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