1 /*
2 * Copyright (c) 1999, 2010, 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.reflect;
27
28 import java.lang.ref.Reference;
29 import java.lang.ref.WeakReference;
30 import java.security.AccessController;
31 import java.security.Permission;
32 import java.security.PrivilegedAction;
33 import java.util.Arrays;
34 import java.util.Collections;
35 import java.util.HashMap;
36 import java.util.HashSet;
37 import java.util.Map;
38 import java.util.Set;
39 import java.util.List;
40 import java.util.WeakHashMap;
41 import sun.misc.ProxyGenerator;
42 import sun.reflect.Reflection;
43 import sun.reflect.misc.ReflectUtil;
44 import sun.security.util.SecurityConstants;
45
46 /**
47 * {@code Proxy} provides static methods for creating dynamic proxy
48 * classes and instances, and it is also the superclass of all
49 * dynamic proxy classes created by those methods.
50 *
51 * <p>To create a proxy for some interface {@code Foo}:
52 * <pre>
53 * InvocationHandler handler = new MyInvocationHandler(...);
54 * Class proxyClass = Proxy.getProxyClass(
55 * Foo.class.getClassLoader(), new Class[] { Foo.class });
56 * Foo f = (Foo) proxyClass.
57 * getConstructor(new Class[] { InvocationHandler.class }).
58 * newInstance(new Object[] { handler });
59 * </pre>
60 * or more simply:
61 * <pre>
62 * Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
63 * new Class[] { Foo.class },
64 * handler);
65 * </pre>
66 *
67 * <p>A <i>dynamic proxy class</i> (simply referred to as a <i>proxy
68 * class</i> below) is a class that implements a list of interfaces
69 * specified at runtime when the class is created, with behavior as
70 * described below.
71 *
72 * A <i>proxy interface</i> is such an interface that is implemented
73 * by a proxy class.
74 *
75 * A <i>proxy instance</i> is an instance of a proxy class.
76 *
77 * Each proxy instance has an associated <i>invocation handler</i>
78 * object, which implements the interface {@link InvocationHandler}.
79 * A method invocation on a proxy instance through one of its proxy
80 * interfaces will be dispatched to the {@link InvocationHandler#invoke
81 * invoke} method of the instance's invocation handler, passing the proxy
82 * instance, a {@code java.lang.reflect.Method} object identifying
83 * the method that was invoked, and an array of type {@code Object}
84 * containing the arguments. The invocation handler processes the
85 * encoded method invocation as appropriate and the result that it
86 * returns will be returned as the result of the method invocation on
87 * the proxy instance.
88 *
89 * <p>A proxy class has the following properties:
90 *
91 * <ul>
92 * <li>Proxy classes are public, final, and not abstract.
93 *
94 * <li>The unqualified name of a proxy class is unspecified. The space
95 * of class names that begin with the string {@code "$Proxy"}
96 * should be, however, reserved for proxy classes.
97 *
98 * <li>A proxy class extends {@code java.lang.reflect.Proxy}.
99 *
100 * <li>A proxy class implements exactly the interfaces specified at its
101 * creation, in the same order.
102 *
103 * <li>If a proxy class implements a non-public interface, then it will
104 * be defined in the same package as that interface. Otherwise, the
105 * package of a proxy class is also unspecified. Note that package
106 * sealing will not prevent a proxy class from being successfully defined
107 * in a particular package at runtime, and neither will classes already
108 * defined by the same class loader and the same package with particular
109 * signers.
110 *
111 * <li>Since a proxy class implements all of the interfaces specified at
112 * its creation, invoking {@code getInterfaces} on its
113 * {@code Class} object will return an array containing the same
114 * list of interfaces (in the order specified at its creation), invoking
115 * {@code getMethods} on its {@code Class} object will return
116 * an array of {@code Method} objects that include all of the
117 * methods in those interfaces, and invoking {@code getMethod} will
118 * find methods in the proxy interfaces as would be expected.
119 *
120 * <li>The {@link Proxy#isProxyClass Proxy.isProxyClass} method will
121 * return true if it is passed a proxy class-- a class returned by
122 * {@code Proxy.getProxyClass} or the class of an object returned by
123 * {@code Proxy.newProxyInstance}-- and false otherwise.
124 *
125 * <li>The {@code java.security.ProtectionDomain} of a proxy class
126 * is the same as that of system classes loaded by the bootstrap class
127 * loader, such as {@code java.lang.Object}, because the code for a
128 * proxy class is generated by trusted system code. This protection
129 * domain will typically be granted
130 * {@code java.security.AllPermission}.
131 *
132 * <li>Each proxy class has one public constructor that takes one argument,
133 * an implementation of the interface {@link InvocationHandler}, to set
134 * the invocation handler for a proxy instance. Rather than having to use
135 * the reflection API to access the public constructor, a proxy instance
136 * can be also be created by calling the {@link Proxy#newProxyInstance
137 * Proxy.newProxyInstance} method, which combines the actions of calling
138 * {@link Proxy#getProxyClass Proxy.getProxyClass} with invoking the
139 * constructor with an invocation handler.
140 * </ul>
141 *
142 * <p>A proxy instance has the following properties:
143 *
144 * <ul>
145 * <li>Given a proxy instance {@code proxy} and one of the
146 * interfaces implemented by its proxy class {@code Foo}, the
147 * following expression will return true:
148 * <pre>
149 * {@code proxy instanceof Foo}
150 * </pre>
151 * and the following cast operation will succeed (rather than throwing
152 * a {@code ClassCastException}):
153 * <pre>
154 * {@code (Foo) proxy}
155 * </pre>
156 *
157 * <li>Each proxy instance has an associated invocation handler, the one
158 * that was passed to its constructor. The static
159 * {@link Proxy#getInvocationHandler Proxy.getInvocationHandler} method
160 * will return the invocation handler associated with the proxy instance
161 * passed as its argument.
162 *
163 * <li>An interface method invocation on a proxy instance will be
164 * encoded and dispatched to the invocation handler's {@link
165 * InvocationHandler#invoke invoke} method as described in the
166 * documentation for that method.
167 *
168 * <li>An invocation of the {@code hashCode},
169 * {@code equals}, or {@code toString} methods declared in
170 * {@code java.lang.Object} on a proxy instance will be encoded and
171 * dispatched to the invocation handler's {@code invoke} method in
172 * the same manner as interface method invocations are encoded and
173 * dispatched, as described above. The declaring class of the
174 * {@code Method} object passed to {@code invoke} will be
175 * {@code java.lang.Object}. Other public methods of a proxy
176 * instance inherited from {@code java.lang.Object} are not
177 * overridden by a proxy class, so invocations of those methods behave
178 * like they do for instances of {@code java.lang.Object}.
179 * </ul>
180 *
181 * <h3>Methods Duplicated in Multiple Proxy Interfaces</h3>
182 *
183 * <p>When two or more interfaces of a proxy class contain a method with
184 * the same name and parameter signature, the order of the proxy class's
185 * interfaces becomes significant. When such a <i>duplicate method</i>
186 * is invoked on a proxy instance, the {@code Method} object passed
187 * to the invocation handler will not necessarily be the one whose
188 * declaring class is assignable from the reference type of the interface
189 * that the proxy's method was invoked through. This limitation exists
190 * because the corresponding method implementation in the generated proxy
191 * class cannot determine which interface it was invoked through.
192 * Therefore, when a duplicate method is invoked on a proxy instance,
193 * the {@code Method} object for the method in the foremost interface
194 * that contains the method (either directly or inherited through a
195 * superinterface) in the proxy class's list of interfaces is passed to
196 * the invocation handler's {@code invoke} method, regardless of the
197 * reference type through which the method invocation occurred.
198 *
199 * <p>If a proxy interface contains a method with the same name and
200 * parameter signature as the {@code hashCode}, {@code equals},
201 * or {@code toString} methods of {@code java.lang.Object},
202 * when such a method is invoked on a proxy instance, the
203 * {@code Method} object passed to the invocation handler will have
204 * {@code java.lang.Object} as its declaring class. In other words,
205 * the public, non-final methods of {@code java.lang.Object}
206 * logically precede all of the proxy interfaces for the determination of
207 * which {@code Method} object to pass to the invocation handler.
208 *
209 * <p>Note also that when a duplicate method is dispatched to an
210 * invocation handler, the {@code invoke} method may only throw
211 * checked exception types that are assignable to one of the exception
212 * types in the {@code throws} clause of the method in <i>all</i> of
213 * the proxy interfaces that it can be invoked through. If the
214 * {@code invoke} method throws a checked exception that is not
215 * assignable to any of the exception types declared by the method in one
216 * of the proxy interfaces that it can be invoked through, then an
217 * unchecked {@code UndeclaredThrowableException} will be thrown by
218 * the invocation on the proxy instance. This restriction means that not
219 * all of the exception types returned by invoking
220 * {@code getExceptionTypes} on the {@code Method} object
221 * passed to the {@code invoke} method can necessarily be thrown
222 * successfully by the {@code invoke} method.
223 *
224 * @author Peter Jones
225 * @see InvocationHandler
226 * @since 1.3
227 */
228 public class Proxy implements java.io.Serializable {
229
230 private static final long serialVersionUID = -2222568056686623797L;
231
232 /** prefix for all proxy class names */
233 private final static String proxyClassNamePrefix = "$Proxy";
234
235 /** parameter types of a proxy class constructor */
236 private final static Class[] constructorParams =
237 { InvocationHandler.class };
238
239 /** maps a class loader to the proxy class cache for that loader */
240 private static Map<ClassLoader, Map<List<String>, Object>> loaderToCache
241 = new WeakHashMap<>();
242
243 /** marks that a particular proxy class is currently being generated */
244 private static Object pendingGenerationMarker = new Object();
245
246 /** next number to use for generation of unique proxy class names */
247 private static long nextUniqueNumber = 0;
248 private static Object nextUniqueNumberLock = new Object();
249
250 /** set of all generated proxy classes, for isProxyClass implementation */
251 private static Map<Class<?>, Void> proxyClasses =
252 Collections.synchronizedMap(new WeakHashMap<Class<?>, Void>());
253
254 /**
255 * the invocation handler for this proxy instance.
256 * @serial
257 */
258 protected InvocationHandler h;
259
260 /**
261 * Prohibits instantiation.
262 */
263 private Proxy() {
264 }
265
266 /**
267 * Constructs a new {@code Proxy} instance from a subclass
268 * (typically, a dynamic proxy class) with the specified value
269 * for its invocation handler.
270 *
271 * @param h the invocation handler for this proxy instance
272 */
273 protected Proxy(InvocationHandler h) {
274 doNewInstanceCheck();
275 this.h = h;
276 }
277
278 private static class ProxyAccessHelper {
279 // The permission is implementation specific.
280 static final Permission PROXY_PERMISSION =
281 new ReflectPermission("proxyConstructorNewInstance");
282 // These system properties are defined to provide a short-term
283 // workaround if customers need to disable the new security checks.
284 static final boolean allowNewInstance;
285 static final boolean allowNullLoader;
286 static {
287 allowNewInstance = getBooleanProperty("sun.reflect.proxy.allowsNewInstance");
288 allowNullLoader = getBooleanProperty("sun.reflect.proxy.allowsNullLoader");
289 }
290
291 private static boolean getBooleanProperty(final String key) {
292 String s = AccessController.doPrivileged(new PrivilegedAction<String>() {
293 public String run() {
294 return System.getProperty(key);
295 }
296 });
297 return Boolean.valueOf(s);
298 }
299
300 static boolean needsNewInstanceCheck(Class<?> proxyClass) {
301 if (!Proxy.isProxyClass(proxyClass) || allowNewInstance) {
302 return false;
303 }
304
305 if (proxyClass.getName().startsWith(ReflectUtil.PROXY_PACKAGE + ".")) {
306 // all proxy interfaces are public
307 return false;
308 }
309 for (Class<?> intf : proxyClass.getInterfaces()) {
310 if (!Modifier.isPublic(intf.getModifiers())) {
311 return true;
312 }
313 }
314 return false;
315 }
316 }
317
318 /*
319 * Access check on a proxy class that implements any non-public interface.
320 *
321 * @throws SecurityException if a security manager exists, and
322 * the caller does not have the permission.
323 */
324 private void doNewInstanceCheck() {
325 SecurityManager sm = System.getSecurityManager();
326 Class<?> proxyClass = this.getClass();
327 if (sm != null && ProxyAccessHelper.needsNewInstanceCheck(proxyClass)) {
328 try {
329 sm.checkPermission(ProxyAccessHelper.PROXY_PERMISSION);
330 } catch (SecurityException e) {
331 throw new SecurityException("Not allowed to construct a Proxy "
332 + "instance that implements a non-public interface", e);
333 }
334 }
335 }
336
337 /**
338 * Returns the {@code java.lang.Class} object for a proxy class
339 * given a class loader and an array of interfaces. The proxy class
340 * will be defined by the specified class loader and will implement
341 * all of the supplied interfaces. If a proxy class for the same
342 * permutation of interfaces has already been defined by the class
343 * loader, then the existing proxy class will be returned; otherwise,
344 * a proxy class for those interfaces will be generated dynamically
345 * and defined by the class loader.
346 *
347 * <p>There are several restrictions on the parameters that may be
348 * passed to {@code Proxy.getProxyClass}:
349 *
350 * <ul>
351 * <li>All of the {@code Class} objects in the
352 * {@code interfaces} array must represent interfaces, not
353 * classes or primitive types.
354 *
355 * <li>No two elements in the {@code interfaces} array may
356 * refer to identical {@code Class} objects.
357 *
358 * <li>All of the interface types must be visible by name through the
359 * specified class loader. In other words, for class loader
360 * {@code cl} and every interface {@code i}, the following
361 * expression must be true:
362 * <pre>
363 * Class.forName(i.getName(), false, cl) == i
364 * </pre>
365 *
366 * <li>All non-public interfaces must be in the same package;
367 * otherwise, it would not be possible for the proxy class to
368 * implement all of the interfaces, regardless of what package it is
369 * defined in.
370 *
371 * <li>For any set of member methods of the specified interfaces
372 * that have the same signature:
373 * <ul>
374 * <li>If the return type of any of the methods is a primitive
375 * type or void, then all of the methods must have that same
376 * return type.
377 * <li>Otherwise, one of the methods must have a return type that
378 * is assignable to all of the return types of the rest of the
379 * methods.
380 * </ul>
381 *
382 * <li>The resulting proxy class must not exceed any limits imposed
383 * on classes by the virtual machine. For example, the VM may limit
384 * the number of interfaces that a class may implement to 65535; in
385 * that case, the size of the {@code interfaces} array must not
386 * exceed 65535.
387 * </ul>
388 *
389 * <p>If any of these restrictions are violated,
390 * {@code Proxy.getProxyClass} will throw an
391 * {@code IllegalArgumentException}. If the {@code interfaces}
392 * array argument or any of its elements are {@code null}, a
393 * {@code NullPointerException} will be thrown.
394 *
395 * <p>Note that the order of the specified proxy interfaces is
396 * significant: two requests for a proxy class with the same combination
397 * of interfaces but in a different order will result in two distinct
398 * proxy classes.
399 *
400 * @param loader the class loader to define the proxy class
401 * @param interfaces the list of interfaces for the proxy class
402 * to implement
403 * @return a proxy class that is defined in the specified class loader
404 * and that implements the specified interfaces
405 * @throws IllegalArgumentException if any of the restrictions on the
406 * parameters that may be passed to {@code getProxyClass}
407 * are violated
408 * @throws NullPointerException if the {@code interfaces} array
409 * argument or any of its elements are {@code null}
410 */
411 public static Class<?> getProxyClass(ClassLoader loader,
412 Class<?>... interfaces)
413 throws IllegalArgumentException
414 {
415 return getProxyClass0(loader, interfaces); // stack walk magic: do not refactor
416 }
417
418 private static void checkProxyLoader(ClassLoader ccl,
419 ClassLoader loader)
420 {
421 SecurityManager sm = System.getSecurityManager();
422 if (sm != null) {
423 if (loader == null && ccl != null) {
424 if (!ProxyAccessHelper.allowNullLoader) {
425 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
426 }
427 }
428 }
429 }
430
431 /*
432 * Generate a proxy class (caller-sensitive).
433 *
434 * To define a proxy class, it performs the access checks as in
435 * Class.forName (VM will invoke ClassLoader.checkPackageAccess):
436 * 1. "getClassLoader" permission check if loader == null
437 * 2. checkPackageAccess on the interfaces it implements
438 *
439 * To get a constructor and new instance of a proxy class, it performs
440 * the package access check on the interfaces it implements
441 * as in Class.getConstructor.
442 *
443 * If an interface is non-public, the proxy class must be defined by
444 * the defining loader of the interface. If the caller's class loader
445 * is not the same as the defining loader of the interface, the VM
446 * will throw IllegalAccessError when the generated proxy class is
447 * being defined via the defineClass0 method.
448 */
449 private static Class<?> getProxyClass0(ClassLoader loader,
450 Class<?>... interfaces) {
451 SecurityManager sm = System.getSecurityManager();
452 if (sm != null) {
453 final int CALLER_FRAME = 3; // 0: Reflection, 1: getProxyClass0 2: Proxy 3: caller
454 final Class<?> caller = Reflection.getCallerClass(CALLER_FRAME);
455 final ClassLoader ccl = caller.getClassLoader();
456 checkProxyLoader(ccl, loader);
457 ReflectUtil.checkProxyPackageAccess(ccl, interfaces);
458 }
459
460 if (interfaces.length > 65535) {
461 throw new IllegalArgumentException("interface limit exceeded");
462 }
463
464 Class<?> proxyClass = null;
465
466 /* collect interface names to use as key for proxy class cache */
467 String[] interfaceNames = new String[interfaces.length];
468
469 // for detecting duplicates
470 Set<Class<?>> interfaceSet = new HashSet<>();
471
472 for (int i = 0; i < interfaces.length; i++) {
473 /*
474 * Verify that the class loader resolves the name of this
475 * interface to the same Class object.
476 */
477 String interfaceName = interfaces[i].getName();
478 Class<?> interfaceClass = null;
479 try {
480 interfaceClass = Class.forName(interfaceName, false, loader);
481 } catch (ClassNotFoundException e) {
482 }
483 if (interfaceClass != interfaces[i]) {
484 throw new IllegalArgumentException(
485 interfaces[i] + " is not visible from class loader");
486 }
487
488 /*
489 * Verify that the Class object actually represents an
490 * interface.
491 */
492 if (!interfaceClass.isInterface()) {
493 throw new IllegalArgumentException(
494 interfaceClass.getName() + " is not an interface");
495 }
496
497 /*
498 * Verify that this interface is not a duplicate.
499 */
500 if (interfaceSet.contains(interfaceClass)) {
501 throw new IllegalArgumentException(
502 "repeated interface: " + interfaceClass.getName());
503 }
504 interfaceSet.add(interfaceClass);
505
506 interfaceNames[i] = interfaceName;
507 }
508
509 /*
510 * Using string representations of the proxy interfaces as
511 * keys in the proxy class cache (instead of their Class
512 * objects) is sufficient because we require the proxy
513 * interfaces to be resolvable by name through the supplied
514 * class loader, and it has the advantage that using a string
515 * representation of a class makes for an implicit weak
516 * reference to the class.
517 */
518 List<String> key = Arrays.asList(interfaceNames);
519
520 /*
521 * Find or create the proxy class cache for the class loader.
522 */
523 Map<List<String>, Object> cache;
524 synchronized (loaderToCache) {
525 cache = loaderToCache.get(loader);
526 if (cache == null) {
527 cache = new HashMap<>();
528 loaderToCache.put(loader, cache);
529 }
530 /*
531 * This mapping will remain valid for the duration of this
532 * method, without further synchronization, because the mapping
533 * will only be removed if the class loader becomes unreachable.
534 */
535 }
536
537 /*
538 * Look up the list of interfaces in the proxy class cache using
539 * the key. This lookup will result in one of three possible
540 * kinds of values:
541 * null, if there is currently no proxy class for the list of
542 * interfaces in the class loader,
543 * the pendingGenerationMarker object, if a proxy class for the
544 * list of interfaces is currently being generated,
545 * or a weak reference to a Class object, if a proxy class for
546 * the list of interfaces has already been generated.
547 */
548 synchronized (cache) {
549 /*
550 * Note that we need not worry about reaping the cache for
551 * entries with cleared weak references because if a proxy class
552 * has been garbage collected, its class loader will have been
553 * garbage collected as well, so the entire cache will be reaped
554 * from the loaderToCache map.
555 */
556 do {
557 Object value = cache.get(key);
558 if (value instanceof Reference) {
559 proxyClass = (Class<?>) ((Reference) value).get();
560 }
561 if (proxyClass != null) {
562 // proxy class already generated: return it
563 return proxyClass;
564 } else if (value == pendingGenerationMarker) {
565 // proxy class being generated: wait for it
566 try {
567 cache.wait();
568 } catch (InterruptedException e) {
569 /*
570 * The class generation that we are waiting for should
571 * take a small, bounded time, so we can safely ignore
572 * thread interrupts here.
573 */
574 }
575 continue;
576 } else {
577 /*
578 * No proxy class for this list of interfaces has been
579 * generated or is being generated, so we will go and
580 * generate it now. Mark it as pending generation.
581 */
582 cache.put(key, pendingGenerationMarker);
583 break;
584 }
585 } while (true);
586 }
587
588 try {
589 String proxyPkg = null; // package to define proxy class in
590
591 /*
592 * Record the package of a non-public proxy interface so that the
593 * proxy class will be defined in the same package. Verify that
594 * all non-public proxy interfaces are in the same package.
595 */
596 for (int i = 0; i < interfaces.length; i++) {
597 int flags = interfaces[i].getModifiers();
598 if (!Modifier.isPublic(flags)) {
599 String name = interfaces[i].getName();
600 int n = name.lastIndexOf('.');
601 String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
602 if (proxyPkg == null) {
603 proxyPkg = pkg;
604 } else if (!pkg.equals(proxyPkg)) {
605 throw new IllegalArgumentException(
606 "non-public interfaces from different packages");
607 }
608 }
609 }
610
611 if (proxyPkg == null) {
612 // if no non-public proxy interfaces, use sun.proxy package
613 proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
614 }
615
616 {
617 /*
618 * Choose a name for the proxy class to generate.
619 */
620 long num;
621 synchronized (nextUniqueNumberLock) {
622 num = nextUniqueNumber++;
623 }
624 String proxyName = proxyPkg + proxyClassNamePrefix + num;
625 /*
626 * Verify that the class loader hasn't already
627 * defined a class with the chosen name.
628 */
629
630 /*
631 * Generate the specified proxy class.
632 */
633 byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
634 proxyName, interfaces);
635 try {
636 proxyClass = defineClass0(loader, proxyName,
637 proxyClassFile, 0, proxyClassFile.length);
638 } catch (ClassFormatError e) {
639 /*
640 * A ClassFormatError here means that (barring bugs in the
641 * proxy class generation code) there was some other
642 * invalid aspect of the arguments supplied to the proxy
643 * class creation (such as virtual machine limitations
644 * exceeded).
645 */
646 throw new IllegalArgumentException(e.toString());
647 }
648 }
649 // add to set of all generated proxy classes, for isProxyClass
650 proxyClasses.put(proxyClass, null);
651
652 } finally {
653 /*
654 * We must clean up the "pending generation" state of the proxy
655 * class cache entry somehow. If a proxy class was successfully
656 * generated, store it in the cache (with a weak reference);
657 * otherwise, remove the reserved entry. In all cases, notify
658 * all waiters on reserved entries in this cache.
659 */
660 synchronized (cache) {
661 if (proxyClass != null) {
662 cache.put(key, new WeakReference<Class<?>>(proxyClass));
663 } else {
664 cache.remove(key);
665 }
666 cache.notifyAll();
667 }
668 }
669 return proxyClass;
670 }
671
672 /**
673 * Returns an instance of a proxy class for the specified interfaces
674 * that dispatches method invocations to the specified invocation
675 * handler. This method is equivalent to:
676 * <pre>
677 * Proxy.getProxyClass(loader, interfaces).
678 * getConstructor(new Class[] { InvocationHandler.class }).
679 * newInstance(new Object[] { handler });
680 * </pre>
681 *
682 * <p>{@code Proxy.newProxyInstance} throws
683 * {@code IllegalArgumentException} for the same reasons that
684 * {@code Proxy.getProxyClass} does.
685 *
686 * @param loader the class loader to define the proxy class
687 * @param interfaces the list of interfaces for the proxy class
688 * to implement
689 * @param h the invocation handler to dispatch method invocations to
690 * @return a proxy instance with the specified invocation handler of a
691 * proxy class that is defined by the specified class loader
692 * and that implements the specified interfaces
693 * @throws IllegalArgumentException if any of the restrictions on the
694 * parameters that may be passed to {@code getProxyClass}
695 * are violated
696 * @throws NullPointerException if the {@code interfaces} array
697 * argument or any of its elements are {@code null}, or
698 * if the invocation handler, {@code h}, is
699 * {@code null}
700 */
701 public static Object newProxyInstance(ClassLoader loader,
702 Class<?>[] interfaces,
703 InvocationHandler h)
704 throws IllegalArgumentException
705 {
706 if (h == null) {
707 throw new NullPointerException();
708 }
709
710 /*
711 * Look up or generate the designated proxy class.
712 */
713 Class<?> cl = getProxyClass0(loader, interfaces); // stack walk magic: do not refactor
714
715 /*
716 * Invoke its constructor with the designated invocation handler.
717 */
718 try {
719 final Constructor<?> cons = cl.getConstructor(constructorParams);
720 final InvocationHandler ih = h;
721 SecurityManager sm = System.getSecurityManager();
722 if (sm != null && ProxyAccessHelper.needsNewInstanceCheck(cl)) {
723 // create proxy instance with doPrivilege as the proxy class may
724 // implement non-public interfaces that requires a special permission
725 return AccessController.doPrivileged(new PrivilegedAction<Object>() {
726 public Object run() {
727 return newInstance(cons, ih);
728 }
729 });
730 } else {
731 return newInstance(cons, ih);
732 }
733 } catch (NoSuchMethodException e) {
734 throw new InternalError(e.toString());
735 }
736 }
737
738 private static Object newInstance(Constructor<?> cons, InvocationHandler h) {
739 try {
740 return cons.newInstance(new Object[] {h} );
741 } catch (IllegalAccessException | InstantiationException e) {
742 throw new InternalError(e.toString());
743 } catch (InvocationTargetException e) {
744 Throwable t = e.getCause();
745 if (t instanceof RuntimeException) {
746 throw (RuntimeException) t;
747 } else {
748 throw new InternalError(t.toString());
749 }
750 }
751 }
752
753 /**
754 * Returns true if and only if the specified class was dynamically
755 * generated to be a proxy class using the {@code getProxyClass}
756 * method or the {@code newProxyInstance} method.
757 *
758 * <p>The reliability of this method is important for the ability
759 * to use it to make security decisions, so its implementation should
760 * not just test if the class in question extends {@code Proxy}.
761 *
762 * @param cl the class to test
763 * @return {@code true} if the class is a proxy class and
764 * {@code false} otherwise
765 * @throws NullPointerException if {@code cl} is {@code null}
766 */
767 public static boolean isProxyClass(Class<?> cl) {
768 if (cl == null) {
769 throw new NullPointerException();
770 }
771
772 return proxyClasses.containsKey(cl);
773 }
774
775 /**
776 * Returns the invocation handler for the specified proxy instance.
777 *
778 * @param proxy the proxy instance to return the invocation handler for
779 * @return the invocation handler for the proxy instance
780 * @throws IllegalArgumentException if the argument is not a
781 * proxy instance
782 */
783 public static InvocationHandler getInvocationHandler(Object proxy)
784 throws IllegalArgumentException
785 {
786 /*
787 * Verify that the object is actually a proxy instance.
788 */
789 if (!isProxyClass(proxy.getClass())) {
790 throw new IllegalArgumentException("not a proxy instance");
791 }
792
793 Proxy p = (Proxy) proxy;
794 return p.h;
795 }
796
797 private static native Class defineClass0(ClassLoader loader, String name,
798 byte[] b, int off, int len);
799 }