1 /*
2 * Copyright (c) 2013, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import java.io.InputStream;
29 import java.io.IOException;
30 import java.io.UncheckedIOException;
31 import java.io.File;
32 import java.lang.reflect.Constructor;
33 import java.lang.reflect.Field;
34 import java.lang.reflect.Module;
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.Collections;
43 import java.util.Enumeration;
44 import java.util.HashMap;
45 import java.util.HashSet;
46 import java.util.Hashtable;
47 import java.util.Map;
48 import java.util.Objects;
49 import java.util.Set;
50 import java.util.Spliterator;
51 import java.util.Spliterators;
52 import java.util.Stack;
53 import java.util.NoSuchElementException;
54 import java.util.Vector;
55 import java.util.WeakHashMap;
56 import java.util.concurrent.ConcurrentHashMap;
57 import java.util.function.Supplier;
58 import java.util.stream.Stream;
59 import java.util.stream.StreamSupport;
60
61 import jdk.internal.perf.PerfCounter;
62 import jdk.internal.module.ServicesCatalog;
63 import jdk.internal.loader.BootLoader;
64 import jdk.internal.loader.ClassLoaders;
65 import jdk.internal.misc.SharedSecrets;
66 import jdk.internal.misc.Unsafe;
67 import jdk.internal.misc.VM;
68 import jdk.internal.reflect.CallerSensitive;
69 import jdk.internal.reflect.Reflection;
70 import sun.reflect.misc.ReflectUtil;
71 import sun.security.util.SecurityConstants;
72
73 /**
74 * A class loader is an object that is responsible for loading classes. The
75 * class <tt>ClassLoader</tt> is an abstract class. Given the <a
76 * href="#name">binary name</a> of a class, a class loader should attempt to
77 * locate or generate data that constitutes a definition for the class. A
78 * typical strategy is to transform the name into a file name and then read a
79 * "class file" of that name from a file system.
80 *
81 * <p> Every {@link Class <tt>Class</tt>} object contains a {@link
82 * Class#getClassLoader() reference} to the <tt>ClassLoader</tt> that defined
83 * it.
84 *
85 * <p> <tt>Class</tt> objects for array classes are not created by class
86 * loaders, but are created automatically as required by the Java runtime.
87 * The class loader for an array class, as returned by {@link
88 * Class#getClassLoader()} is the same as the class loader for its element
89 * type; if the element type is a primitive type, then the array class has no
90 * class loader.
91 *
92 * <p> Applications implement subclasses of <tt>ClassLoader</tt> in order to
93 * extend the manner in which the Java virtual machine dynamically loads
94 * classes.
95 *
96 * <p> Class loaders may typically be used by security managers to indicate
97 * security domains.
98 *
99 * <p> The <tt>ClassLoader</tt> class uses a delegation model to search for
100 * classes and resources. Each instance of <tt>ClassLoader</tt> has an
101 * associated parent class loader. When requested to find a class or
102 * resource, a <tt>ClassLoader</tt> instance will delegate the search for the
103 * class or resource to its parent class loader before attempting to find the
104 * class or resource itself.
105 *
106 * <p> Class loaders that support concurrent loading of classes are known as
107 * <em>parallel capable</em> class loaders and are required to register
108 * themselves at their class initialization time by invoking the
109 * {@link
110 * #registerAsParallelCapable <tt>ClassLoader.registerAsParallelCapable</tt>}
111 * method. Note that the <tt>ClassLoader</tt> class is registered as parallel
112 * capable by default. However, its subclasses still need to register themselves
113 * if they are parallel capable.
114 * In environments in which the delegation model is not strictly
115 * hierarchical, class loaders need to be parallel capable, otherwise class
116 * loading can lead to deadlocks because the loader lock is held for the
117 * duration of the class loading process (see {@link #loadClass
118 * <tt>loadClass</tt>} methods).
119 *
120 * <h3> <a name="builtinLoaders">Run-time Built-in Class Loaders</a></h3>
121 *
122 * The Java run-time has the following built-in class loaders:
123 *
124 * <ul>
125 * <li>Bootstrap class loader.
126 * It is the virtual machine's built-in class loader, typically represented
127 * as {@code null}, and does not have a parent.</li>
128 * <li>{@linkplain #getPlatformClassLoader() Platform class loader}.
129 * All <em>platform classes</em> are visible to the platform class loader
130 * that can be used as the parent of a {@code ClassLoader} instance.
131 * Platform classes include Java SE platform APIs, their implementation
132 * classes and JDK-specific run-time classes that are defined by the
133 * platform class loader or its ancestors.</li>
134 * <li>{@linkplain #getSystemClassLoader() System class loader}.
135 * It is also known as <em>application class
136 * loader</em> and is distinct from the platform class loader.
137 * The system class loader is typically used to define classes on the
138 * application class path, module path, and JDK-specific tools.
139 * The platform class loader is a parent or an ancestor of the system class
140 * loader that all platform classes are visible to it.</li>
141 * </ul>
142 *
143 * <p> Normally, the Java virtual machine loads classes from the local file
144 * system in a platform-dependent manner.
145 * However, some classes may not originate from a file; they may originate
146 * from other sources, such as the network, or they could be constructed by an
147 * application. The method {@link #defineClass(String, byte[], int, int)
148 * <tt>defineClass</tt>} converts an array of bytes into an instance of class
149 * <tt>Class</tt>. Instances of this newly defined class can be created using
150 * {@link Class#newInstance <tt>Class.newInstance</tt>}.
151 *
152 * <p> The methods and constructors of objects created by a class loader may
153 * reference other classes. To determine the class(es) referred to, the Java
154 * virtual machine invokes the {@link #loadClass <tt>loadClass</tt>} method of
155 * the class loader that originally created the class.
156 *
157 * <p> For example, an application could create a network class loader to
158 * download class files from a server. Sample code might look like:
159 *
160 * <blockquote><pre>
161 * ClassLoader loader = new NetworkClassLoader(host, port);
162 * Object main = loader.loadClass("Main", true).newInstance();
163 * . . .
164 * </pre></blockquote>
165 *
166 * <p> The network class loader subclass must define the methods {@link
167 * #findClass <tt>findClass</tt>} and <tt>loadClassData</tt> to load a class
168 * from the network. Once it has downloaded the bytes that make up the class,
169 * it should use the method {@link #defineClass <tt>defineClass</tt>} to
170 * create a class instance. A sample implementation is:
171 *
172 * <blockquote><pre>
173 * class NetworkClassLoader extends ClassLoader {
174 * String host;
175 * int port;
176 *
177 * public Class findClass(String name) {
178 * byte[] b = loadClassData(name);
179 * return defineClass(name, b, 0, b.length);
180 * }
181 *
182 * private byte[] loadClassData(String name) {
183 * // load the class data from the connection
184 * . . .
185 * }
186 * }
187 * </pre></blockquote>
188 *
189 * <h3> <a name="name">Binary names</a> </h3>
190 *
191 * <p> Any class name provided as a {@code String} parameter to methods in
192 * {@code ClassLoader} must be a binary name as defined by
193 * <cite>The Java™ Language Specification</cite>.
194 *
195 * <p> Examples of valid class names include:
196 * <blockquote><pre>
197 * "java.lang.String"
198 * "javax.swing.JSpinner$DefaultEditor"
199 * "java.security.KeyStore$Builder$FileBuilder$1"
200 * "java.net.URLClassLoader$3$1"
201 * </pre></blockquote>
202 *
203 * <p> Any package name provided as a {@code String} parameter to methods in
204 * {@code ClassLoader} must be either the empty string (denoting an unnamed package)
205 * or a fully qualified name as defined by
206 * <cite>The Java™ Language Specification</cite>.
207 *
208 * @jls 6.7 Fully Qualified Names
209 * @jls 13.1 The Form of a Binary
210 * @see #resolveClass(Class)
211 * @since 1.0
212 */
213 public abstract class ClassLoader {
214
215 private static native void registerNatives();
216 static {
217 registerNatives();
218 }
219
220 // The parent class loader for delegation
221 // Note: VM hardcoded the offset of this field, thus all new fields
222 // must be added *after* it.
223 private final ClassLoader parent;
224
225 // class loader name
226 private final String name;
227
228 // the unnamed module for this ClassLoader
229 private final Module unnamedModule;
230
231 /**
232 * Encapsulates the set of parallel capable loader types.
233 */
234 private static class ParallelLoaders {
235 private ParallelLoaders() {}
236
237 // the set of parallel capable loader types
238 private static final Set<Class<? extends ClassLoader>> loaderTypes =
239 Collections.newSetFromMap(new WeakHashMap<>());
240 static {
241 synchronized (loaderTypes) { loaderTypes.add(ClassLoader.class); }
242 }
243
244 /**
245 * Registers the given class loader type as parallel capable.
246 * Returns {@code true} is successfully registered; {@code false} if
247 * loader's super class is not registered.
248 */
249 static boolean register(Class<? extends ClassLoader> c) {
250 synchronized (loaderTypes) {
251 if (loaderTypes.contains(c.getSuperclass())) {
252 // register the class loader as parallel capable
253 // if and only if all of its super classes are.
254 // Note: given current classloading sequence, if
255 // the immediate super class is parallel capable,
256 // all the super classes higher up must be too.
257 loaderTypes.add(c);
258 return true;
259 } else {
260 return false;
261 }
262 }
263 }
264
265 /**
266 * Returns {@code true} if the given class loader type is
267 * registered as parallel capable.
268 */
269 static boolean isRegistered(Class<? extends ClassLoader> c) {
270 synchronized (loaderTypes) {
271 return loaderTypes.contains(c);
272 }
273 }
274 }
275
276 // Maps class name to the corresponding lock object when the current
277 // class loader is parallel capable.
278 // Note: VM also uses this field to decide if the current class loader
279 // is parallel capable and the appropriate lock object for class loading.
280 private final ConcurrentHashMap<String, Object> parallelLockMap;
281
282 // Maps packages to certs
283 private final Map <String, Certificate[]> package2certs;
284
285 // Shared among all packages with unsigned classes
286 private static final Certificate[] nocerts = new Certificate[0];
287
288 // The classes loaded by this class loader. The only purpose of this table
289 // is to keep the classes from being GC'ed until the loader is GC'ed.
290 private final Vector<Class<?>> classes = new Vector<>();
291
292 // The "default" domain. Set as the default ProtectionDomain on newly
293 // created classes.
294 private final ProtectionDomain defaultDomain =
295 new ProtectionDomain(new CodeSource(null, (Certificate[]) null),
296 null, this, null);
297
298 // Invoked by the VM to record every loaded class with this loader.
299 void addClass(Class<?> c) {
300 classes.addElement(c);
301 }
302
303 // The packages defined in this class loader. Each package name is
304 // mapped to its corresponding NamedPackage object.
305 //
306 // The value is a Package object if ClassLoader::definePackage,
307 // Class::getPackage, ClassLoader::getDefinePackage(s) or
308 // Package::getPackage(s) method is called to define it.
309 // Otherwise, the value is a NamedPackage object.
310 private final ConcurrentHashMap<String, NamedPackage> packages
311 = new ConcurrentHashMap<>();
312
313 /*
314 * Returns a named package for the given module.
315 */
316 private NamedPackage getNamedPackage(String pn, Module m) {
317 NamedPackage p = packages.get(pn);
318 if (p == null) {
319 p = new NamedPackage(pn, m);
320
321 NamedPackage value = packages.putIfAbsent(pn, p);
322 if (value != null) {
323 // Package object already be defined for the named package
324 p = value;
325 // if definePackage is called by this class loader to define
326 // a package in a named module, this will return Package
327 // object of the same name. Package object may contain
328 // unexpected information but it does not impact the runtime.
329 // this assertion may be helpful for troubleshooting
330 assert value.module() == m;
331 }
332 }
333 return p;
334 }
335
336 private static Void checkCreateClassLoader() {
337 SecurityManager security = System.getSecurityManager();
338 if (security != null) {
339 security.checkCreateClassLoader();
340 }
341 return null;
342 }
343
344 private ClassLoader(Void unused, String name, ClassLoader parent) {
345 this.name = name;
346 this.parent = parent;
347 this.unnamedModule
348 = SharedSecrets.getJavaLangReflectModuleAccess()
349 .defineUnnamedModule(this);
350 if (ParallelLoaders.isRegistered(this.getClass())) {
351 parallelLockMap = new ConcurrentHashMap<>();
352 package2certs = new ConcurrentHashMap<>();
353 assertionLock = new Object();
354 } else {
355 // no finer-grained lock; lock on the classloader instance
356 parallelLockMap = null;
357 package2certs = new Hashtable<>();
358 assertionLock = this;
359 }
360 }
361
362 /**
363 * Creates a new class loader of the specified name and using the
364 * specified parent class loader for delegation.
365 *
366 * @param name class loader name; or {@code null} if not named
367 * @param parent the parent class loader
368 *
369 * @throws SecurityException
370 * If a security manager exists and its
371 * {@link SecurityManager#checkCreateClassLoader()}
372 * method doesn't allow creation of a new class loader.
373 *
374 * @since 9
375 */
376 protected ClassLoader(String name, ClassLoader parent) {
377 this(checkCreateClassLoader(), name, parent);
378 }
379
380
381 /**
382 * Creates a new class loader using the specified parent class loader for
383 * delegation.
384 *
385 * <p> If there is a security manager, its {@link
386 * SecurityManager#checkCreateClassLoader()
387 * <tt>checkCreateClassLoader</tt>} method is invoked. This may result in
388 * a security exception. </p>
389 *
390 * @param parent
391 * The parent class loader
392 *
393 * @throws SecurityException
394 * If a security manager exists and its
395 * <tt>checkCreateClassLoader</tt> method doesn't allow creation
396 * of a new class loader.
397 *
398 * @since 1.2
399 */
400 protected ClassLoader(ClassLoader parent) {
401 this(checkCreateClassLoader(), null, parent);
402 }
403
404
405 /**
406 * Creates a new class loader using the <tt>ClassLoader</tt> returned by
407 * the method {@link #getSystemClassLoader()
408 * <tt>getSystemClassLoader()</tt>} as the parent class loader.
409 *
410 * <p> If there is a security manager, its {@link
411 * SecurityManager#checkCreateClassLoader()
412 * <tt>checkCreateClassLoader</tt>} method is invoked. This may result in
413 * a security exception. </p>
414 *
415 * @throws SecurityException
416 * If a security manager exists and its
417 * <tt>checkCreateClassLoader</tt> method doesn't allow creation
418 * of a new class loader.
419 */
420 protected ClassLoader() {
421 this(checkCreateClassLoader(), null, getSystemClassLoader());
422 }
423
424
425 /**
426 * Returns the name of this class loader or {@code null} if
427 * this class loader is not named.
428 *
429 * @return name of this class loader; or {@code null} if
430 * this class loader is not named.
431 *
432 * @since 9
433 */
434 public String getName() {
435 return name;
436 }
437
438
439 // -- Class --
440
441 /**
442 * Loads the class with the specified <a href="#name">binary name</a>.
443 * This method searches for classes in the same manner as the {@link
444 * #loadClass(String, boolean)} method. It is invoked by the Java virtual
445 * machine to resolve class references. Invoking this method is equivalent
446 * to invoking {@link #loadClass(String, boolean) <tt>loadClass(name,
447 * false)</tt>}.
448 *
449 * @param name
450 * The <a href="#name">binary name</a> of the class
451 *
452 * @return The resulting <tt>Class</tt> object
453 *
454 * @throws ClassNotFoundException
455 * If the class was not found
456 */
457 public Class<?> loadClass(String name) throws ClassNotFoundException {
458 return loadClass(name, false);
459 }
460
461 /**
462 * Loads the class with the specified <a href="#name">binary name</a>. The
463 * default implementation of this method searches for classes in the
464 * following order:
465 *
466 * <ol>
467 *
468 * <li><p> Invoke {@link #findLoadedClass(String)} to check if the class
469 * has already been loaded. </p></li>
470 *
471 * <li><p> Invoke the {@link #loadClass(String) <tt>loadClass</tt>} method
472 * on the parent class loader. If the parent is <tt>null</tt> the class
473 * loader built-in to the virtual machine is used, instead. </p></li>
474 *
475 * <li><p> Invoke the {@link #findClass(String)} method to find the
476 * class. </p></li>
477 *
478 * </ol>
479 *
480 * <p> If the class was found using the above steps, and the
481 * <tt>resolve</tt> flag is true, this method will then invoke the {@link
482 * #resolveClass(Class)} method on the resulting <tt>Class</tt> object.
483 *
484 * <p> Subclasses of <tt>ClassLoader</tt> are encouraged to override {@link
485 * #findClass(String)}, rather than this method. </p>
486 *
487 * <p> Unless overridden, this method synchronizes on the result of
488 * {@link #getClassLoadingLock <tt>getClassLoadingLock</tt>} method
489 * during the entire class loading process.
490 *
491 * @param name
492 * The <a href="#name">binary name</a> of the class
493 *
494 * @param resolve
495 * If <tt>true</tt> then resolve the class
496 *
497 * @return The resulting <tt>Class</tt> object
498 *
499 * @throws ClassNotFoundException
500 * If the class could not be found
501 */
502 protected Class<?> loadClass(String name, boolean resolve)
503 throws ClassNotFoundException
504 {
505 synchronized (getClassLoadingLock(name)) {
506 // First, check if the class has already been loaded
507 Class<?> c = findLoadedClass(name);
508 if (c == null) {
509 long t0 = System.nanoTime();
510 try {
511 if (parent != null) {
512 c = parent.loadClass(name, false);
513 } else {
514 c = findBootstrapClassOrNull(name);
515 }
516 } catch (ClassNotFoundException e) {
517 // ClassNotFoundException thrown if class not found
518 // from the non-null parent class loader
519 }
520
521 if (c == null) {
522 // If still not found, then invoke findClass in order
523 // to find the class.
524 long t1 = System.nanoTime();
525 c = findClass(name);
526
527 // this is the defining class loader; record the stats
528 PerfCounter.getParentDelegationTime().addTime(t1 - t0);
529 PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
530 PerfCounter.getFindClasses().increment();
531 }
532 }
533 if (resolve) {
534 resolveClass(c);
535 }
536 return c;
537 }
538 }
539
540 /**
541 * Loads the class with the specified <a href="#name">binary name</a>
542 * in a module defined to this class loader. This method returns {@code null}
543 * if the class could not be found.
544 *
545 * @apiNote This method does not delegate to the parent class loader.
546 *
547 * @implSpec The default implementation of this method searches for classes
548 * in the following order:
549 *
550 * <ol>
551 * <li>Invoke {@link #findLoadedClass(String)} to check if the class
552 * has already been loaded.</li>
553 * <li>Invoke the {@link #findClass(String, String)} method to find the
554 * class in the given module.</li>
555 * </ol>
556 *
557 * @param module
558 * The module
559 * @param name
560 * The <a href="#name">binary name</a> of the class
561 *
562 * @return The resulting {@code Class} object in a module defined by
563 * this class loader, or {@code null} if the class could not be found.
564 */
565 final Class<?> loadLocalClass(Module module, String name) {
566 synchronized (getClassLoadingLock(name)) {
567 // First, check if the class has already been loaded
568 Class<?> c = findLoadedClass(name);
569 if (c == null) {
570 c = findClass(module.getName(), name);
571 }
572 if (c != null && c.getModule() == module) {
573 return c;
574 } else {
575 return null;
576 }
577 }
578 }
579
580 /**
581 * Loads the class with the specified <a href="#name">binary name</a>
582 * defined by this class loader. This method returns {@code null}
583 * if the class could not be found.
584 *
585 * @apiNote This method does not delegate to the parent class loader.
586 *
587 * @param name
588 * The <a href="#name">binary name</a> of the class
589 *
590 * @return The resulting {@code Class} object in a module defined by
591 * this class loader, or {@code null} if the class could not be found.
592 */
593 final Class<?> loadLocalClass(String name) {
594 synchronized (getClassLoadingLock(name)) {
595 // First, check if the class has already been loaded
596 Class<?> c = findLoadedClass(name);
597 if (c == null) {
598 try {
599 return findClass(name);
600 } catch (ClassNotFoundException e) {
601 // ignore
602 }
603 }
604 return c;
605 }
606 }
607
608 /**
609 * Returns the lock object for class loading operations.
610 * For backward compatibility, the default implementation of this method
611 * behaves as follows. If this ClassLoader object is registered as
612 * parallel capable, the method returns a dedicated object associated
613 * with the specified class name. Otherwise, the method returns this
614 * ClassLoader object.
615 *
616 * @param className
617 * The name of the to-be-loaded class
618 *
619 * @return the lock for class loading operations
620 *
621 * @throws NullPointerException
622 * If registered as parallel capable and <tt>className</tt> is null
623 *
624 * @see #loadClass(String, boolean)
625 *
626 * @since 1.7
627 */
628 protected Object getClassLoadingLock(String className) {
629 Object lock = this;
630 if (parallelLockMap != null) {
631 Object newLock = new Object();
632 lock = parallelLockMap.putIfAbsent(className, newLock);
633 if (lock == null) {
634 lock = newLock;
635 }
636 }
637 return lock;
638 }
639
640 // This method is invoked by the virtual machine to load a class.
641 private Class<?> loadClassInternal(String name)
642 throws ClassNotFoundException
643 {
644 // For backward compatibility, explicitly lock on 'this' when
645 // the current class loader is not parallel capable.
646 if (parallelLockMap == null) {
647 synchronized (this) {
648 return loadClass(name);
649 }
650 } else {
651 return loadClass(name);
652 }
653 }
654
655 // Invoked by the VM after loading class with this loader.
656 private void checkPackageAccess(Class<?> cls, ProtectionDomain pd) {
657 final SecurityManager sm = System.getSecurityManager();
658 if (sm != null) {
659 if (ReflectUtil.isNonPublicProxyClass(cls)) {
660 for (Class<?> intf: cls.getInterfaces()) {
661 checkPackageAccess(intf, pd);
662 }
663 return;
664 }
665
666 final String name = cls.getName();
667 final int i = name.lastIndexOf('.');
668 if (i != -1) {
669 AccessController.doPrivileged(new PrivilegedAction<>() {
670 public Void run() {
671 sm.checkPackageAccess(name.substring(0, i));
672 return null;
673 }
674 }, new AccessControlContext(new ProtectionDomain[] {pd}));
675 }
676 }
677 }
678
679 /**
680 * Finds the class with the specified <a href="#name">binary name</a>.
681 * This method should be overridden by class loader implementations that
682 * follow the delegation model for loading classes, and will be invoked by
683 * the {@link #loadClass <tt>loadClass</tt>} method after checking the
684 * parent class loader for the requested class. The default implementation
685 * throws a <tt>ClassNotFoundException</tt>.
686 *
687 * @param name
688 * The <a href="#name">binary name</a> of the class
689 *
690 * @return The resulting <tt>Class</tt> object
691 *
692 * @throws ClassNotFoundException
693 * If the class could not be found
694 *
695 * @since 1.2
696 */
697 protected Class<?> findClass(String name) throws ClassNotFoundException {
698 throw new ClassNotFoundException(name);
699 }
700
701 /**
702 * Finds the class with the given <a href="#name">binary name</a>
703 * in a module defined to this class loader.
704 * Class loader implementations that support the loading from modules
705 * should override this method.
706 *
707 * @apiNote This method returns {@code null} rather than throwing
708 * {@code ClassNotFoundException} if the class could not be found
709 *
710 * @implSpec The default implementation returns {@code null}.
711 *
712 * @param moduleName
713 * The module name
714 * @param name
715 * The <a href="#name">binary name</a> of the class
716 *
717 * @return The resulting {@code Class} object, or {@code null}
718 * if the class could not be found.
719 *
720 * @since 9
721 */
722 protected Class<?> findClass(String moduleName, String name) {
723 return null;
724 }
725
726
727 /**
728 * Converts an array of bytes into an instance of class <tt>Class</tt>.
729 * Before the <tt>Class</tt> can be used it must be resolved. This method
730 * is deprecated in favor of the version that takes a <a
731 * href="#name">binary name</a> as its first argument, and is more secure.
732 *
733 * @param b
734 * The bytes that make up the class data. The bytes in positions
735 * <tt>off</tt> through <tt>off+len-1</tt> should have the format
736 * of a valid class file as defined by
737 * <cite>The Java™ Virtual Machine Specification</cite>.
738 *
739 * @param off
740 * The start offset in <tt>b</tt> of the class data
741 *
742 * @param len
743 * The length of the class data
744 *
745 * @return The <tt>Class</tt> object that was created from the specified
746 * class data
747 *
748 * @throws ClassFormatError
749 * If the data did not contain a valid class
750 *
751 * @throws IndexOutOfBoundsException
752 * If either <tt>off</tt> or <tt>len</tt> is negative, or if
753 * <tt>off+len</tt> is greater than <tt>b.length</tt>.
754 *
755 * @throws SecurityException
756 * If an attempt is made to add this class to a package that
757 * contains classes that were signed by a different set of
758 * certificates than this class, or if an attempt is made
759 * to define a class in a package with a fully-qualified name
760 * that starts with "{@code java.}".
761 *
762 * @see #loadClass(String, boolean)
763 * @see #resolveClass(Class)
764 *
765 * @deprecated Replaced by {@link #defineClass(String, byte[], int, int)
766 * defineClass(String, byte[], int, int)}
767 */
768 @Deprecated(since="1.1")
769 protected final Class<?> defineClass(byte[] b, int off, int len)
770 throws ClassFormatError
771 {
772 return defineClass(null, b, off, len, null);
773 }
774
775 /**
776 * Converts an array of bytes into an instance of class {@code Class}.
777 * Before the {@code Class} can be used it must be resolved.
778 *
779 * <p> This method assigns a default {@link java.security.ProtectionDomain
780 * ProtectionDomain} to the newly defined class. The
781 * {@code ProtectionDomain} is effectively granted the same set of
782 * permissions returned when {@link
783 * java.security.Policy#getPermissions(java.security.CodeSource)
784 * Policy.getPolicy().getPermissions(new CodeSource(null, null))}
785 * is invoked. The default protection domain is created on the first invocation
786 * of {@link #defineClass(String, byte[], int, int) defineClass},
787 * and re-used on subsequent invocations.
788 *
789 * <p> To assign a specific {@code ProtectionDomain} to the class, use
790 * the {@link #defineClass(String, byte[], int, int,
791 * java.security.ProtectionDomain) defineClass} method that takes a
792 * {@code ProtectionDomain} as one of its arguments. </p>
793 *
794 * <p>
795 * This method defines a package in this class loader corresponding to the
796 * package of the {@code Class} (if such a package has not already been defined
797 * in this class loader). The name of the defined package is derived from
798 * the <a href="#name">binary name</a> of the class specified by
799 * the byte array {@code b}.
800 * Other properties of the defined package are as specified by {@link Package}.
801 *
802 * @param name
803 * The expected <a href="#name">binary name</a> of the class, or
804 * {@code null} if not known
805 *
806 * @param b
807 * The bytes that make up the class data. The bytes in positions
808 * {@code off} through {@code off+len-1} should have the format
809 * of a valid class file as defined by
810 * <cite>The Java™ Virtual Machine Specification</cite>.
811 *
812 * @param off
813 * The start offset in {@code b} of the class data
814 *
815 * @param len
816 * The length of the class data
817 *
818 * @return The {@code Class} object that was created from the specified
819 * class data.
820 *
821 * @throws ClassFormatError
822 * If the data did not contain a valid class
823 *
824 * @throws IndexOutOfBoundsException
825 * If either {@code off} or {@code len} is negative, or if
826 * {@code off+len} is greater than {@code b.length}.
827 *
828 * @throws SecurityException
829 * If an attempt is made to add this class to a package that
830 * contains classes that were signed by a different set of
831 * certificates than this class (which is unsigned), or if
832 * {@code name} begins with "{@code java.}".
833 *
834 * @see #loadClass(String, boolean)
835 * @see #resolveClass(Class)
836 * @see java.security.CodeSource
837 * @see java.security.SecureClassLoader
838 *
839 * @since 1.1
840 */
841 protected final Class<?> defineClass(String name, byte[] b, int off, int len)
842 throws ClassFormatError
843 {
844 return defineClass(name, b, off, len, null);
845 }
846
847 /* Determine protection domain, and check that:
848 - not define java.* class,
849 - signer of this class matches signers for the rest of the classes in
850 package.
851 */
852 private ProtectionDomain preDefineClass(String name,
853 ProtectionDomain pd)
854 {
855 if (!checkName(name))
856 throw new NoClassDefFoundError("IllegalName: " + name);
857
858 // Note: Checking logic in java.lang.invoke.MemberName.checkForTypeAlias
859 // relies on the fact that spoofing is impossible if a class has a name
860 // of the form "java.*"
861 if ((name != null) && name.startsWith("java.")
862 && this != getBuiltinPlatformClassLoader()) {
863 throw new SecurityException
864 ("Prohibited package name: " +
865 name.substring(0, name.lastIndexOf('.')));
866 }
867 if (pd == null) {
868 pd = defaultDomain;
869 }
870
871 if (name != null) {
872 checkCerts(name, pd.getCodeSource());
873 }
874
875 return pd;
876 }
877
878 private String defineClassSourceLocation(ProtectionDomain pd) {
879 CodeSource cs = pd.getCodeSource();
880 String source = null;
881 if (cs != null && cs.getLocation() != null) {
882 source = cs.getLocation().toString();
883 }
884 return source;
885 }
886
887 private void postDefineClass(Class<?> c, ProtectionDomain pd) {
888 // define a named package, if not present
889 getNamedPackage(c.getPackageName(), c.getModule());
890
891 if (pd.getCodeSource() != null) {
892 Certificate certs[] = pd.getCodeSource().getCertificates();
893 if (certs != null)
894 setSigners(c, certs);
895 }
896 }
897
898 /**
899 * Converts an array of bytes into an instance of class {@code Class},
900 * with a given {@code ProtectionDomain}.
901 *
902 * <p> If the given {@code ProtectionDomain} is {@code null},
903 * then a default protection domain will be assigned to the class as specified
904 * in the documentation for {@link #defineClass(String, byte[], int, int)}.
905 * Before the class can be used it must be resolved.
906 *
907 * <p> The first class defined in a package determines the exact set of
908 * certificates that all subsequent classes defined in that package must
909 * contain. The set of certificates for a class is obtained from the
910 * {@link java.security.CodeSource CodeSource} within the
911 * {@code ProtectionDomain} of the class. Any classes added to that
912 * package must contain the same set of certificates or a
913 * {@code SecurityException} will be thrown. Note that if
914 * {@code name} is {@code null}, this check is not performed.
915 * You should always pass in the <a href="#name">binary name</a> of the
916 * class you are defining as well as the bytes. This ensures that the
917 * class you are defining is indeed the class you think it is.
918 *
919 * <p> If the specified {@code name} begins with "{@code java.}", it can
920 * only be defined by the {@linkplain #getPlatformClassLoader()
921 * platform class loader} or its ancestors; otherwise {@code SecurityException}
922 * will be thrown. If {@code name} is not {@code null}, it must be equal to
923 * the <a href="#name">binary name</a> of the class
924 * specified by the byte array {@code b}, otherwise a {@link
925 * NoClassDefFoundError NoClassDefFoundError} will be thrown.
926 *
927 * <p> This method defines a package in this class loader corresponding to the
928 * package of the {@code Class} (if such a package has not already been defined
929 * in this class loader). The name of the defined package is derived from
930 * the <a href="#name">binary name</a> of the class specified by
931 * the byte array {@code b}.
932 * Other properties of the defined package are as specified by {@link Package}.
933 *
934 * @param name
935 * The expected <a href="#name">binary name</a> of the class, or
936 * {@code null} if not known
937 *
938 * @param b
939 * The bytes that make up the class data. The bytes in positions
940 * {@code off} through {@code off+len-1} should have the format
941 * of a valid class file as defined by
942 * <cite>The Java™ Virtual Machine Specification</cite>.
943 *
944 * @param off
945 * The start offset in {@code b} of the class data
946 *
947 * @param len
948 * The length of the class data
949 *
950 * @param protectionDomain
951 * The {@code ProtectionDomain} of the class
952 *
953 * @return The {@code Class} object created from the data,
954 * and {@code ProtectionDomain}.
955 *
956 * @throws ClassFormatError
957 * If the data did not contain a valid class
958 *
959 * @throws NoClassDefFoundError
960 * If {@code name} is not {@code null} and not equal to the
961 * <a href="#name">binary name</a> of the class specified by {@code b}
962 *
963 * @throws IndexOutOfBoundsException
964 * If either {@code off} or {@code len} is negative, or if
965 * {@code off+len} is greater than {@code b.length}.
966 *
967 * @throws SecurityException
968 * If an attempt is made to add this class to a package that
969 * contains classes that were signed by a different set of
970 * certificates than this class, or if {@code name} begins with
971 * "{@code java.}" and this class loader is not the platform
972 * class loader or its ancestor.
973 */
974 protected final Class<?> defineClass(String name, byte[] b, int off, int len,
975 ProtectionDomain protectionDomain)
976 throws ClassFormatError
977 {
978 protectionDomain = preDefineClass(name, protectionDomain);
979 String source = defineClassSourceLocation(protectionDomain);
980 Class<?> c = defineClass1(name, b, off, len, protectionDomain, source);
981 postDefineClass(c, protectionDomain);
982 return c;
983 }
984
985 /**
986 * Converts a {@link java.nio.ByteBuffer ByteBuffer} into an instance
987 * of class {@code Class}, with the given {@code ProtectionDomain}.
988 * If the given {@code ProtectionDomain} is {@code null}, then a default
989 * protection domain will be assigned to the class as
990 * specified in the documentation for {@link #defineClass(String, byte[],
991 * int, int)}. Before the class can be used it must be resolved.
992 *
993 * <p>The rules about the first class defined in a package determining the
994 * set of certificates for the package, the restrictions on class names,
995 * and the defined package of the class
996 * are identical to those specified in the documentation for {@link
997 * #defineClass(String, byte[], int, int, ProtectionDomain)}.
998 *
999 * <p> An invocation of this method of the form
1000 * <i>cl</i><tt>.defineClass(</tt><i>name</i><tt>,</tt>
1001 * <i>bBuffer</i><tt>,</tt> <i>pd</i><tt>)</tt> yields exactly the same
1002 * result as the statements
1003 *
1004 *<p> <tt>
1005 * ...<br>
1006 * byte[] temp = new byte[bBuffer.{@link
1007 * java.nio.ByteBuffer#remaining remaining}()];<br>
1008 * bBuffer.{@link java.nio.ByteBuffer#get(byte[])
1009 * get}(temp);<br>
1010 * return {@link #defineClass(String, byte[], int, int, ProtectionDomain)
1011 * cl.defineClass}(name, temp, 0,
1012 * temp.length, pd);<br>
1013 * </tt></p>
1014 *
1015 * @param name
1016 * The expected <a href="#name">binary name</a>. of the class, or
1017 * <tt>null</tt> if not known
1018 *
1019 * @param b
1020 * The bytes that make up the class data. The bytes from positions
1021 * <tt>b.position()</tt> through <tt>b.position() + b.limit() -1
1022 * </tt> should have the format of a valid class file as defined by
1023 * <cite>The Java™ Virtual Machine Specification</cite>.
1024 *
1025 * @param protectionDomain
1026 * The {@code ProtectionDomain} of the class, or {@code null}.
1027 *
1028 * @return The {@code Class} object created from the data,
1029 * and {@code ProtectionDomain}.
1030 *
1031 * @throws ClassFormatError
1032 * If the data did not contain a valid class.
1033 *
1034 * @throws NoClassDefFoundError
1035 * If {@code name} is not {@code null} and not equal to the
1036 * <a href="#name">binary name</a> of the class specified by {@code b}
1037 *
1038 * @throws SecurityException
1039 * If an attempt is made to add this class to a package that
1040 * contains classes that were signed by a different set of
1041 * certificates than this class, or if {@code name} begins with
1042 * "{@code java.}".
1043 *
1044 * @see #defineClass(String, byte[], int, int, ProtectionDomain)
1045 *
1046 * @since 1.5
1047 */
1048 protected final Class<?> defineClass(String name, java.nio.ByteBuffer b,
1049 ProtectionDomain protectionDomain)
1050 throws ClassFormatError
1051 {
1052 int len = b.remaining();
1053
1054 // Use byte[] if not a direct ByteBuffer:
1055 if (!b.isDirect()) {
1056 if (b.hasArray()) {
1057 return defineClass(name, b.array(),
1058 b.position() + b.arrayOffset(), len,
1059 protectionDomain);
1060 } else {
1061 // no array, or read-only array
1062 byte[] tb = new byte[len];
1063 b.get(tb); // get bytes out of byte buffer.
1064 return defineClass(name, tb, 0, len, protectionDomain);
1065 }
1066 }
1067
1068 protectionDomain = preDefineClass(name, protectionDomain);
1069 String source = defineClassSourceLocation(protectionDomain);
1070 Class<?> c = defineClass2(name, b, b.position(), len, protectionDomain, source);
1071 postDefineClass(c, protectionDomain);
1072 return c;
1073 }
1074
1075 private native Class<?> defineClass1(String name, byte[] b, int off, int len,
1076 ProtectionDomain pd, String source);
1077
1078 private native Class<?> defineClass2(String name, java.nio.ByteBuffer b,
1079 int off, int len, ProtectionDomain pd,
1080 String source);
1081
1082 // true if the name is null or has the potential to be a valid binary name
1083 private boolean checkName(String name) {
1084 if ((name == null) || (name.length() == 0))
1085 return true;
1086 if ((name.indexOf('/') != -1) || (name.charAt(0) == '['))
1087 return false;
1088 return true;
1089 }
1090
1091 private void checkCerts(String name, CodeSource cs) {
1092 int i = name.lastIndexOf('.');
1093 String pname = (i == -1) ? "" : name.substring(0, i);
1094
1095 Certificate[] certs = null;
1096 if (cs != null) {
1097 certs = cs.getCertificates();
1098 }
1099 Certificate[] pcerts = null;
1100 if (parallelLockMap == null) {
1101 synchronized (this) {
1102 pcerts = package2certs.get(pname);
1103 if (pcerts == null) {
1104 package2certs.put(pname, (certs == null? nocerts:certs));
1105 }
1106 }
1107 } else {
1108 pcerts = ((ConcurrentHashMap<String, Certificate[]>)package2certs).
1109 putIfAbsent(pname, (certs == null? nocerts:certs));
1110 }
1111 if (pcerts != null && !compareCerts(pcerts, certs)) {
1112 throw new SecurityException("class \""+ name +
1113 "\"'s signer information does not match signer information of other classes in the same package");
1114 }
1115 }
1116
1117 /**
1118 * check to make sure the certs for the new class (certs) are the same as
1119 * the certs for the first class inserted in the package (pcerts)
1120 */
1121 private boolean compareCerts(Certificate[] pcerts,
1122 Certificate[] certs)
1123 {
1124 // certs can be null, indicating no certs.
1125 if ((certs == null) || (certs.length == 0)) {
1126 return pcerts.length == 0;
1127 }
1128
1129 // the length must be the same at this point
1130 if (certs.length != pcerts.length)
1131 return false;
1132
1133 // go through and make sure all the certs in one array
1134 // are in the other and vice-versa.
1135 boolean match;
1136 for (Certificate cert : certs) {
1137 match = false;
1138 for (Certificate pcert : pcerts) {
1139 if (cert.equals(pcert)) {
1140 match = true;
1141 break;
1142 }
1143 }
1144 if (!match) return false;
1145 }
1146
1147 // now do the same for pcerts
1148 for (Certificate pcert : pcerts) {
1149 match = false;
1150 for (Certificate cert : certs) {
1151 if (pcert.equals(cert)) {
1152 match = true;
1153 break;
1154 }
1155 }
1156 if (!match) return false;
1157 }
1158
1159 return true;
1160 }
1161
1162 /**
1163 * Links the specified class. This (misleadingly named) method may be
1164 * used by a class loader to link a class. If the class <tt>c</tt> has
1165 * already been linked, then this method simply returns. Otherwise, the
1166 * class is linked as described in the "Execution" chapter of
1167 * <cite>The Java™ Language Specification</cite>.
1168 *
1169 * @param c
1170 * The class to link
1171 *
1172 * @throws NullPointerException
1173 * If <tt>c</tt> is <tt>null</tt>.
1174 *
1175 * @see #defineClass(String, byte[], int, int)
1176 */
1177 protected final void resolveClass(Class<?> c) {
1178 if (c == null) {
1179 throw new NullPointerException();
1180 }
1181 }
1182
1183 /**
1184 * Finds a class with the specified <a href="#name">binary name</a>,
1185 * loading it if necessary.
1186 *
1187 * <p> This method loads the class through the system class loader (see
1188 * {@link #getSystemClassLoader()}). The <tt>Class</tt> object returned
1189 * might have more than one <tt>ClassLoader</tt> associated with it.
1190 * Subclasses of <tt>ClassLoader</tt> need not usually invoke this method,
1191 * because most class loaders need to override just {@link
1192 * #findClass(String)}. </p>
1193 *
1194 * @param name
1195 * The <a href="#name">binary name</a> of the class
1196 *
1197 * @return The <tt>Class</tt> object for the specified <tt>name</tt>
1198 *
1199 * @throws ClassNotFoundException
1200 * If the class could not be found
1201 *
1202 * @see #ClassLoader(ClassLoader)
1203 * @see #getParent()
1204 */
1205 protected final Class<?> findSystemClass(String name)
1206 throws ClassNotFoundException
1207 {
1208 return getSystemClassLoader().loadClass(name);
1209 }
1210
1211 /**
1212 * Returns a class loaded by the bootstrap class loader;
1213 * or return null if not found.
1214 */
1215 Class<?> findBootstrapClassOrNull(String name) {
1216 if (!checkName(name)) return null;
1217
1218 return findBootstrapClass(name);
1219 }
1220
1221 // return null if not found
1222 private native Class<?> findBootstrapClass(String name);
1223
1224 /**
1225 * Returns the class with the given <a href="#name">binary name</a> if this
1226 * loader has been recorded by the Java virtual machine as an initiating
1227 * loader of a class with that <a href="#name">binary name</a>. Otherwise
1228 * <tt>null</tt> is returned.
1229 *
1230 * @param name
1231 * The <a href="#name">binary name</a> of the class
1232 *
1233 * @return The <tt>Class</tt> object, or <tt>null</tt> if the class has
1234 * not been loaded
1235 *
1236 * @since 1.1
1237 */
1238 protected final Class<?> findLoadedClass(String name) {
1239 if (!checkName(name))
1240 return null;
1241 return findLoadedClass0(name);
1242 }
1243
1244 private final native Class<?> findLoadedClass0(String name);
1245
1246 /**
1247 * Sets the signers of a class. This should be invoked after defining a
1248 * class.
1249 *
1250 * @param c
1251 * The <tt>Class</tt> object
1252 *
1253 * @param signers
1254 * The signers for the class
1255 *
1256 * @since 1.1
1257 */
1258 protected final void setSigners(Class<?> c, Object[] signers) {
1259 c.setSigners(signers);
1260 }
1261
1262
1263 // -- Resources --
1264
1265 /**
1266 * Returns a URL to a resource in a module defined to this class loader.
1267 * Class loader implementations that support the loading from modules
1268 * should override this method.
1269 *
1270 * @implSpec The default implementation returns {@code null}.
1271 *
1272 * @param moduleName
1273 * The module name
1274 * @param name
1275 * The resource name
1276 *
1277 * @return A URL to the resource; {@code null} if the resource could not be
1278 * found, a URL could not be constructed to locate the resource,
1279 * access to the resource is denied by the security manager, or
1280 * there isn't a module of the given name defined to the class
1281 * loader.
1282 *
1283 * @throws IOException
1284 * If I/O errors occur
1285 *
1286 * @see java.lang.module.ModuleReader#find(String)
1287 * @since 9
1288 */
1289 protected URL findResource(String moduleName, String name) throws IOException {
1290 return null;
1291 }
1292
1293 /**
1294 * Finds the resource with the given name. A resource is some data
1295 * (images, audio, text, etc) that can be accessed by class code in a way
1296 * that is independent of the location of the code.
1297 *
1298 * Resources in a named module are private to that module. This method does
1299 * not find resource in named modules.
1300 *
1301 * <p> The name of a resource is a '<tt>/</tt>'-separated path name that
1302 * identifies the resource.
1303 *
1304 * <p> This method will first search the parent class loader for the
1305 * resource; if the parent is <tt>null</tt> the path of the class loader
1306 * built-in to the virtual machine is searched. That failing, this method
1307 * will invoke {@link #findResource(String)} to find the resource. </p>
1308 *
1309 * @apiNote When overriding this method it is recommended that an
1310 * implementation ensures that any delegation is consistent with the {@link
1311 * #getResources(java.lang.String) getResources(String)} method.
1312 *
1313 * @param name
1314 * The resource name
1315 *
1316 * @return A <tt>URL</tt> object for reading the resource, or
1317 * <tt>null</tt> if the resource could not be found or the invoker
1318 * doesn't have adequate privileges to get the resource.
1319 *
1320 * @since 1.1
1321 */
1322 public URL getResource(String name) {
1323 URL url;
1324 if (parent != null) {
1325 url = parent.getResource(name);
1326 } else {
1327 url = BootLoader.findResource(name);
1328 }
1329 if (url == null) {
1330 url = findResource(name);
1331 }
1332 return url;
1333 }
1334
1335 /**
1336 * Finds all the resources with the given name. A resource is some data
1337 * (images, audio, text, etc) that can be accessed by class code in a way
1338 * that is independent of the location of the code.
1339 *
1340 * Resources in a named module are private to that module. This method does
1341 * not find resources in named modules.
1342 *
1343 * <p>The name of a resource is a <tt>/</tt>-separated path name that
1344 * identifies the resource.
1345 *
1346 * <p> The search order is described in the documentation for {@link
1347 * #getResource(String)}. </p>
1348 *
1349 * @apiNote When overriding this method it is recommended that an
1350 * implementation ensures that any delegation is consistent with the {@link
1351 * #getResource(java.lang.String) getResource(String)} method. This should
1352 * ensure that the first element returned by the Enumeration's
1353 * {@code nextElement} method is the same resource that the
1354 * {@code getResource(String)} method would return.
1355 *
1356 * @param name
1357 * The resource name
1358 *
1359 * @return An enumeration of {@link java.net.URL <tt>URL</tt>} objects for
1360 * the resource. If no resources could be found, the enumeration
1361 * will be empty. Resources that the class loader doesn't have
1362 * access to will not be in the enumeration.
1363 *
1364 * @throws IOException
1365 * If I/O errors occur
1366 *
1367 * @see #findResources(String)
1368 *
1369 * @since 1.2
1370 */
1371 public Enumeration<URL> getResources(String name) throws IOException {
1372 @SuppressWarnings("unchecked")
1373 Enumeration<URL>[] tmp = (Enumeration<URL>[]) new Enumeration<?>[2];
1374 if (parent != null) {
1375 tmp[0] = parent.getResources(name);
1376 } else {
1377 tmp[0] = BootLoader.findResources(name);
1378 }
1379 tmp[1] = findResources(name);
1380
1381 return new CompoundEnumeration<>(tmp);
1382 }
1383
1384 /**
1385 * Returns a stream whose elements are the URLs of all the resources with
1386 * the given name. A resource is some data (images, audio, text, etc) that
1387 * can be accessed by class code in a way that is independent of the
1388 * location of the code.
1389 *
1390 * Resources in a named module are private to that module. This method does
1391 * not find resources in named modules.
1392 *
1393 * <p> The name of a resource is a {@code /}-separated path name that
1394 * identifies the resource.
1395 *
1396 * <p> The search order is described in the documentation for {@link
1397 * #getResource(String)}.
1398 *
1399 * <p> The resources will be located when the returned stream is evaluated.
1400 * If the evaluation results in an {@code IOException} then the I/O
1401 * exception is wrapped in an {@link UncheckedIOException} that is then
1402 * thrown.
1403 *
1404 * @apiNote When overriding this method it is recommended that an
1405 * implementation ensures that any delegation is consistent with the {@link
1406 * #getResource(java.lang.String) getResource(String)} method. This should
1407 * ensure that the first element returned by the stream is the same
1408 * resource that the {@code getResource(String)} method would return.
1409 *
1410 * @param name
1411 * The resource name
1412 *
1413 * @return A stream of resource {@link java.net.URL URL} objects. If no
1414 * resources could be found, the stream will be empty. Resources
1415 * that the class loader doesn't have access to will not be in the
1416 * stream.
1417 *
1418 * @see #findResources(String)
1419 *
1420 * @since 9
1421 */
1422 public Stream<URL> resources(String name) {
1423 int characteristics = Spliterator.NONNULL | Spliterator.IMMUTABLE;
1424 Supplier<Spliterator<URL>> si = () -> {
1425 try {
1426 return Spliterators.spliteratorUnknownSize(
1427 getResources(name).asIterator(), characteristics);
1428 } catch (IOException e) {
1429 throw new UncheckedIOException(e);
1430 }
1431 };
1432 return StreamSupport.stream(si, characteristics, false);
1433 }
1434
1435 /**
1436 * Finds the resource with the given name. Class loader implementations
1437 * should override this method to specify where to find resources.
1438 *
1439 * Resources in a named module are private to that module. This method does
1440 * not find resources in named modules defined to this class loader.
1441 *
1442 * @param name
1443 * The resource name
1444 *
1445 * @return A <tt>URL</tt> object for reading the resource, or
1446 * <tt>null</tt> if the resource could not be found
1447 *
1448 * @since 1.2
1449 */
1450 protected URL findResource(String name) {
1451 return null;
1452 }
1453
1454 /**
1455 * Returns an enumeration of {@link java.net.URL <tt>URL</tt>} objects
1456 * representing all the resources with the given name. Class loader
1457 * implementations should override this method to specify where to load
1458 * resources from.
1459 *
1460 * Resources in a named module are private to that module. This method does
1461 * not find resources in named modules defined to this class loader.
1462 *
1463 * @param name
1464 * The resource name
1465 *
1466 * @return An enumeration of {@link java.net.URL <tt>URL</tt>} objects for
1467 * the resources
1468 *
1469 * @throws IOException
1470 * If I/O errors occur
1471 *
1472 * @since 1.2
1473 */
1474 protected Enumeration<URL> findResources(String name) throws IOException {
1475 return java.util.Collections.emptyEnumeration();
1476 }
1477
1478 /**
1479 * Registers the caller as parallel capable.
1480 * The registration succeeds if and only if all of the following
1481 * conditions are met:
1482 * <ol>
1483 * <li> no instance of the caller has been created</li>
1484 * <li> all of the super classes (except class Object) of the caller are
1485 * registered as parallel capable</li>
1486 * </ol>
1487 * <p>Note that once a class loader is registered as parallel capable, there
1488 * is no way to change it back.</p>
1489 *
1490 * @return true if the caller is successfully registered as
1491 * parallel capable and false if otherwise.
1492 *
1493 * @since 1.7
1494 */
1495 @CallerSensitive
1496 protected static boolean registerAsParallelCapable() {
1497 Class<? extends ClassLoader> callerClass =
1498 Reflection.getCallerClass().asSubclass(ClassLoader.class);
1499 return ParallelLoaders.register(callerClass);
1500 }
1501
1502 /**
1503 * Find a resource of the specified name from the search path used to load
1504 * classes. This method locates the resource through the system class
1505 * loader (see {@link #getSystemClassLoader()}).
1506 *
1507 * Resources in a named module are private to that module. This method does
1508 * not find resources in named modules.
1509 *
1510 * @param name
1511 * The resource name
1512 *
1513 * @return A {@link java.net.URL <tt>URL</tt>} object for reading the
1514 * resource, or <tt>null</tt> if the resource could not be found
1515 *
1516 * @since 1.1
1517 */
1518 public static URL getSystemResource(String name) {
1519 return getSystemClassLoader().getResource(name);
1520 }
1521
1522 /**
1523 * Finds all resources of the specified name from the search path used to
1524 * load classes. The resources thus found are returned as an
1525 * {@link java.util.Enumeration <tt>Enumeration</tt>} of {@link
1526 * java.net.URL <tt>URL</tt>} objects.
1527 *
1528 * Resources in a named module are private to that module. This method does
1529 * not find resources in named modules.
1530 *
1531 * <p> The search order is described in the documentation for {@link
1532 * #getSystemResource(String)}. </p>
1533 *
1534 * @param name
1535 * The resource name
1536 *
1537 * @return An enumeration of resource {@link java.net.URL <tt>URL</tt>}
1538 * objects
1539 *
1540 * @throws IOException
1541 * If I/O errors occur
1542 *
1543 * @since 1.2
1544 */
1545 public static Enumeration<URL> getSystemResources(String name)
1546 throws IOException
1547 {
1548 return getSystemClassLoader().getResources(name);
1549 }
1550
1551 /**
1552 * Returns an input stream for reading the specified resource.
1553 *
1554 * Resources in a named module are private to that module. This method does
1555 * not find resources in named modules.
1556 *
1557 * <p> The search order is described in the documentation for {@link
1558 * #getResource(String)}. </p>
1559 *
1560 * @param name
1561 * The resource name
1562 *
1563 * @return An input stream for reading the resource, or <tt>null</tt>
1564 * if the resource could not be found
1565 *
1566 * @since 1.1
1567 */
1568 public InputStream getResourceAsStream(String name) {
1569 URL url = getResource(name);
1570 try {
1571 return url != null ? url.openStream() : null;
1572 } catch (IOException e) {
1573 return null;
1574 }
1575 }
1576
1577 /**
1578 * Open for reading, a resource of the specified name from the search path
1579 * used to load classes. This method locates the resource through the
1580 * system class loader (see {@link #getSystemClassLoader()}).
1581 *
1582 * Resources in a named module are private to that module. This method does
1583 * not find resources in named modules.
1584 *
1585 * @param name
1586 * The resource name
1587 *
1588 * @return An input stream for reading the resource, or <tt>null</tt>
1589 * if the resource could not be found
1590 *
1591 * @since 1.1
1592 */
1593 public static InputStream getSystemResourceAsStream(String name) {
1594 URL url = getSystemResource(name);
1595 try {
1596 return url != null ? url.openStream() : null;
1597 } catch (IOException e) {
1598 return null;
1599 }
1600 }
1601
1602
1603 // -- Hierarchy --
1604
1605 /**
1606 * Returns the parent class loader for delegation. Some implementations may
1607 * use <tt>null</tt> to represent the bootstrap class loader. This method
1608 * will return <tt>null</tt> in such implementations if this class loader's
1609 * parent is the bootstrap class loader.
1610 *
1611 * @return The parent <tt>ClassLoader</tt>
1612 *
1613 * @throws SecurityException
1614 * If a security manager is present, and the caller's class loader
1615 * is not {@code null} and is not an ancestor of this class loader,
1616 * and the caller does not have the
1617 * {@link RuntimePermission}{@code ("getClassLoader")}
1618 *
1619 * @since 1.2
1620 */
1621 @CallerSensitive
1622 public final ClassLoader getParent() {
1623 if (parent == null)
1624 return null;
1625 SecurityManager sm = System.getSecurityManager();
1626 if (sm != null) {
1627 // Check access to the parent class loader
1628 // If the caller's class loader is same as this class loader,
1629 // permission check is performed.
1630 checkClassLoaderPermission(parent, Reflection.getCallerClass());
1631 }
1632 return parent;
1633 }
1634
1635 /**
1636 * Returns the unnamed {@code Module} for this class loader.
1637 *
1638 * @return The unnamed Module for this class loader
1639 *
1640 * @see Module#isNamed()
1641 * @since 9
1642 */
1643 public final Module getUnnamedModule() {
1644 return unnamedModule;
1645 }
1646
1647 /**
1648 * Returns the platform class loader for delegation. All
1649 * <a href="#builtinLoaders">platform classes</a> are visible to
1650 * the platform class loader.
1651 *
1652 * @return The platform {@code ClassLoader}.
1653 *
1654 * @throws SecurityException
1655 * If a security manager is present, and the caller's class loader is
1656 * not {@code null}, and the caller's class loader is not the same
1657 * as or an ancestor of the platform class loader,
1658 * and the caller does not have the
1659 * {@link RuntimePermission}{@code ("getClassLoader")}
1660 *
1661 * @since 9
1662 */
1663 @CallerSensitive
1664 public static ClassLoader getPlatformClassLoader() {
1665 SecurityManager sm = System.getSecurityManager();
1666 ClassLoader loader = getBuiltinPlatformClassLoader();
1667 if (sm != null) {
1668 checkClassLoaderPermission(loader, Reflection.getCallerClass());
1669 }
1670 return loader;
1671 }
1672
1673 /**
1674 * Returns the system class loader for delegation. This is the default
1675 * delegation parent for new <tt>ClassLoader</tt> instances, and is
1676 * typically the class loader used to start the application.
1677 *
1678 * <p> This method is first invoked early in the runtime's startup
1679 * sequence, at which point it creates the system class loader. This
1680 * class loader will be the context class loader for the main application
1681 * thread (for example, the thread that invokes the {@code main} method of
1682 * the main class).
1683 *
1684 * <p> The default system class loader is an implementation-dependent
1685 * instance of this class.
1686 *
1687 * <p> If the system property "<tt>java.system.class.loader</tt>" is defined
1688 * when this method is first invoked then the value of that property is
1689 * taken to be the name of a class that will be returned as the system
1690 * class loader. The class is loaded using the default system class loader
1691 * and must define a public constructor that takes a single parameter of
1692 * type <tt>ClassLoader</tt> which is used as the delegation parent. An
1693 * instance is then created using this constructor with the default system
1694 * class loader as the parameter. The resulting class loader is defined
1695 * to be the system class loader. During construction, the class loader
1696 * should take great care to avoid calling {@code getSystemClassLoader()}.
1697 * If circular initialization of the system class loader is detected then
1698 * an unspecified error or exception is thrown.
1699 *
1700 * @implNote The system property to override the system class loader is not
1701 * examined until the VM is almost fully initialized. Code that executes
1702 * this method during startup should take care not to cache the return
1703 * value until the system is fully initialized.
1704 *
1705 * @return The system <tt>ClassLoader</tt> for delegation
1706 *
1707 * @throws SecurityException
1708 * If a security manager is present, and the caller's class loader
1709 * is not {@code null} and is not the same as or an ancestor of the
1710 * system class loader, and the caller does not have the
1711 * {@link RuntimePermission}{@code ("getClassLoader")}
1712 *
1713 * @throws IllegalStateException
1714 * If invoked recursively during the construction of the class
1715 * loader specified by the "<tt>java.system.class.loader</tt>"
1716 * property.
1717 *
1718 * @throws Error
1719 * If the system property "<tt>java.system.class.loader</tt>"
1720 * is defined but the named class could not be loaded, the
1721 * provider class does not define the required constructor, or an
1722 * exception is thrown by that constructor when it is invoked. The
1723 * underlying cause of the error can be retrieved via the
1724 * {@link Throwable#getCause()} method.
1725 *
1726 * @revised 1.4
1727 */
1728 @CallerSensitive
1729 public static ClassLoader getSystemClassLoader() {
1730 switch (VM.initLevel()) {
1731 case 0:
1732 case 1:
1733 case 2:
1734 // the system class loader is the built-in app class loader during startup
1735 return getBuiltinAppClassLoader();
1736 case 3:
1737 throw new InternalError("getSystemClassLoader should only be called after VM booted");
1738 case 4:
1739 // system fully initialized
1740 assert VM.isBooted() && scl != null;
1741 SecurityManager sm = System.getSecurityManager();
1742 if (sm != null) {
1743 checkClassLoaderPermission(scl, Reflection.getCallerClass());
1744 }
1745 return scl;
1746 default:
1747 throw new InternalError("should not reach here");
1748 }
1749 }
1750
1751 static ClassLoader getBuiltinPlatformClassLoader() {
1752 return ClassLoaders.platformClassLoader();
1753 }
1754
1755 static ClassLoader getBuiltinAppClassLoader() {
1756 return ClassLoaders.appClassLoader();
1757 }
1758
1759 /*
1760 * Initialize the system class loader that may be a custom class on the
1761 * application class path or application module path.
1762 *
1763 * @see java.lang.System#initPhase3
1764 */
1765 static synchronized ClassLoader initSystemClassLoader() {
1766 if (VM.initLevel() != 3) {
1767 throw new InternalError("system class loader cannot be set at initLevel " +
1768 VM.initLevel());
1769 }
1770
1771 // detect recursive initialization
1772 if (scl != null) {
1773 throw new IllegalStateException("recursive invocation");
1774 }
1775
1776 ClassLoader builtinLoader = getBuiltinAppClassLoader();
1777
1778 // All are privileged frames. No need to call doPrivileged.
1779 String cn = System.getProperty("java.system.class.loader");
1780 if (cn != null) {
1781 try {
1782 // custom class loader is only supported to be loaded from unnamed module
1783 Constructor<?> ctor = Class.forName(cn, false, builtinLoader)
1784 .getDeclaredConstructor(ClassLoader.class);
1785 scl = (ClassLoader) ctor.newInstance(builtinLoader);
1786 } catch (Exception e) {
1787 throw new Error(e);
1788 }
1789 } else {
1790 scl = builtinLoader;
1791 }
1792 return scl;
1793 }
1794
1795 // Returns true if the specified class loader can be found in this class
1796 // loader's delegation chain.
1797 boolean isAncestor(ClassLoader cl) {
1798 ClassLoader acl = this;
1799 do {
1800 acl = acl.parent;
1801 if (cl == acl) {
1802 return true;
1803 }
1804 } while (acl != null);
1805 return false;
1806 }
1807
1808 // Tests if class loader access requires "getClassLoader" permission
1809 // check. A class loader 'from' can access class loader 'to' if
1810 // class loader 'from' is same as class loader 'to' or an ancestor
1811 // of 'to'. The class loader in a system domain can access
1812 // any class loader.
1813 private static boolean needsClassLoaderPermissionCheck(ClassLoader from,
1814 ClassLoader to)
1815 {
1816 if (from == to)
1817 return false;
1818
1819 if (from == null)
1820 return false;
1821
1822 return !to.isAncestor(from);
1823 }
1824
1825 // Returns the class's class loader, or null if none.
1826 static ClassLoader getClassLoader(Class<?> caller) {
1827 // This can be null if the VM is requesting it
1828 if (caller == null) {
1829 return null;
1830 }
1831 // Circumvent security check since this is package-private
1832 return caller.getClassLoader0();
1833 }
1834
1835 /*
1836 * Checks RuntimePermission("getClassLoader") permission
1837 * if caller's class loader is not null and caller's class loader
1838 * is not the same as or an ancestor of the given cl argument.
1839 */
1840 static void checkClassLoaderPermission(ClassLoader cl, Class<?> caller) {
1841 SecurityManager sm = System.getSecurityManager();
1842 if (sm != null) {
1843 // caller can be null if the VM is requesting it
1844 ClassLoader ccl = getClassLoader(caller);
1845 if (needsClassLoaderPermissionCheck(ccl, cl)) {
1846 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1847 }
1848 }
1849 }
1850
1851 // The system class loader
1852 // @GuardedBy("ClassLoader.class")
1853 private static volatile ClassLoader scl;
1854
1855 // -- Package --
1856
1857 /**
1858 * Define a Package of the given Class object.
1859 *
1860 * If the given class represents an array type, a primitive type or void,
1861 * this method returns {@code null}.
1862 *
1863 * This method does not throw IllegalArgumentException.
1864 */
1865 Package definePackage(Class<?> c) {
1866 if (c.isPrimitive() || c.isArray()) {
1867 return null;
1868 }
1869
1870 return definePackage(c.getPackageName(), c.getModule());
1871 }
1872
1873 /**
1874 * Defines a Package of the given name and module
1875 *
1876 * This method does not throw IllegalArgumentException.
1877 *
1878 * @param name package name
1879 * @param m module
1880 */
1881 Package definePackage(String name, Module m) {
1882 if (name.isEmpty() && m.isNamed()) {
1883 throw new InternalError("unnamed package in " + m);
1884 }
1885
1886 // check if Package object is already defined
1887 NamedPackage pkg = packages.get(name);
1888 if (pkg instanceof Package)
1889 return (Package)pkg;
1890
1891 return (Package)packages.compute(name, (n, p) -> toPackage(n, p, m));
1892 }
1893
1894 /*
1895 * Returns a Package object for the named package
1896 */
1897 private Package toPackage(String name, NamedPackage p, Module m) {
1898 // define Package object if the named package is not yet defined
1899 if (p == null)
1900 return NamedPackage.toPackage(name, m);
1901
1902 // otherwise, replace the NamedPackage object with Package object
1903 if (p instanceof Package)
1904 return (Package)p;
1905
1906 return NamedPackage.toPackage(p.packageName(), p.module());
1907 }
1908
1909 /**
1910 * Defines a package by <a href="#name">name</a> in this {@code ClassLoader}.
1911 * <p>
1912 * <a href="#name">Package names</a> must be unique within a class loader and
1913 * cannot be redefined or changed once created.
1914 * <p>
1915 * If a class loader wishes to define a package with specific properties,
1916 * such as version information, then the class loader should call this
1917 * {@code definePackage} method before calling {@code defineClass}.
1918 * Otherwise, the
1919 * {@link #defineClass(String, byte[], int, int, ProtectionDomain) defineClass}
1920 * method will define a package in this class loader corresponding to the package
1921 * of the newly defined class; the properties of this defined package are
1922 * specified by {@link Package}.
1923 *
1924 * @apiNote
1925 * A class loader that wishes to define a package for classes in a JAR
1926 * typically uses the specification and implementation titles, versions, and
1927 * vendors from the JAR's manifest. If the package is specified as
1928 * {@linkplain java.util.jar.Attributes.Name#SEALED sealed} in the JAR's manifest,
1929 * the {@code URL} of the JAR file is typically used as the {@code sealBase}.
1930 * If classes of package {@code 'p'} defined by this class loader
1931 * are loaded from multiple JARs, the {@code Package} object may contain
1932 * different information depending on the first class of package {@code 'p'}
1933 * defined and which JAR's manifest is read first to explicitly define
1934 * package {@code 'p'}.
1935 *
1936 * <p> It is strongly recommended that a class loader does not call this
1937 * method to explicitly define packages in <em>named modules</em>; instead,
1938 * the package will be automatically defined when a class is {@linkplain
1939 * #defineClass(String, byte[], int, int, ProtectionDomain) being defined}.
1940 * If it is desirable to define {@code Package} explicitly, it should ensure
1941 * that all packages in a named module are defined with the properties
1942 * specified by {@link Package}. Otherwise, some {@code Package} objects
1943 * in a named module may be for example sealed with different seal base.
1944 *
1945 * @param name
1946 * The <a href="#name">package name</a>
1947 *
1948 * @param specTitle
1949 * The specification title
1950 *
1951 * @param specVersion
1952 * The specification version
1953 *
1954 * @param specVendor
1955 * The specification vendor
1956 *
1957 * @param implTitle
1958 * The implementation title
1959 *
1960 * @param implVersion
1961 * The implementation version
1962 *
1963 * @param implVendor
1964 * The implementation vendor
1965 *
1966 * @param sealBase
1967 * If not {@code null}, then this package is sealed with
1968 * respect to the given code source {@link java.net.URL URL}
1969 * object. Otherwise, the package is not sealed.
1970 *
1971 * @return The newly defined {@code Package} object
1972 *
1973 * @throws NullPointerException
1974 * if {@code name} is {@code null}.
1975 *
1976 * @throws IllegalArgumentException
1977 * if a package of the given {@code name} is already
1978 * defined by this class loader
1979 *
1980 * @since 1.2
1981 *
1982 * @see <a href="../../../technotes/guides/jar/jar.html#versioning">
1983 * The JAR File Specification: Package Versioning</a>
1984 * @see <a href="../../../technotes/guides/jar/jar.html#sealing">
1985 * The JAR File Specification: Package Sealing</a>
1986 */
1987 protected Package definePackage(String name, String specTitle,
1988 String specVersion, String specVendor,
1989 String implTitle, String implVersion,
1990 String implVendor, URL sealBase)
1991 {
1992 Objects.requireNonNull(name);
1993
1994 // definePackage is not final and may be overridden by custom class loader
1995 Package p = new Package(name, specTitle, specVersion, specVendor,
1996 implTitle, implVersion, implVendor,
1997 sealBase, this);
1998
1999 if (packages.putIfAbsent(name, p) != null)
2000 throw new IllegalArgumentException(name);
2001
2002 return p;
2003 }
2004
2005 /**
2006 * Returns a {@code Package} of the given <a href="#name">name</a> that has been
2007 * defined by this class loader.
2008 *
2009 * @param name The <a href="#name">package name</a>
2010 *
2011 * @return The {@code Package} of the given name defined by this class loader,
2012 * or {@code null} if not found
2013 *
2014 * @throws NullPointerException
2015 * if {@code name} is {@code null}.
2016 *
2017 * @since 9
2018 */
2019 public final Package getDefinedPackage(String name) {
2020 Objects.requireNonNull(name, "name cannot be null");
2021
2022 NamedPackage p = packages.get(name);
2023 if (p == null)
2024 return null;
2025
2026 return definePackage(name, p.module());
2027 }
2028
2029 /**
2030 * Returns all of the {@code Package}s defined by this class loader.
2031 * The returned array has no duplicated {@code Package}s of the same name.
2032 *
2033 * @apiNote This method returns an array rather than a {@code Set} or {@code Stream}
2034 * for consistency with the existing {@link #getPackages} method.
2035 *
2036 * @return The array of {@code Package} objects defined by this class loader;
2037 * or an zero length array if no package has been defined by this class loader.
2038 *
2039 * @since 9
2040 */
2041 public final Package[] getDefinedPackages() {
2042 return packages().toArray(Package[]::new);
2043 }
2044
2045 /**
2046 * Finds a package by <a href="#name">name</a> in this class loader and its ancestors.
2047 * <p>
2048 * If this class loader defines a {@code Package} of the given name,
2049 * the {@code Package} is returned. Otherwise, the ancestors of
2050 * this class loader are searched recursively (parent by parent)
2051 * for a {@code Package} of the given name.
2052 *
2053 * @param name
2054 * The <a href="#name">package name</a>
2055 *
2056 * @return The {@code Package} corresponding to the given name defined by
2057 * this class loader or its ancestors, or {@code null} if not found.
2058 *
2059 * @throws NullPointerException
2060 * if {@code name} is {@code null}.
2061 *
2062 * @deprecated
2063 * If multiple class loaders delegate to each other and define classes
2064 * with the same package name, and one such loader relies on the lookup
2065 * behavior of {@code getPackage} to return a {@code Package} from
2066 * a parent loader, then the properties exposed by the {@code Package}
2067 * may not be as expected in the rest of the program.
2068 * For example, the {@code Package} will only expose annotations from the
2069 * {@code package-info.class} file defined by the parent loader, even if
2070 * annotations exist in a {@code package-info.class} file defined by
2071 * a child loader. A more robust approach is to use the
2072 * {@link ClassLoader#getDefinedPackage} method which returns
2073 * a {@code Package} for the specified class loader.
2074 *
2075 * @since 1.2
2076 */
2077 @Deprecated(since="9")
2078 protected Package getPackage(String name) {
2079 Package pkg = getDefinedPackage(name);
2080 if (pkg == null) {
2081 if (parent != null) {
2082 pkg = parent.getPackage(name);
2083 } else {
2084 pkg = BootLoader.getDefinedPackage(name);
2085 }
2086 }
2087 return pkg;
2088 }
2089
2090 /**
2091 * Returns all of the {@code Package}s defined by this class loader
2092 * and its ancestors. The returned array may contain more than one
2093 * {@code Package} object of the same package name, each defined by
2094 * a different class loader in the class loader hierarchy.
2095 *
2096 * @return The array of {@code Package} objects defined by this
2097 * class loader and its ancestors
2098 *
2099 * @since 1.2
2100 */
2101 protected Package[] getPackages() {
2102 Stream<Package> pkgs = packages();
2103 ClassLoader ld = parent;
2104 while (ld != null) {
2105 pkgs = Stream.concat(ld.packages(), pkgs);
2106 ld = ld.parent;
2107 }
2108 return Stream.concat(BootLoader.packages(), pkgs)
2109 .toArray(Package[]::new);
2110 }
2111
2112
2113
2114 // package-private
2115
2116 /**
2117 * Returns a stream of Packages defined in this class loader
2118 */
2119 Stream<Package> packages() {
2120 return packages.values().stream()
2121 .map(p -> definePackage(p.packageName(), p.module()));
2122 }
2123
2124 // -- Native library access --
2125
2126 /**
2127 * Returns the absolute path name of a native library. The VM invokes this
2128 * method to locate the native libraries that belong to classes loaded with
2129 * this class loader. If this method returns <tt>null</tt>, the VM
2130 * searches the library along the path specified as the
2131 * "<tt>java.library.path</tt>" property.
2132 *
2133 * @param libname
2134 * The library name
2135 *
2136 * @return The absolute path of the native library
2137 *
2138 * @see System#loadLibrary(String)
2139 * @see System#mapLibraryName(String)
2140 *
2141 * @since 1.2
2142 */
2143 protected String findLibrary(String libname) {
2144 return null;
2145 }
2146
2147 /**
2148 * The inner class NativeLibrary denotes a loaded native library instance.
2149 * Every classloader contains a vector of loaded native libraries in the
2150 * private field <tt>nativeLibraries</tt>. The native libraries loaded
2151 * into the system are entered into the <tt>systemNativeLibraries</tt>
2152 * vector.
2153 *
2154 * <p> Every native library requires a particular version of JNI. This is
2155 * denoted by the private <tt>jniVersion</tt> field. This field is set by
2156 * the VM when it loads the library, and used by the VM to pass the correct
2157 * version of JNI to the native methods. </p>
2158 *
2159 * @see ClassLoader
2160 * @since 1.2
2161 */
2162 static class NativeLibrary {
2163 // opaque handle to native library, used in native code.
2164 long handle;
2165 // the version of JNI environment the native library requires.
2166 private int jniVersion;
2167 // the class from which the library is loaded, also indicates
2168 // the loader this native library belongs.
2169 private final Class<?> fromClass;
2170 // the canonicalized name of the native library.
2171 // or static library name
2172 String name;
2173 // Indicates if the native library is linked into the VM
2174 boolean isBuiltin;
2175 // Indicates if the native library is loaded
2176 boolean loaded;
2177 native void load(String name, boolean isBuiltin);
2178
2179 native long find(String name);
2180 native void unload(String name, boolean isBuiltin);
2181
2182 public NativeLibrary(Class<?> fromClass, String name, boolean isBuiltin) {
2183 this.name = name;
2184 this.fromClass = fromClass;
2185 this.isBuiltin = isBuiltin;
2186 }
2187
2188 protected void finalize() {
2189 synchronized (loadedLibraryNames) {
2190 if (fromClass.getClassLoader() != null && loaded) {
2191 /* remove the native library name */
2192 int size = loadedLibraryNames.size();
2193 for (int i = 0; i < size; i++) {
2194 if (name.equals(loadedLibraryNames.elementAt(i))) {
2195 loadedLibraryNames.removeElementAt(i);
2196 break;
2197 }
2198 }
2199 /* unload the library. */
2200 ClassLoader.nativeLibraryContext.push(this);
2201 try {
2202 unload(name, isBuiltin);
2203 } finally {
2204 ClassLoader.nativeLibraryContext.pop();
2205 }
2206 }
2207 }
2208 }
2209 // Invoked in the VM to determine the context class in
2210 // JNI_Load/JNI_Unload
2211 static Class<?> getFromClass() {
2212 return ClassLoader.nativeLibraryContext.peek().fromClass;
2213 }
2214 }
2215
2216 // All native library names we've loaded.
2217 private static Vector<String> loadedLibraryNames = new Vector<>();
2218
2219 // Native libraries belonging to system classes.
2220 private static Vector<NativeLibrary> systemNativeLibraries
2221 = new Vector<>();
2222
2223 // Native libraries associated with the class loader.
2224 private Vector<NativeLibrary> nativeLibraries = new Vector<>();
2225
2226 // native libraries being loaded/unloaded.
2227 private static Stack<NativeLibrary> nativeLibraryContext = new Stack<>();
2228
2229 // The paths searched for libraries
2230 private static String usr_paths[];
2231 private static String sys_paths[];
2232
2233 private static String[] initializePath(String propName) {
2234 String ldPath = System.getProperty(propName, "");
2235 int ldLen = ldPath.length();
2236 char ps = File.pathSeparatorChar;
2237 int psCount = 0;
2238
2239 if (ClassLoaderHelper.allowsQuotedPathElements &&
2240 ldPath.indexOf('\"') >= 0) {
2241 // First, remove quotes put around quoted parts of paths.
2242 // Second, use a quotation mark as a new path separator.
2243 // This will preserve any quoted old path separators.
2244 char[] buf = new char[ldLen];
2245 int bufLen = 0;
2246 for (int i = 0; i < ldLen; ++i) {
2247 char ch = ldPath.charAt(i);
2248 if (ch == '\"') {
2249 while (++i < ldLen &&
2250 (ch = ldPath.charAt(i)) != '\"') {
2251 buf[bufLen++] = ch;
2252 }
2253 } else {
2254 if (ch == ps) {
2255 psCount++;
2256 ch = '\"';
2257 }
2258 buf[bufLen++] = ch;
2259 }
2260 }
2261 ldPath = new String(buf, 0, bufLen);
2262 ldLen = bufLen;
2263 ps = '\"';
2264 } else {
2265 for (int i = ldPath.indexOf(ps); i >= 0;
2266 i = ldPath.indexOf(ps, i + 1)) {
2267 psCount++;
2268 }
2269 }
2270
2271 String[] paths = new String[psCount + 1];
2272 int pathStart = 0;
2273 for (int j = 0; j < psCount; ++j) {
2274 int pathEnd = ldPath.indexOf(ps, pathStart);
2275 paths[j] = (pathStart < pathEnd) ?
2276 ldPath.substring(pathStart, pathEnd) : ".";
2277 pathStart = pathEnd + 1;
2278 }
2279 paths[psCount] = (pathStart < ldLen) ?
2280 ldPath.substring(pathStart, ldLen) : ".";
2281 return paths;
2282 }
2283
2284 // Invoked in the java.lang.Runtime class to implement load and loadLibrary.
2285 static void loadLibrary(Class<?> fromClass, String name,
2286 boolean isAbsolute) {
2287 ClassLoader loader =
2288 (fromClass == null) ? null : fromClass.getClassLoader();
2289 if (sys_paths == null) {
2290 usr_paths = initializePath("java.library.path");
2291 sys_paths = initializePath("sun.boot.library.path");
2292 }
2293 if (isAbsolute) {
2294 if (loadLibrary0(fromClass, new File(name))) {
2295 return;
2296 }
2297 throw new UnsatisfiedLinkError("Can't load library: " + name);
2298 }
2299 if (loader != null) {
2300 String libfilename = loader.findLibrary(name);
2301 if (libfilename != null) {
2302 File libfile = new File(libfilename);
2303 if (!libfile.isAbsolute()) {
2304 throw new UnsatisfiedLinkError(
2305 "ClassLoader.findLibrary failed to return an absolute path: " + libfilename);
2306 }
2307 if (loadLibrary0(fromClass, libfile)) {
2308 return;
2309 }
2310 throw new UnsatisfiedLinkError("Can't load " + libfilename);
2311 }
2312 }
2313 for (String sys_path : sys_paths) {
2314 File libfile = new File(sys_path, System.mapLibraryName(name));
2315 if (loadLibrary0(fromClass, libfile)) {
2316 return;
2317 }
2318 libfile = ClassLoaderHelper.mapAlternativeName(libfile);
2319 if (libfile != null && loadLibrary0(fromClass, libfile)) {
2320 return;
2321 }
2322 }
2323 if (loader != null) {
2324 for (String usr_path : usr_paths) {
2325 File libfile = new File(usr_path, System.mapLibraryName(name));
2326 if (loadLibrary0(fromClass, libfile)) {
2327 return;
2328 }
2329 libfile = ClassLoaderHelper.mapAlternativeName(libfile);
2330 if (libfile != null && loadLibrary0(fromClass, libfile)) {
2331 return;
2332 }
2333 }
2334 }
2335 // Oops, it failed
2336 throw new UnsatisfiedLinkError("no " + name + " in java.library.path");
2337 }
2338
2339 static native String findBuiltinLib(String name);
2340
2341 private static boolean loadLibrary0(Class<?> fromClass, final File file) {
2342 // Check to see if we're attempting to access a static library
2343 String name = findBuiltinLib(file.getName());
2344 boolean isBuiltin = (name != null);
2345 if (!isBuiltin) {
2346 name = AccessController.doPrivileged(
2347 new PrivilegedAction<>() {
2348 public String run() {
2349 try {
2350 return file.exists() ? file.getCanonicalPath() : null;
2351 } catch (IOException e) {
2352 return null;
2353 }
2354 }
2355 });
2356 if (name == null) {
2357 return false;
2358 }
2359 }
2360 ClassLoader loader =
2361 (fromClass == null) ? null : fromClass.getClassLoader();
2362 Vector<NativeLibrary> libs =
2363 loader != null ? loader.nativeLibraries : systemNativeLibraries;
2364 synchronized (libs) {
2365 int size = libs.size();
2366 for (int i = 0; i < size; i++) {
2367 NativeLibrary lib = libs.elementAt(i);
2368 if (name.equals(lib.name)) {
2369 return true;
2370 }
2371 }
2372
2373 synchronized (loadedLibraryNames) {
2374 if (loadedLibraryNames.contains(name)) {
2375 throw new UnsatisfiedLinkError
2376 ("Native Library " +
2377 name +
2378 " already loaded in another classloader");
2379 }
2380 /* If the library is being loaded (must be by the same thread,
2381 * because Runtime.load and Runtime.loadLibrary are
2382 * synchronous). The reason is can occur is that the JNI_OnLoad
2383 * function can cause another loadLibrary invocation.
2384 *
2385 * Thus we can use a static stack to hold the list of libraries
2386 * we are loading.
2387 *
2388 * If there is a pending load operation for the library, we
2389 * immediately return success; otherwise, we raise
2390 * UnsatisfiedLinkError.
2391 */
2392 int n = nativeLibraryContext.size();
2393 for (int i = 0; i < n; i++) {
2394 NativeLibrary lib = nativeLibraryContext.elementAt(i);
2395 if (name.equals(lib.name)) {
2396 if (loader == lib.fromClass.getClassLoader()) {
2397 return true;
2398 } else {
2399 throw new UnsatisfiedLinkError
2400 ("Native Library " +
2401 name +
2402 " is being loaded in another classloader");
2403 }
2404 }
2405 }
2406 NativeLibrary lib = new NativeLibrary(fromClass, name, isBuiltin);
2407 nativeLibraryContext.push(lib);
2408 try {
2409 lib.load(name, isBuiltin);
2410 } finally {
2411 nativeLibraryContext.pop();
2412 }
2413 if (lib.loaded) {
2414 loadedLibraryNames.addElement(name);
2415 libs.addElement(lib);
2416 return true;
2417 }
2418 return false;
2419 }
2420 }
2421 }
2422
2423 // Invoked in the VM class linking code.
2424 static long findNative(ClassLoader loader, String name) {
2425 Vector<NativeLibrary> libs =
2426 loader != null ? loader.nativeLibraries : systemNativeLibraries;
2427 synchronized (libs) {
2428 int size = libs.size();
2429 for (int i = 0; i < size; i++) {
2430 NativeLibrary lib = libs.elementAt(i);
2431 long entry = lib.find(name);
2432 if (entry != 0)
2433 return entry;
2434 }
2435 }
2436 return 0;
2437 }
2438
2439
2440 // -- Assertion management --
2441
2442 final Object assertionLock;
2443
2444 // The default toggle for assertion checking.
2445 // @GuardedBy("assertionLock")
2446 private boolean defaultAssertionStatus = false;
2447
2448 // Maps String packageName to Boolean package default assertion status Note
2449 // that the default package is placed under a null map key. If this field
2450 // is null then we are delegating assertion status queries to the VM, i.e.,
2451 // none of this ClassLoader's assertion status modification methods have
2452 // been invoked.
2453 // @GuardedBy("assertionLock")
2454 private Map<String, Boolean> packageAssertionStatus = null;
2455
2456 // Maps String fullyQualifiedClassName to Boolean assertionStatus If this
2457 // field is null then we are delegating assertion status queries to the VM,
2458 // i.e., none of this ClassLoader's assertion status modification methods
2459 // have been invoked.
2460 // @GuardedBy("assertionLock")
2461 Map<String, Boolean> classAssertionStatus = null;
2462
2463 /**
2464 * Sets the default assertion status for this class loader. This setting
2465 * determines whether classes loaded by this class loader and initialized
2466 * in the future will have assertions enabled or disabled by default.
2467 * This setting may be overridden on a per-package or per-class basis by
2468 * invoking {@link #setPackageAssertionStatus(String, boolean)} or {@link
2469 * #setClassAssertionStatus(String, boolean)}.
2470 *
2471 * @param enabled
2472 * <tt>true</tt> if classes loaded by this class loader will
2473 * henceforth have assertions enabled by default, <tt>false</tt>
2474 * if they will have assertions disabled by default.
2475 *
2476 * @since 1.4
2477 */
2478 public void setDefaultAssertionStatus(boolean enabled) {
2479 synchronized (assertionLock) {
2480 if (classAssertionStatus == null)
2481 initializeJavaAssertionMaps();
2482
2483 defaultAssertionStatus = enabled;
2484 }
2485 }
2486
2487 /**
2488 * Sets the package default assertion status for the named package. The
2489 * package default assertion status determines the assertion status for
2490 * classes initialized in the future that belong to the named package or
2491 * any of its "subpackages".
2492 *
2493 * <p> A subpackage of a package named p is any package whose name begins
2494 * with "<tt>p.</tt>". For example, <tt>javax.swing.text</tt> is a
2495 * subpackage of <tt>javax.swing</tt>, and both <tt>java.util</tt> and
2496 * <tt>java.lang.reflect</tt> are subpackages of <tt>java</tt>.
2497 *
2498 * <p> In the event that multiple package defaults apply to a given class,
2499 * the package default pertaining to the most specific package takes
2500 * precedence over the others. For example, if <tt>javax.lang</tt> and
2501 * <tt>javax.lang.reflect</tt> both have package defaults associated with
2502 * them, the latter package default applies to classes in
2503 * <tt>javax.lang.reflect</tt>.
2504 *
2505 * <p> Package defaults take precedence over the class loader's default
2506 * assertion status, and may be overridden on a per-class basis by invoking
2507 * {@link #setClassAssertionStatus(String, boolean)}. </p>
2508 *
2509 * @param packageName
2510 * The name of the package whose package default assertion status
2511 * is to be set. A <tt>null</tt> value indicates the unnamed
2512 * package that is "current"
2513 * (see section 7.4.2 of
2514 * <cite>The Java™ Language Specification</cite>.)
2515 *
2516 * @param enabled
2517 * <tt>true</tt> if classes loaded by this classloader and
2518 * belonging to the named package or any of its subpackages will
2519 * have assertions enabled by default, <tt>false</tt> if they will
2520 * have assertions disabled by default.
2521 *
2522 * @since 1.4
2523 */
2524 public void setPackageAssertionStatus(String packageName,
2525 boolean enabled) {
2526 synchronized (assertionLock) {
2527 if (packageAssertionStatus == null)
2528 initializeJavaAssertionMaps();
2529
2530 packageAssertionStatus.put(packageName, enabled);
2531 }
2532 }
2533
2534 /**
2535 * Sets the desired assertion status for the named top-level class in this
2536 * class loader and any nested classes contained therein. This setting
2537 * takes precedence over the class loader's default assertion status, and
2538 * over any applicable per-package default. This method has no effect if
2539 * the named class has already been initialized. (Once a class is
2540 * initialized, its assertion status cannot change.)
2541 *
2542 * <p> If the named class is not a top-level class, this invocation will
2543 * have no effect on the actual assertion status of any class. </p>
2544 *
2545 * @param className
2546 * The fully qualified class name of the top-level class whose
2547 * assertion status is to be set.
2548 *
2549 * @param enabled
2550 * <tt>true</tt> if the named class is to have assertions
2551 * enabled when (and if) it is initialized, <tt>false</tt> if the
2552 * class is to have assertions disabled.
2553 *
2554 * @since 1.4
2555 */
2556 public void setClassAssertionStatus(String className, boolean enabled) {
2557 synchronized (assertionLock) {
2558 if (classAssertionStatus == null)
2559 initializeJavaAssertionMaps();
2560
2561 classAssertionStatus.put(className, enabled);
2562 }
2563 }
2564
2565 /**
2566 * Sets the default assertion status for this class loader to
2567 * <tt>false</tt> and discards any package defaults or class assertion
2568 * status settings associated with the class loader. This method is
2569 * provided so that class loaders can be made to ignore any command line or
2570 * persistent assertion status settings and "start with a clean slate."
2571 *
2572 * @since 1.4
2573 */
2574 public void clearAssertionStatus() {
2575 /*
2576 * Whether or not "Java assertion maps" are initialized, set
2577 * them to empty maps, effectively ignoring any present settings.
2578 */
2579 synchronized (assertionLock) {
2580 classAssertionStatus = new HashMap<>();
2581 packageAssertionStatus = new HashMap<>();
2582 defaultAssertionStatus = false;
2583 }
2584 }
2585
2586 /**
2587 * Returns the assertion status that would be assigned to the specified
2588 * class if it were to be initialized at the time this method is invoked.
2589 * If the named class has had its assertion status set, the most recent
2590 * setting will be returned; otherwise, if any package default assertion
2591 * status pertains to this class, the most recent setting for the most
2592 * specific pertinent package default assertion status is returned;
2593 * otherwise, this class loader's default assertion status is returned.
2594 * </p>
2595 *
2596 * @param className
2597 * The fully qualified class name of the class whose desired
2598 * assertion status is being queried.
2599 *
2600 * @return The desired assertion status of the specified class.
2601 *
2602 * @see #setClassAssertionStatus(String, boolean)
2603 * @see #setPackageAssertionStatus(String, boolean)
2604 * @see #setDefaultAssertionStatus(boolean)
2605 *
2606 * @since 1.4
2607 */
2608 boolean desiredAssertionStatus(String className) {
2609 synchronized (assertionLock) {
2610 // assert classAssertionStatus != null;
2611 // assert packageAssertionStatus != null;
2612
2613 // Check for a class entry
2614 Boolean result = classAssertionStatus.get(className);
2615 if (result != null)
2616 return result.booleanValue();
2617
2618 // Check for most specific package entry
2619 int dotIndex = className.lastIndexOf('.');
2620 if (dotIndex < 0) { // default package
2621 result = packageAssertionStatus.get(null);
2622 if (result != null)
2623 return result.booleanValue();
2624 }
2625 while(dotIndex > 0) {
2626 className = className.substring(0, dotIndex);
2627 result = packageAssertionStatus.get(className);
2628 if (result != null)
2629 return result.booleanValue();
2630 dotIndex = className.lastIndexOf('.', dotIndex-1);
2631 }
2632
2633 // Return the classloader default
2634 return defaultAssertionStatus;
2635 }
2636 }
2637
2638 // Set up the assertions with information provided by the VM.
2639 // Note: Should only be called inside a synchronized block
2640 private void initializeJavaAssertionMaps() {
2641 // assert Thread.holdsLock(assertionLock);
2642
2643 classAssertionStatus = new HashMap<>();
2644 packageAssertionStatus = new HashMap<>();
2645 AssertionStatusDirectives directives = retrieveDirectives();
2646
2647 for(int i = 0; i < directives.classes.length; i++)
2648 classAssertionStatus.put(directives.classes[i],
2649 directives.classEnabled[i]);
2650
2651 for(int i = 0; i < directives.packages.length; i++)
2652 packageAssertionStatus.put(directives.packages[i],
2653 directives.packageEnabled[i]);
2654
2655 defaultAssertionStatus = directives.deflt;
2656 }
2657
2658 // Retrieves the assertion directives from the VM.
2659 private static native AssertionStatusDirectives retrieveDirectives();
2660
2661
2662 /**
2663 * Returns the ServiceCatalog for modules defined to this class loader
2664 * or {@code null} if this class loader does not have a services catalog.
2665 */
2666 ServicesCatalog getServicesCatalog() {
2667 return servicesCatalog;
2668 }
2669
2670 /**
2671 * Returns the ServiceCatalog for modules defined to this class loader,
2672 * creating it if it doesn't already exist.
2673 */
2674 ServicesCatalog createOrGetServicesCatalog() {
2675 ServicesCatalog catalog = servicesCatalog;
2676 if (catalog == null) {
2677 catalog = ServicesCatalog.create();
2678 boolean set = trySetObjectField("servicesCatalog", catalog);
2679 if (!set) {
2680 // beaten by someone else
2681 catalog = servicesCatalog;
2682 }
2683 }
2684 return catalog;
2685 }
2686
2687 // the ServiceCatalog for modules associated with this class loader.
2688 private volatile ServicesCatalog servicesCatalog;
2689
2690 /**
2691 * Returns the ConcurrentHashMap used as a storage for ClassLoaderValue(s)
2692 * associated with this ClassLoader, creating it if it doesn't already exist.
2693 */
2694 ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap() {
2695 ConcurrentHashMap<?, ?> map = classLoaderValueMap;
2696 if (map == null) {
2697 map = new ConcurrentHashMap<>();
2698 boolean set = trySetObjectField("classLoaderValueMap", map);
2699 if (!set) {
2700 // beaten by someone else
2701 map = classLoaderValueMap;
2702 }
2703 }
2704 return map;
2705 }
2706
2707 // the storage for ClassLoaderValue(s) associated with this ClassLoader
2708 private volatile ConcurrentHashMap<?, ?> classLoaderValueMap;
2709
2710 /**
2711 * Attempts to atomically set a volatile field in this object. Returns
2712 * {@code true} if not beaten by another thread. Avoids the use of
2713 * AtomicReferenceFieldUpdater in this class.
2714 */
2715 private boolean trySetObjectField(String name, Object obj) {
2716 Unsafe unsafe = Unsafe.getUnsafe();
2717 Class<?> k = ClassLoader.class;
2718 long offset;
2719 try {
2720 Field f = k.getDeclaredField(name);
2721 offset = unsafe.objectFieldOffset(f);
2722 } catch (NoSuchFieldException e) {
2723 throw new InternalError(e);
2724 }
2725 return unsafe.compareAndSwapObject(this, offset, null, obj);
2726 }
2727 }
2728
2729 /*
2730 * A utility class that will enumerate over an array of enumerations.
2731 */
2732 final class CompoundEnumeration<E> implements Enumeration<E> {
2733 private final Enumeration<E>[] enums;
2734 private int index;
2735
2736 public CompoundEnumeration(Enumeration<E>[] enums) {
2737 this.enums = enums;
2738 }
2739
2740 private boolean next() {
2741 while (index < enums.length) {
2742 if (enums[index] != null && enums[index].hasMoreElements()) {
2743 return true;
2744 }
2745 index++;
2746 }
2747 return false;
2748 }
2749
2750 public boolean hasMoreElements() {
2751 return next();
2752 }
2753
2754 public E nextElement() {
2755 if (!next()) {
2756 throw new NoSuchElementException();
2757 }
2758 return enums[index].nextElement();
2759 }
2760 }