800 */
801 @Deprecated(since="1.1")
802 protected final Class<?> defineClass(byte[] b, int off, int len)
803 throws ClassFormatError
804 {
805 return defineClass(null, b, off, len, null);
806 }
807
808 /**
809 * Converts an array of bytes into an instance of class {@code Class}.
810 * Before the {@code Class} can be used it must be resolved.
811 *
812 * <p> This method assigns a default {@link java.security.ProtectionDomain
813 * ProtectionDomain} to the newly defined class. The
814 * {@code ProtectionDomain} is effectively granted the same set of
815 * permissions returned when {@link
816 * java.security.Policy#getPermissions(java.security.CodeSource)
817 * Policy.getPolicy().getPermissions(new CodeSource(null, null))}
818 * is invoked. The default protection domain is created on the first invocation
819 * of {@link #defineClass(String, byte[], int, int) defineClass},
820 * and re-used on subsequent invocations.
821 *
822 * <p> To assign a specific {@code ProtectionDomain} to the class, use
823 * the {@link #defineClass(String, byte[], int, int,
824 * java.security.ProtectionDomain) defineClass} method that takes a
825 * {@code ProtectionDomain} as one of its arguments. </p>
826 *
827 * <p>
828 * This method defines a package in this class loader corresponding to the
829 * package of the {@code Class} (if such a package has not already been defined
830 * in this class loader). The name of the defined package is derived from
831 * the <a href="#binary-name">binary name</a> of the class specified by
832 * the byte array {@code b}.
833 * Other properties of the defined package are as specified by {@link Package}.
834 *
835 * @param name
836 * The expected <a href="#binary-name">binary name</a> of the class, or
837 * {@code null} if not known
838 *
839 * @param b
840 * The bytes that make up the class data. The bytes in positions
841 * {@code off} through {@code off+len-1} should have the format
842 * of a valid class file as defined by
843 * <cite>The Java™ Virtual Machine Specification</cite>.
844 *
845 * @param off
846 * The start offset in {@code b} of the class data
847 *
848 * @param len
849 * The length of the class data
850 *
851 * @return The {@code Class} object that was created from the specified
852 * class data.
853 *
854 * @throws ClassFormatError
855 * If the data did not contain a valid class
856 *
857 * @throws IndexOutOfBoundsException
858 * If either {@code off} or {@code len} is negative, or if
859 * {@code off+len} is greater than {@code b.length}.
860 *
861 * @throws SecurityException
862 * If an attempt is made to add this class to a package that
863 * contains classes that were signed by a different set of
864 * certificates than this class (which is unsigned), or if
865 * {@code name} begins with "{@code java.}".
866 *
867 * @see #loadClass(String, boolean)
868 * @see #resolveClass(Class)
869 * @see java.security.CodeSource
870 * @see java.security.SecureClassLoader
871 *
872 * @since 1.1
873 * @revised 9
874 * @spec JPMS
875 */
876 protected final Class<?> defineClass(String name, byte[] b, int off, int len)
877 throws ClassFormatError
878 {
879 return defineClass(name, b, off, len, null);
880 }
881
882 /* Determine protection domain, and check that:
883 - not define java.* class,
884 - signer of this class matches signers for the rest of the classes in
885 package.
886 */
887 private ProtectionDomain preDefineClass(String name,
888 ProtectionDomain pd)
889 {
890 if (!checkName(name))
891 throw new NoClassDefFoundError("IllegalName: " + name);
892
893 // Note: Checking logic in java.lang.invoke.MemberName.checkForTypeAlias
894 // relies on the fact that spoofing is impossible if a class has a name
895 // of the form "java.*"
896 if ((name != null) && name.startsWith("java.")
897 && this != getBuiltinPlatformClassLoader()) {
898 throw new SecurityException
899 ("Prohibited package name: " +
900 name.substring(0, name.lastIndexOf('.')));
901 }
902 if (pd == null) {
903 pd = defaultDomain;
904 }
905
906 if (name != null) {
907 checkCerts(name, pd.getCodeSource());
908 }
909
910 return pd;
911 }
912
913 private String defineClassSourceLocation(ProtectionDomain pd) {
914 CodeSource cs = pd.getCodeSource();
915 String source = null;
916 if (cs != null && cs.getLocation() != null) {
917 source = cs.getLocation().toString();
918 }
919 return source;
920 }
921
922 private void postDefineClass(Class<?> c, ProtectionDomain pd) {
923 // define a named package, if not present
924 getNamedPackage(c.getPackageName(), c.getModule());
925
926 if (pd.getCodeSource() != null) {
927 Certificate certs[] = pd.getCodeSource().getCertificates();
928 if (certs != null)
929 setSigners(c, certs);
930 }
931 }
932
933 /**
934 * Converts an array of bytes into an instance of class {@code Class},
935 * with a given {@code ProtectionDomain}.
936 *
937 * <p> If the given {@code ProtectionDomain} is {@code null},
938 * then a default protection domain will be assigned to the class as specified
939 * in the documentation for {@link #defineClass(String, byte[], int, int)}.
940 * Before the class can be used it must be resolved.
941 *
942 * <p> The first class defined in a package determines the exact set of
943 * certificates that all subsequent classes defined in that package must
944 * contain. The set of certificates for a class is obtained from the
945 * {@link java.security.CodeSource CodeSource} within the
946 * {@code ProtectionDomain} of the class. Any classes added to that
947 * package must contain the same set of certificates or a
948 * {@code SecurityException} will be thrown. Note that if
949 * {@code name} is {@code null}, this check is not performed.
950 * You should always pass in the <a href="#binary-name">binary name</a> of the
951 * class you are defining as well as the bytes. This ensures that the
952 * class you are defining is indeed the class you think it is.
953 *
954 * <p> If the specified {@code name} begins with "{@code java.}", it can
955 * only be defined by the {@linkplain #getPlatformClassLoader()
956 * platform class loader} or its ancestors; otherwise {@code SecurityException}
957 * will be thrown. If {@code name} is not {@code null}, it must be equal to
958 * the <a href="#binary-name">binary name</a> of the class
959 * specified by the byte array {@code b}, otherwise a {@link
960 * NoClassDefFoundError NoClassDefFoundError} will be thrown.
961 *
962 * <p> This method defines a package in this class loader corresponding to the
963 * package of the {@code Class} (if such a package has not already been defined
964 * in this class loader). The name of the defined package is derived from
965 * the <a href="#binary-name">binary name</a> of the class specified by
966 * the byte array {@code b}.
967 * Other properties of the defined package are as specified by {@link Package}.
968 *
969 * @param name
970 * The expected <a href="#binary-name">binary name</a> of the class, or
971 * {@code null} if not known
972 *
973 * @param b
974 * The bytes that make up the class data. The bytes in positions
975 * {@code off} through {@code off+len-1} should have the format
976 * of a valid class file as defined by
977 * <cite>The Java™ Virtual Machine Specification</cite>.
978 *
979 * @param off
980 * The start offset in {@code b} of the class data
981 *
982 * @param len
983 * The length of the class data
984 *
985 * @param protectionDomain
986 * The {@code ProtectionDomain} of the class
987 *
988 * @return The {@code Class} object created from the data,
989 * and {@code ProtectionDomain}.
990 *
991 * @throws ClassFormatError
992 * If the data did not contain a valid class
993 *
994 * @throws NoClassDefFoundError
995 * If {@code name} is not {@code null} and not equal to the
996 * <a href="#binary-name">binary name</a> of the class specified by {@code b}
997 *
998 * @throws IndexOutOfBoundsException
999 * If either {@code off} or {@code len} is negative, or if
1000 * {@code off+len} is greater than {@code b.length}.
1001 *
1002 * @throws SecurityException
1003 * If an attempt is made to add this class to a package that
1004 * contains classes that were signed by a different set of
1005 * certificates than this class, or if {@code name} begins with
1006 * "{@code java.}" and this class loader is not the platform
1007 * class loader or its ancestor.
1008 *
1009 * @revised 9
1010 * @spec JPMS
1011 */
1012 protected final Class<?> defineClass(String name, byte[] b, int off, int len,
1013 ProtectionDomain protectionDomain)
1014 throws ClassFormatError
1015 {
1016 protectionDomain = preDefineClass(name, protectionDomain);
1017 String source = defineClassSourceLocation(protectionDomain);
1018 Class<?> c = defineClass1(this, name, b, off, len, protectionDomain, source);
1019 postDefineClass(c, protectionDomain);
1020 return c;
1021 }
1022
1023 /**
1024 * Converts a {@link java.nio.ByteBuffer ByteBuffer} into an instance
1025 * of class {@code Class}, with the given {@code ProtectionDomain}.
1026 * If the given {@code ProtectionDomain} is {@code null}, then a default
1027 * protection domain will be assigned to the class as
1028 * specified in the documentation for {@link #defineClass(String, byte[],
1029 * int, int)}. Before the class can be used it must be resolved.
1030 *
1031 * <p>The rules about the first class defined in a package determining the
1032 * set of certificates for the package, the restrictions on class names,
1033 * and the defined package of the class
1034 * are identical to those specified in the documentation for {@link
1035 * #defineClass(String, byte[], int, int, ProtectionDomain)}.
1036 *
1037 * <p> An invocation of this method of the form
1038 * <i>cl</i>{@code .defineClass(}<i>name</i>{@code ,}
1039 * <i>bBuffer</i>{@code ,} <i>pd</i>{@code )} yields exactly the same
1040 * result as the statements
1041 *
1042 *<p> <code>
1043 * ...<br>
1044 * byte[] temp = new byte[bBuffer.{@link
1045 * java.nio.ByteBuffer#remaining remaining}()];<br>
1046 * bBuffer.{@link java.nio.ByteBuffer#get(byte[])
1047 * get}(temp);<br>
1048 * return {@link #defineClass(String, byte[], int, int, ProtectionDomain)
1049 * cl.defineClass}(name, temp, 0,
1050 * temp.length, pd);<br>
1051 * </code></p>
1052 *
1053 * @param name
1054 * The expected <a href="#binary-name">binary name</a>. of the class, or
1055 * {@code null} if not known
1056 *
1057 * @param b
1058 * The bytes that make up the class data. The bytes from positions
1059 * {@code b.position()} through {@code b.position() + b.limit() -1
1060 * } should have the format of a valid class file as defined by
1061 * <cite>The Java™ Virtual Machine Specification</cite>.
1062 *
1063 * @param protectionDomain
1064 * The {@code ProtectionDomain} of the class, or {@code null}.
1065 *
1066 * @return The {@code Class} object created from the data,
1067 * and {@code ProtectionDomain}.
1068 *
1069 * @throws ClassFormatError
1070 * If the data did not contain a valid class.
1071 *
1072 * @throws NoClassDefFoundError
1073 * If {@code name} is not {@code null} and not equal to the
1074 * <a href="#binary-name">binary name</a> of the class specified by {@code b}
1075 *
1076 * @throws SecurityException
1077 * If an attempt is made to add this class to a package that
1078 * contains classes that were signed by a different set of
1079 * certificates than this class, or if {@code name} begins with
1080 * "{@code java.}".
1081 *
1082 * @see #defineClass(String, byte[], int, int, ProtectionDomain)
1083 *
1084 * @since 1.5
1085 * @revised 9
1086 * @spec JPMS
1087 */
1088 protected final Class<?> defineClass(String name, java.nio.ByteBuffer b,
1089 ProtectionDomain protectionDomain)
1090 throws ClassFormatError
1091 {
1092 int len = b.remaining();
1093
1094 // Use byte[] if not a direct ByteBuffer:
1095 if (!b.isDirect()) {
1096 if (b.hasArray()) {
1097 return defineClass(name, b.array(),
1098 b.position() + b.arrayOffset(), len,
1099 protectionDomain);
1100 } else {
1101 // no array, or read-only array
1102 byte[] tb = new byte[len];
1103 b.get(tb); // get bytes out of byte buffer.
1104 return defineClass(name, tb, 0, len, protectionDomain);
1105 }
1106 }
1107
1108 protectionDomain = preDefineClass(name, protectionDomain);
1109 String source = defineClassSourceLocation(protectionDomain);
1110 Class<?> c = defineClass2(this, name, b, b.position(), len, protectionDomain, source);
1111 postDefineClass(c, protectionDomain);
1112 return c;
1113 }
1114
1115 static native Class<?> defineClass1(ClassLoader loader, String name, byte[] b, int off, int len,
1116 ProtectionDomain pd, String source);
1117
1118 static native Class<?> defineClass2(ClassLoader loader, String name, java.nio.ByteBuffer b,
1119 int off, int len, ProtectionDomain pd,
1120 String source);
1121
1122 // true if the name is null or has the potential to be a valid binary name
1123 private boolean checkName(String name) {
1124 if ((name == null) || (name.isEmpty()))
1125 return true;
1126 if ((name.indexOf('/') != -1) || (name.charAt(0) == '['))
1127 return false;
1128 return true;
1129 }
1130
1131 private void checkCerts(String name, CodeSource cs) {
1132 int i = name.lastIndexOf('.');
1133 String pname = (i == -1) ? "" : name.substring(0, i);
1134
1135 Certificate[] certs = null;
1136 if (cs != null) {
1137 certs = cs.getCertificates();
1138 }
1139 certs = certs == null ? nocerts : certs;
1140 Certificate[] pcerts = package2certs.putIfAbsent(pname, certs);
1141 if (pcerts != null && !compareCerts(pcerts, certs)) {
1142 throw new SecurityException("class \"" + name
1143 + "\"'s signer information does not match signer information"
1144 + " of other classes in the same package");
1145 }
1146 }
1147
1148 /**
1149 * check to make sure the certs for the new class (certs) are the same as
1150 * the certs for the first class inserted in the package (pcerts)
1151 */
1152 private boolean compareCerts(Certificate[] pcerts, Certificate[] certs) {
1153 // empty array fast-path
1154 if (certs.length == 0)
1155 return pcerts.length == 0;
1156
1157 // the length must be the same at this point
1158 if (certs.length != pcerts.length)
1159 return false;
1160
1161 // go through and make sure all the certs in one array
1162 // are in the other and vice-versa.
1163 boolean match;
1164 for (Certificate cert : certs) {
1165 match = false;
1166 for (Certificate pcert : pcerts) {
1167 if (cert.equals(pcert)) {
1168 match = true;
1169 break;
1170 }
1171 }
1172 if (!match) return false;
1173 }
1174
1175 // now do the same for pcerts
1176 for (Certificate pcert : pcerts) {
1177 match = false;
1178 for (Certificate cert : certs) {
1179 if (pcert.equals(cert)) {
1180 match = true;
1181 break;
1182 }
1183 }
1184 if (!match) return false;
1185 }
1186
1187 return true;
1188 }
1189
1190 /**
1191 * Links the specified class. This (misleadingly named) method may be
1192 * used by a class loader to link a class. If the class {@code c} has
1193 * already been linked, then this method simply returns. Otherwise, the
1194 * class is linked as described in the "Execution" chapter of
1195 * <cite>The Java™ Language Specification</cite>.
1196 *
1197 * @param c
1198 * The class to link
1199 *
1200 * @throws NullPointerException
1201 * If {@code c} is {@code null}.
1202 *
1203 * @see #defineClass(String, byte[], int, int)
1204 */
1205 protected final void resolveClass(Class<?> c) {
1206 if (c == null) {
1207 throw new NullPointerException();
1208 }
1209 }
1210
1211 /**
1212 * Finds a class with the specified <a href="#binary-name">binary name</a>,
1213 * loading it if necessary.
1214 *
1215 * <p> This method loads the class through the system class loader (see
1216 * {@link #getSystemClassLoader()}). The {@code Class} object returned
1217 * might have more than one {@code ClassLoader} associated with it.
1218 * Subclasses of {@code ClassLoader} need not usually invoke this method,
1219 * because most class loaders need to override just {@link
1220 * #findClass(String)}. </p>
1221 *
1222 * @param name
1223 * The <a href="#binary-name">binary name</a> of the class
1224 *
1225 * @return The {@code Class} object for the specified {@code name}
1226 *
1227 * @throws ClassNotFoundException
1228 * If the class could not be found
1229 *
1230 * @see #ClassLoader(ClassLoader)
1231 * @see #getParent()
1232 */
1233 protected final Class<?> findSystemClass(String name)
1234 throws ClassNotFoundException
1235 {
1236 return getSystemClassLoader().loadClass(name);
1237 }
1238
1239 /**
1240 * Returns a class loaded by the bootstrap class loader;
1241 * or return null if not found.
1242 */
1243 Class<?> findBootstrapClassOrNull(String name) {
1244 if (!checkName(name)) return null;
1245
1246 return findBootstrapClass(name);
1247 }
1248
1249 // return null if not found
1250 private native Class<?> findBootstrapClass(String name);
1251
1252 /**
1253 * Returns the class with the given <a href="#binary-name">binary name</a> if this
1254 * loader has been recorded by the Java virtual machine as an initiating
1255 * loader of a class with that <a href="#binary-name">binary name</a>. Otherwise
1256 * {@code null} is returned.
1257 *
1258 * @param name
1259 * The <a href="#binary-name">binary name</a> of the class
1260 *
1261 * @return The {@code Class} object, or {@code null} if the class has
1262 * not been loaded
1263 *
1264 * @since 1.1
1265 */
1266 protected final Class<?> findLoadedClass(String name) {
1267 if (!checkName(name))
1268 return null;
1269 return findLoadedClass0(name);
1270 }
1271
1272 private final native Class<?> findLoadedClass0(String name);
1273
1274 /**
1275 * Sets the signers of a class. This should be invoked after defining a
1276 * class.
1277 *
1278 * @param c
1279 * The {@code Class} object
1280 *
1281 * @param signers
1282 * The signers for the class
1283 *
1284 * @since 1.1
1285 */
1286 protected final void setSigners(Class<?> c, Object[] signers) {
1287 c.setSigners(signers);
1288 }
1289
1290
1291 // -- Resources --
1292
1293 /**
1294 * Returns a URL to a resource in a module defined to this class loader.
1295 * Class loader implementations that support loading from modules
1296 * should override this method.
1297 *
1298 * @apiNote This method is the basis for the {@link
1299 * Class#getResource Class.getResource}, {@link Class#getResourceAsStream
1300 * Class.getResourceAsStream}, and {@link Module#getResourceAsStream
1301 * Module.getResourceAsStream} methods. It is not subject to the rules for
1302 * encapsulation specified by {@code Module.getResourceAsStream}.
1303 *
1304 * @implSpec The default implementation attempts to find the resource by
1305 * invoking {@link #findResource(String)} when the {@code moduleName} is
1306 * {@code null}. It otherwise returns {@code null}.
1307 *
1308 * @param moduleName
1309 * The module name; or {@code null} to find a resource in the
1310 * {@linkplain #getUnnamedModule() unnamed module} for this
1311 * class loader
1312 * @param name
1313 * The resource name
1314 *
1315 * @return A URL to the resource; {@code null} if the resource could not be
1316 * found, a URL could not be constructed to locate the resource,
1317 * access to the resource is denied by the security manager, or
1318 * there isn't a module of the given name defined to the class
1319 * loader.
1320 *
1321 * @throws IOException
1322 * If I/O errors occur
1323 *
1324 * @see java.lang.module.ModuleReader#find(String)
1325 * @since 9
1326 * @spec JPMS
1327 */
1328 protected URL findResource(String moduleName, String name) throws IOException {
1329 if (moduleName == null) {
1330 return findResource(name);
1331 } else {
1332 return null;
1333 }
1334 }
1335
1336 /**
1337 * Finds the resource with the given name. A resource is some data
1338 * (images, audio, text, etc) that can be accessed by class code in a way
1339 * that is independent of the location of the code.
1340 *
1341 * <p> The name of a resource is a '{@code /}'-separated path name that
1342 * identifies the resource. </p>
1343 *
1344 * <p> Resources in named modules are subject to the encapsulation rules
1345 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1346 * Additionally, and except for the special case where the resource has a
1347 * name ending with "{@code .class}", this method will only find resources in
1348 * packages of named modules when the package is {@link Module#isOpen(String)
1349 * opened} unconditionally (even if the caller of this method is in the
1350 * same module as the resource). </p>
1351 *
1352 * @implSpec The default implementation will first search the parent class
1353 * loader for the resource; if the parent is {@code null} the path of the
1354 * class loader built into the virtual machine is searched. If not found,
1355 * this method will invoke {@link #findResource(String)} to find the resource.
1356 *
1357 * @apiNote Where several modules are defined to the same class loader,
1358 * and where more than one module contains a resource with the given name,
1359 * then the ordering that modules are searched is not specified and may be
1360 * very unpredictable.
1361 * When overriding this method it is recommended that an implementation
1362 * ensures that any delegation is consistent with the {@link
1363 * #getResources(java.lang.String) getResources(String)} method.
1364 *
1365 * @param name
1366 * The resource name
1367 *
1368 * @return {@code URL} object for reading the resource; {@code null} if
1369 * the resource could not be found, a {@code URL} could not be
1370 * constructed to locate the resource, the resource is in a package
1371 * that is not opened unconditionally, or access to the resource is
1372 * denied by the security manager.
1373 *
1374 * @throws NullPointerException If {@code name} is {@code null}
1375 *
1376 * @since 1.1
1377 * @revised 9
1378 * @spec JPMS
1379 */
1380 public URL getResource(String name) {
1381 Objects.requireNonNull(name);
1382 URL url;
1383 if (parent != null) {
1384 url = parent.getResource(name);
1385 } else {
1386 url = BootLoader.findResource(name);
1387 }
1388 if (url == null) {
1389 url = findResource(name);
1390 }
1391 return url;
1392 }
1393
1394 /**
1395 * Finds all the resources with the given name. A resource is some data
1396 * (images, audio, text, etc) that can be accessed by class code in a way
1397 * that is independent of the location of the code.
1398 *
1399 * <p> The name of a resource is a {@code /}-separated path name that
1400 * identifies the resource. </p>
1401 *
1402 * <p> Resources in named modules are subject to the encapsulation rules
1403 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1404 * Additionally, and except for the special case where the resource has a
1405 * name ending with "{@code .class}", this method will only find resources in
1406 * packages of named modules when the package is {@link Module#isOpen(String)
1407 * opened} unconditionally (even if the caller of this method is in the
1408 * same module as the resource). </p>
1409 *
1410 * @implSpec The default implementation will first search the parent class
1411 * loader for the resource; if the parent is {@code null} the path of the
1412 * class loader built into the virtual machine is searched. It then
1413 * invokes {@link #findResources(String)} to find the resources with the
1414 * name in this class loader. It returns an enumeration whose elements
1415 * are the URLs found by searching the parent class loader followed by
1416 * the elements found with {@code findResources}.
1417 *
1418 * @apiNote Where several modules are defined to the same class loader,
1419 * and where more than one module contains a resource with the given name,
1420 * then the ordering is not specified and may be very unpredictable.
1421 * When overriding this method it is recommended that an
1422 * implementation ensures that any delegation is consistent with the {@link
1423 * #getResource(java.lang.String) getResource(String)} method. This should
1424 * ensure that the first element returned by the Enumeration's
1425 * {@code nextElement} method is the same resource that the
1426 * {@code getResource(String)} method would return.
1427 *
1428 * @param name
1429 * The resource name
1430 *
1431 * @return An enumeration of {@link java.net.URL URL} objects for the
1432 * resource. If no resources could be found, the enumeration will
1433 * be empty. Resources for which a {@code URL} cannot be
1434 * constructed, are in a package that is not opened
1435 * unconditionally, or access to the resource is denied by the
1436 * security manager, are not returned in the enumeration.
1437 *
1438 * @throws IOException
1439 * If I/O errors occur
1440 * @throws NullPointerException If {@code name} is {@code null}
1441 *
1442 * @since 1.2
1443 * @revised 9
1444 * @spec JPMS
1445 */
1446 public Enumeration<URL> getResources(String name) throws IOException {
1447 Objects.requireNonNull(name);
1448 @SuppressWarnings("unchecked")
1449 Enumeration<URL>[] tmp = (Enumeration<URL>[]) new Enumeration<?>[2];
1450 if (parent != null) {
1451 tmp[0] = parent.getResources(name);
1452 } else {
1453 tmp[0] = BootLoader.findResources(name);
1454 }
1455 tmp[1] = findResources(name);
1456
1457 return new CompoundEnumeration<>(tmp);
1458 }
1459
1460 /**
1461 * Returns a stream whose elements are the URLs of all the resources with
1462 * the given name. A resource is some data (images, audio, text, etc) that
1463 * can be accessed by class code in a way that is independent of the
1464 * location of the code.
1465 *
1466 * <p> The name of a resource is a {@code /}-separated path name that
1467 * identifies the resource.
1468 *
1469 * <p> The resources will be located when the returned stream is evaluated.
1470 * If the evaluation results in an {@code IOException} then the I/O
1471 * exception is wrapped in an {@link UncheckedIOException} that is then
1472 * thrown.
1473 *
1474 * <p> Resources in named modules are subject to the encapsulation rules
1475 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1476 * Additionally, and except for the special case where the resource has a
1477 * name ending with "{@code .class}", this method will only find resources in
1478 * packages of named modules when the package is {@link Module#isOpen(String)
1479 * opened} unconditionally (even if the caller of this method is in the
1480 * same module as the resource). </p>
1481 *
1482 * @implSpec The default implementation invokes {@link #getResources(String)
1483 * getResources} to find all the resources with the given name and returns
1484 * a stream with the elements in the enumeration as the source.
1485 *
1486 * @apiNote When overriding this method it is recommended that an
1487 * implementation ensures that any delegation is consistent with the {@link
1488 * #getResource(java.lang.String) getResource(String)} method. This should
1489 * ensure that the first element returned by the stream is the same
1490 * resource that the {@code getResource(String)} method would return.
1491 *
1492 * @param name
1493 * The resource name
1494 *
1495 * @return A stream of resource {@link java.net.URL URL} objects. If no
1496 * resources could be found, the stream will be empty. Resources
1497 * for which a {@code URL} cannot be constructed, are in a package
1498 * that is not opened unconditionally, or access to the resource
1499 * is denied by the security manager, will not be in the stream.
1500 *
1501 * @throws NullPointerException If {@code name} is {@code null}
1502 *
1503 * @since 9
1504 */
1505 public Stream<URL> resources(String name) {
1506 Objects.requireNonNull(name);
1507 int characteristics = Spliterator.NONNULL | Spliterator.IMMUTABLE;
1508 Supplier<Spliterator<URL>> si = () -> {
1509 try {
1510 return Spliterators.spliteratorUnknownSize(
1511 getResources(name).asIterator(), characteristics);
1512 } catch (IOException e) {
1513 throw new UncheckedIOException(e);
1514 }
1515 };
1516 return StreamSupport.stream(si, characteristics, false);
1517 }
1518
1519 /**
1520 * Finds the resource with the given name. Class loader implementations
1521 * should override this method.
1522 *
1523 * <p> For resources in named modules then the method must implement the
1524 * rules for encapsulation specified in the {@code Module} {@link
1525 * Module#getResourceAsStream getResourceAsStream} method. Additionally,
1526 * it must not find non-"{@code .class}" resources in packages of named
1527 * modules unless the package is {@link Module#isOpen(String) opened}
1528 * unconditionally. </p>
1529 *
1530 * @implSpec The default implementation returns {@code null}.
1531 *
1532 * @param name
1533 * The resource name
1534 *
1535 * @return {@code URL} object for reading the resource; {@code null} if
1536 * the resource could not be found, a {@code URL} could not be
1537 * constructed to locate the resource, the resource is in a package
1538 * that is not opened unconditionally, or access to the resource is
1539 * denied by the security manager.
1540 *
1541 * @since 1.2
1542 * @revised 9
1543 * @spec JPMS
1544 */
1545 protected URL findResource(String name) {
1546 return null;
1547 }
1548
1549 /**
1550 * Returns an enumeration of {@link java.net.URL URL} objects
1551 * representing all the resources with the given name. Class loader
1552 * implementations should override this method.
1553 *
1554 * <p> For resources in named modules then the method must implement the
1555 * rules for encapsulation specified in the {@code Module} {@link
1556 * Module#getResourceAsStream getResourceAsStream} method. Additionally,
1557 * it must not find non-"{@code .class}" resources in packages of named
1558 * modules unless the package is {@link Module#isOpen(String) opened}
1559 * unconditionally. </p>
1560 *
1561 * @implSpec The default implementation returns an enumeration that
1562 * contains no elements.
1563 *
1564 * @param name
1565 * The resource name
1566 *
1567 * @return An enumeration of {@link java.net.URL URL} objects for
1568 * the resource. If no resources could be found, the enumeration
1569 * will be empty. Resources for which a {@code URL} cannot be
1570 * constructed, are in a package that is not opened unconditionally,
1571 * or access to the resource is denied by the security manager,
1572 * are not returned in the enumeration.
1573 *
1574 * @throws IOException
1575 * If I/O errors occur
1576 *
1577 * @since 1.2
1578 * @revised 9
1579 * @spec JPMS
1580 */
1581 protected Enumeration<URL> findResources(String name) throws IOException {
1582 return Collections.emptyEnumeration();
1583 }
1584
1585 /**
1586 * Registers the caller as
1587 * {@linkplain #isRegisteredAsParallelCapable() parallel capable}.
1588 * The registration succeeds if and only if all of the following
1589 * conditions are met:
1590 * <ol>
1591 * <li> no instance of the caller has been created</li>
1592 * <li> all of the super classes (except class Object) of the caller are
1593 * registered as parallel capable</li>
1594 * </ol>
1595 * <p>Note that once a class loader is registered as parallel capable, there
1596 * is no way to change it back.</p>
1597 *
1598 * @return {@code true} if the caller is successfully registered as
1599 * parallel capable and {@code false} if otherwise.
1600 *
1601 * @see #isRegisteredAsParallelCapable()
1602 *
1603 * @since 1.7
1604 */
1605 @CallerSensitive
1606 protected static boolean registerAsParallelCapable() {
1607 Class<? extends ClassLoader> callerClass =
1608 Reflection.getCallerClass().asSubclass(ClassLoader.class);
1609 return ParallelLoaders.register(callerClass);
1610 }
1611
1612 /**
1613 * Returns {@code true} if this class loader is registered as
1614 * {@linkplain #registerAsParallelCapable parallel capable}, otherwise
1615 * {@code false}.
1616 *
1617 * @return {@code true} if this class loader is parallel capable,
1618 * otherwise {@code false}.
1619 *
1620 * @see #registerAsParallelCapable()
1621 *
1622 * @since 9
1623 */
1624 public final boolean isRegisteredAsParallelCapable() {
1625 return ParallelLoaders.isRegistered(this.getClass());
1626 }
1627
1628 /**
1629 * Find a resource of the specified name from the search path used to load
1630 * classes. This method locates the resource through the system class
1631 * loader (see {@link #getSystemClassLoader()}).
1632 *
1633 * <p> Resources in named modules are subject to the encapsulation rules
1634 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1635 * Additionally, and except for the special case where the resource has a
1636 * name ending with "{@code .class}", this method will only find resources in
1637 * packages of named modules when the package is {@link Module#isOpen(String)
1638 * opened} unconditionally. </p>
1639 *
1640 * @param name
1641 * The resource name
1642 *
1643 * @return A {@link java.net.URL URL} to the resource; {@code
1644 * null} if the resource could not be found, a URL could not be
1645 * constructed to locate the resource, the resource is in a package
1646 * that is not opened unconditionally or access to the resource is
1647 * denied by the security manager.
1648 *
1649 * @since 1.1
1650 * @revised 9
1651 * @spec JPMS
1652 */
1653 public static URL getSystemResource(String name) {
1654 return getSystemClassLoader().getResource(name);
1655 }
1656
1657 /**
1658 * Finds all resources of the specified name from the search path used to
1659 * load classes. The resources thus found are returned as an
1660 * {@link java.util.Enumeration Enumeration} of {@link
1661 * java.net.URL URL} objects.
1662 *
1663 * <p> The search order is described in the documentation for {@link
1664 * #getSystemResource(String)}. </p>
1665 *
1666 * <p> Resources in named modules are subject to the encapsulation rules
1667 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1668 * Additionally, and except for the special case where the resource has a
1669 * name ending with "{@code .class}", this method will only find resources in
1670 * packages of named modules when the package is {@link Module#isOpen(String)
1671 * opened} unconditionally. </p>
1672 *
1673 * @param name
1674 * The resource name
1675 *
1676 * @return An enumeration of {@link java.net.URL URL} objects for
1677 * the resource. If no resources could be found, the enumeration
1678 * will be empty. Resources for which a {@code URL} cannot be
1679 * constructed, are in a package that is not opened unconditionally,
1680 * or access to the resource is denied by the security manager,
1681 * are not returned in the enumeration.
1682 *
1683 * @throws IOException
1684 * If I/O errors occur
1685 *
1686 * @since 1.2
1687 * @revised 9
1688 * @spec JPMS
1689 */
1690 public static Enumeration<URL> getSystemResources(String name)
1691 throws IOException
1692 {
1693 return getSystemClassLoader().getResources(name);
1694 }
1695
1696 /**
1697 * Returns an input stream for reading the specified resource.
1698 *
1699 * <p> The search order is described in the documentation for {@link
1700 * #getResource(String)}. </p>
1701 *
1702 * <p> Resources in named modules are subject to the encapsulation rules
1703 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1704 * Additionally, and except for the special case where the resource has a
1705 * name ending with "{@code .class}", this method will only find resources in
1706 * packages of named modules when the package is {@link Module#isOpen(String)
1707 * opened} unconditionally. </p>
1708 *
1709 * @param name
1710 * The resource name
1711 *
1712 * @return An input stream for reading the resource; {@code null} if the
1713 * resource could not be found, the resource is in a package that
1714 * is not opened unconditionally, or access to the resource is
1715 * denied by the security manager.
1716 *
1717 * @throws NullPointerException If {@code name} is {@code null}
1718 *
1719 * @since 1.1
1720 * @revised 9
1721 * @spec JPMS
1722 */
1723 public InputStream getResourceAsStream(String name) {
1724 Objects.requireNonNull(name);
1725 URL url = getResource(name);
1726 try {
1727 return url != null ? url.openStream() : null;
1728 } catch (IOException e) {
1729 return null;
1730 }
1731 }
1732
1733 /**
1734 * Open for reading, a resource of the specified name from the search path
1735 * used to load classes. This method locates the resource through the
1736 * system class loader (see {@link #getSystemClassLoader()}).
1737 *
1738 * <p> Resources in named modules are subject to the encapsulation rules
1739 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1740 * Additionally, and except for the special case where the resource has a
1741 * name ending with "{@code .class}", this method will only find resources in
1742 * packages of named modules when the package is {@link Module#isOpen(String)
1743 * opened} unconditionally. </p>
1744 *
1745 * @param name
1746 * The resource name
1747 *
1748 * @return An input stream for reading the resource; {@code null} if the
1749 * resource could not be found, the resource is in a package that
1750 * is not opened unconditionally, or access to the resource is
1751 * denied by the security manager.
1752 *
1753 * @since 1.1
1754 * @revised 9
1755 * @spec JPMS
1756 */
1757 public static InputStream getSystemResourceAsStream(String name) {
1758 URL url = getSystemResource(name);
1759 try {
1760 return url != null ? url.openStream() : null;
1761 } catch (IOException e) {
1762 return null;
1763 }
1764 }
1765
1766
1767 // -- Hierarchy --
1768
1769 /**
1770 * Returns the parent class loader for delegation. Some implementations may
1771 * use {@code null} to represent the bootstrap class loader. This method
1772 * will return {@code null} in such implementations if this class loader's
1773 * parent is the bootstrap class loader.
1774 *
1775 * @return The parent {@code ClassLoader}
1776 *
1777 * @throws SecurityException
1778 * If a security manager is present, and the caller's class loader
1779 * is not {@code null} and is not an ancestor of this class loader,
1780 * and the caller does not have the
1781 * {@link RuntimePermission}{@code ("getClassLoader")}
1782 *
1783 * @since 1.2
1784 */
1785 @CallerSensitive
1786 public final ClassLoader getParent() {
1787 if (parent == null)
1788 return null;
1789 SecurityManager sm = System.getSecurityManager();
1790 if (sm != null) {
1791 // Check access to the parent class loader
1792 // If the caller's class loader is same as this class loader,
1793 // permission check is performed.
1794 checkClassLoaderPermission(parent, Reflection.getCallerClass());
1795 }
1796 return parent;
1797 }
1798
1799 /**
1800 * Returns the unnamed {@code Module} for this class loader.
1801 *
1802 * @return The unnamed Module for this class loader
1803 *
1804 * @see Module#isNamed()
1805 * @since 9
1806 * @spec JPMS
1807 */
1808 public final Module getUnnamedModule() {
1809 return unnamedModule;
1810 }
1811
1812 /**
1813 * Returns the platform class loader. All
1814 * <a href="#builtinLoaders">platform classes</a> are visible to
1815 * the platform class loader.
1816 *
1817 * @implNote The name of the builtin platform class loader is
1818 * {@code "platform"}.
1819 *
1820 * @return The platform {@code ClassLoader}.
1821 *
1822 * @throws SecurityException
1823 * If a security manager is present, and the caller's class loader is
1824 * not {@code null}, and the caller's class loader is not the same
1825 * as or an ancestor of the platform class loader,
1826 * and the caller does not have the
1827 * {@link RuntimePermission}{@code ("getClassLoader")}
1828 *
1829 * @since 9
1830 * @spec JPMS
1831 */
1832 @CallerSensitive
1833 public static ClassLoader getPlatformClassLoader() {
1834 SecurityManager sm = System.getSecurityManager();
1835 ClassLoader loader = getBuiltinPlatformClassLoader();
1836 if (sm != null) {
1837 checkClassLoaderPermission(loader, Reflection.getCallerClass());
1838 }
1839 return loader;
1840 }
1841
1842 /**
1843 * Returns the system class loader. This is the default
1844 * delegation parent for new {@code ClassLoader} instances, and is
1845 * typically the class loader used to start the application.
1846 *
1847 * <p> This method is first invoked early in the runtime's startup
1848 * sequence, at which point it creates the system class loader. This
1849 * class loader will be the context class loader for the main application
1850 * thread (for example, the thread that invokes the {@code main} method of
1851 * the main class).
1852 *
1853 * <p> The default system class loader is an implementation-dependent
1854 * instance of this class.
1855 *
1856 * <p> If the system property "{@systemProperty java.system.class.loader}"
1857 * is defined when this method is first invoked then the value of that
1858 * property is taken to be the name of a class that will be returned as the
1859 * system class loader. The class is loaded using the default system class
1860 * loader and must define a public constructor that takes a single parameter
1861 * of type {@code ClassLoader} which is used as the delegation parent. An
1862 * instance is then created using this constructor with the default system
1863 * class loader as the parameter. The resulting class loader is defined
1864 * to be the system class loader. During construction, the class loader
1865 * should take great care to avoid calling {@code getSystemClassLoader()}.
1866 * If circular initialization of the system class loader is detected then
1867 * an {@code IllegalStateException} is thrown.
1868 *
1869 * @implNote The system property to override the system class loader is not
1870 * examined until the VM is almost fully initialized. Code that executes
1871 * this method during startup should take care not to cache the return
1872 * value until the system is fully initialized.
1873 *
1874 * <p> The name of the built-in system class loader is {@code "app"}.
1875 * The system property "{@code java.class.path}" is read during early
1876 * initialization of the VM to determine the class path.
1877 * An empty value of "{@code java.class.path}" property is interpreted
1878 * differently depending on whether the initial module (the module
1879 * containing the main class) is named or unnamed:
1880 * If named, the built-in system class loader will have no class path and
1881 * will search for classes and resources using the application module path;
1882 * otherwise, if unnamed, it will set the class path to the current
1883 * working directory.
1884 *
1885 * <p> JAR files on the class path may contain a {@code Class-Path} manifest
1886 * attribute to specify dependent JAR files to be included in the class path.
1887 * {@code Class-Path} entries must meet certain conditions for validity (see
1888 * the <a href="{@docRoot}/../specs/jar/jar.html#class-path-attribute">
1889 * JAR File Specification</a> for details). Invalid {@code Class-Path}
1890 * entries are ignored. For debugging purposes, ignored entries can be
1891 * printed to the console if the
1892 * {@systemProperty jdk.net.URLClassPath.showIgnoredClassPathEntries} system
1893 * property is set to {@code true}.
1894 *
1895 * @return The system {@code ClassLoader}
1896 *
1897 * @throws SecurityException
1898 * If a security manager is present, and the caller's class loader
1899 * is not {@code null} and is not the same as or an ancestor of the
1900 * system class loader, and the caller does not have the
1901 * {@link RuntimePermission}{@code ("getClassLoader")}
1902 *
1903 * @throws IllegalStateException
1904 * If invoked recursively during the construction of the class
1905 * loader specified by the "{@code java.system.class.loader}"
1906 * property.
1907 *
1908 * @throws Error
1909 * If the system property "{@code java.system.class.loader}"
1910 * is defined but the named class could not be loaded, the
1911 * provider class does not define the required constructor, or an
1912 * exception is thrown by that constructor when it is invoked. The
1913 * underlying cause of the error can be retrieved via the
1914 * {@link Throwable#getCause()} method.
1915 *
1916 * @revised 1.4
1917 * @revised 9
1918 * @spec JPMS
1919 */
1920 @CallerSensitive
1921 public static ClassLoader getSystemClassLoader() {
1922 switch (VM.initLevel()) {
1923 case 0:
1924 case 1:
1925 case 2:
1926 // the system class loader is the built-in app class loader during startup
1927 return getBuiltinAppClassLoader();
1928 case 3:
1929 String msg = "getSystemClassLoader cannot be called during the system class loader instantiation";
1930 throw new IllegalStateException(msg);
1931 default:
1932 // system fully initialized
1933 assert VM.isBooted() && scl != null;
1934 SecurityManager sm = System.getSecurityManager();
1935 if (sm != null) {
1936 checkClassLoaderPermission(scl, Reflection.getCallerClass());
1937 }
1938 return scl;
1939 }
1940 }
1941
1942 static ClassLoader getBuiltinPlatformClassLoader() {
1943 return ClassLoaders.platformClassLoader();
1944 }
1945
1946 static ClassLoader getBuiltinAppClassLoader() {
1947 return ClassLoaders.appClassLoader();
1948 }
1949
1950 /*
1951 * Initialize the system class loader that may be a custom class on the
1952 * application class path or application module path.
1953 *
1954 * @see java.lang.System#initPhase3
1955 */
1956 static synchronized ClassLoader initSystemClassLoader() {
1957 if (VM.initLevel() != 3) {
1958 throw new InternalError("system class loader cannot be set at initLevel " +
1959 VM.initLevel());
1960 }
1961
1962 // detect recursive initialization
1963 if (scl != null) {
1964 throw new IllegalStateException("recursive invocation");
1965 }
1966
1967 ClassLoader builtinLoader = getBuiltinAppClassLoader();
1968
1969 // All are privileged frames. No need to call doPrivileged.
1970 String cn = System.getProperty("java.system.class.loader");
1971 if (cn != null) {
1972 try {
1973 // custom class loader is only supported to be loaded from unnamed module
1974 Constructor<?> ctor = Class.forName(cn, false, builtinLoader)
1975 .getDeclaredConstructor(ClassLoader.class);
1976 scl = (ClassLoader) ctor.newInstance(builtinLoader);
1977 } catch (Exception e) {
1978 Throwable cause = e;
1979 if (e instanceof InvocationTargetException) {
1980 cause = e.getCause();
1981 if (cause instanceof Error) {
1982 throw (Error) cause;
1983 }
1984 }
1985 if (cause instanceof RuntimeException) {
1986 throw (RuntimeException) cause;
1987 }
1988 throw new Error(cause.getMessage(), cause);
1989 }
1990 } else {
1991 scl = builtinLoader;
1992 }
1993 return scl;
1994 }
1995
1996 // Returns true if the specified class loader can be found in this class
1997 // loader's delegation chain.
1998 boolean isAncestor(ClassLoader cl) {
1999 ClassLoader acl = this;
2000 do {
2001 acl = acl.parent;
2002 if (cl == acl) {
2003 return true;
2004 }
2005 } while (acl != null);
2006 return false;
2007 }
2008
2009 // Tests if class loader access requires "getClassLoader" permission
2010 // check. A class loader 'from' can access class loader 'to' if
2011 // class loader 'from' is same as class loader 'to' or an ancestor
2012 // of 'to'. The class loader in a system domain can access
2013 // any class loader.
2014 private static boolean needsClassLoaderPermissionCheck(ClassLoader from,
2015 ClassLoader to)
2016 {
2017 if (from == to)
2018 return false;
2019
2020 if (from == null)
2021 return false;
2022
2023 return !to.isAncestor(from);
2024 }
2025
2026 // Returns the class's class loader, or null if none.
2027 static ClassLoader getClassLoader(Class<?> caller) {
2028 // This can be null if the VM is requesting it
2029 if (caller == null) {
2030 return null;
2031 }
2032 // Circumvent security check since this is package-private
2033 return caller.getClassLoader0();
2034 }
2035
2036 /*
2037 * Checks RuntimePermission("getClassLoader") permission
2038 * if caller's class loader is not null and caller's class loader
2039 * is not the same as or an ancestor of the given cl argument.
2040 */
2041 static void checkClassLoaderPermission(ClassLoader cl, Class<?> caller) {
2042 SecurityManager sm = System.getSecurityManager();
2043 if (sm != null) {
2044 // caller can be null if the VM is requesting it
2045 ClassLoader ccl = getClassLoader(caller);
2046 if (needsClassLoaderPermissionCheck(ccl, cl)) {
2047 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
2048 }
2049 }
2050 }
2051
2052 // The system class loader
2053 // @GuardedBy("ClassLoader.class")
2054 private static volatile ClassLoader scl;
2055
2056 // -- Package --
2057
2058 /**
2059 * Define a Package of the given Class object.
2060 *
2061 * If the given class represents an array type, a primitive type or void,
2062 * this method returns {@code null}.
2063 *
2064 * This method does not throw IllegalArgumentException.
2065 */
2066 Package definePackage(Class<?> c) {
2067 if (c.isPrimitive() || c.isArray()) {
2068 return null;
2069 }
2070
2071 return definePackage(c.getPackageName(), c.getModule());
2072 }
2073
2074 /**
2075 * Defines a Package of the given name and module
2076 *
2077 * This method does not throw IllegalArgumentException.
2078 *
2079 * @param name package name
2080 * @param m module
2081 */
2082 Package definePackage(String name, Module m) {
2083 if (name.isEmpty() && m.isNamed()) {
2084 throw new InternalError("unnamed package in " + m);
2085 }
2086
2087 // check if Package object is already defined
2088 NamedPackage pkg = packages.get(name);
2089 if (pkg instanceof Package)
2090 return (Package)pkg;
2091
2092 return (Package)packages.compute(name, (n, p) -> toPackage(n, p, m));
2093 }
2094
2095 /*
2096 * Returns a Package object for the named package
2097 */
2098 private Package toPackage(String name, NamedPackage p, Module m) {
2099 // define Package object if the named package is not yet defined
2100 if (p == null)
2101 return NamedPackage.toPackage(name, m);
2102
2103 // otherwise, replace the NamedPackage object with Package object
2104 if (p instanceof Package)
2105 return (Package)p;
2106
2107 return NamedPackage.toPackage(p.packageName(), p.module());
2108 }
2109
2110 /**
2111 * Defines a package by <a href="#binary-name">name</a> in this {@code ClassLoader}.
2112 * <p>
2113 * <a href="#binary-name">Package names</a> must be unique within a class loader and
2114 * cannot be redefined or changed once created.
2115 * <p>
2116 * If a class loader wishes to define a package with specific properties,
2117 * such as version information, then the class loader should call this
2118 * {@code definePackage} method before calling {@code defineClass}.
2119 * Otherwise, the
2120 * {@link #defineClass(String, byte[], int, int, ProtectionDomain) defineClass}
2121 * method will define a package in this class loader corresponding to the package
2122 * of the newly defined class; the properties of this defined package are
2123 * specified by {@link Package}.
2124 *
2125 * @apiNote
2126 * A class loader that wishes to define a package for classes in a JAR
2127 * typically uses the specification and implementation titles, versions, and
2128 * vendors from the JAR's manifest. If the package is specified as
2129 * {@linkplain java.util.jar.Attributes.Name#SEALED sealed} in the JAR's manifest,
2130 * the {@code URL} of the JAR file is typically used as the {@code sealBase}.
2131 * If classes of package {@code 'p'} defined by this class loader
2132 * are loaded from multiple JARs, the {@code Package} object may contain
2133 * different information depending on the first class of package {@code 'p'}
2134 * defined and which JAR's manifest is read first to explicitly define
2135 * package {@code 'p'}.
2136 *
2137 * <p> It is strongly recommended that a class loader does not call this
2138 * method to explicitly define packages in <em>named modules</em>; instead,
2139 * the package will be automatically defined when a class is {@linkplain
2140 * #defineClass(String, byte[], int, int, ProtectionDomain) being defined}.
2141 * If it is desirable to define {@code Package} explicitly, it should ensure
2142 * that all packages in a named module are defined with the properties
2143 * specified by {@link Package}. Otherwise, some {@code Package} objects
2144 * in a named module may be for example sealed with different seal base.
2145 *
2146 * @param name
2147 * The <a href="#binary-name">package name</a>
2148 *
2149 * @param specTitle
2150 * The specification title
2151 *
2152 * @param specVersion
2153 * The specification version
2154 *
2155 * @param specVendor
2156 * The specification vendor
2157 *
2158 * @param implTitle
2159 * The implementation title
2160 *
2161 * @param implVersion
2162 * The implementation version
2163 *
2164 * @param implVendor
2165 * The implementation vendor
2166 *
2167 * @param sealBase
2168 * If not {@code null}, then this package is sealed with
2169 * respect to the given code source {@link java.net.URL URL}
2170 * object. Otherwise, the package is not sealed.
2171 *
2172 * @return The newly defined {@code Package} object
2173 *
2174 * @throws NullPointerException
2175 * if {@code name} is {@code null}.
2176 *
2177 * @throws IllegalArgumentException
2178 * if a package of the given {@code name} is already
2179 * defined by this class loader
2180 *
2181 *
2182 * @since 1.2
2183 * @revised 9
2184 * @spec JPMS
2185 *
2186 * @jvms 5.3 Creation and Loading
2187 * @see <a href="{@docRoot}/../specs/jar/jar.html#package-sealing">
2188 * The JAR File Specification: Package Sealing</a>
2189 */
2190 protected Package definePackage(String name, String specTitle,
2191 String specVersion, String specVendor,
2192 String implTitle, String implVersion,
2193 String implVendor, URL sealBase)
2194 {
2195 Objects.requireNonNull(name);
2196
2197 // definePackage is not final and may be overridden by custom class loader
2198 Package p = new Package(name, specTitle, specVersion, specVendor,
2199 implTitle, implVersion, implVendor,
2200 sealBase, this);
2201
2202 if (packages.putIfAbsent(name, p) != null)
2203 throw new IllegalArgumentException(name);
2204
2205 return p;
2206 }
2207
2208 /**
2209 * Returns a {@code Package} of the given <a href="#binary-name">name</a> that
2210 * has been defined by this class loader.
2211 *
2212 * @param name The <a href="#binary-name">package name</a>
2213 *
2214 * @return The {@code Package} of the given name that has been defined
2215 * by this class loader, or {@code null} if not found
2216 *
2217 * @throws NullPointerException
2218 * if {@code name} is {@code null}.
2219 *
2220 * @jvms 5.3 Creation and Loading
2221 *
2222 * @since 9
2223 * @spec JPMS
2224 */
2225 public final Package getDefinedPackage(String name) {
2226 Objects.requireNonNull(name, "name cannot be null");
2227
2228 NamedPackage p = packages.get(name);
2229 if (p == null)
2230 return null;
2231
2232 return definePackage(name, p.module());
2233 }
2234
2235 /**
2236 * Returns all of the {@code Package}s that have been defined by
2237 * this class loader. The returned array has no duplicated {@code Package}s
2238 * of the same name.
2239 *
2240 * @apiNote This method returns an array rather than a {@code Set} or {@code Stream}
2241 * for consistency with the existing {@link #getPackages} method.
2242 *
2243 * @return The array of {@code Package} objects that have been defined by
2244 * this class loader; or an zero length array if no package has been
2245 * defined by this class loader.
2246 *
2247 * @jvms 5.3 Creation and Loading
2248 *
2249 * @since 9
2250 * @spec JPMS
2251 */
2252 public final Package[] getDefinedPackages() {
2253 return packages().toArray(Package[]::new);
2254 }
2255
2256 /**
2257 * Finds a package by <a href="#binary-name">name</a> in this class loader and its ancestors.
2258 * <p>
2259 * If this class loader defines a {@code Package} of the given name,
2260 * the {@code Package} is returned. Otherwise, the ancestors of
2261 * this class loader are searched recursively (parent by parent)
2262 * for a {@code Package} of the given name.
2263 *
2264 * @apiNote The {@link #getPlatformClassLoader() platform class loader}
2265 * may delegate to the application class loader but the application class
2266 * loader is not its ancestor. When invoked on the platform class loader,
2267 * this method will not find packages defined to the application
2268 * class loader.
2269 *
2270 * @param name
2271 * The <a href="#binary-name">package name</a>
2272 *
2273 * @return The {@code Package} of the given name that has been defined by
2274 * this class loader or its ancestors, or {@code null} if not found.
2275 *
2276 * @throws NullPointerException
2277 * if {@code name} is {@code null}.
2278 *
2279 * @deprecated
2280 * If multiple class loaders delegate to each other and define classes
2281 * with the same package name, and one such loader relies on the lookup
2282 * behavior of {@code getPackage} to return a {@code Package} from
2283 * a parent loader, then the properties exposed by the {@code Package}
2284 * may not be as expected in the rest of the program.
2285 * For example, the {@code Package} will only expose annotations from the
2286 * {@code package-info.class} file defined by the parent loader, even if
2287 * annotations exist in a {@code package-info.class} file defined by
2288 * a child loader. A more robust approach is to use the
2289 * {@link ClassLoader#getDefinedPackage} method which returns
2290 * a {@code Package} for the specified class loader.
2291 *
2292 * @see ClassLoader#getDefinedPackage(String)
2293 *
2294 * @since 1.2
2295 * @revised 9
2296 * @spec JPMS
2297 */
2298 @Deprecated(since="9")
2299 protected Package getPackage(String name) {
2300 Package pkg = getDefinedPackage(name);
2301 if (pkg == null) {
2302 if (parent != null) {
2303 pkg = parent.getPackage(name);
2304 } else {
2305 pkg = BootLoader.getDefinedPackage(name);
2306 }
2307 }
2308 return pkg;
2309 }
2310
2311 /**
2312 * Returns all of the {@code Package}s that have been defined by
2313 * this class loader and its ancestors. The returned array may contain
2314 * more than one {@code Package} object of the same package name, each
2315 * defined by a different class loader in the class loader hierarchy.
2316 *
2317 * @apiNote The {@link #getPlatformClassLoader() platform class loader}
2318 * may delegate to the application class loader. In other words,
2319 * packages in modules defined to the application class loader may be
2320 * visible to the platform class loader. On the other hand,
2321 * the application class loader is not its ancestor and hence
2322 * when invoked on the platform class loader, this method will not
2323 * return any packages defined to the application class loader.
2324 *
2325 * @return The array of {@code Package} objects that have been defined by
2326 * this class loader and its ancestors
2327 *
2328 * @see ClassLoader#getDefinedPackages()
2329 *
2330 * @since 1.2
2331 * @revised 9
2332 * @spec JPMS
2333 */
2334 protected Package[] getPackages() {
2335 Stream<Package> pkgs = packages();
2336 ClassLoader ld = parent;
2337 while (ld != null) {
2338 pkgs = Stream.concat(ld.packages(), pkgs);
2339 ld = ld.parent;
2340 }
2341 return Stream.concat(BootLoader.packages(), pkgs)
2342 .toArray(Package[]::new);
2343 }
2344
2345
2346
2347 // package-private
2348
2349 /**
2350 * Returns a stream of Packages defined in this class loader
2351 */
2352 Stream<Package> packages() {
2353 return packages.values().stream()
2354 .map(p -> definePackage(p.packageName(), p.module()));
2355 }
2356
2357 // -- Native library access --
2358
2359 /**
2360 * Returns the absolute path name of a native library. The VM invokes this
2361 * method to locate the native libraries that belong to classes loaded with
2362 * this class loader. If this method returns {@code null}, the VM
2363 * searches the library along the path specified as the
2364 * "{@code java.library.path}" property.
2365 *
2366 * @param libname
2367 * The library name
2368 *
2369 * @return The absolute path of the native library
2370 *
2371 * @see System#loadLibrary(String)
2372 * @see System#mapLibraryName(String)
2373 *
2374 * @since 1.2
2375 */
2376 protected String findLibrary(String libname) {
2377 return null;
2378 }
2379
2380 /**
2381 * The inner class NativeLibrary denotes a loaded native library instance.
2382 * Every classloader contains a vector of loaded native libraries in the
2383 * private field {@code nativeLibraries}. The native libraries loaded
2384 * into the system are entered into the {@code systemNativeLibraries}
2385 * vector.
2386 *
2387 * <p> Every native library requires a particular version of JNI. This is
2388 * denoted by the private {@code jniVersion} field. This field is set by
2389 * the VM when it loads the library, and used by the VM to pass the correct
2390 * version of JNI to the native methods. </p>
2391 *
2392 * @see ClassLoader
2393 * @since 1.2
2394 */
2395 static class NativeLibrary {
2396 // the class from which the library is loaded, also indicates
2397 // the loader this native library belongs.
2398 final Class<?> fromClass;
2399 // the canonicalized name of the native library.
2400 // or static library name
2401 final String name;
2402 // Indicates if the native library is linked into the VM
2403 final boolean isBuiltin;
2404
2405 // opaque handle to native library, used in native code.
2406 long handle;
2407 // the version of JNI environment the native library requires.
2408 int jniVersion;
2409
2410 native boolean load0(String name, boolean isBuiltin);
2411
2412 native long findEntry(String name);
2413
2414 NativeLibrary(Class<?> fromClass, String name, boolean isBuiltin) {
2415 this.name = name;
2416 this.fromClass = fromClass;
2417 this.isBuiltin = isBuiltin;
2418 }
2419
2420 /*
2421 * Loads the native library and registers for cleanup when its
2422 * associated class loader is unloaded
2423 */
2424 boolean load() {
2425 if (handle != 0) {
2426 throw new InternalError("Native library " + name + " has been loaded");
2427 }
2428
2429 if (!load0(name, isBuiltin)) return false;
2430
2431 // register the class loader for cleanup when unloaded
2432 // builtin class loaders are never unloaded
2433 ClassLoader loader = fromClass.getClassLoader();
2434 if (loader != null &&
2435 loader != getBuiltinPlatformClassLoader() &&
2436 loader != getBuiltinAppClassLoader()) {
2437 CleanerFactory.cleaner().register(loader,
2438 new Unloader(name, handle, isBuiltin));
2439 }
2440 return true;
2441 }
2442
2443 static boolean loadLibrary(Class<?> fromClass, String name, boolean isBuiltin) {
2444 ClassLoader loader =
2445 fromClass == null ? null : fromClass.getClassLoader();
2446
2447 synchronized (loadedLibraryNames) {
2448 Map<String, NativeLibrary> libs =
2449 loader != null ? loader.nativeLibraries() : systemNativeLibraries();
2450 if (libs.containsKey(name)) {
2451 return true;
2452 }
2453
2454 if (loadedLibraryNames.contains(name)) {
2455 throw new UnsatisfiedLinkError("Native Library " + name +
2456 " already loaded in another classloader");
2457 }
2458
2459 /*
2460 * When a library is being loaded, JNI_OnLoad function can cause
2461 * another loadLibrary invocation that should succeed.
2462 *
2463 * We use a static stack to hold the list of libraries we are
2464 * loading because this can happen only when called by the
2465 * same thread because this block is synchronous.
2466 *
2467 * If there is a pending load operation for the library, we
2468 * immediately return success; otherwise, we raise
2469 * UnsatisfiedLinkError.
2470 */
2471 for (NativeLibrary lib : nativeLibraryContext) {
2472 if (name.equals(lib.name)) {
2473 if (loader == lib.fromClass.getClassLoader()) {
2474 return true;
2475 } else {
2476 throw new UnsatisfiedLinkError("Native Library " +
2477 name + " is being loaded in another classloader");
2478 }
2479 }
2480 }
2481 NativeLibrary lib = new NativeLibrary(fromClass, name, isBuiltin);
2482 // load the native library
2483 nativeLibraryContext.push(lib);
2484 try {
2485 if (!lib.load()) return false;
2486 } finally {
2487 nativeLibraryContext.pop();
2488 }
2489 // register the loaded native library
2490 loadedLibraryNames.add(name);
2491 libs.put(name, lib);
2492 }
2493 return true;
2494 }
2495
2496 // Invoked in the VM to determine the context class in JNI_OnLoad
2497 // and JNI_OnUnload
2498 static Class<?> getFromClass() {
2499 return nativeLibraryContext.peek().fromClass;
2500 }
2501
2502 // native libraries being loaded
2503 static Deque<NativeLibrary> nativeLibraryContext = new ArrayDeque<>(8);
2504
2505 /*
2506 * The run() method will be invoked when this class loader becomes
2507 * phantom reachable to unload the native library.
2508 */
2509 static class Unloader implements Runnable {
2510 // This represents the context when a native library is unloaded
2511 // and getFromClass() will return null,
2512 static final NativeLibrary UNLOADER =
2513 new NativeLibrary(null, "dummy", false);
2514 final String name;
2515 final long handle;
2516 final boolean isBuiltin;
2517
2518 Unloader(String name, long handle, boolean isBuiltin) {
2519 if (handle == 0) {
2520 throw new IllegalArgumentException(
2521 "Invalid handle for native library " + name);
2522 }
2523
2524 this.name = name;
2525 this.handle = handle;
2526 this.isBuiltin = isBuiltin;
2527 }
2528
2529 @Override
2530 public void run() {
2531 synchronized (loadedLibraryNames) {
2532 /* remove the native library name */
2533 loadedLibraryNames.remove(name);
2534 nativeLibraryContext.push(UNLOADER);
2535 try {
2536 unload(name, isBuiltin, handle);
2537 } finally {
2538 nativeLibraryContext.pop();
2539 }
2540
2541 }
2542 }
2543 }
2544
2545 // JNI FindClass expects the caller class if invoked from JNI_OnLoad
2546 // and JNI_OnUnload is NativeLibrary class
2547 static native void unload(String name, boolean isBuiltin, long handle);
2548 }
2549
2550 /**
2551 * Holds system and user library paths derived from the
2552 * {@code java.library.path} and {@code sun.boot.library.path} system
2553 * properties. The system properties are eagerly read at bootstrap, then
2554 * lazily parsed on first use to avoid initialization ordering issues.
2555 */
2556 private static class LibraryPaths {
2557 static final String[] USER =
2558 ClassLoaderHelper.parsePath(StaticProperty.javaLibraryPath());
2559 static final String[] SYS =
2560 ClassLoaderHelper.parsePath(StaticProperty.sunBootLibraryPath());
2561 }
2562
2563 // Invoked in the java.lang.Runtime class to implement load and loadLibrary.
2564 static void loadLibrary(Class<?> fromClass, String name,
2565 boolean isAbsolute) {
2566 ClassLoader loader =
2567 (fromClass == null) ? null : fromClass.getClassLoader();
2568
2569 if (isAbsolute) {
2570 if (loadLibrary0(fromClass, new File(name))) {
2571 return;
2572 }
2573 throw new UnsatisfiedLinkError("Can't load library: " + name);
2574 }
2575 if (loader != null) {
2576 String libfilename = loader.findLibrary(name);
2577 if (libfilename != null) {
2578 File libfile = new File(libfilename);
2579 if (!libfile.isAbsolute()) {
2580 throw new UnsatisfiedLinkError(
2581 "ClassLoader.findLibrary failed to return an absolute path: " + libfilename);
2582 }
2583 if (loadLibrary0(fromClass, libfile)) {
2584 return;
2585 }
2586 throw new UnsatisfiedLinkError("Can't load " + libfilename);
2587 }
2588 }
2589 for (String sysPath : LibraryPaths.SYS) {
2590 File libfile = new File(sysPath, System.mapLibraryName(name));
2591 if (loadLibrary0(fromClass, libfile)) {
2592 return;
2593 }
2594 libfile = ClassLoaderHelper.mapAlternativeName(libfile);
2595 if (libfile != null && loadLibrary0(fromClass, libfile)) {
2596 return;
2597 }
2598 }
2599 if (loader != null) {
2600 for (String userPath : LibraryPaths.USER) {
2601 File libfile = new File(userPath, System.mapLibraryName(name));
2602 if (loadLibrary0(fromClass, libfile)) {
2603 return;
2604 }
2605 libfile = ClassLoaderHelper.mapAlternativeName(libfile);
2606 if (libfile != null && loadLibrary0(fromClass, libfile)) {
2607 return;
2608 }
2609 }
2610 }
2611 // Oops, it failed
2612 throw new UnsatisfiedLinkError("no " + name +
2613 " in java.library.path: " + Arrays.toString(LibraryPaths.USER));
2614 }
2615
2616 private static native String findBuiltinLib(String name);
2617
2618 private static boolean loadLibrary0(Class<?> fromClass, final File file) {
2619 // Check to see if we're attempting to access a static library
2620 String name = findBuiltinLib(file.getName());
2621 boolean isBuiltin = (name != null);
2622 if (!isBuiltin) {
2623 name = AccessController.doPrivileged(
2624 new PrivilegedAction<>() {
2625 public String run() {
2626 try {
2627 return file.exists() ? file.getCanonicalPath() : null;
2628 } catch (IOException e) {
2629 return null;
2630 }
2631 }
2632 });
2633 if (name == null) {
2634 return false;
2635 }
2636 }
2637 return NativeLibrary.loadLibrary(fromClass, name, isBuiltin);
2638 }
2639
2640 /*
2641 * Invoked in the VM class linking code.
2642 */
2643 private static long findNative(ClassLoader loader, String entryName) {
2644 Map<String, NativeLibrary> libs =
2645 loader != null ? loader.nativeLibraries() : systemNativeLibraries();
2646 if (libs.isEmpty())
2647 return 0;
2648
2649 // the native libraries map may be updated in another thread
2650 // when a native library is being loaded. No symbol will be
2651 // searched from it yet.
2652 for (NativeLibrary lib : libs.values()) {
2653 long entry = lib.findEntry(entryName);
2654 if (entry != 0) return entry;
2655 }
2656 return 0;
2657 }
2658
2659 // All native library names we've loaded.
2660 // This also serves as the lock to obtain nativeLibraries
2661 // and write to nativeLibraryContext.
2662 private static final Set<String> loadedLibraryNames = new HashSet<>();
2663
2664 // Native libraries belonging to system classes.
2665 private static volatile Map<String, NativeLibrary> systemNativeLibraries;
2666
2667 // Native libraries associated with the class loader.
2668 private volatile Map<String, NativeLibrary> nativeLibraries;
2669
2670 /*
2671 * Returns the native libraries map associated with bootstrap class loader
2672 * This method will create the map at the first time when called.
2673 */
2674 private static Map<String, NativeLibrary> systemNativeLibraries() {
2675 Map<String, NativeLibrary> libs = systemNativeLibraries;
2676 if (libs == null) {
2677 synchronized (loadedLibraryNames) {
2678 libs = systemNativeLibraries;
2679 if (libs == null) {
2680 libs = systemNativeLibraries = new ConcurrentHashMap<>();
2681 }
2682 }
2683 }
2684 return libs;
2685 }
2686
2687 /*
2688 * Returns the native libraries map associated with this class loader
2689 * This method will create the map at the first time when called.
2690 */
2691 private Map<String, NativeLibrary> nativeLibraries() {
2692 Map<String, NativeLibrary> libs = nativeLibraries;
2693 if (libs == null) {
2694 synchronized (loadedLibraryNames) {
2695 libs = nativeLibraries;
2696 if (libs == null) {
2697 libs = nativeLibraries = new ConcurrentHashMap<>();
2698 }
2699 }
2700 }
2701 return libs;
2702 }
2703
2704 // -- Assertion management --
2705
2706 final Object assertionLock;
2707
2708 // The default toggle for assertion checking.
2709 // @GuardedBy("assertionLock")
2710 private boolean defaultAssertionStatus = false;
2711
2712 // Maps String packageName to Boolean package default assertion status Note
2713 // that the default package is placed under a null map key. If this field
2714 // is null then we are delegating assertion status queries to the VM, i.e.,
2715 // none of this ClassLoader's assertion status modification methods have
2716 // been invoked.
2717 // @GuardedBy("assertionLock")
2718 private Map<String, Boolean> packageAssertionStatus = null;
2719
2720 // Maps String fullyQualifiedClassName to Boolean assertionStatus If this
2721 // field is null then we are delegating assertion status queries to the VM,
2722 // i.e., none of this ClassLoader's assertion status modification methods
2723 // have been invoked.
2724 // @GuardedBy("assertionLock")
2725 Map<String, Boolean> classAssertionStatus = null;
2726
2727 /**
2728 * Sets the default assertion status for this class loader. This setting
2729 * determines whether classes loaded by this class loader and initialized
2730 * in the future will have assertions enabled or disabled by default.
2731 * This setting may be overridden on a per-package or per-class basis by
2732 * invoking {@link #setPackageAssertionStatus(String, boolean)} or {@link
2733 * #setClassAssertionStatus(String, boolean)}.
2734 *
2735 * @param enabled
2736 * {@code true} if classes loaded by this class loader will
2737 * henceforth have assertions enabled by default, {@code false}
2738 * if they will have assertions disabled by default.
2739 *
2740 * @since 1.4
2741 */
2742 public void setDefaultAssertionStatus(boolean enabled) {
2743 synchronized (assertionLock) {
2744 if (classAssertionStatus == null)
2745 initializeJavaAssertionMaps();
2746
2747 defaultAssertionStatus = enabled;
2748 }
2749 }
2750
2751 /**
2752 * Sets the package default assertion status for the named package. The
2753 * package default assertion status determines the assertion status for
2754 * classes initialized in the future that belong to the named package or
2755 * any of its "subpackages".
2756 *
2757 * <p> A subpackage of a package named p is any package whose name begins
2758 * with "{@code p.}". For example, {@code javax.swing.text} is a
2759 * subpackage of {@code javax.swing}, and both {@code java.util} and
2760 * {@code java.lang.reflect} are subpackages of {@code java}.
2761 *
2762 * <p> In the event that multiple package defaults apply to a given class,
2763 * the package default pertaining to the most specific package takes
2764 * precedence over the others. For example, if {@code javax.lang} and
2765 * {@code javax.lang.reflect} both have package defaults associated with
2766 * them, the latter package default applies to classes in
2767 * {@code javax.lang.reflect}.
2768 *
2769 * <p> Package defaults take precedence over the class loader's default
2770 * assertion status, and may be overridden on a per-class basis by invoking
2771 * {@link #setClassAssertionStatus(String, boolean)}. </p>
2772 *
2773 * @param packageName
2774 * The name of the package whose package default assertion status
2775 * is to be set. A {@code null} value indicates the unnamed
2776 * package that is "current"
2777 * (see section 7.4.2 of
2778 * <cite>The Java™ Language Specification</cite>.)
2779 *
2780 * @param enabled
2781 * {@code true} if classes loaded by this classloader and
2782 * belonging to the named package or any of its subpackages will
2783 * have assertions enabled by default, {@code false} if they will
2784 * have assertions disabled by default.
2785 *
2786 * @since 1.4
2787 */
2788 public void setPackageAssertionStatus(String packageName,
2789 boolean enabled) {
2790 synchronized (assertionLock) {
2791 if (packageAssertionStatus == null)
2792 initializeJavaAssertionMaps();
2793
2794 packageAssertionStatus.put(packageName, enabled);
2795 }
2796 }
2797
2798 /**
2799 * Sets the desired assertion status for the named top-level class in this
2800 * class loader and any nested classes contained therein. This setting
2801 * takes precedence over the class loader's default assertion status, and
2802 * over any applicable per-package default. This method has no effect if
2803 * the named class has already been initialized. (Once a class is
2804 * initialized, its assertion status cannot change.)
2805 *
2806 * <p> If the named class is not a top-level class, this invocation will
2807 * have no effect on the actual assertion status of any class. </p>
2808 *
2809 * @param className
2810 * The fully qualified class name of the top-level class whose
2811 * assertion status is to be set.
2812 *
2813 * @param enabled
2814 * {@code true} if the named class is to have assertions
2815 * enabled when (and if) it is initialized, {@code false} if the
2816 * class is to have assertions disabled.
2817 *
2818 * @since 1.4
2819 */
2820 public void setClassAssertionStatus(String className, boolean enabled) {
2821 synchronized (assertionLock) {
2822 if (classAssertionStatus == null)
2823 initializeJavaAssertionMaps();
2824
2825 classAssertionStatus.put(className, enabled);
2826 }
2827 }
2828
2829 /**
2830 * Sets the default assertion status for this class loader to
2831 * {@code false} and discards any package defaults or class assertion
2832 * status settings associated with the class loader. This method is
2833 * provided so that class loaders can be made to ignore any command line or
2834 * persistent assertion status settings and "start with a clean slate."
2835 *
2836 * @since 1.4
2837 */
2838 public void clearAssertionStatus() {
2839 /*
2840 * Whether or not "Java assertion maps" are initialized, set
2841 * them to empty maps, effectively ignoring any present settings.
2842 */
2843 synchronized (assertionLock) {
2844 classAssertionStatus = new HashMap<>();
2845 packageAssertionStatus = new HashMap<>();
2846 defaultAssertionStatus = false;
2847 }
2848 }
2849
2850 /**
2851 * Returns the assertion status that would be assigned to the specified
2852 * class if it were to be initialized at the time this method is invoked.
2853 * If the named class has had its assertion status set, the most recent
2854 * setting will be returned; otherwise, if any package default assertion
2855 * status pertains to this class, the most recent setting for the most
2856 * specific pertinent package default assertion status is returned;
2857 * otherwise, this class loader's default assertion status is returned.
2858 * </p>
2859 *
2860 * @param className
2861 * The fully qualified class name of the class whose desired
2862 * assertion status is being queried.
2863 *
2864 * @return The desired assertion status of the specified class.
2865 *
2866 * @see #setClassAssertionStatus(String, boolean)
2867 * @see #setPackageAssertionStatus(String, boolean)
2868 * @see #setDefaultAssertionStatus(boolean)
2869 *
2870 * @since 1.4
2871 */
2872 boolean desiredAssertionStatus(String className) {
2873 synchronized (assertionLock) {
2874 // assert classAssertionStatus != null;
2875 // assert packageAssertionStatus != null;
2876
2877 // Check for a class entry
2878 Boolean result = classAssertionStatus.get(className);
2879 if (result != null)
2880 return result.booleanValue();
2881
2882 // Check for most specific package entry
2883 int dotIndex = className.lastIndexOf('.');
2884 if (dotIndex < 0) { // default package
2885 result = packageAssertionStatus.get(null);
2886 if (result != null)
2887 return result.booleanValue();
2888 }
2889 while(dotIndex > 0) {
2890 className = className.substring(0, dotIndex);
2891 result = packageAssertionStatus.get(className);
2892 if (result != null)
2893 return result.booleanValue();
2894 dotIndex = className.lastIndexOf('.', dotIndex-1);
2895 }
2896
2897 // Return the classloader default
2898 return defaultAssertionStatus;
2899 }
2900 }
2901
2902 // Set up the assertions with information provided by the VM.
2903 // Note: Should only be called inside a synchronized block
2904 private void initializeJavaAssertionMaps() {
2905 // assert Thread.holdsLock(assertionLock);
2906
2907 classAssertionStatus = new HashMap<>();
2908 packageAssertionStatus = new HashMap<>();
2909 AssertionStatusDirectives directives = retrieveDirectives();
2910
2911 for(int i = 0; i < directives.classes.length; i++)
2912 classAssertionStatus.put(directives.classes[i],
2913 directives.classEnabled[i]);
2914
2915 for(int i = 0; i < directives.packages.length; i++)
2916 packageAssertionStatus.put(directives.packages[i],
2917 directives.packageEnabled[i]);
2918
2919 defaultAssertionStatus = directives.deflt;
2920 }
2921
2922 // Retrieves the assertion directives from the VM.
2923 private static native AssertionStatusDirectives retrieveDirectives();
2924
2925
2926 // -- Misc --
2927
2928 /**
2929 * Returns the ConcurrentHashMap used as a storage for ClassLoaderValue(s)
2930 * associated with this ClassLoader, creating it if it doesn't already exist.
2931 */
2932 ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap() {
2933 ConcurrentHashMap<?, ?> map = classLoaderValueMap;
2934 if (map == null) {
2935 map = new ConcurrentHashMap<>();
2936 boolean set = trySetObjectField("classLoaderValueMap", map);
2937 if (!set) {
2938 // beaten by someone else
2939 map = classLoaderValueMap;
2940 }
2941 }
2942 return map;
2943 }
2944
2945 // the storage for ClassLoaderValue(s) associated with this ClassLoader
2946 private volatile ConcurrentHashMap<?, ?> classLoaderValueMap;
2947
2948 /**
2949 * Attempts to atomically set a volatile field in this object. Returns
2950 * {@code true} if not beaten by another thread. Avoids the use of
2951 * AtomicReferenceFieldUpdater in this class.
2952 */
2953 private boolean trySetObjectField(String name, Object obj) {
2954 Unsafe unsafe = Unsafe.getUnsafe();
2955 Class<?> k = ClassLoader.class;
2956 long offset;
2957 offset = unsafe.objectFieldOffset(k, name);
2958 return unsafe.compareAndSetReference(this, offset, null, obj);
2959 }
2960 }
2961
2962 /*
2963 * A utility class that will enumerate over an array of enumerations.
2964 */
2965 final class CompoundEnumeration<E> implements Enumeration<E> {
2966 private final Enumeration<E>[] enums;
2967 private int index;
2968
2969 public CompoundEnumeration(Enumeration<E>[] enums) {
2970 this.enums = enums;
2971 }
2972
2973 private boolean next() {
2974 while (index < enums.length) {
2975 if (enums[index] != null && enums[index].hasMoreElements()) {
2976 return true;
2977 }
2978 index++;
2979 }
2980 return false;
2981 }
2982
2983 public boolean hasMoreElements() {
2984 return next();
2985 }
2986
2987 public E nextElement() {
2988 if (!next()) {
2989 throw new NoSuchElementException();
2990 }
2991 return enums[index].nextElement();
2992 }
2993 }