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