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