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.ArrayList;
43 import java.util.Collections;
44 import java.util.Enumeration;
45 import java.util.HashMap;
46 import java.util.Map;
47 import java.util.NoSuchElementException;
48 import java.util.Objects;
49 import java.util.Set;
50 import java.util.Spliterator;
51 import java.util.Spliterators;
52 import java.util.WeakHashMap;
53 import java.util.concurrent.ConcurrentHashMap;
54 import java.util.function.Supplier;
55 import java.util.stream.Stream;
56 import java.util.stream.StreamSupport;
57
58 import jdk.internal.loader.BootLoader;
59 import jdk.internal.loader.BuiltinClassLoader;
60 import jdk.internal.loader.ClassLoaders;
61 import jdk.internal.loader.NativeLibrary;
62 import jdk.internal.loader.NativeLibraries;
63 import jdk.internal.perf.PerfCounter;
64 import jdk.internal.misc.Unsafe;
65 import jdk.internal.misc.VM;
66 import jdk.internal.reflect.CallerSensitive;
67 import jdk.internal.reflect.Reflection;
68 import jdk.internal.util.StaticProperty;
69 import sun.reflect.misc.ReflectUtil;
70 import sun.security.util.SecurityConstants;
71
72 /**
73 * A class loader is an object that is responsible for loading classes. The
74 * class {@code ClassLoader} is an abstract class. Given the <a
75 * href="#binary-name">binary name</a> of a class, a class loader should attempt to
76 * locate or generate data that constitutes a definition for the class. A
77 * typical strategy is to transform the name into a file name and then read a
78 * "class file" of that name from a file system.
79 *
80 * <p> Every {@link java.lang.Class Class} object contains a {@link
81 * Class#getClassLoader() reference} to the {@code ClassLoader} that defined
82 * it.
83 *
84 * <p> {@code Class} objects for array classes are not created by class
85 * loaders, but are created automatically as required by the Java runtime.
86 * The class loader for an array class, as returned by {@link
87 * Class#getClassLoader()} is the same as the class loader for its element
88 * type; if the element type is a primitive type, then the array class has no
89 * class loader.
90 *
91 * <p> Applications implement subclasses of {@code ClassLoader} in order to
92 * extend the manner in which the Java virtual machine dynamically loads
93 * classes.
94 *
95 * <p> Class loaders may typically be used by security managers to indicate
96 * security domains.
97 *
98 * <p> In addition to loading classes, a class loader is also responsible for
99 * locating resources. A resource is some data (a "{@code .class}" file,
100 * configuration data, or an image for example) that is identified with an
101 * abstract '/'-separated path name. Resources are typically packaged with an
102 * application or library so that they can be located by code in the
103 * application or library. In some cases, the resources are included so that
104 * they can be located by other libraries.
105 *
106 * <p> The {@code ClassLoader} class uses a delegation model to search for
107 * classes and resources. Each instance of {@code ClassLoader} has an
108 * associated parent class loader. When requested to find a class or
109 * resource, a {@code ClassLoader} instance will usually delegate the search
110 * for the class or resource to its parent class loader before attempting to
111 * find the class or resource itself.
112 *
113 * <p> Class loaders that support concurrent loading of classes are known as
114 * <em>{@linkplain #isRegisteredAsParallelCapable() parallel capable}</em> class
115 * loaders and are required to register themselves at their class initialization
116 * time by invoking the {@link
117 * #registerAsParallelCapable ClassLoader.registerAsParallelCapable}
118 * method. Note that the {@code ClassLoader} class is registered as parallel
119 * capable by default. However, its subclasses still need to register themselves
120 * if they are parallel capable.
121 * In environments in which the delegation model is not strictly
122 * hierarchical, class loaders need to be parallel capable, otherwise class
123 * loading can lead to deadlocks because the loader lock is held for the
124 * duration of the class loading process (see {@link #loadClass
125 * loadClass} methods).
126 *
127 * <h2> <a id="builtinLoaders">Run-time Built-in Class Loaders</a></h2>
128 *
129 * The Java run-time has the following built-in class loaders:
130 *
131 * <ul>
132 * <li><p>Bootstrap class loader.
133 * It is the virtual machine's built-in class loader, typically represented
134 * as {@code null}, and does not have a parent.</li>
135 * <li><p>{@linkplain #getPlatformClassLoader() Platform class loader}.
136 * The platform class loader is responsible for loading the
137 * <em>platform classes</em>. Platform classes include Java SE platform APIs,
138 * their implementation classes and JDK-specific run-time classes that are
139 * defined by the platform class loader or its ancestors.
140 * The platform class loader can be used as the parent of a {@code ClassLoader}
141 * instance.
142 * <p> To allow for upgrading/overriding of modules defined to the platform
143 * class loader, and where upgraded modules read modules defined to class
144 * loaders other than the platform class loader and its ancestors, then
145 * the platform class loader may have to delegate to other class loaders,
146 * the application class loader for example.
147 * In other words, classes in named modules defined to class loaders
148 * other than the platform class loader and its ancestors may be visible
149 * to the platform class loader. </li>
150 * <li><p>{@linkplain #getSystemClassLoader() System class loader}.
151 * It is also known as <em>application class loader</em> and is distinct
152 * from the platform class loader.
153 * The system class loader is typically used to define classes on the
154 * application class path, module path, and JDK-specific tools.
155 * The platform class loader is the parent or an ancestor of the system class
156 * loader, so the system class loader can load platform classes by delegating
157 * to its parent.</li>
158 * </ul>
159 *
160 * <p> Normally, the Java virtual machine loads classes from the local file
161 * system in a platform-dependent manner.
162 * However, some classes may not originate from a file; they may originate
163 * from other sources, such as the network, or they could be constructed by an
164 * application. The method {@link #defineClass(String, byte[], int, int)
165 * defineClass} converts an array of bytes into an instance of class
166 * {@code Class}. Instances of this newly defined class can be created using
167 * {@link Class#newInstance Class.newInstance}.
168 *
169 * <p> The methods and constructors of objects created by a class loader may
170 * reference other classes. To determine the class(es) referred to, the Java
171 * virtual machine invokes the {@link #loadClass loadClass} method of
172 * the class loader that originally created the class.
173 *
174 * <p> For example, an application could create a network class loader to
175 * download class files from a server. Sample code might look like:
176 *
177 * <blockquote><pre>
178 * ClassLoader loader = new NetworkClassLoader(host, port);
179 * Object main = loader.loadClass("Main", true).newInstance();
180 * . . .
181 * </pre></blockquote>
182 *
183 * <p> The network class loader subclass must define the methods {@link
184 * #findClass findClass} and {@code loadClassData} to load a class
185 * from the network. Once it has downloaded the bytes that make up the class,
186 * it should use the method {@link #defineClass defineClass} to
187 * create a class instance. A sample implementation is:
188 *
189 * <blockquote><pre>
190 * class NetworkClassLoader extends ClassLoader {
191 * String host;
192 * int port;
193 *
194 * public Class findClass(String name) {
195 * byte[] b = loadClassData(name);
196 * return defineClass(name, b, 0, b.length);
197 * }
198 *
199 * private byte[] loadClassData(String name) {
200 * // load the class data from the connection
201 * . . .
202 * }
203 * }
204 * </pre></blockquote>
205 *
206 * <h3> <a id="binary-name">Binary names</a> </h3>
207 *
208 * <p> Any class name provided as a {@code String} parameter to methods in
209 * {@code ClassLoader} must be a binary name as defined by
210 * <cite>The Java Language Specification</cite>.
211 *
212 * <p> Examples of valid class names include:
213 * <blockquote><pre>
214 * "java.lang.String"
215 * "javax.swing.JSpinner$DefaultEditor"
216 * "java.security.KeyStore$Builder$FileBuilder$1"
217 * "java.net.URLClassLoader$3$1"
218 * </pre></blockquote>
219 *
220 * <p> Any package name provided as a {@code String} parameter to methods in
221 * {@code ClassLoader} must be either the empty string (denoting an unnamed package)
222 * or a fully qualified name as defined by
223 * <cite>The Java Language Specification</cite>.
224 *
225 * @jls 6.7 Fully Qualified Names
226 * @jls 13.1 The Form of a Binary
227 * @see #resolveClass(Class)
228 * @since 1.0
229 * @revised 9
230 * @spec JPMS
231 */
232 public abstract class ClassLoader {
233
234 private static native void registerNatives();
235 static {
236 registerNatives();
237 }
238
239 // The parent class loader for delegation
240 // Note: VM hardcoded the offset of this field, thus all new fields
241 // must be added *after* it.
242 private final ClassLoader parent;
243
244 // class loader name
245 private final String name;
246
247 // the unnamed module for this ClassLoader
248 private final Module unnamedModule;
249
250 // a string for exception message printing
251 private final String nameAndId;
252
253 /**
254 * Encapsulates the set of parallel capable loader types.
255 */
256 private static class ParallelLoaders {
257 private ParallelLoaders() {}
258
259 // the set of parallel capable loader types
260 private static final Set<Class<? extends ClassLoader>> loaderTypes =
261 Collections.newSetFromMap(new WeakHashMap<>());
262 static {
263 synchronized (loaderTypes) { loaderTypes.add(ClassLoader.class); }
264 }
265
266 /**
267 * Registers the given class loader type as parallel capable.
268 * Returns {@code true} is successfully registered; {@code false} if
269 * loader's super class is not registered.
270 */
271 static boolean register(Class<? extends ClassLoader> c) {
272 synchronized (loaderTypes) {
273 if (loaderTypes.contains(c.getSuperclass())) {
274 // register the class loader as parallel capable
275 // if and only if all of its super classes are.
276 // Note: given current classloading sequence, if
277 // the immediate super class is parallel capable,
278 // all the super classes higher up must be too.
279 loaderTypes.add(c);
280 return true;
281 } else {
282 return false;
283 }
284 }
285 }
286
287 /**
288 * Returns {@code true} if the given class loader type is
289 * registered as parallel capable.
290 */
291 static boolean isRegistered(Class<? extends ClassLoader> c) {
292 synchronized (loaderTypes) {
293 return loaderTypes.contains(c);
294 }
295 }
296 }
297
298 // Maps class name to the corresponding lock object when the current
299 // class loader is parallel capable.
300 // Note: VM also uses this field to decide if the current class loader
301 // is parallel capable and the appropriate lock object for class loading.
302 private final ConcurrentHashMap<String, Object> parallelLockMap;
303
304 // Maps packages to certs
305 private final ConcurrentHashMap<String, Certificate[]> package2certs;
306
307 // Shared among all packages with unsigned classes
308 private static final Certificate[] nocerts = new Certificate[0];
309
310 // The classes loaded by this class loader. The only purpose of this table
311 // is to keep the classes from being GC'ed until the loader is GC'ed.
312 private final ArrayList<Class<?>> classes = new ArrayList<>();
313
314 // The "default" domain. Set as the default ProtectionDomain on newly
315 // created classes.
316 private final ProtectionDomain defaultDomain =
317 new ProtectionDomain(new CodeSource(null, (Certificate[]) null),
318 null, this, null);
319
320 // Invoked by the VM to record every loaded class with this loader.
321 void addClass(Class<?> c) {
322 synchronized (classes) {
323 classes.add(c);
324 }
325 }
326
327 // The packages defined in this class loader. Each package name is
328 // mapped to its corresponding NamedPackage object.
329 //
330 // The value is a Package object if ClassLoader::definePackage,
331 // Class::getPackage, ClassLoader::getDefinePackage(s) or
332 // Package::getPackage(s) method is called to define it.
333 // Otherwise, the value is a NamedPackage object.
334 private final ConcurrentHashMap<String, NamedPackage> packages
335 = new ConcurrentHashMap<>();
336
337 /*
338 * Returns a named package for the given module.
339 */
340 private NamedPackage getNamedPackage(String pn, Module m) {
341 NamedPackage p = packages.get(pn);
342 if (p == null) {
343 p = new NamedPackage(pn, m);
344
345 NamedPackage value = packages.putIfAbsent(pn, p);
346 if (value != null) {
347 // Package object already be defined for the named package
348 p = value;
349 // if definePackage is called by this class loader to define
350 // a package in a named module, this will return Package
351 // object of the same name. Package object may contain
352 // unexpected information but it does not impact the runtime.
353 // this assertion may be helpful for troubleshooting
354 assert value.module() == m;
355 }
356 }
357 return p;
358 }
359
360 private static Void checkCreateClassLoader() {
361 return checkCreateClassLoader(null);
362 }
363
364 private static Void checkCreateClassLoader(String name) {
365 if (name != null && name.isEmpty()) {
366 throw new IllegalArgumentException("name must be non-empty or null");
367 }
368
369 SecurityManager security = System.getSecurityManager();
370 if (security != null) {
371 security.checkCreateClassLoader();
372 }
373 return null;
374 }
375
376 private ClassLoader(Void unused, String name, ClassLoader parent) {
377 this.name = name;
378 this.parent = parent;
379 this.unnamedModule = new Module(this);
380 if (ParallelLoaders.isRegistered(this.getClass())) {
381 parallelLockMap = new ConcurrentHashMap<>();
382 assertionLock = new Object();
383 } else {
384 // no finer-grained lock; lock on the classloader instance
385 parallelLockMap = null;
386 assertionLock = this;
387 }
388 this.package2certs = new ConcurrentHashMap<>();
389 this.nameAndId = nameAndId(this);
390 }
391
392 /**
393 * If the defining loader has a name explicitly set then
394 * '<loader-name>' @<id>
395 * If the defining loader has no name then
396 * <qualified-class-name> @<id>
397 * If it's built-in loader then omit `@<id>` as there is only one instance.
398 */
399 private static String nameAndId(ClassLoader ld) {
400 String nid = ld.getName() != null ? "\'" + ld.getName() + "\'"
401 : ld.getClass().getName();
402 if (!(ld instanceof BuiltinClassLoader)) {
403 String id = Integer.toHexString(System.identityHashCode(ld));
404 nid = nid + " @" + id;
405 }
406 return nid;
407 }
408
409 /**
410 * Creates a new class loader of the specified name and using the
411 * specified parent class loader for delegation.
412 *
413 * @apiNote If the parent is specified as {@code null} (for the
414 * bootstrap class loader) then there is no guarantee that all platform
415 * classes are visible.
416 *
417 * @param name class loader name; or {@code null} if not named
418 * @param parent the parent class loader
419 *
420 * @throws IllegalArgumentException if the given name is empty.
421 *
422 * @throws SecurityException
423 * If a security manager exists and its
424 * {@link SecurityManager#checkCreateClassLoader()}
425 * method doesn't allow creation of a new class loader.
426 *
427 * @since 9
428 * @spec JPMS
429 */
430 protected ClassLoader(String name, ClassLoader parent) {
431 this(checkCreateClassLoader(name), name, parent);
432 }
433
434 /**
435 * Creates a new class loader using the specified parent class loader for
436 * delegation.
437 *
438 * <p> If there is a security manager, its {@link
439 * SecurityManager#checkCreateClassLoader() checkCreateClassLoader} method
440 * is invoked. This may result in a security exception. </p>
441 *
442 * @apiNote If the parent is specified as {@code null} (for the
443 * bootstrap class loader) then there is no guarantee that all platform
444 * classes are visible.
445 *
446 * @param parent
447 * The parent class loader
448 *
449 * @throws SecurityException
450 * If a security manager exists and its
451 * {@code checkCreateClassLoader} method doesn't allow creation
452 * of a new class loader.
453 *
454 * @since 1.2
455 */
456 protected ClassLoader(ClassLoader parent) {
457 this(checkCreateClassLoader(), null, parent);
458 }
459
460 /**
461 * Creates a new class loader using the {@code ClassLoader} returned by
462 * the method {@link #getSystemClassLoader()
463 * getSystemClassLoader()} as the parent class loader.
464 *
465 * <p> If there is a security manager, its {@link
466 * SecurityManager#checkCreateClassLoader()
467 * checkCreateClassLoader} method is invoked. This may result in
468 * a security exception. </p>
469 *
470 * @throws SecurityException
471 * If a security manager exists and its
472 * {@code checkCreateClassLoader} method doesn't allow creation
473 * of a new class loader.
474 */
475 protected ClassLoader() {
476 this(checkCreateClassLoader(), null, getSystemClassLoader());
477 }
478
479 /**
480 * Returns the name of this class loader or {@code null} if
481 * this class loader is not named.
482 *
483 * @apiNote This method is non-final for compatibility. If this
484 * method is overridden, this method must return the same name
485 * as specified when this class loader was instantiated.
486 *
487 * @return name of this class loader; or {@code null} if
488 * this class loader is not named.
489 *
490 * @since 9
491 * @spec JPMS
492 */
493 public String getName() {
494 return name;
495 }
496
497 // package-private used by StackTraceElement to avoid
498 // calling the overrideable getName method
499 final String name() {
500 return name;
501 }
502
503 // -- Class --
504
505 /**
506 * Loads the class with the specified <a href="#binary-name">binary name</a>.
507 * This method searches for classes in the same manner as the {@link
508 * #loadClass(String, boolean)} method. It is invoked by the Java virtual
509 * machine to resolve class references. Invoking this method is equivalent
510 * to invoking {@link #loadClass(String, boolean) loadClass(name,
511 * false)}.
512 *
513 * @param name
514 * The <a href="#binary-name">binary name</a> of the class
515 *
516 * @return The resulting {@code Class} object
517 *
518 * @throws ClassNotFoundException
519 * If the class was not found
520 */
521 public Class<?> loadClass(String name) throws ClassNotFoundException {
522 return loadClass(name, false);
523 }
524
525 /**
526 * Loads the class with the specified <a href="#binary-name">binary name</a>. The
527 * default implementation of this method searches for classes in the
528 * following order:
529 *
530 * <ol>
531 *
532 * <li><p> Invoke {@link #findLoadedClass(String)} to check if the class
533 * has already been loaded. </p></li>
534 *
535 * <li><p> Invoke the {@link #loadClass(String) loadClass} method
536 * on the parent class loader. If the parent is {@code null} the class
537 * loader built into the virtual machine is used, instead. </p></li>
538 *
539 * <li><p> Invoke the {@link #findClass(String)} method to find the
540 * class. </p></li>
541 *
542 * </ol>
543 *
544 * <p> If the class was found using the above steps, and the
545 * {@code resolve} flag is true, this method will then invoke the {@link
546 * #resolveClass(Class)} method on the resulting {@code Class} object.
547 *
548 * <p> Subclasses of {@code ClassLoader} are encouraged to override {@link
549 * #findClass(String)}, rather than this method. </p>
550 *
551 * <p> Unless overridden, this method synchronizes on the result of
552 * {@link #getClassLoadingLock getClassLoadingLock} method
553 * during the entire class loading process.
554 *
555 * @param name
556 * The <a href="#binary-name">binary name</a> of the class
557 *
558 * @param resolve
559 * If {@code true} then resolve the class
560 *
561 * @return The resulting {@code Class} object
562 *
563 * @throws ClassNotFoundException
564 * If the class could not be found
565 */
566 protected Class<?> loadClass(String name, boolean resolve)
567 throws ClassNotFoundException
568 {
569 synchronized (getClassLoadingLock(name)) {
570 // First, check if the class has already been loaded
571 Class<?> c = findLoadedClass(name);
572 if (c == null) {
573 long t0 = System.nanoTime();
574 try {
575 if (parent != null) {
576 c = parent.loadClass(name, false);
577 } else {
578 c = findBootstrapClassOrNull(name);
579 }
580 } catch (ClassNotFoundException e) {
581 // ClassNotFoundException thrown if class not found
582 // from the non-null parent class loader
583 }
584
585 if (c == null) {
586 // If still not found, then invoke findClass in order
587 // to find the class.
588 long t1 = System.nanoTime();
589 c = findClass(name);
590
591 // this is the defining class loader; record the stats
592 PerfCounter.getParentDelegationTime().addTime(t1 - t0);
593 PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
594 PerfCounter.getFindClasses().increment();
595 }
596 }
597 if (resolve) {
598 resolveClass(c);
599 }
600 return c;
601 }
602 }
603
604 /**
605 * Loads the class with the specified <a href="#binary-name">binary name</a>
606 * in a module defined to this class loader. This method returns {@code null}
607 * if the class could not be found.
608 *
609 * @apiNote This method does not delegate to the parent class loader.
610 *
611 * @implSpec The default implementation of this method searches for classes
612 * in the following order:
613 *
614 * <ol>
615 * <li>Invoke {@link #findLoadedClass(String)} to check if the class
616 * has already been loaded.</li>
617 * <li>Invoke the {@link #findClass(String, String)} method to find the
618 * class in the given module.</li>
619 * </ol>
620 *
621 * @param module
622 * The module
623 * @param name
624 * The <a href="#binary-name">binary name</a> of the class
625 *
626 * @return The resulting {@code Class} object in a module defined by
627 * this class loader, or {@code null} if the class could not be found.
628 */
629 final Class<?> loadClass(Module module, String name) {
630 synchronized (getClassLoadingLock(name)) {
631 // First, check if the class has already been loaded
632 Class<?> c = findLoadedClass(name);
633 if (c == null) {
634 c = findClass(module.getName(), name);
635 }
636 if (c != null && c.getModule() == module) {
637 return c;
638 } else {
639 return null;
640 }
641 }
642 }
643
644 /**
645 * Returns the lock object for class loading operations.
646 * For backward compatibility, the default implementation of this method
647 * behaves as follows. If this ClassLoader object is registered as
648 * parallel capable, the method returns a dedicated object associated
649 * with the specified class name. Otherwise, the method returns this
650 * ClassLoader object.
651 *
652 * @param className
653 * The name of the to-be-loaded class
654 *
655 * @return the lock for class loading operations
656 *
657 * @throws NullPointerException
658 * If registered as parallel capable and {@code className} is null
659 *
660 * @see #loadClass(String, boolean)
661 *
662 * @since 1.7
663 */
664 protected Object getClassLoadingLock(String className) {
665 Object lock = this;
666 if (parallelLockMap != null) {
667 Object newLock = new Object();
668 lock = parallelLockMap.putIfAbsent(className, newLock);
669 if (lock == null) {
670 lock = newLock;
671 }
672 }
673 return lock;
674 }
675
676 // Invoked by the VM after loading class with this loader.
677 private void checkPackageAccess(Class<?> cls, ProtectionDomain pd) {
678 final SecurityManager sm = System.getSecurityManager();
679 if (sm != null) {
680 if (ReflectUtil.isNonPublicProxyClass(cls)) {
681 for (Class<?> intf: cls.getInterfaces()) {
682 checkPackageAccess(intf, pd);
683 }
684 return;
685 }
686
687 final String packageName = cls.getPackageName();
688 if (!packageName.isEmpty()) {
689 AccessController.doPrivileged(new PrivilegedAction<>() {
690 public Void run() {
691 sm.checkPackageAccess(packageName);
692 return null;
693 }
694 }, new AccessControlContext(new ProtectionDomain[] {pd}));
695 }
696 }
697 }
698
699 /**
700 * Finds the class with the specified <a href="#binary-name">binary name</a>.
701 * This method should be overridden by class loader implementations that
702 * follow the delegation model for loading classes, and will be invoked by
703 * the {@link #loadClass loadClass} method after checking the
704 * parent class loader for the requested class.
705 *
706 * @implSpec The default implementation throws {@code ClassNotFoundException}.
707 *
708 * @param name
709 * The <a href="#binary-name">binary name</a> of the class
710 *
711 * @return The resulting {@code Class} object
712 *
713 * @throws ClassNotFoundException
714 * If the class could not be found
715 *
716 * @since 1.2
717 */
718 protected Class<?> findClass(String name) throws ClassNotFoundException {
719 throw new ClassNotFoundException(name);
720 }
721
722 /**
723 * Finds the class with the given <a href="#binary-name">binary name</a>
724 * in a module defined to this class loader.
725 * Class loader implementations that support loading from modules
726 * should override this method.
727 *
728 * @apiNote This method returns {@code null} rather than throwing
729 * {@code ClassNotFoundException} if the class could not be found.
730 *
731 * @implSpec The default implementation attempts to find the class by
732 * invoking {@link #findClass(String)} when the {@code moduleName} is
733 * {@code null}. It otherwise returns {@code null}.
734 *
735 * @param moduleName
736 * The module name; or {@code null} to find the class in the
737 * {@linkplain #getUnnamedModule() unnamed module} for this
738 * class loader
739 * @param name
740 * The <a href="#binary-name">binary name</a> of the class
741 *
742 * @return The resulting {@code Class} object, or {@code null}
743 * if the class could not be found.
744 *
745 * @since 9
746 * @spec JPMS
747 */
748 protected Class<?> findClass(String moduleName, String name) {
749 if (moduleName == null) {
750 try {
751 return findClass(name);
752 } catch (ClassNotFoundException ignore) { }
753 }
754 return null;
755 }
756
757
758 /**
759 * Converts an array of bytes into an instance of class {@code Class}.
760 * Before the {@code Class} can be used it must be resolved. This method
761 * is deprecated in favor of the version that takes a <a
762 * href="#binary-name">binary name</a> as its first argument, and is more secure.
763 *
764 * @param b
765 * The bytes that make up the class data. The bytes in positions
766 * {@code off} through {@code off+len-1} should have the format
767 * of a valid class file as defined by
768 * <cite>The Java Virtual Machine Specification</cite>.
769 *
770 * @param off
771 * The start offset in {@code b} of the class data
772 *
773 * @param len
774 * The length of the class data
775 *
776 * @return The {@code Class} object that was created from the specified
777 * class data
778 *
779 * @throws ClassFormatError
780 * If the data did not contain a valid class
781 *
782 * @throws IndexOutOfBoundsException
783 * If either {@code off} or {@code len} is negative, or if
784 * {@code off+len} is greater than {@code b.length}.
785 *
786 * @throws SecurityException
787 * If an attempt is made to add this class to a package that
788 * contains classes that were signed by a different set of
789 * certificates than this class, or if an attempt is made
790 * to define a class in a package with a fully-qualified name
791 * that starts with "{@code java.}".
792 *
793 * @see #loadClass(String, boolean)
794 * @see #resolveClass(Class)
795 *
796 * @deprecated Replaced by {@link #defineClass(String, byte[], int, int)
797 * defineClass(String, byte[], int, int)}
798 */
799 @Deprecated(since="1.1")
800 protected final Class<?> defineClass(byte[] b, int off, int len)
801 throws ClassFormatError
802 {
803 return defineClass(null, b, off, len, null);
804 }
805
806 /**
807 * Converts an array of bytes into an instance of class {@code Class}.
808 * Before the {@code Class} can be used it must be resolved.
809 *
810 * <p> This method assigns a default {@link java.security.ProtectionDomain
811 * ProtectionDomain} to the newly defined class. The
812 * {@code ProtectionDomain} is effectively granted the same set of
813 * permissions returned when {@link
814 * java.security.Policy#getPermissions(java.security.CodeSource)
815 * Policy.getPolicy().getPermissions(new CodeSource(null, null))}
816 * is invoked. The default protection domain is created on the first invocation
817 * of {@link #defineClass(String, byte[], int, int) defineClass},
818 * and re-used on subsequent invocations.
819 *
820 * <p> To assign a specific {@code ProtectionDomain} to the class, use
821 * the {@link #defineClass(String, byte[], int, int,
822 * java.security.ProtectionDomain) defineClass} method that takes a
823 * {@code ProtectionDomain} as one of its arguments. </p>
824 *
825 * <p>
826 * This method defines a package in this class loader corresponding to the
827 * package of the {@code Class} (if such a package has not already been defined
828 * in this class loader). The name of the defined package is derived from
829 * the <a href="#binary-name">binary name</a> of the class specified by
830 * the byte array {@code b}.
831 * Other properties of the defined package are as specified by {@link Package}.
832 *
833 * @param name
834 * The expected <a href="#binary-name">binary name</a> of the class, or
835 * {@code null} if not known
836 *
837 * @param b
838 * The bytes that make up the class data. The bytes in positions
839 * {@code off} through {@code off+len-1} should have the format
840 * of a valid class file as defined by
841 * <cite>The Java Virtual Machine Specification</cite>.
842 *
843 * @param off
844 * The start offset in {@code b} of the class data
845 *
846 * @param len
847 * The length of the class data
848 *
849 * @return The {@code Class} object that was created from the specified
850 * class data.
851 *
852 * @throws ClassFormatError
853 * If the data did not contain a valid class
854 *
855 * @throws IndexOutOfBoundsException
856 * If either {@code off} or {@code len} is negative, or if
857 * {@code off+len} is greater than {@code b.length}.
858 *
859 * @throws SecurityException
860 * If an attempt is made to add this class to a package that
861 * contains classes that were signed by a different set of
862 * certificates than this class (which is unsigned), or if
863 * {@code name} begins with "{@code java.}".
864 *
865 * @see #loadClass(String, boolean)
866 * @see #resolveClass(Class)
867 * @see java.security.CodeSource
868 * @see java.security.SecureClassLoader
869 *
870 * @since 1.1
871 * @revised 9
872 * @spec JPMS
873 */
874 protected final Class<?> defineClass(String name, byte[] b, int off, int len)
875 throws ClassFormatError
876 {
877 return defineClass(name, b, off, len, null);
878 }
879
880 /* Determine protection domain, and check that:
881 - not define java.* class,
882 - signer of this class matches signers for the rest of the classes in
883 package.
884 */
885 private ProtectionDomain preDefineClass(String name,
886 ProtectionDomain pd)
887 {
888 if (!checkName(name))
889 throw new NoClassDefFoundError("IllegalName: " + name);
890
891 // Note: Checking logic in java.lang.invoke.MemberName.checkForTypeAlias
892 // relies on the fact that spoofing is impossible if a class has a name
893 // of the form "java.*"
894 if ((name != null) && name.startsWith("java.")
895 && this != getBuiltinPlatformClassLoader()) {
896 throw new SecurityException
897 ("Prohibited package name: " +
898 name.substring(0, name.lastIndexOf('.')));
899 }
900 if (pd == null) {
901 pd = defaultDomain;
902 }
903
904 if (name != null) {
905 checkCerts(name, pd.getCodeSource());
906 }
907
908 return pd;
909 }
910
911 private String defineClassSourceLocation(ProtectionDomain pd) {
912 CodeSource cs = pd.getCodeSource();
913 String source = null;
914 if (cs != null && cs.getLocation() != null) {
915 source = cs.getLocation().toString();
916 }
917 return source;
918 }
919
920 private void postDefineClass(Class<?> c, ProtectionDomain pd) {
921 // define a named package, if not present
922 getNamedPackage(c.getPackageName(), c.getModule());
923
924 if (pd.getCodeSource() != null) {
925 Certificate certs[] = pd.getCodeSource().getCertificates();
926 if (certs != null)
927 setSigners(c, certs);
928 }
929 }
930
931 /**
932 * Converts an array of bytes into an instance of class {@code Class},
933 * with a given {@code ProtectionDomain}.
934 *
935 * <p> If the given {@code ProtectionDomain} is {@code null},
936 * then a default protection domain will be assigned to the class as specified
937 * in the documentation for {@link #defineClass(String, byte[], int, int)}.
938 * Before the class can be used it must be resolved.
939 *
940 * <p> The first class defined in a package determines the exact set of
941 * certificates that all subsequent classes defined in that package must
942 * contain. The set of certificates for a class is obtained from the
943 * {@link java.security.CodeSource CodeSource} within the
944 * {@code ProtectionDomain} of the class. Any classes added to that
945 * package must contain the same set of certificates or a
946 * {@code SecurityException} will be thrown. Note that if
947 * {@code name} is {@code null}, this check is not performed.
948 * You should always pass in the <a href="#binary-name">binary name</a> of the
949 * class you are defining as well as the bytes. This ensures that the
950 * class you are defining is indeed the class you think it is.
951 *
952 * <p> If the specified {@code name} begins with "{@code java.}", it can
953 * only be defined by the {@linkplain #getPlatformClassLoader()
954 * platform class loader} or its ancestors; otherwise {@code SecurityException}
955 * will be thrown. If {@code name} is not {@code null}, it must be equal to
956 * the <a href="#binary-name">binary name</a> of the class
957 * specified by the byte array {@code b}, otherwise a {@link
958 * NoClassDefFoundError NoClassDefFoundError} will be thrown.
959 *
960 * <p> This method defines a package in this class loader corresponding to the
961 * package of the {@code Class} (if such a package has not already been defined
962 * in this class loader). The name of the defined package is derived from
963 * the <a href="#binary-name">binary name</a> of the class specified by
964 * the byte array {@code b}.
965 * Other properties of the defined package are as specified by {@link Package}.
966 *
967 * @param name
968 * The expected <a href="#binary-name">binary name</a> of the class, or
969 * {@code null} if not known
970 *
971 * @param b
972 * The bytes that make up the class data. The bytes in positions
973 * {@code off} through {@code off+len-1} should have the format
974 * of a valid class file as defined by
975 * <cite>The Java Virtual Machine Specification</cite>.
976 *
977 * @param off
978 * The start offset in {@code b} of the class data
979 *
980 * @param len
981 * The length of the class data
982 *
983 * @param protectionDomain
984 * The {@code ProtectionDomain} of the class
985 *
986 * @return The {@code Class} object created from the data,
987 * and {@code ProtectionDomain}.
988 *
989 * @throws ClassFormatError
990 * If the data did not contain a valid class
991 *
992 * @throws NoClassDefFoundError
993 * If {@code name} is not {@code null} and not equal to the
994 * <a href="#binary-name">binary name</a> of the class specified by {@code b}
995 *
996 * @throws IndexOutOfBoundsException
997 * If either {@code off} or {@code len} is negative, or if
998 * {@code off+len} is greater than {@code b.length}.
999 *
1000 * @throws SecurityException
1001 * If an attempt is made to add this class to a package that
1002 * contains classes that were signed by a different set of
1003 * certificates than this class, or if {@code name} begins with
1004 * "{@code java.}" and this class loader is not the platform
1005 * class loader or its ancestor.
1006 *
1007 * @revised 9
1008 * @spec JPMS
1009 */
1010 protected final Class<?> defineClass(String name, byte[] b, int off, int len,
1011 ProtectionDomain protectionDomain)
1012 throws ClassFormatError
1013 {
1014 protectionDomain = preDefineClass(name, protectionDomain);
1015 String source = defineClassSourceLocation(protectionDomain);
1016 Class<?> c = defineClass1(this, name, b, off, len, protectionDomain, source);
1017 postDefineClass(c, protectionDomain);
1018 return c;
1019 }
1020
1021 /**
1022 * Converts a {@link java.nio.ByteBuffer ByteBuffer} into an instance
1023 * of class {@code Class}, with the given {@code ProtectionDomain}.
1024 * If the given {@code ProtectionDomain} is {@code null}, then a default
1025 * protection domain will be assigned to the class as
1026 * specified in the documentation for {@link #defineClass(String, byte[],
1027 * int, int)}. Before the class can be used it must be resolved.
1028 *
1029 * <p>The rules about the first class defined in a package determining the
1030 * set of certificates for the package, the restrictions on class names,
1031 * and the defined package of the class
1032 * are identical to those specified in the documentation for {@link
1033 * #defineClass(String, byte[], int, int, ProtectionDomain)}.
1034 *
1035 * <p> An invocation of this method of the form
1036 * <i>cl</i>{@code .defineClass(}<i>name</i>{@code ,}
1037 * <i>bBuffer</i>{@code ,} <i>pd</i>{@code )} yields exactly the same
1038 * result as the statements
1039 *
1040 *<p> <code>
1041 * ...<br>
1042 * byte[] temp = new byte[bBuffer.{@link
1043 * java.nio.ByteBuffer#remaining remaining}()];<br>
1044 * bBuffer.{@link java.nio.ByteBuffer#get(byte[])
1045 * get}(temp);<br>
1046 * return {@link #defineClass(String, byte[], int, int, ProtectionDomain)
1047 * cl.defineClass}(name, temp, 0,
1048 * temp.length, pd);<br>
1049 * </code></p>
1050 *
1051 * @param name
1052 * The expected <a href="#binary-name">binary name</a>. of the class, or
1053 * {@code null} if not known
1054 *
1055 * @param b
1056 * The bytes that make up the class data. The bytes from positions
1057 * {@code b.position()} through {@code b.position() + b.limit() -1
1058 * } should have the format of a valid class file as defined by
1059 * <cite>The Java Virtual Machine Specification</cite>.
1060 *
1061 * @param protectionDomain
1062 * The {@code ProtectionDomain} of the class, or {@code null}.
1063 *
1064 * @return The {@code Class} object created from the data,
1065 * and {@code ProtectionDomain}.
1066 *
1067 * @throws ClassFormatError
1068 * If the data did not contain a valid class.
1069 *
1070 * @throws NoClassDefFoundError
1071 * If {@code name} is not {@code null} and not equal to the
1072 * <a href="#binary-name">binary name</a> of the class specified by {@code b}
1073 *
1074 * @throws SecurityException
1075 * If an attempt is made to add this class to a package that
1076 * contains classes that were signed by a different set of
1077 * certificates than this class, or if {@code name} begins with
1078 * "{@code java.}".
1079 *
1080 * @see #defineClass(String, byte[], int, int, ProtectionDomain)
1081 *
1082 * @since 1.5
1083 * @revised 9
1084 * @spec JPMS
1085 */
1086 protected final Class<?> defineClass(String name, java.nio.ByteBuffer b,
1087 ProtectionDomain protectionDomain)
1088 throws ClassFormatError
1089 {
1090 int len = b.remaining();
1091
1092 // Use byte[] if not a direct ByteBuffer:
1093 if (!b.isDirect()) {
1094 if (b.hasArray()) {
1095 return defineClass(name, b.array(),
1096 b.position() + b.arrayOffset(), len,
1097 protectionDomain);
1098 } else {
1099 // no array, or read-only array
1100 byte[] tb = new byte[len];
1101 b.get(tb); // get bytes out of byte buffer.
1102 return defineClass(name, tb, 0, len, protectionDomain);
1103 }
1104 }
1105
1106 protectionDomain = preDefineClass(name, protectionDomain);
1107 String source = defineClassSourceLocation(protectionDomain);
1108 Class<?> c = defineClass2(this, name, b, b.position(), len, protectionDomain, source);
1109 postDefineClass(c, protectionDomain);
1110 return c;
1111 }
1112
1113 static native Class<?> defineClass1(ClassLoader loader, String name, byte[] b, int off, int len,
1114 ProtectionDomain pd, String source);
1115
1116 static native Class<?> defineClass2(ClassLoader loader, String name, java.nio.ByteBuffer b,
1117 int off, int len, ProtectionDomain pd,
1118 String source);
1119
1120 /**
1121 * Defines a class of the given flags via Lookup.defineClass.
1122 *
1123 * @param loader the defining loader
1124 * @param lookup nest host of the Class to be defined
1125 * @param name the binary name or {@code null} if not findable
1126 * @param b class bytes
1127 * @param off the start offset in {@code b} of the class bytes
1128 * @param len the length of the class bytes
1129 * @param pd protection domain
1130 * @param initialize initialize the class
1131 * @param flags flags
1132 * @param classData class data
1133 */
1134 static native Class<?> defineClass0(ClassLoader loader,
1135 Class<?> lookup,
1136 String name,
1137 byte[] b, int off, int len,
1138 ProtectionDomain pd,
1139 boolean initialize,
1140 int flags,
1141 Object classData);
1142
1143 // true if the name is null or has the potential to be a valid binary name
1144 private boolean checkName(String name) {
1145 if ((name == null) || (name.isEmpty()))
1146 return true;
1147 if ((name.indexOf('/') != -1) || (name.charAt(0) == '['))
1148 return false;
1149 return true;
1150 }
1151
1152 private void checkCerts(String name, CodeSource cs) {
1153 int i = name.lastIndexOf('.');
1154 String pname = (i == -1) ? "" : name.substring(0, i);
1155
1156 Certificate[] certs = null;
1157 if (cs != null) {
1158 certs = cs.getCertificates();
1159 }
1160 certs = certs == null ? nocerts : certs;
1161 Certificate[] pcerts = package2certs.putIfAbsent(pname, certs);
1162 if (pcerts != null && !compareCerts(pcerts, certs)) {
1163 throw new SecurityException("class \"" + name
1164 + "\"'s signer information does not match signer information"
1165 + " of other classes in the same package");
1166 }
1167 }
1168
1169 /**
1170 * check to make sure the certs for the new class (certs) are the same as
1171 * the certs for the first class inserted in the package (pcerts)
1172 */
1173 private boolean compareCerts(Certificate[] pcerts, Certificate[] certs) {
1174 // empty array fast-path
1175 if (certs.length == 0)
1176 return pcerts.length == 0;
1177
1178 // the length must be the same at this point
1179 if (certs.length != pcerts.length)
1180 return false;
1181
1182 // go through and make sure all the certs in one array
1183 // are in the other and vice-versa.
1184 boolean match;
1185 for (Certificate cert : certs) {
1186 match = false;
1187 for (Certificate pcert : pcerts) {
1188 if (cert.equals(pcert)) {
1189 match = true;
1190 break;
1191 }
1192 }
1193 if (!match) return false;
1194 }
1195
1196 // now do the same for pcerts
1197 for (Certificate pcert : pcerts) {
1198 match = false;
1199 for (Certificate cert : certs) {
1200 if (pcert.equals(cert)) {
1201 match = true;
1202 break;
1203 }
1204 }
1205 if (!match) return false;
1206 }
1207
1208 return true;
1209 }
1210
1211 /**
1212 * Links the specified class. This (misleadingly named) method may be
1213 * used by a class loader to link a class. If the class {@code c} has
1214 * already been linked, then this method simply returns. Otherwise, the
1215 * class is linked as described in the "Execution" chapter of
1216 * <cite>The Java Language Specification</cite>.
1217 *
1218 * @param c
1219 * The class to link
1220 *
1221 * @throws NullPointerException
1222 * If {@code c} is {@code null}.
1223 *
1224 * @see #defineClass(String, byte[], int, int)
1225 */
1226 protected final void resolveClass(Class<?> c) {
1227 if (c == null) {
1228 throw new NullPointerException();
1229 }
1230 }
1231
1232 /**
1233 * Finds a class with the specified <a href="#binary-name">binary name</a>,
1234 * loading it if necessary.
1235 *
1236 * <p> This method loads the class through the system class loader (see
1237 * {@link #getSystemClassLoader()}). The {@code Class} object returned
1238 * might have more than one {@code ClassLoader} associated with it.
1239 * Subclasses of {@code ClassLoader} need not usually invoke this method,
1240 * because most class loaders need to override just {@link
1241 * #findClass(String)}. </p>
1242 *
1243 * @param name
1244 * The <a href="#binary-name">binary name</a> of the class
1245 *
1246 * @return The {@code Class} object for the specified {@code name}
1247 *
1248 * @throws ClassNotFoundException
1249 * If the class could not be found
1250 *
1251 * @see #ClassLoader(ClassLoader)
1252 * @see #getParent()
1253 */
1254 protected final Class<?> findSystemClass(String name)
1255 throws ClassNotFoundException
1256 {
1257 return getSystemClassLoader().loadClass(name);
1258 }
1259
1260 /**
1261 * Returns a class loaded by the bootstrap class loader;
1262 * or return null if not found.
1263 */
1264 Class<?> findBootstrapClassOrNull(String name) {
1265 if (!checkName(name)) return null;
1266
1267 return findBootstrapClass(name);
1268 }
1269
1270 // return null if not found
1271 private native Class<?> findBootstrapClass(String name);
1272
1273 /**
1274 * Returns the class with the given <a href="#binary-name">binary name</a> if this
1275 * loader has been recorded by the Java virtual machine as an initiating
1276 * loader of a class with that <a href="#binary-name">binary name</a>. Otherwise
1277 * {@code null} is returned.
1278 *
1279 * @param name
1280 * The <a href="#binary-name">binary name</a> of the class
1281 *
1282 * @return The {@code Class} object, or {@code null} if the class has
1283 * not been loaded
1284 *
1285 * @since 1.1
1286 */
1287 protected final Class<?> findLoadedClass(String name) {
1288 if (!checkName(name))
1289 return null;
1290 return findLoadedClass0(name);
1291 }
1292
1293 private final native Class<?> findLoadedClass0(String name);
1294
1295 /**
1296 * Sets the signers of a class. This should be invoked after defining a
1297 * class.
1298 *
1299 * @param c
1300 * The {@code Class} object
1301 *
1302 * @param signers
1303 * The signers for the class
1304 *
1305 * @since 1.1
1306 */
1307 protected final void setSigners(Class<?> c, Object[] signers) {
1308 c.setSigners(signers);
1309 }
1310
1311
1312 // -- Resources --
1313
1314 /**
1315 * Returns a URL to a resource in a module defined to this class loader.
1316 * Class loader implementations that support loading from modules
1317 * should override this method.
1318 *
1319 * @apiNote This method is the basis for the {@link
1320 * Class#getResource Class.getResource}, {@link Class#getResourceAsStream
1321 * Class.getResourceAsStream}, and {@link Module#getResourceAsStream
1322 * Module.getResourceAsStream} methods. It is not subject to the rules for
1323 * encapsulation specified by {@code Module.getResourceAsStream}.
1324 *
1325 * @implSpec The default implementation attempts to find the resource by
1326 * invoking {@link #findResource(String)} when the {@code moduleName} is
1327 * {@code null}. It otherwise returns {@code null}.
1328 *
1329 * @param moduleName
1330 * The module name; or {@code null} to find a resource in the
1331 * {@linkplain #getUnnamedModule() unnamed module} for this
1332 * class loader
1333 * @param name
1334 * The resource name
1335 *
1336 * @return A URL to the resource; {@code null} if the resource could not be
1337 * found, a URL could not be constructed to locate the resource,
1338 * access to the resource is denied by the security manager, or
1339 * there isn't a module of the given name defined to the class
1340 * loader.
1341 *
1342 * @throws IOException
1343 * If I/O errors occur
1344 *
1345 * @see java.lang.module.ModuleReader#find(String)
1346 * @since 9
1347 * @spec JPMS
1348 */
1349 protected URL findResource(String moduleName, String name) throws IOException {
1350 if (moduleName == null) {
1351 return findResource(name);
1352 } else {
1353 return null;
1354 }
1355 }
1356
1357 /**
1358 * Finds the resource with the given name. A resource is some data
1359 * (images, audio, text, etc) that can be accessed by class code in a way
1360 * that is independent of the location of the code.
1361 *
1362 * <p> The name of a resource is a '{@code /}'-separated path name that
1363 * identifies the resource. </p>
1364 *
1365 * <p> Resources in named modules are subject to the encapsulation rules
1366 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1367 * Additionally, and except for the special case where the resource has a
1368 * name ending with "{@code .class}", this method will only find resources in
1369 * packages of named modules when the package is {@link Module#isOpen(String)
1370 * opened} unconditionally (even if the caller of this method is in the
1371 * same module as the resource). </p>
1372 *
1373 * @implSpec The default implementation will first search the parent class
1374 * loader for the resource; if the parent is {@code null} the path of the
1375 * class loader built into the virtual machine is searched. If not found,
1376 * this method will invoke {@link #findResource(String)} to find the resource.
1377 *
1378 * @apiNote Where several modules are defined to the same class loader,
1379 * and where more than one module contains a resource with the given name,
1380 * then the ordering that modules are searched is not specified and may be
1381 * very unpredictable.
1382 * When overriding this method it is recommended that an implementation
1383 * ensures that any delegation is consistent with the {@link
1384 * #getResources(java.lang.String) getResources(String)} method.
1385 *
1386 * @param name
1387 * The resource name
1388 *
1389 * @return {@code URL} object for reading the resource; {@code null} if
1390 * the resource could not be found, a {@code URL} could not be
1391 * constructed to locate the resource, the resource is in a package
1392 * that is not opened unconditionally, or access to the resource is
1393 * denied by the security manager.
1394 *
1395 * @throws NullPointerException If {@code name} is {@code null}
1396 *
1397 * @since 1.1
1398 * @revised 9
1399 * @spec JPMS
1400 */
1401 public URL getResource(String name) {
1402 Objects.requireNonNull(name);
1403 URL url;
1404 if (parent != null) {
1405 url = parent.getResource(name);
1406 } else {
1407 url = BootLoader.findResource(name);
1408 }
1409 if (url == null) {
1410 url = findResource(name);
1411 }
1412 return url;
1413 }
1414
1415 /**
1416 * Finds all the resources with the given name. A resource is some data
1417 * (images, audio, text, etc) that can be accessed by class code in a way
1418 * that is independent of the location of the code.
1419 *
1420 * <p> The name of a resource is a {@code /}-separated path name that
1421 * identifies the resource. </p>
1422 *
1423 * <p> Resources in named modules are subject to the encapsulation rules
1424 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1425 * Additionally, and except for the special case where the resource has a
1426 * name ending with "{@code .class}", this method will only find resources in
1427 * packages of named modules when the package is {@link Module#isOpen(String)
1428 * opened} unconditionally (even if the caller of this method is in the
1429 * same module as the resource). </p>
1430 *
1431 * @implSpec The default implementation will first search the parent class
1432 * loader for the resource; if the parent is {@code null} the path of the
1433 * class loader built into the virtual machine is searched. It then
1434 * invokes {@link #findResources(String)} to find the resources with the
1435 * name in this class loader. It returns an enumeration whose elements
1436 * are the URLs found by searching the parent class loader followed by
1437 * the elements found with {@code findResources}.
1438 *
1439 * @apiNote Where several modules are defined to the same class loader,
1440 * and where more than one module contains a resource with the given name,
1441 * then the ordering is not specified and may be very unpredictable.
1442 * When overriding this method it is recommended that an
1443 * implementation ensures that any delegation is consistent with the {@link
1444 * #getResource(java.lang.String) getResource(String)} method. This should
1445 * ensure that the first element returned by the Enumeration's
1446 * {@code nextElement} method is the same resource that the
1447 * {@code getResource(String)} method would return.
1448 *
1449 * @param name
1450 * The resource name
1451 *
1452 * @return An enumeration of {@link java.net.URL URL} objects for the
1453 * resource. If no resources could be found, the enumeration will
1454 * be empty. Resources for which a {@code URL} cannot be
1455 * constructed, are in a package that is not opened
1456 * unconditionally, or access to the resource is denied by the
1457 * security manager, are not returned in the enumeration.
1458 *
1459 * @throws IOException
1460 * If I/O errors occur
1461 * @throws NullPointerException If {@code name} is {@code null}
1462 *
1463 * @since 1.2
1464 * @revised 9
1465 * @spec JPMS
1466 */
1467 public Enumeration<URL> getResources(String name) throws IOException {
1468 Objects.requireNonNull(name);
1469 @SuppressWarnings("unchecked")
1470 Enumeration<URL>[] tmp = (Enumeration<URL>[]) new Enumeration<?>[2];
1471 if (parent != null) {
1472 tmp[0] = parent.getResources(name);
1473 } else {
1474 tmp[0] = BootLoader.findResources(name);
1475 }
1476 tmp[1] = findResources(name);
1477
1478 return new CompoundEnumeration<>(tmp);
1479 }
1480
1481 /**
1482 * Returns a stream whose elements are the URLs of all the resources with
1483 * the given name. A resource is some data (images, audio, text, etc) that
1484 * can be accessed by class code in a way that is independent of the
1485 * location of the code.
1486 *
1487 * <p> The name of a resource is a {@code /}-separated path name that
1488 * identifies the resource.
1489 *
1490 * <p> The resources will be located when the returned stream is evaluated.
1491 * If the evaluation results in an {@code IOException} then the I/O
1492 * exception is wrapped in an {@link UncheckedIOException} that is then
1493 * thrown.
1494 *
1495 * <p> Resources in named modules are subject to the encapsulation rules
1496 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1497 * Additionally, and except for the special case where the resource has a
1498 * name ending with "{@code .class}", this method will only find resources in
1499 * packages of named modules when the package is {@link Module#isOpen(String)
1500 * opened} unconditionally (even if the caller of this method is in the
1501 * same module as the resource). </p>
1502 *
1503 * @implSpec The default implementation invokes {@link #getResources(String)
1504 * getResources} to find all the resources with the given name and returns
1505 * a stream with the elements in the enumeration as the source.
1506 *
1507 * @apiNote When overriding this method it is recommended that an
1508 * implementation ensures that any delegation is consistent with the {@link
1509 * #getResource(java.lang.String) getResource(String)} method. This should
1510 * ensure that the first element returned by the stream is the same
1511 * resource that the {@code getResource(String)} method would return.
1512 *
1513 * @param name
1514 * The resource name
1515 *
1516 * @return A stream of resource {@link java.net.URL URL} objects. If no
1517 * resources could be found, the stream will be empty. Resources
1518 * for which a {@code URL} cannot be constructed, are in a package
1519 * that is not opened unconditionally, or access to the resource
1520 * is denied by the security manager, will not be in the stream.
1521 *
1522 * @throws NullPointerException If {@code name} is {@code null}
1523 *
1524 * @since 9
1525 */
1526 public Stream<URL> resources(String name) {
1527 Objects.requireNonNull(name);
1528 int characteristics = Spliterator.NONNULL | Spliterator.IMMUTABLE;
1529 Supplier<Spliterator<URL>> si = () -> {
1530 try {
1531 return Spliterators.spliteratorUnknownSize(
1532 getResources(name).asIterator(), characteristics);
1533 } catch (IOException e) {
1534 throw new UncheckedIOException(e);
1535 }
1536 };
1537 return StreamSupport.stream(si, characteristics, false);
1538 }
1539
1540 /**
1541 * Finds the resource with the given name. Class loader implementations
1542 * should override this method.
1543 *
1544 * <p> For resources in named modules then the method must implement the
1545 * rules for encapsulation specified in the {@code Module} {@link
1546 * Module#getResourceAsStream getResourceAsStream} method. Additionally,
1547 * it must not find non-"{@code .class}" resources in packages of named
1548 * modules unless the package is {@link Module#isOpen(String) opened}
1549 * unconditionally. </p>
1550 *
1551 * @implSpec The default implementation returns {@code null}.
1552 *
1553 * @param name
1554 * The resource name
1555 *
1556 * @return {@code URL} object for reading the resource; {@code null} if
1557 * the resource could not be found, a {@code URL} could not be
1558 * constructed to locate the resource, the resource is in a package
1559 * that is not opened unconditionally, or access to the resource is
1560 * denied by the security manager.
1561 *
1562 * @since 1.2
1563 * @revised 9
1564 * @spec JPMS
1565 */
1566 protected URL findResource(String name) {
1567 return null;
1568 }
1569
1570 /**
1571 * Returns an enumeration of {@link java.net.URL URL} objects
1572 * representing all the resources with the given name. Class loader
1573 * implementations should override this method.
1574 *
1575 * <p> For resources in named modules then the method must implement the
1576 * rules for encapsulation specified in the {@code Module} {@link
1577 * Module#getResourceAsStream getResourceAsStream} method. Additionally,
1578 * it must not find non-"{@code .class}" resources in packages of named
1579 * modules unless the package is {@link Module#isOpen(String) opened}
1580 * unconditionally. </p>
1581 *
1582 * @implSpec The default implementation returns an enumeration that
1583 * contains no elements.
1584 *
1585 * @param name
1586 * The resource name
1587 *
1588 * @return An enumeration of {@link java.net.URL URL} objects for
1589 * the resource. If no resources could be found, the enumeration
1590 * will be empty. Resources for which a {@code URL} cannot be
1591 * constructed, are in a package that is not opened unconditionally,
1592 * or access to the resource is denied by the security manager,
1593 * are not returned in the enumeration.
1594 *
1595 * @throws IOException
1596 * If I/O errors occur
1597 *
1598 * @since 1.2
1599 * @revised 9
1600 * @spec JPMS
1601 */
1602 protected Enumeration<URL> findResources(String name) throws IOException {
1603 return Collections.emptyEnumeration();
1604 }
1605
1606 /**
1607 * Registers the caller as
1608 * {@linkplain #isRegisteredAsParallelCapable() parallel capable}.
1609 * The registration succeeds if and only if all of the following
1610 * conditions are met:
1611 * <ol>
1612 * <li> no instance of the caller has been created</li>
1613 * <li> all of the super classes (except class Object) of the caller are
1614 * registered as parallel capable</li>
1615 * </ol>
1616 * <p>Note that once a class loader is registered as parallel capable, there
1617 * is no way to change it back.</p>
1618 *
1619 * @return {@code true} if the caller is successfully registered as
1620 * parallel capable and {@code false} if otherwise.
1621 *
1622 * @see #isRegisteredAsParallelCapable()
1623 *
1624 * @since 1.7
1625 */
1626 @CallerSensitive
1627 protected static boolean registerAsParallelCapable() {
1628 Class<? extends ClassLoader> callerClass =
1629 Reflection.getCallerClass().asSubclass(ClassLoader.class);
1630 return ParallelLoaders.register(callerClass);
1631 }
1632
1633 /**
1634 * Returns {@code true} if this class loader is registered as
1635 * {@linkplain #registerAsParallelCapable parallel capable}, otherwise
1636 * {@code false}.
1637 *
1638 * @return {@code true} if this class loader is parallel capable,
1639 * otherwise {@code false}.
1640 *
1641 * @see #registerAsParallelCapable()
1642 *
1643 * @since 9
1644 */
1645 public final boolean isRegisteredAsParallelCapable() {
1646 return ParallelLoaders.isRegistered(this.getClass());
1647 }
1648
1649 /**
1650 * Find a resource of the specified name from the search path used to load
1651 * classes. This method locates the resource through the system class
1652 * loader (see {@link #getSystemClassLoader()}).
1653 *
1654 * <p> Resources in named modules are subject to the encapsulation rules
1655 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1656 * Additionally, and except for the special case where the resource has a
1657 * name ending with "{@code .class}", this method will only find resources in
1658 * packages of named modules when the package is {@link Module#isOpen(String)
1659 * opened} unconditionally. </p>
1660 *
1661 * @param name
1662 * The resource name
1663 *
1664 * @return A {@link java.net.URL URL} to the resource; {@code
1665 * null} if the resource could not be found, a URL could not be
1666 * constructed to locate the resource, the resource is in a package
1667 * that is not opened unconditionally or access to the resource is
1668 * denied by the security manager.
1669 *
1670 * @since 1.1
1671 * @revised 9
1672 * @spec JPMS
1673 */
1674 public static URL getSystemResource(String name) {
1675 return getSystemClassLoader().getResource(name);
1676 }
1677
1678 /**
1679 * Finds all resources of the specified name from the search path used to
1680 * load classes. The resources thus found are returned as an
1681 * {@link java.util.Enumeration Enumeration} of {@link
1682 * java.net.URL URL} objects.
1683 *
1684 * <p> The search order is described in the documentation for {@link
1685 * #getSystemResource(String)}. </p>
1686 *
1687 * <p> Resources in named modules are subject to the encapsulation rules
1688 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1689 * Additionally, and except for the special case where the resource has a
1690 * name ending with "{@code .class}", this method will only find resources in
1691 * packages of named modules when the package is {@link Module#isOpen(String)
1692 * opened} unconditionally. </p>
1693 *
1694 * @param name
1695 * The resource name
1696 *
1697 * @return An enumeration of {@link java.net.URL URL} objects for
1698 * the resource. If no resources could be found, the enumeration
1699 * will be empty. Resources for which a {@code URL} cannot be
1700 * constructed, are in a package that is not opened unconditionally,
1701 * or access to the resource is denied by the security manager,
1702 * are not returned in the enumeration.
1703 *
1704 * @throws IOException
1705 * If I/O errors occur
1706 *
1707 * @since 1.2
1708 * @revised 9
1709 * @spec JPMS
1710 */
1711 public static Enumeration<URL> getSystemResources(String name)
1712 throws IOException
1713 {
1714 return getSystemClassLoader().getResources(name);
1715 }
1716
1717 /**
1718 * Returns an input stream for reading the specified resource.
1719 *
1720 * <p> The search order is described in the documentation for {@link
1721 * #getResource(String)}. </p>
1722 *
1723 * <p> Resources in named modules are subject to the encapsulation rules
1724 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1725 * Additionally, and except for the special case where the resource has a
1726 * name ending with "{@code .class}", this method will only find resources in
1727 * packages of named modules when the package is {@link Module#isOpen(String)
1728 * opened} unconditionally. </p>
1729 *
1730 * @param name
1731 * The resource name
1732 *
1733 * @return An input stream for reading the resource; {@code null} if the
1734 * resource could not be found, the resource is in a package that
1735 * is not opened unconditionally, or access to the resource is
1736 * denied by the security manager.
1737 *
1738 * @throws NullPointerException If {@code name} is {@code null}
1739 *
1740 * @since 1.1
1741 * @revised 9
1742 * @spec JPMS
1743 */
1744 public InputStream getResourceAsStream(String name) {
1745 Objects.requireNonNull(name);
1746 URL url = getResource(name);
1747 try {
1748 return url != null ? url.openStream() : null;
1749 } catch (IOException e) {
1750 return null;
1751 }
1752 }
1753
1754 /**
1755 * Open for reading, a resource of the specified name from the search path
1756 * used to load classes. This method locates the resource through the
1757 * system class loader (see {@link #getSystemClassLoader()}).
1758 *
1759 * <p> Resources in named modules are subject to the encapsulation rules
1760 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1761 * Additionally, and except for the special case where the resource has a
1762 * name ending with "{@code .class}", this method will only find resources in
1763 * packages of named modules when the package is {@link Module#isOpen(String)
1764 * opened} unconditionally. </p>
1765 *
1766 * @param name
1767 * The resource name
1768 *
1769 * @return An input stream for reading the resource; {@code null} if the
1770 * resource could not be found, the resource is in a package that
1771 * is not opened unconditionally, or access to the resource is
1772 * denied by the security manager.
1773 *
1774 * @since 1.1
1775 * @revised 9
1776 * @spec JPMS
1777 */
1778 public static InputStream getSystemResourceAsStream(String name) {
1779 URL url = getSystemResource(name);
1780 try {
1781 return url != null ? url.openStream() : null;
1782 } catch (IOException e) {
1783 return null;
1784 }
1785 }
1786
1787
1788 // -- Hierarchy --
1789
1790 /**
1791 * Returns the parent class loader for delegation. Some implementations may
1792 * use {@code null} to represent the bootstrap class loader. This method
1793 * will return {@code null} in such implementations if this class loader's
1794 * parent is the bootstrap class loader.
1795 *
1796 * @return The parent {@code ClassLoader}
1797 *
1798 * @throws SecurityException
1799 * If a security manager is present, and the caller's class loader
1800 * is not {@code null} and is not an ancestor of this class loader,
1801 * and the caller does not have the
1802 * {@link RuntimePermission}{@code ("getClassLoader")}
1803 *
1804 * @since 1.2
1805 */
1806 @CallerSensitive
1807 public final ClassLoader getParent() {
1808 if (parent == null)
1809 return null;
1810 SecurityManager sm = System.getSecurityManager();
1811 if (sm != null) {
1812 // Check access to the parent class loader
1813 // If the caller's class loader is same as this class loader,
1814 // permission check is performed.
1815 checkClassLoaderPermission(parent, Reflection.getCallerClass());
1816 }
1817 return parent;
1818 }
1819
1820 /**
1821 * Returns the unnamed {@code Module} for this class loader.
1822 *
1823 * @return The unnamed Module for this class loader
1824 *
1825 * @see Module#isNamed()
1826 * @since 9
1827 * @spec JPMS
1828 */
1829 public final Module getUnnamedModule() {
1830 return unnamedModule;
1831 }
1832
1833 /**
1834 * Returns the platform class loader. All
1835 * <a href="#builtinLoaders">platform classes</a> are visible to
1836 * the platform class loader.
1837 *
1838 * @implNote The name of the builtin platform class loader is
1839 * {@code "platform"}.
1840 *
1841 * @return The platform {@code ClassLoader}.
1842 *
1843 * @throws SecurityException
1844 * If a security manager is present, and the caller's class loader is
1845 * not {@code null}, and the caller's class loader is not the same
1846 * as or an ancestor of the platform class loader,
1847 * and the caller does not have the
1848 * {@link RuntimePermission}{@code ("getClassLoader")}
1849 *
1850 * @since 9
1851 * @spec JPMS
1852 */
1853 @CallerSensitive
1854 public static ClassLoader getPlatformClassLoader() {
1855 SecurityManager sm = System.getSecurityManager();
1856 ClassLoader loader = getBuiltinPlatformClassLoader();
1857 if (sm != null) {
1858 checkClassLoaderPermission(loader, Reflection.getCallerClass());
1859 }
1860 return loader;
1861 }
1862
1863 /**
1864 * Returns the system class loader. This is the default
1865 * delegation parent for new {@code ClassLoader} instances, and is
1866 * typically the class loader used to start the application.
1867 *
1868 * <p> This method is first invoked early in the runtime's startup
1869 * sequence, at which point it creates the system class loader. This
1870 * class loader will be the context class loader for the main application
1871 * thread (for example, the thread that invokes the {@code main} method of
1872 * the main class).
1873 *
1874 * <p> The default system class loader is an implementation-dependent
1875 * instance of this class.
1876 *
1877 * <p> If the system property "{@systemProperty java.system.class.loader}"
1878 * is defined when this method is first invoked then the value of that
1879 * property is taken to be the name of a class that will be returned as the
1880 * system class loader. The class is loaded using the default system class
1881 * loader and must define a public constructor that takes a single parameter
1882 * of type {@code ClassLoader} which is used as the delegation parent. An
1883 * instance is then created using this constructor with the default system
1884 * class loader as the parameter. The resulting class loader is defined
1885 * to be the system class loader. During construction, the class loader
1886 * should take great care to avoid calling {@code getSystemClassLoader()}.
1887 * If circular initialization of the system class loader is detected then
1888 * an {@code IllegalStateException} is thrown.
1889 *
1890 * @implNote The system property to override the system class loader is not
1891 * examined until the VM is almost fully initialized. Code that executes
1892 * this method during startup should take care not to cache the return
1893 * value until the system is fully initialized.
1894 *
1895 * <p> The name of the built-in system class loader is {@code "app"}.
1896 * The system property "{@code java.class.path}" is read during early
1897 * initialization of the VM to determine the class path.
1898 * An empty value of "{@code java.class.path}" property is interpreted
1899 * differently depending on whether the initial module (the module
1900 * containing the main class) is named or unnamed:
1901 * If named, the built-in system class loader will have no class path and
1902 * will search for classes and resources using the application module path;
1903 * otherwise, if unnamed, it will set the class path to the current
1904 * working directory.
1905 *
1906 * <p> JAR files on the class path may contain a {@code Class-Path} manifest
1907 * attribute to specify dependent JAR files to be included in the class path.
1908 * {@code Class-Path} entries must meet certain conditions for validity (see
1909 * the <a href="{@docRoot}/../specs/jar/jar.html#class-path-attribute">
1910 * JAR File Specification</a> for details). Invalid {@code Class-Path}
1911 * entries are ignored. For debugging purposes, ignored entries can be
1912 * printed to the console if the
1913 * {@systemProperty jdk.net.URLClassPath.showIgnoredClassPathEntries} system
1914 * property is set to {@code true}.
1915 *
1916 * @return The system {@code ClassLoader}
1917 *
1918 * @throws SecurityException
1919 * If a security manager is present, and the caller's class loader
1920 * is not {@code null} and is not the same as or an ancestor of the
1921 * system class loader, and the caller does not have the
1922 * {@link RuntimePermission}{@code ("getClassLoader")}
1923 *
1924 * @throws IllegalStateException
1925 * If invoked recursively during the construction of the class
1926 * loader specified by the "{@code java.system.class.loader}"
1927 * property.
1928 *
1929 * @throws Error
1930 * If the system property "{@code java.system.class.loader}"
1931 * is defined but the named class could not be loaded, the
1932 * provider class does not define the required constructor, or an
1933 * exception is thrown by that constructor when it is invoked. The
1934 * underlying cause of the error can be retrieved via the
1935 * {@link Throwable#getCause()} method.
1936 *
1937 * @revised 1.4
1938 * @revised 9
1939 * @spec JPMS
1940 */
1941 @CallerSensitive
1942 public static ClassLoader getSystemClassLoader() {
1943 switch (VM.initLevel()) {
1944 case 0:
1945 case 1:
1946 case 2:
1947 // the system class loader is the built-in app class loader during startup
1948 return getBuiltinAppClassLoader();
1949 case 3:
1950 String msg = "getSystemClassLoader cannot be called during the system class loader instantiation";
1951 throw new IllegalStateException(msg);
1952 default:
1953 // system fully initialized
1954 assert VM.isBooted() && scl != null;
1955 SecurityManager sm = System.getSecurityManager();
1956 if (sm != null) {
1957 checkClassLoaderPermission(scl, Reflection.getCallerClass());
1958 }
1959 return scl;
1960 }
1961 }
1962
1963 static ClassLoader getBuiltinPlatformClassLoader() {
1964 return ClassLoaders.platformClassLoader();
1965 }
1966
1967 static ClassLoader getBuiltinAppClassLoader() {
1968 return ClassLoaders.appClassLoader();
1969 }
1970
1971 /*
1972 * Initialize the system class loader that may be a custom class on the
1973 * application class path or application module path.
1974 *
1975 * @see java.lang.System#initPhase3
1976 */
1977 static synchronized ClassLoader initSystemClassLoader() {
1978 if (VM.initLevel() != 3) {
1979 throw new InternalError("system class loader cannot be set at initLevel " +
1980 VM.initLevel());
1981 }
1982
1983 // detect recursive initialization
1984 if (scl != null) {
1985 throw new IllegalStateException("recursive invocation");
1986 }
1987
1988 ClassLoader builtinLoader = getBuiltinAppClassLoader();
1989
1990 // All are privileged frames. No need to call doPrivileged.
1991 String cn = System.getProperty("java.system.class.loader");
1992 if (cn != null) {
1993 try {
1994 // custom class loader is only supported to be loaded from unnamed module
1995 Constructor<?> ctor = Class.forName(cn, false, builtinLoader)
1996 .getDeclaredConstructor(ClassLoader.class);
1997 scl = (ClassLoader) ctor.newInstance(builtinLoader);
1998 } catch (Exception e) {
1999 Throwable cause = e;
2000 if (e instanceof InvocationTargetException) {
2001 cause = e.getCause();
2002 if (cause instanceof Error) {
2003 throw (Error) cause;
2004 }
2005 }
2006 if (cause instanceof RuntimeException) {
2007 throw (RuntimeException) cause;
2008 }
2009 throw new Error(cause.getMessage(), cause);
2010 }
2011 } else {
2012 scl = builtinLoader;
2013 }
2014 return scl;
2015 }
2016
2017 // Returns true if the specified class loader can be found in this class
2018 // loader's delegation chain.
2019 boolean isAncestor(ClassLoader cl) {
2020 ClassLoader acl = this;
2021 do {
2022 acl = acl.parent;
2023 if (cl == acl) {
2024 return true;
2025 }
2026 } while (acl != null);
2027 return false;
2028 }
2029
2030 // Tests if class loader access requires "getClassLoader" permission
2031 // check. A class loader 'from' can access class loader 'to' if
2032 // class loader 'from' is same as class loader 'to' or an ancestor
2033 // of 'to'. The class loader in a system domain can access
2034 // any class loader.
2035 private static boolean needsClassLoaderPermissionCheck(ClassLoader from,
2036 ClassLoader to)
2037 {
2038 if (from == to)
2039 return false;
2040
2041 if (from == null)
2042 return false;
2043
2044 return !to.isAncestor(from);
2045 }
2046
2047 // Returns the class's class loader, or null if none.
2048 static ClassLoader getClassLoader(Class<?> caller) {
2049 // This can be null if the VM is requesting it
2050 if (caller == null) {
2051 return null;
2052 }
2053 // Circumvent security check since this is package-private
2054 return caller.getClassLoader0();
2055 }
2056
2057 /*
2058 * Checks RuntimePermission("getClassLoader") permission
2059 * if caller's class loader is not null and caller's class loader
2060 * is not the same as or an ancestor of the given cl argument.
2061 */
2062 static void checkClassLoaderPermission(ClassLoader cl, Class<?> caller) {
2063 SecurityManager sm = System.getSecurityManager();
2064 if (sm != null) {
2065 // caller can be null if the VM is requesting it
2066 ClassLoader ccl = getClassLoader(caller);
2067 if (needsClassLoaderPermissionCheck(ccl, cl)) {
2068 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
2069 }
2070 }
2071 }
2072
2073 // The system class loader
2074 // @GuardedBy("ClassLoader.class")
2075 private static volatile ClassLoader scl;
2076
2077 // -- Package --
2078
2079 /**
2080 * Define a Package of the given Class object.
2081 *
2082 * If the given class represents an array type, a primitive type or void,
2083 * this method returns {@code null}.
2084 *
2085 * This method does not throw IllegalArgumentException.
2086 */
2087 Package definePackage(Class<?> c) {
2088 if (c.isPrimitive() || c.isArray()) {
2089 return null;
2090 }
2091
2092 return definePackage(c.getPackageName(), c.getModule());
2093 }
2094
2095 /**
2096 * Defines a Package of the given name and module
2097 *
2098 * This method does not throw IllegalArgumentException.
2099 *
2100 * @param name package name
2101 * @param m module
2102 */
2103 Package definePackage(String name, Module m) {
2104 if (name.isEmpty() && m.isNamed()) {
2105 throw new InternalError("unnamed package in " + m);
2106 }
2107
2108 // check if Package object is already defined
2109 NamedPackage pkg = packages.get(name);
2110 if (pkg instanceof Package)
2111 return (Package)pkg;
2112
2113 return (Package)packages.compute(name, (n, p) -> toPackage(n, p, m));
2114 }
2115
2116 /*
2117 * Returns a Package object for the named package
2118 */
2119 private Package toPackage(String name, NamedPackage p, Module m) {
2120 // define Package object if the named package is not yet defined
2121 if (p == null)
2122 return NamedPackage.toPackage(name, m);
2123
2124 // otherwise, replace the NamedPackage object with Package object
2125 if (p instanceof Package)
2126 return (Package)p;
2127
2128 return NamedPackage.toPackage(p.packageName(), p.module());
2129 }
2130
2131 /**
2132 * Defines a package by <a href="#binary-name">name</a> in this {@code ClassLoader}.
2133 * <p>
2134 * <a href="#binary-name">Package names</a> must be unique within a class loader and
2135 * cannot be redefined or changed once created.
2136 * <p>
2137 * If a class loader wishes to define a package with specific properties,
2138 * such as version information, then the class loader should call this
2139 * {@code definePackage} method before calling {@code defineClass}.
2140 * Otherwise, the
2141 * {@link #defineClass(String, byte[], int, int, ProtectionDomain) defineClass}
2142 * method will define a package in this class loader corresponding to the package
2143 * of the newly defined class; the properties of this defined package are
2144 * specified by {@link Package}.
2145 *
2146 * @apiNote
2147 * A class loader that wishes to define a package for classes in a JAR
2148 * typically uses the specification and implementation titles, versions, and
2149 * vendors from the JAR's manifest. If the package is specified as
2150 * {@linkplain java.util.jar.Attributes.Name#SEALED sealed} in the JAR's manifest,
2151 * the {@code URL} of the JAR file is typically used as the {@code sealBase}.
2152 * If classes of package {@code 'p'} defined by this class loader
2153 * are loaded from multiple JARs, the {@code Package} object may contain
2154 * different information depending on the first class of package {@code 'p'}
2155 * defined and which JAR's manifest is read first to explicitly define
2156 * package {@code 'p'}.
2157 *
2158 * <p> It is strongly recommended that a class loader does not call this
2159 * method to explicitly define packages in <em>named modules</em>; instead,
2160 * the package will be automatically defined when a class is {@linkplain
2161 * #defineClass(String, byte[], int, int, ProtectionDomain) being defined}.
2162 * If it is desirable to define {@code Package} explicitly, it should ensure
2163 * that all packages in a named module are defined with the properties
2164 * specified by {@link Package}. Otherwise, some {@code Package} objects
2165 * in a named module may be for example sealed with different seal base.
2166 *
2167 * @param name
2168 * The <a href="#binary-name">package name</a>
2169 *
2170 * @param specTitle
2171 * The specification title
2172 *
2173 * @param specVersion
2174 * The specification version
2175 *
2176 * @param specVendor
2177 * The specification vendor
2178 *
2179 * @param implTitle
2180 * The implementation title
2181 *
2182 * @param implVersion
2183 * The implementation version
2184 *
2185 * @param implVendor
2186 * The implementation vendor
2187 *
2188 * @param sealBase
2189 * If not {@code null}, then this package is sealed with
2190 * respect to the given code source {@link java.net.URL URL}
2191 * object. Otherwise, the package is not sealed.
2192 *
2193 * @return The newly defined {@code Package} object
2194 *
2195 * @throws NullPointerException
2196 * if {@code name} is {@code null}.
2197 *
2198 * @throws IllegalArgumentException
2199 * if a package of the given {@code name} is already
2200 * defined by this class loader
2201 *
2202 *
2203 * @since 1.2
2204 * @revised 9
2205 * @spec JPMS
2206 *
2207 * @jvms 5.3 Creation and Loading
2208 * @see <a href="{@docRoot}/../specs/jar/jar.html#package-sealing">
2209 * The JAR File Specification: Package Sealing</a>
2210 */
2211 protected Package definePackage(String name, String specTitle,
2212 String specVersion, String specVendor,
2213 String implTitle, String implVersion,
2214 String implVendor, URL sealBase)
2215 {
2216 Objects.requireNonNull(name);
2217
2218 // definePackage is not final and may be overridden by custom class loader
2219 Package p = new Package(name, specTitle, specVersion, specVendor,
2220 implTitle, implVersion, implVendor,
2221 sealBase, this);
2222
2223 if (packages.putIfAbsent(name, p) != null)
2224 throw new IllegalArgumentException(name);
2225
2226 return p;
2227 }
2228
2229 /**
2230 * Returns a {@code Package} of the given <a href="#binary-name">name</a> that
2231 * has been defined by this class loader.
2232 *
2233 * @param name The <a href="#binary-name">package name</a>
2234 *
2235 * @return The {@code Package} of the given name that has been defined
2236 * by this class loader, or {@code null} if not found
2237 *
2238 * @throws NullPointerException
2239 * if {@code name} is {@code null}.
2240 *
2241 * @jvms 5.3 Creation and Loading
2242 *
2243 * @since 9
2244 * @spec JPMS
2245 */
2246 public final Package getDefinedPackage(String name) {
2247 Objects.requireNonNull(name, "name cannot be null");
2248
2249 NamedPackage p = packages.get(name);
2250 if (p == null)
2251 return null;
2252
2253 return definePackage(name, p.module());
2254 }
2255
2256 /**
2257 * Returns all of the {@code Package}s that have been defined by
2258 * this class loader. The returned array has no duplicated {@code Package}s
2259 * of the same name.
2260 *
2261 * @apiNote This method returns an array rather than a {@code Set} or {@code Stream}
2262 * for consistency with the existing {@link #getPackages} method.
2263 *
2264 * @return The array of {@code Package} objects that have been defined by
2265 * this class loader; or an zero length array if no package has been
2266 * defined by this class loader.
2267 *
2268 * @jvms 5.3 Creation and Loading
2269 *
2270 * @since 9
2271 * @spec JPMS
2272 */
2273 public final Package[] getDefinedPackages() {
2274 return packages().toArray(Package[]::new);
2275 }
2276
2277 /**
2278 * Finds a package by <a href="#binary-name">name</a> in this class loader and its ancestors.
2279 * <p>
2280 * If this class loader defines a {@code Package} of the given name,
2281 * the {@code Package} is returned. Otherwise, the ancestors of
2282 * this class loader are searched recursively (parent by parent)
2283 * for a {@code Package} of the given name.
2284 *
2285 * @apiNote The {@link #getPlatformClassLoader() platform class loader}
2286 * may delegate to the application class loader but the application class
2287 * loader is not its ancestor. When invoked on the platform class loader,
2288 * this method will not find packages defined to the application
2289 * class loader.
2290 *
2291 * @param name
2292 * The <a href="#binary-name">package name</a>
2293 *
2294 * @return The {@code Package} of the given name that has been defined by
2295 * this class loader or its ancestors, or {@code null} if not found.
2296 *
2297 * @throws NullPointerException
2298 * if {@code name} is {@code null}.
2299 *
2300 * @deprecated
2301 * If multiple class loaders delegate to each other and define classes
2302 * with the same package name, and one such loader relies on the lookup
2303 * behavior of {@code getPackage} to return a {@code Package} from
2304 * a parent loader, then the properties exposed by the {@code Package}
2305 * may not be as expected in the rest of the program.
2306 * For example, the {@code Package} will only expose annotations from the
2307 * {@code package-info.class} file defined by the parent loader, even if
2308 * annotations exist in a {@code package-info.class} file defined by
2309 * a child loader. A more robust approach is to use the
2310 * {@link ClassLoader#getDefinedPackage} method which returns
2311 * a {@code Package} for the specified class loader.
2312 *
2313 * @see ClassLoader#getDefinedPackage(String)
2314 *
2315 * @since 1.2
2316 * @revised 9
2317 * @spec JPMS
2318 */
2319 @Deprecated(since="9")
2320 protected Package getPackage(String name) {
2321 Package pkg = getDefinedPackage(name);
2322 if (pkg == null) {
2323 if (parent != null) {
2324 pkg = parent.getPackage(name);
2325 } else {
2326 pkg = BootLoader.getDefinedPackage(name);
2327 }
2328 }
2329 return pkg;
2330 }
2331
2332 /**
2333 * Returns all of the {@code Package}s that have been defined by
2334 * this class loader and its ancestors. The returned array may contain
2335 * more than one {@code Package} object of the same package name, each
2336 * defined by a different class loader in the class loader hierarchy.
2337 *
2338 * @apiNote The {@link #getPlatformClassLoader() platform class loader}
2339 * may delegate to the application class loader. In other words,
2340 * packages in modules defined to the application class loader may be
2341 * visible to the platform class loader. On the other hand,
2342 * the application class loader is not its ancestor and hence
2343 * when invoked on the platform class loader, this method will not
2344 * return any packages defined to the application class loader.
2345 *
2346 * @return The array of {@code Package} objects that have been defined by
2347 * this class loader and its ancestors
2348 *
2349 * @see ClassLoader#getDefinedPackages()
2350 *
2351 * @since 1.2
2352 * @revised 9
2353 * @spec JPMS
2354 */
2355 protected Package[] getPackages() {
2356 Stream<Package> pkgs = packages();
2357 ClassLoader ld = parent;
2358 while (ld != null) {
2359 pkgs = Stream.concat(ld.packages(), pkgs);
2360 ld = ld.parent;
2361 }
2362 return Stream.concat(BootLoader.packages(), pkgs)
2363 .toArray(Package[]::new);
2364 }
2365
2366
2367
2368 // package-private
2369
2370 /**
2371 * Returns a stream of Packages defined in this class loader
2372 */
2373 Stream<Package> packages() {
2374 return packages.values().stream()
2375 .map(p -> definePackage(p.packageName(), p.module()));
2376 }
2377
2378 // -- Native library access --
2379
2380 /**
2381 * Returns the absolute path name of a native library. The VM invokes this
2382 * method to locate the native libraries that belong to classes loaded with
2383 * this class loader. If this method returns {@code null}, the VM
2384 * searches the library along the path specified as the
2385 * "{@code java.library.path}" property.
2386 *
2387 * @param libname
2388 * The library name
2389 *
2390 * @return The absolute path of the native library
2391 *
2392 * @see System#loadLibrary(String)
2393 * @see System#mapLibraryName(String)
2394 *
2395 * @since 1.2
2396 */
2397 protected String findLibrary(String libname) {
2398 return null;
2399 }
2400
2401 private final NativeLibraries libraries = NativeLibraries.jniNativeLibraries(this);
2402
2403 // Invoked in the java.lang.Runtime class to implement load and loadLibrary.
2404 static NativeLibrary loadLibrary(Class<?> fromClass, File file) {
2405 ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
2406 NativeLibraries libs = loader != null ? loader.libraries : BootLoader.getNativeLibraries();
2407 NativeLibrary nl = libs.loadLibrary(fromClass, file);
2408 if (nl != null) {
2409 return nl;
2410 }
2411 throw new UnsatisfiedLinkError("Can't load library: " + file);
2412 }
2413 static NativeLibrary loadLibrary(Class<?> fromClass, String name) {
2414 ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
2415 if (loader == null) {
2416 NativeLibrary nl = BootLoader.getNativeLibraries().loadLibrary(fromClass, name);
2417 if (nl != null) {
2418 return nl;
2419 }
2420 throw new UnsatisfiedLinkError("no " + name +
2421 " in system library path: " + StaticProperty.sunBootLibraryPath());
2422 }
2423
2424 NativeLibraries libs = loader.libraries;
2425 // First load from the file returned from ClassLoader::findLibrary, if found.
2426 String libfilename = loader.findLibrary(name);
2427 if (libfilename != null) {
2428 File libfile = new File(libfilename);
2429 if (!libfile.isAbsolute()) {
2430 throw new UnsatisfiedLinkError(
2431 "ClassLoader.findLibrary failed to return an absolute path: " + libfilename);
2432 }
2433 NativeLibrary nl = libs.loadLibrary(fromClass, libfile);
2434 if (nl != null) {
2435 return nl;
2436 }
2437 throw new UnsatisfiedLinkError("Can't load " + libfilename);
2438 }
2439 // Then load from system library path and java library path
2440 NativeLibrary nl = libs.loadLibrary(fromClass, name);
2441 if (nl != null) {
2442 return nl;
2443 }
2444
2445 // Oops, it failed
2446 throw new UnsatisfiedLinkError("no " + name +
2447 " in java.library.path: " + StaticProperty.javaLibraryPath());
2448 }
2449
2450 /*
2451 * Invoked in the VM class linking code.
2452 */
2453 private static long findNative(ClassLoader loader, String entryName) {
2454 if (loader == null) {
2455 return BootLoader.getNativeLibraries().find(entryName);
2456 } else {
2457 return loader.libraries.find(entryName);
2458 }
2459 }
2460
2461 // -- Assertion management --
2462
2463 final Object assertionLock;
2464
2465 // The default toggle for assertion checking.
2466 // @GuardedBy("assertionLock")
2467 private boolean defaultAssertionStatus = false;
2468
2469 // Maps String packageName to Boolean package default assertion status Note
2470 // that the default package is placed under a null map key. If this field
2471 // is null then we are delegating assertion status queries to the VM, i.e.,
2472 // none of this ClassLoader's assertion status modification methods have
2473 // been invoked.
2474 // @GuardedBy("assertionLock")
2475 private Map<String, Boolean> packageAssertionStatus = null;
2476
2477 // Maps String fullyQualifiedClassName to Boolean assertionStatus If this
2478 // field is null then we are delegating assertion status queries to the VM,
2479 // i.e., none of this ClassLoader's assertion status modification methods
2480 // have been invoked.
2481 // @GuardedBy("assertionLock")
2482 Map<String, Boolean> classAssertionStatus = null;
2483
2484 /**
2485 * Sets the default assertion status for this class loader. This setting
2486 * determines whether classes loaded by this class loader and initialized
2487 * in the future will have assertions enabled or disabled by default.
2488 * This setting may be overridden on a per-package or per-class basis by
2489 * invoking {@link #setPackageAssertionStatus(String, boolean)} or {@link
2490 * #setClassAssertionStatus(String, boolean)}.
2491 *
2492 * @param enabled
2493 * {@code true} if classes loaded by this class loader will
2494 * henceforth have assertions enabled by default, {@code false}
2495 * if they will have assertions disabled by default.
2496 *
2497 * @since 1.4
2498 */
2499 public void setDefaultAssertionStatus(boolean enabled) {
2500 synchronized (assertionLock) {
2501 if (classAssertionStatus == null)
2502 initializeJavaAssertionMaps();
2503
2504 defaultAssertionStatus = enabled;
2505 }
2506 }
2507
2508 /**
2509 * Sets the package default assertion status for the named package. The
2510 * package default assertion status determines the assertion status for
2511 * classes initialized in the future that belong to the named package or
2512 * any of its "subpackages".
2513 *
2514 * <p> A subpackage of a package named p is any package whose name begins
2515 * with "{@code p.}". For example, {@code javax.swing.text} is a
2516 * subpackage of {@code javax.swing}, and both {@code java.util} and
2517 * {@code java.lang.reflect} are subpackages of {@code java}.
2518 *
2519 * <p> In the event that multiple package defaults apply to a given class,
2520 * the package default pertaining to the most specific package takes
2521 * precedence over the others. For example, if {@code javax.lang} and
2522 * {@code javax.lang.reflect} both have package defaults associated with
2523 * them, the latter package default applies to classes in
2524 * {@code javax.lang.reflect}.
2525 *
2526 * <p> Package defaults take precedence over the class loader's default
2527 * assertion status, and may be overridden on a per-class basis by invoking
2528 * {@link #setClassAssertionStatus(String, boolean)}. </p>
2529 *
2530 * @param packageName
2531 * The name of the package whose package default assertion status
2532 * is to be set. A {@code null} value indicates the unnamed
2533 * package that is "current"
2534 * (see section 7.4.2 of
2535 * <cite>The Java Language Specification</cite>.)
2536 *
2537 * @param enabled
2538 * {@code true} if classes loaded by this classloader and
2539 * belonging to the named package or any of its subpackages will
2540 * have assertions enabled by default, {@code false} if they will
2541 * have assertions disabled by default.
2542 *
2543 * @since 1.4
2544 */
2545 public void setPackageAssertionStatus(String packageName,
2546 boolean enabled) {
2547 synchronized (assertionLock) {
2548 if (packageAssertionStatus == null)
2549 initializeJavaAssertionMaps();
2550
2551 packageAssertionStatus.put(packageName, enabled);
2552 }
2553 }
2554
2555 /**
2556 * Sets the desired assertion status for the named top-level class in this
2557 * class loader and any nested classes contained therein. This setting
2558 * takes precedence over the class loader's default assertion status, and
2559 * over any applicable per-package default. This method has no effect if
2560 * the named class has already been initialized. (Once a class is
2561 * initialized, its assertion status cannot change.)
2562 *
2563 * <p> If the named class is not a top-level class, this invocation will
2564 * have no effect on the actual assertion status of any class. </p>
2565 *
2566 * @param className
2567 * The fully qualified class name of the top-level class whose
2568 * assertion status is to be set.
2569 *
2570 * @param enabled
2571 * {@code true} if the named class is to have assertions
2572 * enabled when (and if) it is initialized, {@code false} if the
2573 * class is to have assertions disabled.
2574 *
2575 * @since 1.4
2576 */
2577 public void setClassAssertionStatus(String className, boolean enabled) {
2578 synchronized (assertionLock) {
2579 if (classAssertionStatus == null)
2580 initializeJavaAssertionMaps();
2581
2582 classAssertionStatus.put(className, enabled);
2583 }
2584 }
2585
2586 /**
2587 * Sets the default assertion status for this class loader to
2588 * {@code false} and discards any package defaults or class assertion
2589 * status settings associated with the class loader. This method is
2590 * provided so that class loaders can be made to ignore any command line or
2591 * persistent assertion status settings and "start with a clean slate."
2592 *
2593 * @since 1.4
2594 */
2595 public void clearAssertionStatus() {
2596 /*
2597 * Whether or not "Java assertion maps" are initialized, set
2598 * them to empty maps, effectively ignoring any present settings.
2599 */
2600 synchronized (assertionLock) {
2601 classAssertionStatus = new HashMap<>();
2602 packageAssertionStatus = new HashMap<>();
2603 defaultAssertionStatus = false;
2604 }
2605 }
2606
2607 /**
2608 * Returns the assertion status that would be assigned to the specified
2609 * class if it were to be initialized at the time this method is invoked.
2610 * If the named class has had its assertion status set, the most recent
2611 * setting will be returned; otherwise, if any package default assertion
2612 * status pertains to this class, the most recent setting for the most
2613 * specific pertinent package default assertion status is returned;
2614 * otherwise, this class loader's default assertion status is returned.
2615 * </p>
2616 *
2617 * @param className
2618 * The fully qualified class name of the class whose desired
2619 * assertion status is being queried.
2620 *
2621 * @return The desired assertion status of the specified class.
2622 *
2623 * @see #setClassAssertionStatus(String, boolean)
2624 * @see #setPackageAssertionStatus(String, boolean)
2625 * @see #setDefaultAssertionStatus(boolean)
2626 *
2627 * @since 1.4
2628 */
2629 boolean desiredAssertionStatus(String className) {
2630 synchronized (assertionLock) {
2631 // assert classAssertionStatus != null;
2632 // assert packageAssertionStatus != null;
2633
2634 // Check for a class entry
2635 Boolean result = classAssertionStatus.get(className);
2636 if (result != null)
2637 return result.booleanValue();
2638
2639 // Check for most specific package entry
2640 int dotIndex = className.lastIndexOf('.');
2641 if (dotIndex < 0) { // default package
2642 result = packageAssertionStatus.get(null);
2643 if (result != null)
2644 return result.booleanValue();
2645 }
2646 while(dotIndex > 0) {
2647 className = className.substring(0, dotIndex);
2648 result = packageAssertionStatus.get(className);
2649 if (result != null)
2650 return result.booleanValue();
2651 dotIndex = className.lastIndexOf('.', dotIndex-1);
2652 }
2653
2654 // Return the classloader default
2655 return defaultAssertionStatus;
2656 }
2657 }
2658
2659 // Set up the assertions with information provided by the VM.
2660 // Note: Should only be called inside a synchronized block
2661 private void initializeJavaAssertionMaps() {
2662 // assert Thread.holdsLock(assertionLock);
2663
2664 classAssertionStatus = new HashMap<>();
2665 packageAssertionStatus = new HashMap<>();
2666 AssertionStatusDirectives directives = retrieveDirectives();
2667
2668 for(int i = 0; i < directives.classes.length; i++)
2669 classAssertionStatus.put(directives.classes[i],
2670 directives.classEnabled[i]);
2671
2672 for(int i = 0; i < directives.packages.length; i++)
2673 packageAssertionStatus.put(directives.packages[i],
2674 directives.packageEnabled[i]);
2675
2676 defaultAssertionStatus = directives.deflt;
2677 }
2678
2679 // Retrieves the assertion directives from the VM.
2680 private static native AssertionStatusDirectives retrieveDirectives();
2681
2682
2683 // -- Misc --
2684
2685 /**
2686 * Returns the ConcurrentHashMap used as a storage for ClassLoaderValue(s)
2687 * associated with this ClassLoader, creating it if it doesn't already exist.
2688 */
2689 ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap() {
2690 ConcurrentHashMap<?, ?> map = classLoaderValueMap;
2691 if (map == null) {
2692 map = new ConcurrentHashMap<>();
2693 boolean set = trySetObjectField("classLoaderValueMap", map);
2694 if (!set) {
2695 // beaten by someone else
2696 map = classLoaderValueMap;
2697 }
2698 }
2699 return map;
2700 }
2701
2702 // the storage for ClassLoaderValue(s) associated with this ClassLoader
2703 private volatile ConcurrentHashMap<?, ?> classLoaderValueMap;
2704
2705 /**
2706 * Attempts to atomically set a volatile field in this object. Returns
2707 * {@code true} if not beaten by another thread. Avoids the use of
2708 * AtomicReferenceFieldUpdater in this class.
2709 */
2710 private boolean trySetObjectField(String name, Object obj) {
2711 Unsafe unsafe = Unsafe.getUnsafe();
2712 Class<?> k = ClassLoader.class;
2713 long offset;
2714 offset = unsafe.objectFieldOffset(k, name);
2715 return unsafe.compareAndSetReference(this, offset, null, obj);
2716 }
2717 }
2718
2719 /*
2720 * A utility class that will enumerate over an array of enumerations.
2721 */
2722 final class CompoundEnumeration<E> implements Enumeration<E> {
2723 private final Enumeration<E>[] enums;
2724 private int index;
2725
2726 public CompoundEnumeration(Enumeration<E>[] enums) {
2727 this.enums = enums;
2728 }
2729
2730 private boolean next() {
2731 while (index < enums.length) {
2732 if (enums[index] != null && enums[index].hasMoreElements()) {
2733 return true;
2734 }
2735 index++;
2736 }
2737 return false;
2738 }
2739
2740 public boolean hasMoreElements() {
2741 return next();
2742 }
2743
2744 public E nextElement() {
2745 if (!next()) {
2746 throw new NoSuchElementException();
2747 }
2748 return enums[index].nextElement();
2749 }
2750 }