1 /*
2 * Copyright (c) 2013, 2020, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2019, Azul Systems, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation. Oracle designates this
9 * particular file as subject to the "Classpath" exception as provided
10 * by Oracle in the LICENSE file that accompanied this code.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
23 * or visit www.oracle.com if you need additional information or have any
24 * questions.
25 */
26
27 package java.lang;
28
29 import java.io.InputStream;
30 import java.io.IOException;
31 import java.io.UncheckedIOException;
32 import java.io.File;
33 import java.lang.reflect.Constructor;
34 import java.lang.reflect.InvocationTargetException;
35 import java.net.URL;
36 import java.security.AccessController;
37 import java.security.AccessControlContext;
38 import java.security.CodeSource;
39 import java.security.PrivilegedAction;
40 import java.security.ProtectionDomain;
41 import java.security.cert.Certificate;
42 import java.util.ArrayList;
43 import java.util.Collections;
44 import java.util.Enumeration;
45 import java.util.HashMap;
46 import java.util.Map;
47 import java.util.NoSuchElementException;
48 import java.util.Objects;
49 import java.util.Set;
50 import java.util.Spliterator;
51 import java.util.Spliterators;
52 import java.util.WeakHashMap;
53 import java.util.concurrent.ConcurrentHashMap;
54 import java.util.function.Supplier;
55 import java.util.stream.Stream;
56 import java.util.stream.StreamSupport;
57
58 import jdk.internal.loader.BootLoader;
59 import jdk.internal.loader.BuiltinClassLoader;
60 import jdk.internal.loader.ClassLoaders;
61 import jdk.internal.loader.NativeLibrary;
62 import jdk.internal.loader.NativeLibraries;
63 import jdk.internal.perf.PerfCounter;
64 import jdk.internal.misc.Unsafe;
65 import jdk.internal.misc.VM;
66 import jdk.internal.reflect.CallerSensitive;
67 import jdk.internal.reflect.Reflection;
68 import jdk.internal.util.StaticProperty;
69 import sun.reflect.misc.ReflectUtil;
70 import sun.security.util.SecurityConstants;
71
72 /**
73 * A class loader is an object that is responsible for loading classes. The
74 * class {@code ClassLoader} is an abstract class. Given the <a
75 * href="#binary-name">binary name</a> of a class, a class loader should attempt to
76 * locate or generate data that constitutes a definition for the class. A
77 * typical strategy is to transform the name into a file name and then read a
78 * "class file" of that name from a file system.
79 *
80 * <p> Every {@link java.lang.Class Class} object contains a {@link
81 * Class#getClassLoader() reference} to the {@code ClassLoader} that defined
82 * it.
83 *
84 * <p> {@code Class} objects for array classes are not created by class
85 * loaders, but are created automatically as required by the Java runtime.
86 * The class loader for an array class, as returned by {@link
87 * Class#getClassLoader()} is the same as the class loader for its element
88 * type; if the element type is a primitive type, then the array class has no
89 * class loader.
90 *
91 * <p> Applications implement subclasses of {@code ClassLoader} in order to
92 * extend the manner in which the Java virtual machine dynamically loads
93 * classes.
94 *
95 * <p> Class loaders may typically be used by security managers to indicate
96 * security domains.
97 *
98 * <p> In addition to loading classes, a class loader is also responsible for
99 * locating resources. A resource is some data (a "{@code .class}" file,
100 * configuration data, or an image for example) that is identified with an
101 * abstract '/'-separated path name. Resources are typically packaged with an
102 * application or library so that they can be located by code in the
103 * application or library. In some cases, the resources are included so that
104 * they can be located by other libraries.
105 *
106 * <p> The {@code ClassLoader} class uses a delegation model to search for
107 * classes and resources. Each instance of {@code ClassLoader} has an
108 * associated parent class loader. When requested to find a class or
109 * resource, a {@code ClassLoader} instance will usually delegate the search
110 * for the class or resource to its parent class loader before attempting to
111 * find the class or resource itself.
112 *
113 * <p> Class loaders that support concurrent loading of classes are known as
114 * <em>{@linkplain #isRegisteredAsParallelCapable() parallel capable}</em> class
115 * loaders and are required to register themselves at their class initialization
116 * time by invoking the {@link
117 * #registerAsParallelCapable ClassLoader.registerAsParallelCapable}
118 * method. Note that the {@code ClassLoader} class is registered as parallel
119 * capable by default. However, its subclasses still need to register themselves
120 * if they are parallel capable.
121 * In environments in which the delegation model is not strictly
122 * hierarchical, class loaders need to be parallel capable, otherwise class
123 * loading can lead to deadlocks because the loader lock is held for the
124 * duration of the class loading process (see {@link #loadClass
125 * loadClass} methods).
126 *
127 * <h2> <a id="builtinLoaders">Run-time Built-in Class Loaders</a></h2>
128 *
129 * The Java run-time has the following built-in class loaders:
130 *
131 * <ul>
132 * <li><p>Bootstrap class loader.
133 * It is the virtual machine's built-in class loader, typically represented
134 * as {@code null}, and does not have a parent.</li>
135 * <li><p>{@linkplain #getPlatformClassLoader() Platform class loader}.
136 * All <em>platform classes</em> are visible to the platform class loader
137 * that can be used as the parent of a {@code ClassLoader} instance.
138 * Platform classes include Java SE platform APIs, their implementation
139 * classes and JDK-specific run-time classes that are defined by the
140 * platform class loader or its ancestors.
141 * <p> To allow for upgrading/overriding of modules defined to the platform
142 * class loader, and where upgraded modules read modules defined to class
143 * loaders other than the platform class loader and its ancestors, then
144 * the platform class loader may have to delegate to other class loaders,
145 * the application class loader for example.
146 * In other words, classes in named modules defined to class loaders
147 * other than the platform class loader and its ancestors may be visible
148 * to the platform class loader. </li>
149 * <li><p>{@linkplain #getSystemClassLoader() System class loader}.
150 * It is also known as <em>application class loader</em> and is distinct
151 * from the platform class loader.
152 * The system class loader is typically used to define classes on the
153 * application class path, module path, and JDK-specific tools.
154 * The platform class loader is a parent or an ancestor of the system class
155 * loader that all platform classes are visible to it.</li>
156 * </ul>
157 *
158 * <p> Normally, the Java virtual machine loads classes from the local file
159 * system in a platform-dependent manner.
160 * However, some classes may not originate from a file; they may originate
161 * from other sources, such as the network, or they could be constructed by an
162 * application. The method {@link #defineClass(String, byte[], int, int)
163 * defineClass} converts an array of bytes into an instance of class
164 * {@code Class}. Instances of this newly defined class can be created using
165 * {@link Class#newInstance Class.newInstance}.
166 *
167 * <p> The methods and constructors of objects created by a class loader may
168 * reference other classes. To determine the class(es) referred to, the Java
169 * virtual machine invokes the {@link #loadClass loadClass} method of
170 * the class loader that originally created the class.
171 *
172 * <p> For example, an application could create a network class loader to
173 * download class files from a server. Sample code might look like:
174 *
175 * <blockquote><pre>
176 * ClassLoader loader = new NetworkClassLoader(host, port);
177 * Object main = loader.loadClass("Main", true).newInstance();
178 * . . .
179 * </pre></blockquote>
180 *
181 * <p> The network class loader subclass must define the methods {@link
182 * #findClass findClass} and {@code loadClassData} to load a class
183 * from the network. Once it has downloaded the bytes that make up the class,
184 * it should use the method {@link #defineClass defineClass} to
185 * create a class instance. A sample implementation is:
186 *
187 * <blockquote><pre>
188 * class NetworkClassLoader extends ClassLoader {
189 * String host;
190 * int port;
191 *
192 * public Class findClass(String name) {
193 * byte[] b = loadClassData(name);
194 * return defineClass(name, b, 0, b.length);
195 * }
196 *
197 * private byte[] loadClassData(String name) {
198 * // load the class data from the connection
199 * . . .
200 * }
201 * }
202 * </pre></blockquote>
203 *
204 * <h3> <a id="binary-name">Binary names</a> </h3>
205 *
206 * <p> Any class name provided as a {@code String} parameter to methods in
207 * {@code ClassLoader} must be a binary name as defined by
208 * <cite>The Java™ Language Specification</cite>.
209 *
210 * <p> Examples of valid class names include:
211 * <blockquote><pre>
212 * "java.lang.String"
213 * "javax.swing.JSpinner$DefaultEditor"
214 * "java.security.KeyStore$Builder$FileBuilder$1"
215 * "java.net.URLClassLoader$3$1"
216 * </pre></blockquote>
217 *
218 * <p> Any package name provided as a {@code String} parameter to methods in
219 * {@code ClassLoader} must be either the empty string (denoting an unnamed package)
220 * or a fully qualified name as defined by
221 * <cite>The Java™ Language Specification</cite>.
222 *
223 * @jls 6.7 Fully Qualified Names
224 * @jls 13.1 The Form of a Binary
225 * @see #resolveClass(Class)
226 * @since 1.0
227 * @revised 9
228 * @spec JPMS
229 */
230 public abstract class ClassLoader {
231
232 private static native void registerNatives();
233 static {
234 registerNatives();
235 }
236
237 // The parent class loader for delegation
238 // Note: VM hardcoded the offset of this field, thus all new fields
239 // must be added *after* it.
240 private final ClassLoader parent;
241
242 // class loader name
243 private final String name;
244
245 // the unnamed module for this ClassLoader
246 private final Module unnamedModule;
247
248 // a string for exception message printing
249 private final String nameAndId;
250
251 /**
252 * Encapsulates the set of parallel capable loader types.
253 */
254 private static class ParallelLoaders {
255 private ParallelLoaders() {}
256
257 // the set of parallel capable loader types
258 private static final Set<Class<? extends ClassLoader>> loaderTypes =
259 Collections.newSetFromMap(new WeakHashMap<>());
260 static {
261 synchronized (loaderTypes) { loaderTypes.add(ClassLoader.class); }
262 }
263
264 /**
265 * Registers the given class loader type as parallel capable.
266 * Returns {@code true} is successfully registered; {@code false} if
267 * loader's super class is not registered.
268 */
269 static boolean register(Class<? extends ClassLoader> c) {
270 synchronized (loaderTypes) {
271 if (loaderTypes.contains(c.getSuperclass())) {
272 // register the class loader as parallel capable
273 // if and only if all of its super classes are.
274 // Note: given current classloading sequence, if
275 // the immediate super class is parallel capable,
276 // all the super classes higher up must be too.
277 loaderTypes.add(c);
278 return true;
279 } else {
280 return false;
281 }
282 }
283 }
284
285 /**
286 * Returns {@code true} if the given class loader type is
287 * registered as parallel capable.
288 */
289 static boolean isRegistered(Class<? extends ClassLoader> c) {
290 synchronized (loaderTypes) {
291 return loaderTypes.contains(c);
292 }
293 }
294 }
295
296 // Maps class name to the corresponding lock object when the current
297 // class loader is parallel capable.
298 // Note: VM also uses this field to decide if the current class loader
299 // is parallel capable and the appropriate lock object for class loading.
300 private final ConcurrentHashMap<String, Object> parallelLockMap;
301
302 // Maps packages to certs
303 private final ConcurrentHashMap<String, Certificate[]> package2certs;
304
305 // Shared among all packages with unsigned classes
306 private static final Certificate[] nocerts = new Certificate[0];
307
308 // The classes loaded by this class loader. The only purpose of this table
309 // is to keep the classes from being GC'ed until the loader is GC'ed.
310 private final ArrayList<Class<?>> classes = new ArrayList<>();
311
312 // The "default" domain. Set as the default ProtectionDomain on newly
313 // created classes.
314 private final ProtectionDomain defaultDomain =
315 new ProtectionDomain(new CodeSource(null, (Certificate[]) null),
316 null, this, null);
317
318 // Invoked by the VM to record every loaded class with this loader.
319 void addClass(Class<?> c) {
320 synchronized (classes) {
321 classes.add(c);
322 }
323 }
324
325 // The packages defined in this class loader. Each package name is
326 // mapped to its corresponding NamedPackage object.
327 //
328 // The value is a Package object if ClassLoader::definePackage,
329 // Class::getPackage, ClassLoader::getDefinePackage(s) or
330 // Package::getPackage(s) method is called to define it.
331 // Otherwise, the value is a NamedPackage object.
332 private final ConcurrentHashMap<String, NamedPackage> packages
333 = new ConcurrentHashMap<>();
334
335 /*
336 * Returns a named package for the given module.
337 */
338 private NamedPackage getNamedPackage(String pn, Module m) {
339 NamedPackage p = packages.get(pn);
340 if (p == null) {
341 p = new NamedPackage(pn, m);
342
343 NamedPackage value = packages.putIfAbsent(pn, p);
344 if (value != null) {
345 // Package object already be defined for the named package
346 p = value;
347 // if definePackage is called by this class loader to define
348 // a package in a named module, this will return Package
349 // object of the same name. Package object may contain
350 // unexpected information but it does not impact the runtime.
351 // this assertion may be helpful for troubleshooting
352 assert value.module() == m;
353 }
354 }
355 return p;
356 }
357
358 private static Void checkCreateClassLoader() {
359 return checkCreateClassLoader(null);
360 }
361
362 private static Void checkCreateClassLoader(String name) {
363 if (name != null && name.isEmpty()) {
364 throw new IllegalArgumentException("name must be non-empty or null");
365 }
366
367 SecurityManager security = System.getSecurityManager();
368 if (security != null) {
369 security.checkCreateClassLoader();
370 }
371 return null;
372 }
373
374 private ClassLoader(Void unused, String name, ClassLoader parent) {
375 this.name = name;
376 this.parent = parent;
377 this.unnamedModule = new Module(this);
378 if (ParallelLoaders.isRegistered(this.getClass())) {
379 parallelLockMap = new ConcurrentHashMap<>();
380 assertionLock = new Object();
381 } else {
382 // no finer-grained lock; lock on the classloader instance
383 parallelLockMap = null;
384 assertionLock = this;
385 }
386 this.package2certs = new ConcurrentHashMap<>();
387 this.nameAndId = nameAndId(this);
388 }
389
390 /**
391 * If the defining loader has a name explicitly set then
392 * '<loader-name>' @<id>
393 * If the defining loader has no name then
394 * <qualified-class-name> @<id>
395 * If it's built-in loader then omit `@<id>` as there is only one instance.
396 */
397 private static String nameAndId(ClassLoader ld) {
398 String nid = ld.getName() != null ? "\'" + ld.getName() + "\'"
399 : ld.getClass().getName();
400 if (!(ld instanceof BuiltinClassLoader)) {
401 String id = Integer.toHexString(System.identityHashCode(ld));
402 nid = nid + " @" + id;
403 }
404 return nid;
405 }
406
407 /**
408 * Creates a new class loader of the specified name and using the
409 * specified parent class loader for delegation.
410 *
411 * @apiNote If the parent is specified as {@code null} (for the
412 * bootstrap class loader) then there is no guarantee that all platform
413 * classes are visible.
414 *
415 * @param name class loader name; or {@code null} if not named
416 * @param parent the parent class loader
417 *
418 * @throws IllegalArgumentException if the given name is empty.
419 *
420 * @throws SecurityException
421 * If a security manager exists and its
422 * {@link SecurityManager#checkCreateClassLoader()}
423 * method doesn't allow creation of a new class loader.
424 *
425 * @since 9
426 * @spec JPMS
427 */
428 protected ClassLoader(String name, ClassLoader parent) {
429 this(checkCreateClassLoader(name), name, parent);
430 }
431
432 /**
433 * Creates a new class loader using the specified parent class loader for
434 * delegation.
435 *
436 * <p> If there is a security manager, its {@link
437 * SecurityManager#checkCreateClassLoader() checkCreateClassLoader} method
438 * is invoked. This may result in a security exception. </p>
439 *
440 * @apiNote If the parent is specified as {@code null} (for the
441 * bootstrap class loader) then there is no guarantee that all platform
442 * classes are visible.
443 *
444 * @param parent
445 * The parent class loader
446 *
447 * @throws SecurityException
448 * If a security manager exists and its
449 * {@code checkCreateClassLoader} method doesn't allow creation
450 * of a new class loader.
451 *
452 * @since 1.2
453 */
454 protected ClassLoader(ClassLoader parent) {
455 this(checkCreateClassLoader(), null, parent);
456 }
457
458 /**
459 * Creates a new class loader using the {@code ClassLoader} returned by
460 * the method {@link #getSystemClassLoader()
461 * getSystemClassLoader()} as the parent class loader.
462 *
463 * <p> If there is a security manager, its {@link
464 * SecurityManager#checkCreateClassLoader()
465 * checkCreateClassLoader} method is invoked. This may result in
466 * a security exception. </p>
467 *
468 * @throws SecurityException
469 * If a security manager exists and its
470 * {@code checkCreateClassLoader} method doesn't allow creation
471 * of a new class loader.
472 */
473 protected ClassLoader() {
474 this(checkCreateClassLoader(), null, getSystemClassLoader());
475 }
476
477 /**
478 * Returns the name of this class loader or {@code null} if
479 * this class loader is not named.
480 *
481 * @apiNote This method is non-final for compatibility. If this
482 * method is overridden, this method must return the same name
483 * as specified when this class loader was instantiated.
484 *
485 * @return name of this class loader; or {@code null} if
486 * this class loader is not named.
487 *
488 * @since 9
489 * @spec JPMS
490 */
491 public String getName() {
492 return name;
493 }
494
495 // package-private used by StackTraceElement to avoid
496 // calling the overrideable getName method
497 final String name() {
498 return name;
499 }
500
501 // -- Class --
502
503 /**
504 * Loads the class with the specified <a href="#binary-name">binary name</a>.
505 * This method searches for classes in the same manner as the {@link
506 * #loadClass(String, boolean)} method. It is invoked by the Java virtual
507 * machine to resolve class references. Invoking this method is equivalent
508 * to invoking {@link #loadClass(String, boolean) loadClass(name,
509 * false)}.
510 *
511 * @param name
512 * The <a href="#binary-name">binary name</a> of the class
513 *
514 * @return The resulting {@code Class} object
515 *
516 * @throws ClassNotFoundException
517 * If the class was not found
518 */
519 public Class<?> loadClass(String name) throws ClassNotFoundException {
520 return loadClass(name, false);
521 }
522
523 /**
524 * Loads the class with the specified <a href="#binary-name">binary name</a>. The
525 * default implementation of this method searches for classes in the
526 * following order:
527 *
528 * <ol>
529 *
530 * <li><p> Invoke {@link #findLoadedClass(String)} to check if the class
531 * has already been loaded. </p></li>
532 *
533 * <li><p> Invoke the {@link #loadClass(String) loadClass} method
534 * on the parent class loader. If the parent is {@code null} the class
535 * loader built into the virtual machine is used, instead. </p></li>
536 *
537 * <li><p> Invoke the {@link #findClass(String)} method to find the
538 * class. </p></li>
539 *
540 * </ol>
541 *
542 * <p> If the class was found using the above steps, and the
543 * {@code resolve} flag is true, this method will then invoke the {@link
544 * #resolveClass(Class)} method on the resulting {@code Class} object.
545 *
546 * <p> Subclasses of {@code ClassLoader} are encouraged to override {@link
547 * #findClass(String)}, rather than this method. </p>
548 *
549 * <p> Unless overridden, this method synchronizes on the result of
550 * {@link #getClassLoadingLock getClassLoadingLock} method
551 * during the entire class loading process.
552 *
553 * @param name
554 * The <a href="#binary-name">binary name</a> of the class
555 *
556 * @param resolve
557 * If {@code true} then resolve the class
558 *
559 * @return The resulting {@code Class} object
560 *
561 * @throws ClassNotFoundException
562 * If the class could not be found
563 */
564 protected Class<?> loadClass(String name, boolean resolve)
565 throws ClassNotFoundException
566 {
567 synchronized (getClassLoadingLock(name)) {
568 // First, check if the class has already been loaded
569 Class<?> c = findLoadedClass(name);
570 if (c == null) {
571 long t0 = System.nanoTime();
572 try {
573 if (parent != null) {
574 c = parent.loadClass(name, false);
575 } else {
576 c = findBootstrapClassOrNull(name);
577 }
578 } catch (ClassNotFoundException e) {
579 // ClassNotFoundException thrown if class not found
580 // from the non-null parent class loader
581 }
582
583 if (c == null) {
584 // If still not found, then invoke findClass in order
585 // to find the class.
586 long t1 = System.nanoTime();
587 c = findClass(name);
588
589 // this is the defining class loader; record the stats
590 PerfCounter.getParentDelegationTime().addTime(t1 - t0);
591 PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
592 PerfCounter.getFindClasses().increment();
593 }
594 }
595 if (resolve) {
596 resolveClass(c);
597 }
598 return c;
599 }
600 }
601
602 /**
603 * Loads the class with the specified <a href="#binary-name">binary name</a>
604 * in a module defined to this class loader. This method returns {@code null}
605 * if the class could not be found.
606 *
607 * @apiNote This method does not delegate to the parent class loader.
608 *
609 * @implSpec The default implementation of this method searches for classes
610 * in the following order:
611 *
612 * <ol>
613 * <li>Invoke {@link #findLoadedClass(String)} to check if the class
614 * has already been loaded.</li>
615 * <li>Invoke the {@link #findClass(String, String)} method to find the
616 * class in the given module.</li>
617 * </ol>
618 *
619 * @param module
620 * The module
621 * @param name
622 * The <a href="#binary-name">binary name</a> of the class
623 *
624 * @return The resulting {@code Class} object in a module defined by
625 * this class loader, or {@code null} if the class could not be found.
626 */
627 final Class<?> loadClass(Module module, String name) {
628 synchronized (getClassLoadingLock(name)) {
629 // First, check if the class has already been loaded
630 Class<?> c = findLoadedClass(name);
631 if (c == null) {
632 c = findClass(module.getName(), name);
633 }
634 if (c != null && c.getModule() == module) {
635 return c;
636 } else {
637 return null;
638 }
639 }
640 }
641
642 /**
643 * Returns the lock object for class loading operations.
644 * For backward compatibility, the default implementation of this method
645 * behaves as follows. If this ClassLoader object is registered as
646 * parallel capable, the method returns a dedicated object associated
647 * with the specified class name. Otherwise, the method returns this
648 * ClassLoader object.
649 *
650 * @param className
651 * The name of the to-be-loaded class
652 *
653 * @return the lock for class loading operations
654 *
655 * @throws NullPointerException
656 * If registered as parallel capable and {@code className} is null
657 *
658 * @see #loadClass(String, boolean)
659 *
660 * @since 1.7
661 */
662 protected Object getClassLoadingLock(String className) {
663 Object lock = this;
664 if (parallelLockMap != null) {
665 Object newLock = new Object();
666 lock = parallelLockMap.putIfAbsent(className, newLock);
667 if (lock == null) {
668 lock = newLock;
669 }
670 }
671 return lock;
672 }
673
674 // Invoked by the VM after loading class with this loader.
675 private void checkPackageAccess(Class<?> cls, ProtectionDomain pd) {
676 final SecurityManager sm = System.getSecurityManager();
677 if (sm != null) {
678 if (ReflectUtil.isNonPublicProxyClass(cls)) {
679 for (Class<?> intf: cls.getInterfaces()) {
680 checkPackageAccess(intf, pd);
681 }
682 return;
683 }
684
685 final String packageName = cls.getPackageName();
686 if (!packageName.isEmpty()) {
687 AccessController.doPrivileged(new PrivilegedAction<>() {
688 public Void run() {
689 sm.checkPackageAccess(packageName);
690 return null;
691 }
692 }, new AccessControlContext(new ProtectionDomain[] {pd}));
693 }
694 }
695 }
696
697 /**
698 * Finds the class with the specified <a href="#binary-name">binary name</a>.
699 * This method should be overridden by class loader implementations that
700 * follow the delegation model for loading classes, and will be invoked by
701 * the {@link #loadClass loadClass} method after checking the
702 * parent class loader for the requested class.
703 *
704 * @implSpec The default implementation throws {@code ClassNotFoundException}.
705 *
706 * @param name
707 * The <a href="#binary-name">binary name</a> of the class
708 *
709 * @return The resulting {@code Class} object
710 *
711 * @throws ClassNotFoundException
712 * If the class could not be found
713 *
714 * @since 1.2
715 */
716 protected Class<?> findClass(String name) throws ClassNotFoundException {
717 throw new ClassNotFoundException(name);
718 }
719
720 /**
721 * Finds the class with the given <a href="#binary-name">binary name</a>
722 * in a module defined to this class loader.
723 * Class loader implementations that support loading from modules
724 * should override this method.
725 *
726 * @apiNote This method returns {@code null} rather than throwing
727 * {@code ClassNotFoundException} if the class could not be found.
728 *
729 * @implSpec The default implementation attempts to find the class by
730 * invoking {@link #findClass(String)} when the {@code moduleName} is
731 * {@code null}. It otherwise returns {@code null}.
732 *
733 * @param moduleName
734 * The module name; or {@code null} to find the class in the
735 * {@linkplain #getUnnamedModule() unnamed module} for this
736 * class loader
737
738 * @param name
739 * The <a href="#binary-name">binary name</a> of the class
740 *
741 * @return The resulting {@code Class} object, or {@code null}
742 * if the class could not be found.
743 *
744 * @since 9
745 * @spec JPMS
746 */
747 protected Class<?> findClass(String moduleName, String name) {
748 if (moduleName == null) {
749 try {
750 return findClass(name);
751 } catch (ClassNotFoundException ignore) { }
752 }
753 return null;
754 }
755
756
757 /**
758 * Converts an array of bytes into an instance of class {@code Class}.
759 * Before the {@code Class} can be used it must be resolved. This method
760 * is deprecated in favor of the version that takes a <a
761 * href="#binary-name">binary name</a> as its first argument, and is more secure.
762 *
763 * @param b
764 * The bytes that make up the class data. The bytes in positions
765 * {@code off} through {@code off+len-1} should have the format
766 * of a valid class file as defined by
767 * <cite>The Java™ Virtual Machine Specification</cite>.
768 *
769 * @param off
770 * The start offset in {@code b} of the class data
771 *
772 * @param len
773 * The length of the class data
774 *
775 * @return The {@code Class} object that was created from the specified
776 * class data
777 *
778 * @throws ClassFormatError
779 * If the data did not contain a valid class
780 *
781 * @throws IndexOutOfBoundsException
782 * If either {@code off} or {@code len} is negative, or if
783 * {@code off+len} is greater than {@code b.length}.
784 *
785 * @throws SecurityException
786 * If an attempt is made to add this class to a package that
787 * contains classes that were signed by a different set of
788 * certificates than this class, or if an attempt is made
789 * to define a class in a package with a fully-qualified name
790 * that starts with "{@code java.}".
791 *
792 * @see #loadClass(String, boolean)
793 * @see #resolveClass(Class)
794 *
795 * @deprecated Replaced by {@link #defineClass(String, byte[], int, int)
796 * defineClass(String, byte[], int, int)}
797 */
798 @Deprecated(since="1.1")
799 protected final Class<?> defineClass(byte[] b, int off, int len)
800 throws ClassFormatError
801 {
802 return defineClass(null, b, off, len, null);
803 }
804
805 /**
806 * Converts an array of bytes into an instance of class {@code Class}.
807 * Before the {@code Class} can be used it must be resolved.
808 *
809 * <p> This method assigns a default {@link java.security.ProtectionDomain
810 * ProtectionDomain} to the newly defined class. The
811 * {@code ProtectionDomain} is effectively granted the same set of
812 * permissions returned when {@link
813 * java.security.Policy#getPermissions(java.security.CodeSource)
814 * Policy.getPolicy().getPermissions(new CodeSource(null, null))}
815 * is invoked. The default protection domain is created on the first invocation
816 * of {@link #defineClass(String, byte[], int, int) defineClass},
817 * and re-used on subsequent invocations.
818 *
819 * <p> To assign a specific {@code ProtectionDomain} to the class, use
820 * the {@link #defineClass(String, byte[], int, int,
821 * java.security.ProtectionDomain) defineClass} method that takes a
822 * {@code ProtectionDomain} as one of its arguments. </p>
823 *
824 * <p>
825 * This method defines a package in this class loader corresponding to the
826 * package of the {@code Class} (if such a package has not already been defined
827 * in this class loader). The name of the defined package is derived from
828 * the <a href="#binary-name">binary name</a> of the class specified by
829 * the byte array {@code b}.
830 * Other properties of the defined package are as specified by {@link Package}.
831 *
832 * @param name
833 * The expected <a href="#binary-name">binary name</a> of the class, or
834 * {@code null} if not known
835 *
836 * @param b
837 * The bytes that make up the class data. The bytes in positions
838 * {@code off} through {@code off+len-1} should have the format
839 * of a valid class file as defined by
840 * <cite>The Java™ Virtual Machine Specification</cite>.
841 *
842 * @param off
843 * The start offset in {@code b} of the class data
844 *
845 * @param len
846 * The length of the class data
847 *
848 * @return The {@code Class} object that was created from the specified
849 * class data.
850 *
851 * @throws ClassFormatError
852 * If the data did not contain a valid class
853 *
854 * @throws IndexOutOfBoundsException
855 * If either {@code off} or {@code len} is negative, or if
856 * {@code off+len} is greater than {@code b.length}.
857 *
858 * @throws SecurityException
859 * If an attempt is made to add this class to a package that
860 * contains classes that were signed by a different set of
861 * certificates than this class (which is unsigned), or if
862 * {@code name} begins with "{@code java.}".
863 *
864 * @see #loadClass(String, boolean)
865 * @see #resolveClass(Class)
866 * @see java.security.CodeSource
867 * @see java.security.SecureClassLoader
868 *
869 * @since 1.1
870 * @revised 9
871 * @spec JPMS
872 */
873 protected final Class<?> defineClass(String name, byte[] b, int off, int len)
874 throws ClassFormatError
875 {
876 return defineClass(name, b, off, len, null);
877 }
878
879 /* Determine protection domain, and check that:
880 - not define java.* class,
881 - signer of this class matches signers for the rest of the classes in
882 package.
883 */
884 private ProtectionDomain preDefineClass(String name,
885 ProtectionDomain pd)
886 {
887 if (!checkName(name))
888 throw new NoClassDefFoundError("IllegalName: " + name);
889
890 // Note: Checking logic in java.lang.invoke.MemberName.checkForTypeAlias
891 // relies on the fact that spoofing is impossible if a class has a name
892 // of the form "java.*"
893 if ((name != null) && name.startsWith("java.")
894 && this != getBuiltinPlatformClassLoader()) {
895 throw new SecurityException
896 ("Prohibited package name: " +
897 name.substring(0, name.lastIndexOf('.')));
898 }
899 if (pd == null) {
900 pd = defaultDomain;
901 }
902
903 if (name != null) {
904 checkCerts(name, pd.getCodeSource());
905 }
906
907 return pd;
908 }
909
910 private String defineClassSourceLocation(ProtectionDomain pd) {
911 CodeSource cs = pd.getCodeSource();
912 String source = null;
913 if (cs != null && cs.getLocation() != null) {
914 source = cs.getLocation().toString();
915 }
916 return source;
917 }
918
919 private void postDefineClass(Class<?> c, ProtectionDomain pd) {
920 // define a named package, if not present
921 getNamedPackage(c.getPackageName(), c.getModule());
922
923 if (pd.getCodeSource() != null) {
924 Certificate certs[] = pd.getCodeSource().getCertificates();
925 if (certs != null)
926 setSigners(c, certs);
927 }
928 }
929
930 /**
931 * Converts an array of bytes into an instance of class {@code Class},
932 * with a given {@code ProtectionDomain}.
933 *
934 * <p> If the given {@code ProtectionDomain} is {@code null},
935 * then a default protection domain will be assigned to the class as specified
936 * in the documentation for {@link #defineClass(String, byte[], int, int)}.
937 * Before the class can be used it must be resolved.
938 *
939 * <p> The first class defined in a package determines the exact set of
940 * certificates that all subsequent classes defined in that package must
941 * contain. The set of certificates for a class is obtained from the
942 * {@link java.security.CodeSource CodeSource} within the
943 * {@code ProtectionDomain} of the class. Any classes added to that
944 * package must contain the same set of certificates or a
945 * {@code SecurityException} will be thrown. Note that if
946 * {@code name} is {@code null}, this check is not performed.
947 * You should always pass in the <a href="#binary-name">binary name</a> of the
948 * class you are defining as well as the bytes. This ensures that the
949 * class you are defining is indeed the class you think it is.
950 *
951 * <p> If the specified {@code name} begins with "{@code java.}", it can
952 * only be defined by the {@linkplain #getPlatformClassLoader()
953 * platform class loader} or its ancestors; otherwise {@code SecurityException}
954 * will be thrown. If {@code name} is not {@code null}, it must be equal to
955 * the <a href="#binary-name">binary name</a> of the class
956 * specified by the byte array {@code b}, otherwise a {@link
957 * NoClassDefFoundError NoClassDefFoundError} will be thrown.
958 *
959 * <p> This method defines a package in this class loader corresponding to the
960 * package of the {@code Class} (if such a package has not already been defined
961 * in this class loader). The name of the defined package is derived from
962 * the <a href="#binary-name">binary name</a> of the class specified by
963 * the byte array {@code b}.
964 * Other properties of the defined package are as specified by {@link Package}.
965 *
966 * @param name
967 * The expected <a href="#binary-name">binary name</a> of the class, or
968 * {@code null} if not known
969 *
970 * @param b
971 * The bytes that make up the class data. The bytes in positions
972 * {@code off} through {@code off+len-1} should have the format
973 * of a valid class file as defined by
974 * <cite>The Java™ Virtual Machine Specification</cite>.
975 *
976 * @param off
977 * The start offset in {@code b} of the class data
978 *
979 * @param len
980 * The length of the class data
981 *
982 * @param protectionDomain
983 * The {@code ProtectionDomain} of the class
984 *
985 * @return The {@code Class} object created from the data,
986 * and {@code ProtectionDomain}.
987 *
988 * @throws ClassFormatError
989 * If the data did not contain a valid class
990 *
991 * @throws NoClassDefFoundError
992 * If {@code name} is not {@code null} and not equal to the
993 * <a href="#binary-name">binary name</a> of the class specified by {@code b}
994 *
995 * @throws IndexOutOfBoundsException
996 * If either {@code off} or {@code len} is negative, or if
997 * {@code off+len} is greater than {@code b.length}.
998 *
999 * @throws SecurityException
1000 * If an attempt is made to add this class to a package that
1001 * contains classes that were signed by a different set of
1002 * certificates than this class, or if {@code name} begins with
1003 * "{@code java.}" and this class loader is not the platform
1004 * class loader or its ancestor.
1005 *
1006 * @revised 9
1007 * @spec JPMS
1008 */
1009 protected final Class<?> defineClass(String name, byte[] b, int off, int len,
1010 ProtectionDomain protectionDomain)
1011 throws ClassFormatError
1012 {
1013 protectionDomain = preDefineClass(name, protectionDomain);
1014 String source = defineClassSourceLocation(protectionDomain);
1015 Class<?> c = defineClass1(this, name, b, off, len, protectionDomain, source);
1016 postDefineClass(c, protectionDomain);
1017 return c;
1018 }
1019
1020 /**
1021 * Converts a {@link java.nio.ByteBuffer ByteBuffer} into an instance
1022 * of class {@code Class}, with the given {@code ProtectionDomain}.
1023 * If the given {@code ProtectionDomain} is {@code null}, then a default
1024 * protection domain will be assigned to the class as
1025 * specified in the documentation for {@link #defineClass(String, byte[],
1026 * int, int)}. Before the class can be used it must be resolved.
1027 *
1028 * <p>The rules about the first class defined in a package determining the
1029 * set of certificates for the package, the restrictions on class names,
1030 * and the defined package of the class
1031 * are identical to those specified in the documentation for {@link
1032 * #defineClass(String, byte[], int, int, ProtectionDomain)}.
1033 *
1034 * <p> An invocation of this method of the form
1035 * <i>cl</i>{@code .defineClass(}<i>name</i>{@code ,}
1036 * <i>bBuffer</i>{@code ,} <i>pd</i>{@code )} yields exactly the same
1037 * result as the statements
1038 *
1039 *<p> <code>
1040 * ...<br>
1041 * byte[] temp = new byte[bBuffer.{@link
1042 * java.nio.ByteBuffer#remaining remaining}()];<br>
1043 * bBuffer.{@link java.nio.ByteBuffer#get(byte[])
1044 * get}(temp);<br>
1045 * return {@link #defineClass(String, byte[], int, int, ProtectionDomain)
1046 * cl.defineClass}(name, temp, 0,
1047 * temp.length, pd);<br>
1048 * </code></p>
1049 *
1050 * @param name
1051 * The expected <a href="#binary-name">binary name</a>. of the class, or
1052 * {@code null} if not known
1053 *
1054 * @param b
1055 * The bytes that make up the class data. The bytes from positions
1056 * {@code b.position()} through {@code b.position() + b.limit() -1
1057 * } should have the format of a valid class file as defined by
1058 * <cite>The Java™ Virtual Machine Specification</cite>.
1059 *
1060 * @param protectionDomain
1061 * The {@code ProtectionDomain} of the class, or {@code null}.
1062 *
1063 * @return The {@code Class} object created from the data,
1064 * and {@code ProtectionDomain}.
1065 *
1066 * @throws ClassFormatError
1067 * If the data did not contain a valid class.
1068 *
1069 * @throws NoClassDefFoundError
1070 * If {@code name} is not {@code null} and not equal to the
1071 * <a href="#binary-name">binary name</a> of the class specified by {@code b}
1072 *
1073 * @throws SecurityException
1074 * If an attempt is made to add this class to a package that
1075 * contains classes that were signed by a different set of
1076 * certificates than this class, or if {@code name} begins with
1077 * "{@code java.}".
1078 *
1079 * @see #defineClass(String, byte[], int, int, ProtectionDomain)
1080 *
1081 * @since 1.5
1082 * @revised 9
1083 * @spec JPMS
1084 */
1085 protected final Class<?> defineClass(String name, java.nio.ByteBuffer b,
1086 ProtectionDomain protectionDomain)
1087 throws ClassFormatError
1088 {
1089 int len = b.remaining();
1090
1091 // Use byte[] if not a direct ByteBuffer:
1092 if (!b.isDirect()) {
1093 if (b.hasArray()) {
1094 return defineClass(name, b.array(),
1095 b.position() + b.arrayOffset(), len,
1096 protectionDomain);
1097 } else {
1098 // no array, or read-only array
1099 byte[] tb = new byte[len];
1100 b.get(tb); // get bytes out of byte buffer.
1101 return defineClass(name, tb, 0, len, protectionDomain);
1102 }
1103 }
1104
1105 protectionDomain = preDefineClass(name, protectionDomain);
1106 String source = defineClassSourceLocation(protectionDomain);
1107 Class<?> c = defineClass2(this, name, b, b.position(), len, protectionDomain, source);
1108 postDefineClass(c, protectionDomain);
1109 return c;
1110 }
1111
1112 static native Class<?> defineClass1(ClassLoader loader, String name, byte[] b, int off, int len,
1113 ProtectionDomain pd, String source);
1114
1115 static native Class<?> defineClass2(ClassLoader loader, String name, java.nio.ByteBuffer b,
1116 int off, int len, ProtectionDomain pd,
1117 String source);
1118
1119 // true if the name is null or has the potential to be a valid binary name
1120 private boolean checkName(String name) {
1121 if ((name == null) || (name.isEmpty()))
1122 return true;
1123 if ((name.indexOf('/') != -1) || (name.charAt(0) == '['))
1124 return false;
1125 return true;
1126 }
1127
1128 private void checkCerts(String name, CodeSource cs) {
1129 int i = name.lastIndexOf('.');
1130 String pname = (i == -1) ? "" : name.substring(0, i);
1131
1132 Certificate[] certs = null;
1133 if (cs != null) {
1134 certs = cs.getCertificates();
1135 }
1136 certs = certs == null ? nocerts : certs;
1137 Certificate[] pcerts = package2certs.putIfAbsent(pname, certs);
1138 if (pcerts != null && !compareCerts(pcerts, certs)) {
1139 throw new SecurityException("class \"" + name
1140 + "\"'s signer information does not match signer information"
1141 + " of other classes in the same package");
1142 }
1143 }
1144
1145 /**
1146 * check to make sure the certs for the new class (certs) are the same as
1147 * the certs for the first class inserted in the package (pcerts)
1148 */
1149 private boolean compareCerts(Certificate[] pcerts, Certificate[] certs) {
1150 // empty array fast-path
1151 if (certs.length == 0)
1152 return pcerts.length == 0;
1153
1154 // the length must be the same at this point
1155 if (certs.length != pcerts.length)
1156 return false;
1157
1158 // go through and make sure all the certs in one array
1159 // are in the other and vice-versa.
1160 boolean match;
1161 for (Certificate cert : certs) {
1162 match = false;
1163 for (Certificate pcert : pcerts) {
1164 if (cert.equals(pcert)) {
1165 match = true;
1166 break;
1167 }
1168 }
1169 if (!match) return false;
1170 }
1171
1172 // now do the same for pcerts
1173 for (Certificate pcert : pcerts) {
1174 match = false;
1175 for (Certificate cert : certs) {
1176 if (pcert.equals(cert)) {
1177 match = true;
1178 break;
1179 }
1180 }
1181 if (!match) return false;
1182 }
1183
1184 return true;
1185 }
1186
1187 /**
1188 * Links the specified class. This (misleadingly named) method may be
1189 * used by a class loader to link a class. If the class {@code c} has
1190 * already been linked, then this method simply returns. Otherwise, the
1191 * class is linked as described in the "Execution" chapter of
1192 * <cite>The Java™ Language Specification</cite>.
1193 *
1194 * @param c
1195 * The class to link
1196 *
1197 * @throws NullPointerException
1198 * If {@code c} is {@code null}.
1199 *
1200 * @see #defineClass(String, byte[], int, int)
1201 */
1202 protected final void resolveClass(Class<?> c) {
1203 if (c == null) {
1204 throw new NullPointerException();
1205 }
1206 }
1207
1208 /**
1209 * Finds a class with the specified <a href="#binary-name">binary name</a>,
1210 * loading it if necessary.
1211 *
1212 * <p> This method loads the class through the system class loader (see
1213 * {@link #getSystemClassLoader()}). The {@code Class} object returned
1214 * might have more than one {@code ClassLoader} associated with it.
1215 * Subclasses of {@code ClassLoader} need not usually invoke this method,
1216 * because most class loaders need to override just {@link
1217 * #findClass(String)}. </p>
1218 *
1219 * @param name
1220 * The <a href="#binary-name">binary name</a> of the class
1221 *
1222 * @return The {@code Class} object for the specified {@code name}
1223 *
1224 * @throws ClassNotFoundException
1225 * If the class could not be found
1226 *
1227 * @see #ClassLoader(ClassLoader)
1228 * @see #getParent()
1229 */
1230 protected final Class<?> findSystemClass(String name)
1231 throws ClassNotFoundException
1232 {
1233 return getSystemClassLoader().loadClass(name);
1234 }
1235
1236 /**
1237 * Returns a class loaded by the bootstrap class loader;
1238 * or return null if not found.
1239 */
1240 Class<?> findBootstrapClassOrNull(String name) {
1241 if (!checkName(name)) return null;
1242
1243 return findBootstrapClass(name);
1244 }
1245
1246 // return null if not found
1247 private native Class<?> findBootstrapClass(String name);
1248
1249 /**
1250 * Returns the class with the given <a href="#binary-name">binary name</a> if this
1251 * loader has been recorded by the Java virtual machine as an initiating
1252 * loader of a class with that <a href="#binary-name">binary name</a>. Otherwise
1253 * {@code null} is returned.
1254 *
1255 * @param name
1256 * The <a href="#binary-name">binary name</a> of the class
1257 *
1258 * @return The {@code Class} object, or {@code null} if the class has
1259 * not been loaded
1260 *
1261 * @since 1.1
1262 */
1263 protected final Class<?> findLoadedClass(String name) {
1264 if (!checkName(name))
1265 return null;
1266 return findLoadedClass0(name);
1267 }
1268
1269 private final native Class<?> findLoadedClass0(String name);
1270
1271 /**
1272 * Sets the signers of a class. This should be invoked after defining a
1273 * class.
1274 *
1275 * @param c
1276 * The {@code Class} object
1277 *
1278 * @param signers
1279 * The signers for the class
1280 *
1281 * @since 1.1
1282 */
1283 protected final void setSigners(Class<?> c, Object[] signers) {
1284 c.setSigners(signers);
1285 }
1286
1287
1288 // -- Resources --
1289
1290 /**
1291 * Returns a URL to a resource in a module defined to this class loader.
1292 * Class loader implementations that support loading from modules
1293 * should override this method.
1294 *
1295 * @apiNote This method is the basis for the {@link
1296 * Class#getResource Class.getResource}, {@link Class#getResourceAsStream
1297 * Class.getResourceAsStream}, and {@link Module#getResourceAsStream
1298 * Module.getResourceAsStream} methods. It is not subject to the rules for
1299 * encapsulation specified by {@code Module.getResourceAsStream}.
1300 *
1301 * @implSpec The default implementation attempts to find the resource by
1302 * invoking {@link #findResource(String)} when the {@code moduleName} is
1303 * {@code null}. It otherwise returns {@code null}.
1304 *
1305 * @param moduleName
1306 * The module name; or {@code null} to find a resource in the
1307 * {@linkplain #getUnnamedModule() unnamed module} for this
1308 * class loader
1309 * @param name
1310 * The resource name
1311 *
1312 * @return A URL to the resource; {@code null} if the resource could not be
1313 * found, a URL could not be constructed to locate the resource,
1314 * access to the resource is denied by the security manager, or
1315 * there isn't a module of the given name defined to the class
1316 * loader.
1317 *
1318 * @throws IOException
1319 * If I/O errors occur
1320 *
1321 * @see java.lang.module.ModuleReader#find(String)
1322 * @since 9
1323 * @spec JPMS
1324 */
1325 protected URL findResource(String moduleName, String name) throws IOException {
1326 if (moduleName == null) {
1327 return findResource(name);
1328 } else {
1329 return null;
1330 }
1331 }
1332
1333 /**
1334 * Finds the resource with the given name. A resource is some data
1335 * (images, audio, text, etc) that can be accessed by class code in a way
1336 * that is independent of the location of the code.
1337 *
1338 * <p> The name of a resource is a '{@code /}'-separated path name that
1339 * identifies the resource. </p>
1340 *
1341 * <p> Resources in named modules are subject to the encapsulation rules
1342 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1343 * Additionally, and except for the special case where the resource has a
1344 * name ending with "{@code .class}", this method will only find resources in
1345 * packages of named modules when the package is {@link Module#isOpen(String)
1346 * opened} unconditionally (even if the caller of this method is in the
1347 * same module as the resource). </p>
1348 *
1349 * @implSpec The default implementation will first search the parent class
1350 * loader for the resource; if the parent is {@code null} the path of the
1351 * class loader built into the virtual machine is searched. If not found,
1352 * this method will invoke {@link #findResource(String)} to find the resource.
1353 *
1354 * @apiNote Where several modules are defined to the same class loader,
1355 * and where more than one module contains a resource with the given name,
1356 * then the ordering that modules are searched is not specified and may be
1357 * very unpredictable.
1358 * When overriding this method it is recommended that an implementation
1359 * ensures that any delegation is consistent with the {@link
1360 * #getResources(java.lang.String) getResources(String)} method.
1361 *
1362 * @param name
1363 * The resource name
1364 *
1365 * @return {@code URL} object for reading the resource; {@code null} if
1366 * the resource could not be found, a {@code URL} could not be
1367 * constructed to locate the resource, the resource is in a package
1368 * that is not opened unconditionally, or access to the resource is
1369 * denied by the security manager.
1370 *
1371 * @throws NullPointerException If {@code name} is {@code null}
1372 *
1373 * @since 1.1
1374 * @revised 9
1375 * @spec JPMS
1376 */
1377 public URL getResource(String name) {
1378 Objects.requireNonNull(name);
1379 URL url;
1380 if (parent != null) {
1381 url = parent.getResource(name);
1382 } else {
1383 url = BootLoader.findResource(name);
1384 }
1385 if (url == null) {
1386 url = findResource(name);
1387 }
1388 return url;
1389 }
1390
1391 /**
1392 * Finds all the resources with the given name. A resource is some data
1393 * (images, audio, text, etc) that can be accessed by class code in a way
1394 * that is independent of the location of the code.
1395 *
1396 * <p> The name of a resource is a {@code /}-separated path name that
1397 * identifies the resource. </p>
1398 *
1399 * <p> Resources in named modules are subject to the encapsulation rules
1400 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1401 * Additionally, and except for the special case where the resource has a
1402 * name ending with "{@code .class}", this method will only find resources in
1403 * packages of named modules when the package is {@link Module#isOpen(String)
1404 * opened} unconditionally (even if the caller of this method is in the
1405 * same module as the resource). </p>
1406 *
1407 * @implSpec The default implementation will first search the parent class
1408 * loader for the resource; if the parent is {@code null} the path of the
1409 * class loader built into the virtual machine is searched. It then
1410 * invokes {@link #findResources(String)} to find the resources with the
1411 * name in this class loader. It returns an enumeration whose elements
1412 * are the URLs found by searching the parent class loader followed by
1413 * the elements found with {@code findResources}.
1414 *
1415 * @apiNote Where several modules are defined to the same class loader,
1416 * and where more than one module contains a resource with the given name,
1417 * then the ordering is not specified and may be very unpredictable.
1418 * When overriding this method it is recommended that an
1419 * implementation ensures that any delegation is consistent with the {@link
1420 * #getResource(java.lang.String) getResource(String)} method. This should
1421 * ensure that the first element returned by the Enumeration's
1422 * {@code nextElement} method is the same resource that the
1423 * {@code getResource(String)} method would return.
1424 *
1425 * @param name
1426 * The resource name
1427 *
1428 * @return An enumeration of {@link java.net.URL URL} objects for the
1429 * resource. If no resources could be found, the enumeration will
1430 * be empty. Resources for which a {@code URL} cannot be
1431 * constructed, are in a package that is not opened
1432 * unconditionally, or access to the resource is denied by the
1433 * security manager, are not returned in the enumeration.
1434 *
1435 * @throws IOException
1436 * If I/O errors occur
1437 * @throws NullPointerException If {@code name} is {@code null}
1438 *
1439 * @since 1.2
1440 * @revised 9
1441 * @spec JPMS
1442 */
1443 public Enumeration<URL> getResources(String name) throws IOException {
1444 Objects.requireNonNull(name);
1445 @SuppressWarnings("unchecked")
1446 Enumeration<URL>[] tmp = (Enumeration<URL>[]) new Enumeration<?>[2];
1447 if (parent != null) {
1448 tmp[0] = parent.getResources(name);
1449 } else {
1450 tmp[0] = BootLoader.findResources(name);
1451 }
1452 tmp[1] = findResources(name);
1453
1454 return new CompoundEnumeration<>(tmp);
1455 }
1456
1457 /**
1458 * Returns a stream whose elements are the URLs of all the resources with
1459 * the given name. A resource is some data (images, audio, text, etc) that
1460 * can be accessed by class code in a way that is independent of the
1461 * location of the code.
1462 *
1463 * <p> The name of a resource is a {@code /}-separated path name that
1464 * identifies the resource.
1465 *
1466 * <p> The resources will be located when the returned stream is evaluated.
1467 * If the evaluation results in an {@code IOException} then the I/O
1468 * exception is wrapped in an {@link UncheckedIOException} that is then
1469 * thrown.
1470 *
1471 * <p> Resources in named modules are subject to the encapsulation rules
1472 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1473 * Additionally, and except for the special case where the resource has a
1474 * name ending with "{@code .class}", this method will only find resources in
1475 * packages of named modules when the package is {@link Module#isOpen(String)
1476 * opened} unconditionally (even if the caller of this method is in the
1477 * same module as the resource). </p>
1478 *
1479 * @implSpec The default implementation invokes {@link #getResources(String)
1480 * getResources} to find all the resources with the given name and returns
1481 * a stream with the elements in the enumeration as the source.
1482 *
1483 * @apiNote When overriding this method it is recommended that an
1484 * implementation ensures that any delegation is consistent with the {@link
1485 * #getResource(java.lang.String) getResource(String)} method. This should
1486 * ensure that the first element returned by the stream is the same
1487 * resource that the {@code getResource(String)} method would return.
1488 *
1489 * @param name
1490 * The resource name
1491 *
1492 * @return A stream of resource {@link java.net.URL URL} objects. If no
1493 * resources could be found, the stream will be empty. Resources
1494 * for which a {@code URL} cannot be constructed, are in a package
1495 * that is not opened unconditionally, or access to the resource
1496 * is denied by the security manager, will not be in the stream.
1497 *
1498 * @throws NullPointerException If {@code name} is {@code null}
1499 *
1500 * @since 9
1501 */
1502 public Stream<URL> resources(String name) {
1503 Objects.requireNonNull(name);
1504 int characteristics = Spliterator.NONNULL | Spliterator.IMMUTABLE;
1505 Supplier<Spliterator<URL>> si = () -> {
1506 try {
1507 return Spliterators.spliteratorUnknownSize(
1508 getResources(name).asIterator(), characteristics);
1509 } catch (IOException e) {
1510 throw new UncheckedIOException(e);
1511 }
1512 };
1513 return StreamSupport.stream(si, characteristics, false);
1514 }
1515
1516 /**
1517 * Finds the resource with the given name. Class loader implementations
1518 * should override this method.
1519 *
1520 * <p> For resources in named modules then the method must implement the
1521 * rules for encapsulation specified in the {@code Module} {@link
1522 * Module#getResourceAsStream getResourceAsStream} method. Additionally,
1523 * it must not find non-"{@code .class}" resources in packages of named
1524 * modules unless the package is {@link Module#isOpen(String) opened}
1525 * unconditionally. </p>
1526 *
1527 * @implSpec The default implementation returns {@code null}.
1528 *
1529 * @param name
1530 * The resource name
1531 *
1532 * @return {@code URL} object for reading the resource; {@code null} if
1533 * the resource could not be found, a {@code URL} could not be
1534 * constructed to locate the resource, the resource is in a package
1535 * that is not opened unconditionally, or access to the resource is
1536 * denied by the security manager.
1537 *
1538 * @since 1.2
1539 * @revised 9
1540 * @spec JPMS
1541 */
1542 protected URL findResource(String name) {
1543 return null;
1544 }
1545
1546 /**
1547 * Returns an enumeration of {@link java.net.URL URL} objects
1548 * representing all the resources with the given name. Class loader
1549 * implementations should override this method.
1550 *
1551 * <p> For resources in named modules then the method must implement the
1552 * rules for encapsulation specified in the {@code Module} {@link
1553 * Module#getResourceAsStream getResourceAsStream} method. Additionally,
1554 * it must not find non-"{@code .class}" resources in packages of named
1555 * modules unless the package is {@link Module#isOpen(String) opened}
1556 * unconditionally. </p>
1557 *
1558 * @implSpec The default implementation returns an enumeration that
1559 * contains no elements.
1560 *
1561 * @param name
1562 * The resource name
1563 *
1564 * @return An enumeration of {@link java.net.URL URL} objects for
1565 * the resource. If no resources could be found, the enumeration
1566 * will be empty. Resources for which a {@code URL} cannot be
1567 * constructed, are in a package that is not opened unconditionally,
1568 * or access to the resource is denied by the security manager,
1569 * are not returned in the enumeration.
1570 *
1571 * @throws IOException
1572 * If I/O errors occur
1573 *
1574 * @since 1.2
1575 * @revised 9
1576 * @spec JPMS
1577 */
1578 protected Enumeration<URL> findResources(String name) throws IOException {
1579 return Collections.emptyEnumeration();
1580 }
1581
1582 /**
1583 * Registers the caller as
1584 * {@linkplain #isRegisteredAsParallelCapable() parallel capable}.
1585 * The registration succeeds if and only if all of the following
1586 * conditions are met:
1587 * <ol>
1588 * <li> no instance of the caller has been created</li>
1589 * <li> all of the super classes (except class Object) of the caller are
1590 * registered as parallel capable</li>
1591 * </ol>
1592 * <p>Note that once a class loader is registered as parallel capable, there
1593 * is no way to change it back.</p>
1594 *
1595 * @return {@code true} if the caller is successfully registered as
1596 * parallel capable and {@code false} if otherwise.
1597 *
1598 * @see #isRegisteredAsParallelCapable()
1599 *
1600 * @since 1.7
1601 */
1602 @CallerSensitive
1603 protected static boolean registerAsParallelCapable() {
1604 Class<? extends ClassLoader> callerClass =
1605 Reflection.getCallerClass().asSubclass(ClassLoader.class);
1606 return ParallelLoaders.register(callerClass);
1607 }
1608
1609 /**
1610 * Returns {@code true} if this class loader is registered as
1611 * {@linkplain #registerAsParallelCapable parallel capable}, otherwise
1612 * {@code false}.
1613 *
1614 * @return {@code true} if this class loader is parallel capable,
1615 * otherwise {@code false}.
1616 *
1617 * @see #registerAsParallelCapable()
1618 *
1619 * @since 9
1620 */
1621 public final boolean isRegisteredAsParallelCapable() {
1622 return ParallelLoaders.isRegistered(this.getClass());
1623 }
1624
1625 /**
1626 * Find a resource of the specified name from the search path used to load
1627 * classes. This method locates the resource through the system class
1628 * loader (see {@link #getSystemClassLoader()}).
1629 *
1630 * <p> Resources in named modules are subject to the encapsulation rules
1631 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1632 * Additionally, and except for the special case where the resource has a
1633 * name ending with "{@code .class}", this method will only find resources in
1634 * packages of named modules when the package is {@link Module#isOpen(String)
1635 * opened} unconditionally. </p>
1636 *
1637 * @param name
1638 * The resource name
1639 *
1640 * @return A {@link java.net.URL URL} to the resource; {@code
1641 * null} if the resource could not be found, a URL could not be
1642 * constructed to locate the resource, the resource is in a package
1643 * that is not opened unconditionally or access to the resource is
1644 * denied by the security manager.
1645 *
1646 * @since 1.1
1647 * @revised 9
1648 * @spec JPMS
1649 */
1650 public static URL getSystemResource(String name) {
1651 return getSystemClassLoader().getResource(name);
1652 }
1653
1654 /**
1655 * Finds all resources of the specified name from the search path used to
1656 * load classes. The resources thus found are returned as an
1657 * {@link java.util.Enumeration Enumeration} of {@link
1658 * java.net.URL URL} objects.
1659 *
1660 * <p> The search order is described in the documentation for {@link
1661 * #getSystemResource(String)}. </p>
1662 *
1663 * <p> Resources in named modules are subject to the encapsulation rules
1664 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1665 * Additionally, and except for the special case where the resource has a
1666 * name ending with "{@code .class}", this method will only find resources in
1667 * packages of named modules when the package is {@link Module#isOpen(String)
1668 * opened} unconditionally. </p>
1669 *
1670 * @param name
1671 * The resource name
1672 *
1673 * @return An enumeration of {@link java.net.URL URL} objects for
1674 * the resource. If no resources could be found, the enumeration
1675 * will be empty. Resources for which a {@code URL} cannot be
1676 * constructed, are in a package that is not opened unconditionally,
1677 * or access to the resource is denied by the security manager,
1678 * are not returned in the enumeration.
1679 *
1680 * @throws IOException
1681 * If I/O errors occur
1682 *
1683 * @since 1.2
1684 * @revised 9
1685 * @spec JPMS
1686 */
1687 public static Enumeration<URL> getSystemResources(String name)
1688 throws IOException
1689 {
1690 return getSystemClassLoader().getResources(name);
1691 }
1692
1693 /**
1694 * Returns an input stream for reading the specified resource.
1695 *
1696 * <p> The search order is described in the documentation for {@link
1697 * #getResource(String)}. </p>
1698 *
1699 * <p> Resources in named modules are subject to the encapsulation rules
1700 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1701 * Additionally, and except for the special case where the resource has a
1702 * name ending with "{@code .class}", this method will only find resources in
1703 * packages of named modules when the package is {@link Module#isOpen(String)
1704 * opened} unconditionally. </p>
1705 *
1706 * @param name
1707 * The resource name
1708 *
1709 * @return An input stream for reading the resource; {@code null} if the
1710 * resource could not be found, the resource is in a package that
1711 * is not opened unconditionally, or access to the resource is
1712 * denied by the security manager.
1713 *
1714 * @throws NullPointerException If {@code name} is {@code null}
1715 *
1716 * @since 1.1
1717 * @revised 9
1718 * @spec JPMS
1719 */
1720 public InputStream getResourceAsStream(String name) {
1721 Objects.requireNonNull(name);
1722 URL url = getResource(name);
1723 try {
1724 return url != null ? url.openStream() : null;
1725 } catch (IOException e) {
1726 return null;
1727 }
1728 }
1729
1730 /**
1731 * Open for reading, a resource of the specified name from the search path
1732 * used to load classes. This method locates the resource through the
1733 * system class loader (see {@link #getSystemClassLoader()}).
1734 *
1735 * <p> Resources in named modules are subject to the encapsulation rules
1736 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1737 * Additionally, and except for the special case where the resource has a
1738 * name ending with "{@code .class}", this method will only find resources in
1739 * packages of named modules when the package is {@link Module#isOpen(String)
1740 * opened} unconditionally. </p>
1741 *
1742 * @param name
1743 * The resource name
1744 *
1745 * @return An input stream for reading the resource; {@code null} if the
1746 * resource could not be found, the resource is in a package that
1747 * is not opened unconditionally, or access to the resource is
1748 * denied by the security manager.
1749 *
1750 * @since 1.1
1751 * @revised 9
1752 * @spec JPMS
1753 */
1754 public static InputStream getSystemResourceAsStream(String name) {
1755 URL url = getSystemResource(name);
1756 try {
1757 return url != null ? url.openStream() : null;
1758 } catch (IOException e) {
1759 return null;
1760 }
1761 }
1762
1763
1764 // -- Hierarchy --
1765
1766 /**
1767 * Returns the parent class loader for delegation. Some implementations may
1768 * use {@code null} to represent the bootstrap class loader. This method
1769 * will return {@code null} in such implementations if this class loader's
1770 * parent is the bootstrap class loader.
1771 *
1772 * @return The parent {@code ClassLoader}
1773 *
1774 * @throws SecurityException
1775 * If a security manager is present, and the caller's class loader
1776 * is not {@code null} and is not an ancestor of this class loader,
1777 * and the caller does not have the
1778 * {@link RuntimePermission}{@code ("getClassLoader")}
1779 *
1780 * @since 1.2
1781 */
1782 @CallerSensitive
1783 public final ClassLoader getParent() {
1784 if (parent == null)
1785 return null;
1786 SecurityManager sm = System.getSecurityManager();
1787 if (sm != null) {
1788 // Check access to the parent class loader
1789 // If the caller's class loader is same as this class loader,
1790 // permission check is performed.
1791 checkClassLoaderPermission(parent, Reflection.getCallerClass());
1792 }
1793 return parent;
1794 }
1795
1796 /**
1797 * Returns the unnamed {@code Module} for this class loader.
1798 *
1799 * @return The unnamed Module for this class loader
1800 *
1801 * @see Module#isNamed()
1802 * @since 9
1803 * @spec JPMS
1804 */
1805 public final Module getUnnamedModule() {
1806 return unnamedModule;
1807 }
1808
1809 /**
1810 * Returns the platform class loader. All
1811 * <a href="#builtinLoaders">platform classes</a> are visible to
1812 * the platform class loader.
1813 *
1814 * @implNote The name of the builtin platform class loader is
1815 * {@code "platform"}.
1816 *
1817 * @return The platform {@code ClassLoader}.
1818 *
1819 * @throws SecurityException
1820 * If a security manager is present, and the caller's class loader is
1821 * not {@code null}, and the caller's class loader is not the same
1822 * as or an ancestor of the platform class loader,
1823 * and the caller does not have the
1824 * {@link RuntimePermission}{@code ("getClassLoader")}
1825 *
1826 * @since 9
1827 * @spec JPMS
1828 */
1829 @CallerSensitive
1830 public static ClassLoader getPlatformClassLoader() {
1831 SecurityManager sm = System.getSecurityManager();
1832 ClassLoader loader = getBuiltinPlatformClassLoader();
1833 if (sm != null) {
1834 checkClassLoaderPermission(loader, Reflection.getCallerClass());
1835 }
1836 return loader;
1837 }
1838
1839 /**
1840 * Returns the system class loader. This is the default
1841 * delegation parent for new {@code ClassLoader} instances, and is
1842 * typically the class loader used to start the application.
1843 *
1844 * <p> This method is first invoked early in the runtime's startup
1845 * sequence, at which point it creates the system class loader. This
1846 * class loader will be the context class loader for the main application
1847 * thread (for example, the thread that invokes the {@code main} method of
1848 * the main class).
1849 *
1850 * <p> The default system class loader is an implementation-dependent
1851 * instance of this class.
1852 *
1853 * <p> If the system property "{@systemProperty java.system.class.loader}"
1854 * is defined when this method is first invoked then the value of that
1855 * property is taken to be the name of a class that will be returned as the
1856 * system class loader. The class is loaded using the default system class
1857 * loader and must define a public constructor that takes a single parameter
1858 * of type {@code ClassLoader} which is used as the delegation parent. An
1859 * instance is then created using this constructor with the default system
1860 * class loader as the parameter. The resulting class loader is defined
1861 * to be the system class loader. During construction, the class loader
1862 * should take great care to avoid calling {@code getSystemClassLoader()}.
1863 * If circular initialization of the system class loader is detected then
1864 * an {@code IllegalStateException} is thrown.
1865 *
1866 * @implNote The system property to override the system class loader is not
1867 * examined until the VM is almost fully initialized. Code that executes
1868 * this method during startup should take care not to cache the return
1869 * value until the system is fully initialized.
1870 *
1871 * <p> The name of the built-in system class loader is {@code "app"}.
1872 * The system property "{@code java.class.path}" is read during early
1873 * initialization of the VM to determine the class path.
1874 * An empty value of "{@code java.class.path}" property is interpreted
1875 * differently depending on whether the initial module (the module
1876 * containing the main class) is named or unnamed:
1877 * If named, the built-in system class loader will have no class path and
1878 * will search for classes and resources using the application module path;
1879 * otherwise, if unnamed, it will set the class path to the current
1880 * working directory.
1881 *
1882 * <p> JAR files on the class path may contain a {@code Class-Path} manifest
1883 * attribute to specify dependent JAR files to be included in the class path.
1884 * {@code Class-Path} entries must meet certain conditions for validity (see
1885 * the <a href="{@docRoot}/../specs/jar/jar.html#class-path-attribute">
1886 * JAR File Specification</a> for details). Invalid {@code Class-Path}
1887 * entries are ignored. For debugging purposes, ignored entries can be
1888 * printed to the console if the
1889 * {@systemProperty jdk.net.URLClassPath.showIgnoredClassPathEntries} system
1890 * property is set to {@code true}.
1891 *
1892 * @return The system {@code ClassLoader}
1893 *
1894 * @throws SecurityException
1895 * If a security manager is present, and the caller's class loader
1896 * is not {@code null} and is not the same as or an ancestor of the
1897 * system class loader, and the caller does not have the
1898 * {@link RuntimePermission}{@code ("getClassLoader")}
1899 *
1900 * @throws IllegalStateException
1901 * If invoked recursively during the construction of the class
1902 * loader specified by the "{@code java.system.class.loader}"
1903 * property.
1904 *
1905 * @throws Error
1906 * If the system property "{@code java.system.class.loader}"
1907 * is defined but the named class could not be loaded, the
1908 * provider class does not define the required constructor, or an
1909 * exception is thrown by that constructor when it is invoked. The
1910 * underlying cause of the error can be retrieved via the
1911 * {@link Throwable#getCause()} method.
1912 *
1913 * @revised 1.4
1914 * @revised 9
1915 * @spec JPMS
1916 */
1917 @CallerSensitive
1918 public static ClassLoader getSystemClassLoader() {
1919 switch (VM.initLevel()) {
1920 case 0:
1921 case 1:
1922 case 2:
1923 // the system class loader is the built-in app class loader during startup
1924 return getBuiltinAppClassLoader();
1925 case 3:
1926 String msg = "getSystemClassLoader cannot be called during the system class loader instantiation";
1927 throw new IllegalStateException(msg);
1928 default:
1929 // system fully initialized
1930 assert VM.isBooted() && scl != null;
1931 SecurityManager sm = System.getSecurityManager();
1932 if (sm != null) {
1933 checkClassLoaderPermission(scl, Reflection.getCallerClass());
1934 }
1935 return scl;
1936 }
1937 }
1938
1939 static ClassLoader getBuiltinPlatformClassLoader() {
1940 return ClassLoaders.platformClassLoader();
1941 }
1942
1943 static ClassLoader getBuiltinAppClassLoader() {
1944 return ClassLoaders.appClassLoader();
1945 }
1946
1947 /*
1948 * Initialize the system class loader that may be a custom class on the
1949 * application class path or application module path.
1950 *
1951 * @see java.lang.System#initPhase3
1952 */
1953 static synchronized ClassLoader initSystemClassLoader() {
1954 if (VM.initLevel() != 3) {
1955 throw new InternalError("system class loader cannot be set at initLevel " +
1956 VM.initLevel());
1957 }
1958
1959 // detect recursive initialization
1960 if (scl != null) {
1961 throw new IllegalStateException("recursive invocation");
1962 }
1963
1964 ClassLoader builtinLoader = getBuiltinAppClassLoader();
1965
1966 // All are privileged frames. No need to call doPrivileged.
1967 String cn = System.getProperty("java.system.class.loader");
1968 if (cn != null) {
1969 try {
1970 // custom class loader is only supported to be loaded from unnamed module
1971 Constructor<?> ctor = Class.forName(cn, false, builtinLoader)
1972 .getDeclaredConstructor(ClassLoader.class);
1973 scl = (ClassLoader) ctor.newInstance(builtinLoader);
1974 } catch (Exception e) {
1975 Throwable cause = e;
1976 if (e instanceof InvocationTargetException) {
1977 cause = e.getCause();
1978 if (cause instanceof Error) {
1979 throw (Error) cause;
1980 }
1981 }
1982 if (cause instanceof RuntimeException) {
1983 throw (RuntimeException) cause;
1984 }
1985 throw new Error(cause.getMessage(), cause);
1986 }
1987 } else {
1988 scl = builtinLoader;
1989 }
1990 return scl;
1991 }
1992
1993 // Returns true if the specified class loader can be found in this class
1994 // loader's delegation chain.
1995 boolean isAncestor(ClassLoader cl) {
1996 ClassLoader acl = this;
1997 do {
1998 acl = acl.parent;
1999 if (cl == acl) {
2000 return true;
2001 }
2002 } while (acl != null);
2003 return false;
2004 }
2005
2006 // Tests if class loader access requires "getClassLoader" permission
2007 // check. A class loader 'from' can access class loader 'to' if
2008 // class loader 'from' is same as class loader 'to' or an ancestor
2009 // of 'to'. The class loader in a system domain can access
2010 // any class loader.
2011 private static boolean needsClassLoaderPermissionCheck(ClassLoader from,
2012 ClassLoader to)
2013 {
2014 if (from == to)
2015 return false;
2016
2017 if (from == null)
2018 return false;
2019
2020 return !to.isAncestor(from);
2021 }
2022
2023 // Returns the class's class loader, or null if none.
2024 static ClassLoader getClassLoader(Class<?> caller) {
2025 // This can be null if the VM is requesting it
2026 if (caller == null) {
2027 return null;
2028 }
2029 // Circumvent security check since this is package-private
2030 return caller.getClassLoader0();
2031 }
2032
2033 /*
2034 * Checks RuntimePermission("getClassLoader") permission
2035 * if caller's class loader is not null and caller's class loader
2036 * is not the same as or an ancestor of the given cl argument.
2037 */
2038 static void checkClassLoaderPermission(ClassLoader cl, Class<?> caller) {
2039 SecurityManager sm = System.getSecurityManager();
2040 if (sm != null) {
2041 // caller can be null if the VM is requesting it
2042 ClassLoader ccl = getClassLoader(caller);
2043 if (needsClassLoaderPermissionCheck(ccl, cl)) {
2044 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
2045 }
2046 }
2047 }
2048
2049 // The system class loader
2050 // @GuardedBy("ClassLoader.class")
2051 private static volatile ClassLoader scl;
2052
2053 // -- Package --
2054
2055 /**
2056 * Define a Package of the given Class object.
2057 *
2058 * If the given class represents an array type, a primitive type or void,
2059 * this method returns {@code null}.
2060 *
2061 * This method does not throw IllegalArgumentException.
2062 */
2063 Package definePackage(Class<?> c) {
2064 if (c.isPrimitive() || c.isArray()) {
2065 return null;
2066 }
2067
2068 return definePackage(c.getPackageName(), c.getModule());
2069 }
2070
2071 /**
2072 * Defines a Package of the given name and module
2073 *
2074 * This method does not throw IllegalArgumentException.
2075 *
2076 * @param name package name
2077 * @param m module
2078 */
2079 Package definePackage(String name, Module m) {
2080 if (name.isEmpty() && m.isNamed()) {
2081 throw new InternalError("unnamed package in " + m);
2082 }
2083
2084 // check if Package object is already defined
2085 NamedPackage pkg = packages.get(name);
2086 if (pkg instanceof Package)
2087 return (Package)pkg;
2088
2089 return (Package)packages.compute(name, (n, p) -> toPackage(n, p, m));
2090 }
2091
2092 /*
2093 * Returns a Package object for the named package
2094 */
2095 private Package toPackage(String name, NamedPackage p, Module m) {
2096 // define Package object if the named package is not yet defined
2097 if (p == null)
2098 return NamedPackage.toPackage(name, m);
2099
2100 // otherwise, replace the NamedPackage object with Package object
2101 if (p instanceof Package)
2102 return (Package)p;
2103
2104 return NamedPackage.toPackage(p.packageName(), p.module());
2105 }
2106
2107 /**
2108 * Defines a package by <a href="#binary-name">name</a> in this {@code ClassLoader}.
2109 * <p>
2110 * <a href="#binary-name">Package names</a> must be unique within a class loader and
2111 * cannot be redefined or changed once created.
2112 * <p>
2113 * If a class loader wishes to define a package with specific properties,
2114 * such as version information, then the class loader should call this
2115 * {@code definePackage} method before calling {@code defineClass}.
2116 * Otherwise, the
2117 * {@link #defineClass(String, byte[], int, int, ProtectionDomain) defineClass}
2118 * method will define a package in this class loader corresponding to the package
2119 * of the newly defined class; the properties of this defined package are
2120 * specified by {@link Package}.
2121 *
2122 * @apiNote
2123 * A class loader that wishes to define a package for classes in a JAR
2124 * typically uses the specification and implementation titles, versions, and
2125 * vendors from the JAR's manifest. If the package is specified as
2126 * {@linkplain java.util.jar.Attributes.Name#SEALED sealed} in the JAR's manifest,
2127 * the {@code URL} of the JAR file is typically used as the {@code sealBase}.
2128 * If classes of package {@code 'p'} defined by this class loader
2129 * are loaded from multiple JARs, the {@code Package} object may contain
2130 * different information depending on the first class of package {@code 'p'}
2131 * defined and which JAR's manifest is read first to explicitly define
2132 * package {@code 'p'}.
2133 *
2134 * <p> It is strongly recommended that a class loader does not call this
2135 * method to explicitly define packages in <em>named modules</em>; instead,
2136 * the package will be automatically defined when a class is {@linkplain
2137 * #defineClass(String, byte[], int, int, ProtectionDomain) being defined}.
2138 * If it is desirable to define {@code Package} explicitly, it should ensure
2139 * that all packages in a named module are defined with the properties
2140 * specified by {@link Package}. Otherwise, some {@code Package} objects
2141 * in a named module may be for example sealed with different seal base.
2142 *
2143 * @param name
2144 * The <a href="#binary-name">package name</a>
2145 *
2146 * @param specTitle
2147 * The specification title
2148 *
2149 * @param specVersion
2150 * The specification version
2151 *
2152 * @param specVendor
2153 * The specification vendor
2154 *
2155 * @param implTitle
2156 * The implementation title
2157 *
2158 * @param implVersion
2159 * The implementation version
2160 *
2161 * @param implVendor
2162 * The implementation vendor
2163 *
2164 * @param sealBase
2165 * If not {@code null}, then this package is sealed with
2166 * respect to the given code source {@link java.net.URL URL}
2167 * object. Otherwise, the package is not sealed.
2168 *
2169 * @return The newly defined {@code Package} object
2170 *
2171 * @throws NullPointerException
2172 * if {@code name} is {@code null}.
2173 *
2174 * @throws IllegalArgumentException
2175 * if a package of the given {@code name} is already
2176 * defined by this class loader
2177 *
2178 *
2179 * @since 1.2
2180 * @revised 9
2181 * @spec JPMS
2182 *
2183 * @jvms 5.3 Creation and Loading
2184 * @see <a href="{@docRoot}/../specs/jar/jar.html#package-sealing">
2185 * The JAR File Specification: Package Sealing</a>
2186 */
2187 protected Package definePackage(String name, String specTitle,
2188 String specVersion, String specVendor,
2189 String implTitle, String implVersion,
2190 String implVendor, URL sealBase)
2191 {
2192 Objects.requireNonNull(name);
2193
2194 // definePackage is not final and may be overridden by custom class loader
2195 Package p = new Package(name, specTitle, specVersion, specVendor,
2196 implTitle, implVersion, implVendor,
2197 sealBase, this);
2198
2199 if (packages.putIfAbsent(name, p) != null)
2200 throw new IllegalArgumentException(name);
2201
2202 return p;
2203 }
2204
2205 /**
2206 * Returns a {@code Package} of the given <a href="#binary-name">name</a> that
2207 * has been defined by this class loader.
2208 *
2209 * @param name The <a href="#binary-name">package name</a>
2210 *
2211 * @return The {@code Package} of the given name that has been defined
2212 * by this class loader, or {@code null} if not found
2213 *
2214 * @throws NullPointerException
2215 * if {@code name} is {@code null}.
2216 *
2217 * @jvms 5.3 Creation and Loading
2218 *
2219 * @since 9
2220 * @spec JPMS
2221 */
2222 public final Package getDefinedPackage(String name) {
2223 Objects.requireNonNull(name, "name cannot be null");
2224
2225 NamedPackage p = packages.get(name);
2226 if (p == null)
2227 return null;
2228
2229 return definePackage(name, p.module());
2230 }
2231
2232 /**
2233 * Returns all of the {@code Package}s that have been defined by
2234 * this class loader. The returned array has no duplicated {@code Package}s
2235 * of the same name.
2236 *
2237 * @apiNote This method returns an array rather than a {@code Set} or {@code Stream}
2238 * for consistency with the existing {@link #getPackages} method.
2239 *
2240 * @return The array of {@code Package} objects that have been defined by
2241 * this class loader; or an zero length array if no package has been
2242 * defined by this class loader.
2243 *
2244 * @jvms 5.3 Creation and Loading
2245 *
2246 * @since 9
2247 * @spec JPMS
2248 */
2249 public final Package[] getDefinedPackages() {
2250 return packages().toArray(Package[]::new);
2251 }
2252
2253 /**
2254 * Finds a package by <a href="#binary-name">name</a> in this class loader and its ancestors.
2255 * <p>
2256 * If this class loader defines a {@code Package} of the given name,
2257 * the {@code Package} is returned. Otherwise, the ancestors of
2258 * this class loader are searched recursively (parent by parent)
2259 * for a {@code Package} of the given name.
2260 *
2261 * @apiNote The {@link #getPlatformClassLoader() platform class loader}
2262 * may delegate to the application class loader but the application class
2263 * loader is not its ancestor. When invoked on the platform class loader,
2264 * this method will not find packages defined to the application
2265 * class loader.
2266 *
2267 * @param name
2268 * The <a href="#binary-name">package name</a>
2269 *
2270 * @return The {@code Package} of the given name that has been defined by
2271 * this class loader or its ancestors, or {@code null} if not found.
2272 *
2273 * @throws NullPointerException
2274 * if {@code name} is {@code null}.
2275 *
2276 * @deprecated
2277 * If multiple class loaders delegate to each other and define classes
2278 * with the same package name, and one such loader relies on the lookup
2279 * behavior of {@code getPackage} to return a {@code Package} from
2280 * a parent loader, then the properties exposed by the {@code Package}
2281 * may not be as expected in the rest of the program.
2282 * For example, the {@code Package} will only expose annotations from the
2283 * {@code package-info.class} file defined by the parent loader, even if
2284 * annotations exist in a {@code package-info.class} file defined by
2285 * a child loader. A more robust approach is to use the
2286 * {@link ClassLoader#getDefinedPackage} method which returns
2287 * a {@code Package} for the specified class loader.
2288 *
2289 * @see ClassLoader#getDefinedPackage(String)
2290 *
2291 * @since 1.2
2292 * @revised 9
2293 * @spec JPMS
2294 */
2295 @Deprecated(since="9")
2296 protected Package getPackage(String name) {
2297 Package pkg = getDefinedPackage(name);
2298 if (pkg == null) {
2299 if (parent != null) {
2300 pkg = parent.getPackage(name);
2301 } else {
2302 pkg = BootLoader.getDefinedPackage(name);
2303 }
2304 }
2305 return pkg;
2306 }
2307
2308 /**
2309 * Returns all of the {@code Package}s that have been defined by
2310 * this class loader and its ancestors. The returned array may contain
2311 * more than one {@code Package} object of the same package name, each
2312 * defined by a different class loader in the class loader hierarchy.
2313 *
2314 * @apiNote The {@link #getPlatformClassLoader() platform class loader}
2315 * may delegate to the application class loader. In other words,
2316 * packages in modules defined to the application class loader may be
2317 * visible to the platform class loader. On the other hand,
2318 * the application class loader is not its ancestor and hence
2319 * when invoked on the platform class loader, this method will not
2320 * return any packages defined to the application class loader.
2321 *
2322 * @return The array of {@code Package} objects that have been defined by
2323 * this class loader and its ancestors
2324 *
2325 * @see ClassLoader#getDefinedPackages()
2326 *
2327 * @since 1.2
2328 * @revised 9
2329 * @spec JPMS
2330 */
2331 protected Package[] getPackages() {
2332 Stream<Package> pkgs = packages();
2333 ClassLoader ld = parent;
2334 while (ld != null) {
2335 pkgs = Stream.concat(ld.packages(), pkgs);
2336 ld = ld.parent;
2337 }
2338 return Stream.concat(BootLoader.packages(), pkgs)
2339 .toArray(Package[]::new);
2340 }
2341
2342
2343
2344 // package-private
2345
2346 /**
2347 * Returns a stream of Packages defined in this class loader
2348 */
2349 Stream<Package> packages() {
2350 return packages.values().stream()
2351 .map(p -> definePackage(p.packageName(), p.module()));
2352 }
2353
2354 // -- Native library access --
2355
2356 /**
2357 * Returns the absolute path name of a native library. The VM invokes this
2358 * method to locate the native libraries that belong to classes loaded with
2359 * this class loader. If this method returns {@code null}, the VM
2360 * searches the library along the path specified as the
2361 * "{@code java.library.path}" property.
2362 *
2363 * @param libname
2364 * The library name
2365 *
2366 * @return The absolute path of the native library
2367 *
2368 * @see System#loadLibrary(String)
2369 * @see System#mapLibraryName(String)
2370 *
2371 * @since 1.2
2372 */
2373 protected String findLibrary(String libname) {
2374 return null;
2375 }
2376
2377 private final NativeLibraries libraries = NativeLibraries.jniNativeLibraries(this);
2378
2379 // Invoked in the java.lang.Runtime class to implement load and loadLibrary.
2380 static NativeLibrary loadLibrary(Class<?> fromClass, File file) {
2381 ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
2382 NativeLibraries libs = loader != null ? loader.libraries : BootLoader.getNativeLibraries();
2383 NativeLibrary nl = libs.loadLibrary(fromClass, file);
2384 if (nl != null) {
2385 return nl;
2386 }
2387 throw new UnsatisfiedLinkError("Can't load library: " + file);
2388 }
2389 static NativeLibrary loadLibrary(Class<?> fromClass, String name) {
2390 ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
2391 if (loader == null) {
2392 NativeLibrary nl = BootLoader.getNativeLibraries().loadLibrary(fromClass, name);
2393 if (nl != null) {
2394 return nl;
2395 }
2396 throw new UnsatisfiedLinkError("no " + name +
2397 " in system library path: " + StaticProperty.sunBootLibraryPath());
2398 }
2399
2400 NativeLibraries libs = loader.libraries;
2401 // First load from the file returned from ClassLoader::findLibrary, if found.
2402 String libfilename = loader.findLibrary(name);
2403 if (libfilename != null) {
2404 File libfile = new File(libfilename);
2405 if (!libfile.isAbsolute()) {
2406 throw new UnsatisfiedLinkError(
2407 "ClassLoader.findLibrary failed to return an absolute path: " + libfilename);
2408 }
2409 NativeLibrary nl = libs.loadLibrary(fromClass, libfile);
2410 if (nl != null) {
2411 return nl;
2412 }
2413 throw new UnsatisfiedLinkError("Can't load " + libfilename);
2414 }
2415 // Then load from system library path and java library path
2416 NativeLibrary nl = libs.loadLibrary(fromClass, name);
2417 if (nl != null) {
2418 return nl;
2419 }
2420
2421 // Oops, it failed
2422 throw new UnsatisfiedLinkError("no " + name +
2423 " in java.library.path: " + StaticProperty.javaLibraryPath());
2424 }
2425
2426 /*
2427 * Invoked in the VM class linking code.
2428 */
2429 private static long findNative(ClassLoader loader, String entryName) {
2430 if (loader == null) {
2431 return BootLoader.getNativeLibraries().find(entryName);
2432 } else {
2433 return loader.libraries.find(entryName);
2434 }
2435 }
2436
2437 // -- Assertion management --
2438
2439 final Object assertionLock;
2440
2441 // The default toggle for assertion checking.
2442 // @GuardedBy("assertionLock")
2443 private boolean defaultAssertionStatus = false;
2444
2445 // Maps String packageName to Boolean package default assertion status Note
2446 // that the default package is placed under a null map key. If this field
2447 // is null then we are delegating assertion status queries to the VM, i.e.,
2448 // none of this ClassLoader's assertion status modification methods have
2449 // been invoked.
2450 // @GuardedBy("assertionLock")
2451 private Map<String, Boolean> packageAssertionStatus = null;
2452
2453 // Maps String fullyQualifiedClassName to Boolean assertionStatus If this
2454 // field is null then we are delegating assertion status queries to the VM,
2455 // i.e., none of this ClassLoader's assertion status modification methods
2456 // have been invoked.
2457 // @GuardedBy("assertionLock")
2458 Map<String, Boolean> classAssertionStatus = null;
2459
2460 /**
2461 * Sets the default assertion status for this class loader. This setting
2462 * determines whether classes loaded by this class loader and initialized
2463 * in the future will have assertions enabled or disabled by default.
2464 * This setting may be overridden on a per-package or per-class basis by
2465 * invoking {@link #setPackageAssertionStatus(String, boolean)} or {@link
2466 * #setClassAssertionStatus(String, boolean)}.
2467 *
2468 * @param enabled
2469 * {@code true} if classes loaded by this class loader will
2470 * henceforth have assertions enabled by default, {@code false}
2471 * if they will have assertions disabled by default.
2472 *
2473 * @since 1.4
2474 */
2475 public void setDefaultAssertionStatus(boolean enabled) {
2476 synchronized (assertionLock) {
2477 if (classAssertionStatus == null)
2478 initializeJavaAssertionMaps();
2479
2480 defaultAssertionStatus = enabled;
2481 }
2482 }
2483
2484 /**
2485 * Sets the package default assertion status for the named package. The
2486 * package default assertion status determines the assertion status for
2487 * classes initialized in the future that belong to the named package or
2488 * any of its "subpackages".
2489 *
2490 * <p> A subpackage of a package named p is any package whose name begins
2491 * with "{@code p.}". For example, {@code javax.swing.text} is a
2492 * subpackage of {@code javax.swing}, and both {@code java.util} and
2493 * {@code java.lang.reflect} are subpackages of {@code java}.
2494 *
2495 * <p> In the event that multiple package defaults apply to a given class,
2496 * the package default pertaining to the most specific package takes
2497 * precedence over the others. For example, if {@code javax.lang} and
2498 * {@code javax.lang.reflect} both have package defaults associated with
2499 * them, the latter package default applies to classes in
2500 * {@code javax.lang.reflect}.
2501 *
2502 * <p> Package defaults take precedence over the class loader's default
2503 * assertion status, and may be overridden on a per-class basis by invoking
2504 * {@link #setClassAssertionStatus(String, boolean)}. </p>
2505 *
2506 * @param packageName
2507 * The name of the package whose package default assertion status
2508 * is to be set. A {@code null} value indicates the unnamed
2509 * package that is "current"
2510 * (see section 7.4.2 of
2511 * <cite>The Java™ Language Specification</cite>.)
2512 *
2513 * @param enabled
2514 * {@code true} if classes loaded by this classloader and
2515 * belonging to the named package or any of its subpackages will
2516 * have assertions enabled by default, {@code false} if they will
2517 * have assertions disabled by default.
2518 *
2519 * @since 1.4
2520 */
2521 public void setPackageAssertionStatus(String packageName,
2522 boolean enabled) {
2523 synchronized (assertionLock) {
2524 if (packageAssertionStatus == null)
2525 initializeJavaAssertionMaps();
2526
2527 packageAssertionStatus.put(packageName, enabled);
2528 }
2529 }
2530
2531 /**
2532 * Sets the desired assertion status for the named top-level class in this
2533 * class loader and any nested classes contained therein. This setting
2534 * takes precedence over the class loader's default assertion status, and
2535 * over any applicable per-package default. This method has no effect if
2536 * the named class has already been initialized. (Once a class is
2537 * initialized, its assertion status cannot change.)
2538 *
2539 * <p> If the named class is not a top-level class, this invocation will
2540 * have no effect on the actual assertion status of any class. </p>
2541 *
2542 * @param className
2543 * The fully qualified class name of the top-level class whose
2544 * assertion status is to be set.
2545 *
2546 * @param enabled
2547 * {@code true} if the named class is to have assertions
2548 * enabled when (and if) it is initialized, {@code false} if the
2549 * class is to have assertions disabled.
2550 *
2551 * @since 1.4
2552 */
2553 public void setClassAssertionStatus(String className, boolean enabled) {
2554 synchronized (assertionLock) {
2555 if (classAssertionStatus == null)
2556 initializeJavaAssertionMaps();
2557
2558 classAssertionStatus.put(className, enabled);
2559 }
2560 }
2561
2562 /**
2563 * Sets the default assertion status for this class loader to
2564 * {@code false} and discards any package defaults or class assertion
2565 * status settings associated with the class loader. This method is
2566 * provided so that class loaders can be made to ignore any command line or
2567 * persistent assertion status settings and "start with a clean slate."
2568 *
2569 * @since 1.4
2570 */
2571 public void clearAssertionStatus() {
2572 /*
2573 * Whether or not "Java assertion maps" are initialized, set
2574 * them to empty maps, effectively ignoring any present settings.
2575 */
2576 synchronized (assertionLock) {
2577 classAssertionStatus = new HashMap<>();
2578 packageAssertionStatus = new HashMap<>();
2579 defaultAssertionStatus = false;
2580 }
2581 }
2582
2583 /**
2584 * Returns the assertion status that would be assigned to the specified
2585 * class if it were to be initialized at the time this method is invoked.
2586 * If the named class has had its assertion status set, the most recent
2587 * setting will be returned; otherwise, if any package default assertion
2588 * status pertains to this class, the most recent setting for the most
2589 * specific pertinent package default assertion status is returned;
2590 * otherwise, this class loader's default assertion status is returned.
2591 * </p>
2592 *
2593 * @param className
2594 * The fully qualified class name of the class whose desired
2595 * assertion status is being queried.
2596 *
2597 * @return The desired assertion status of the specified class.
2598 *
2599 * @see #setClassAssertionStatus(String, boolean)
2600 * @see #setPackageAssertionStatus(String, boolean)
2601 * @see #setDefaultAssertionStatus(boolean)
2602 *
2603 * @since 1.4
2604 */
2605 boolean desiredAssertionStatus(String className) {
2606 synchronized (assertionLock) {
2607 // assert classAssertionStatus != null;
2608 // assert packageAssertionStatus != null;
2609
2610 // Check for a class entry
2611 Boolean result = classAssertionStatus.get(className);
2612 if (result != null)
2613 return result.booleanValue();
2614
2615 // Check for most specific package entry
2616 int dotIndex = className.lastIndexOf('.');
2617 if (dotIndex < 0) { // default package
2618 result = packageAssertionStatus.get(null);
2619 if (result != null)
2620 return result.booleanValue();
2621 }
2622 while(dotIndex > 0) {
2623 className = className.substring(0, dotIndex);
2624 result = packageAssertionStatus.get(className);
2625 if (result != null)
2626 return result.booleanValue();
2627 dotIndex = className.lastIndexOf('.', dotIndex-1);
2628 }
2629
2630 // Return the classloader default
2631 return defaultAssertionStatus;
2632 }
2633 }
2634
2635 // Set up the assertions with information provided by the VM.
2636 // Note: Should only be called inside a synchronized block
2637 private void initializeJavaAssertionMaps() {
2638 // assert Thread.holdsLock(assertionLock);
2639
2640 classAssertionStatus = new HashMap<>();
2641 packageAssertionStatus = new HashMap<>();
2642 AssertionStatusDirectives directives = retrieveDirectives();
2643
2644 for(int i = 0; i < directives.classes.length; i++)
2645 classAssertionStatus.put(directives.classes[i],
2646 directives.classEnabled[i]);
2647
2648 for(int i = 0; i < directives.packages.length; i++)
2649 packageAssertionStatus.put(directives.packages[i],
2650 directives.packageEnabled[i]);
2651
2652 defaultAssertionStatus = directives.deflt;
2653 }
2654
2655 // Retrieves the assertion directives from the VM.
2656 private static native AssertionStatusDirectives retrieveDirectives();
2657
2658
2659 // -- Misc --
2660
2661 /**
2662 * Returns the ConcurrentHashMap used as a storage for ClassLoaderValue(s)
2663 * associated with this ClassLoader, creating it if it doesn't already exist.
2664 */
2665 ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap() {
2666 ConcurrentHashMap<?, ?> map = classLoaderValueMap;
2667 if (map == null) {
2668 map = new ConcurrentHashMap<>();
2669 boolean set = trySetObjectField("classLoaderValueMap", map);
2670 if (!set) {
2671 // beaten by someone else
2672 map = classLoaderValueMap;
2673 }
2674 }
2675 return map;
2676 }
2677
2678 // the storage for ClassLoaderValue(s) associated with this ClassLoader
2679 private volatile ConcurrentHashMap<?, ?> classLoaderValueMap;
2680
2681 /**
2682 * Attempts to atomically set a volatile field in this object. Returns
2683 * {@code true} if not beaten by another thread. Avoids the use of
2684 * AtomicReferenceFieldUpdater in this class.
2685 */
2686 private boolean trySetObjectField(String name, Object obj) {
2687 Unsafe unsafe = Unsafe.getUnsafe();
2688 Class<?> k = ClassLoader.class;
2689 long offset;
2690 offset = unsafe.objectFieldOffset(k, name);
2691 return unsafe.compareAndSetReference(this, offset, null, obj);
2692 }
2693 }
2694
2695 /*
2696 * A utility class that will enumerate over an array of enumerations.
2697 */
2698 final class CompoundEnumeration<E> implements Enumeration<E> {
2699 private final Enumeration<E>[] enums;
2700 private int index;
2701
2702 public CompoundEnumeration(Enumeration<E>[] enums) {
2703 this.enums = enums;
2704 }
2705
2706 private boolean next() {
2707 while (index < enums.length) {
2708 if (enums[index] != null && enums[index].hasMoreElements()) {
2709 return true;
2710 }
2711 index++;
2712 }
2713 return false;
2714 }
2715
2716 public boolean hasMoreElements() {
2717 return next();
2718 }
2719
2720 public E nextElement() {
2721 if (!next()) {
2722 throw new NoSuchElementException();
2723 }
2724 return enums[index].nextElement();
2725 }
2726 }