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