1 /*
2 * Copyright (c) 1999, 2024, 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.invoke.MethodHandle;
29 import java.lang.invoke.MethodHandles;
30 import java.lang.invoke.MethodType;
31 import java.lang.invoke.WrongMethodTypeException;
32 import java.lang.module.ModuleDescriptor;
33 import java.util.ArrayDeque;
34 import java.util.Arrays;
35 import java.util.Collections;
36 import java.util.Deque;
37 import java.util.HashMap;
38 import java.util.HashSet;
39 import java.util.IdentityHashMap;
40 import java.util.List;
41 import java.util.Map;
42 import java.util.Objects;
43 import java.util.Set;
44 import java.util.concurrent.ConcurrentHashMap;
45 import java.util.concurrent.atomic.AtomicInteger;
46 import java.util.concurrent.atomic.AtomicLong;
47 import java.util.function.BooleanSupplier;
48
49 import jdk.internal.access.JavaLangAccess;
50 import jdk.internal.access.SharedSecrets;
51 import jdk.internal.module.Modules;
52 import jdk.internal.misc.VM;
53 import jdk.internal.loader.ClassLoaderValue;
54 import jdk.internal.vm.annotation.Stable;
55
56 import static java.lang.invoke.MethodType.methodType;
57 import static java.lang.module.ModuleDescriptor.Modifier.SYNTHETIC;
58
59 /**
60 *
61 * {@code Proxy} provides static methods for creating objects that act like instances
62 * of interfaces but allow for customized method invocation.
63 * To create a proxy instance for some interface {@code Foo}:
64 * <pre>{@code
65 * InvocationHandler handler = new MyInvocationHandler(...);
66 * Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
67 * new Class<?>[] { Foo.class },
68 * handler);
69 * }</pre>
70 *
71 * <p>
72 * A <em>proxy class</em> is a class created at runtime that implements a specified
73 * list of interfaces, known as <em>proxy interfaces</em>. A <em>proxy instance</em>
74 * is an instance of a proxy class.
75 *
76 * Each proxy instance has an associated <i>invocation handler</i>
77 * object, which implements the interface {@link InvocationHandler}.
78 * A method invocation on a proxy instance through one of its proxy
79 * interfaces will be dispatched to the {@link InvocationHandler#invoke
80 * invoke} method of the instance's invocation handler, passing the proxy
81 * instance, a {@code java.lang.reflect.Method} object identifying
82 * the method that was invoked, and an array of type {@code Object}
83 * containing the arguments. The invocation handler processes the
84 * encoded method invocation as appropriate and the result that it
85 * returns will be returned as the result of the method invocation on
86 * the proxy instance.
87 *
88 * <p>A proxy class has the following properties:
89 *
90 * <ul>
91 * <li>The unqualified name of a proxy class is unspecified. The space
92 * of class names that begin with the string {@code "$Proxy"}
93 * should be, however, reserved for proxy classes.
94 *
95 * <li>The package and module in which a proxy class is defined is specified
96 * <a href="#membership">below</a>.
97 *
98 * <li>A proxy class is <em>final and non-abstract</em>.
99 *
100 * <li>A proxy class extends {@code java.lang.reflect.Proxy}.
101 *
102 * <li>A proxy class implements exactly the interfaces specified at its
103 * creation, in the same order. Invoking {@link Class#getInterfaces() getInterfaces}
104 * on its {@code Class} object will return an array containing the same
105 * list of interfaces (in the order specified at its creation), invoking
106 * {@link Class#getMethods getMethods} on its {@code Class} object will return
107 * an array of {@code Method} objects that include all of the
108 * methods in those interfaces, and invoking {@code getMethod} will
109 * find methods in the proxy interfaces as would be expected.
110 *
111 * <li>The {@link java.security.ProtectionDomain} of a proxy class
112 * is the same as that of system classes loaded by the bootstrap class
113 * loader, such as {@code java.lang.Object}.
114 *
115 * <li>The {@link Proxy#isProxyClass Proxy.isProxyClass} method can be used
116 * to determine if a given class is a proxy class.
117 * </ul>
118 *
119 * <p>A proxy instance has the following properties:
120 *
121 * <ul>
122 * <li>Given a proxy instance {@code proxy} and one of the
123 * interfaces, {@code Foo}, implemented by its proxy class, the
124 * following expression will return true:
125 * <pre>
126 * {@code proxy instanceof Foo}
127 * </pre>
128 * and the following cast operation will succeed (rather than throwing
129 * a {@code ClassCastException}):
130 * <pre>
131 * {@code (Foo) proxy}
132 * </pre>
133 *
134 * <li>Each proxy instance has an associated invocation handler, the one
135 * that was passed to its constructor. The static
136 * {@link Proxy#getInvocationHandler Proxy.getInvocationHandler} method
137 * will return the invocation handler associated with the proxy instance
138 * passed as its argument.
139 *
140 * <li>An interface method invocation on a proxy instance will be
141 * encoded and dispatched to the invocation handler's {@link
142 * InvocationHandler#invoke invoke} method as described in the
143 * documentation for that method.
144 *
145 * <li>A proxy interface may define a default method or inherit
146 * a default method from its superinterface directly or indirectly.
147 * An invocation handler can invoke a default method of a proxy interface
148 * by calling {@link InvocationHandler#invokeDefault(Object, Method, Object...)
149 * InvocationHandler::invokeDefault}.
150 *
151 * <li>An invocation of the {@code hashCode},
152 * {@code equals}, or {@code toString} methods declared in
153 * {@code java.lang.Object} on a proxy instance will be encoded and
154 * dispatched to the invocation handler's {@code invoke} method in
155 * the same manner as interface method invocations are encoded and
156 * dispatched, as described above. The declaring class of the
157 * {@code Method} object passed to {@code invoke} will be
158 * {@code java.lang.Object}. Other public methods of a proxy
159 * instance inherited from {@code java.lang.Object} are not
160 * overridden by a proxy class, so invocations of those methods behave
161 * like they do for instances of {@code java.lang.Object}.
162 * </ul>
163 *
164 * <h2><a id="membership">Package and Module Membership of Proxy Class</a></h2>
165 *
166 * The package and module to which a proxy class belongs are chosen such that
167 * the accessibility of the proxy class is in line with the accessibility of
168 * the proxy interfaces. Specifically, the package and the module membership
169 * of a proxy class defined via the
170 * {@link Proxy#getProxyClass(ClassLoader, Class[])} or
171 * {@link Proxy#newProxyInstance(ClassLoader, Class[], InvocationHandler)}
172 * methods is specified as follows:
173 *
174 * <ol>
175 * <li>If all the proxy interfaces are in <em>exported</em> or <em>open</em>
176 * packages:
177 * <ol type="a">
178 * <li>if all the proxy interfaces are <em>public</em>, then the proxy class is
179 * <em>public</em> in an unconditionally exported but non-open package.
180 * The name of the package and the module are unspecified.</li>
181 *
182 * <li>if at least one of all the proxy interfaces is <em>non-public</em>, then
183 * the proxy class is <em>non-public</em> in the package and module of the
184 * non-public interfaces. All the non-public interfaces must be in the same
185 * package and module; otherwise, proxying them is
186 * <a href="#restrictions">not possible</a>.</li>
187 * </ol>
188 * </li>
189 * <li>If at least one proxy interface is in a package that is
190 * <em>non-exported</em> and <em>non-open</em>:
191 * <ol type="a">
192 * <li>if all the proxy interfaces are <em>public</em>, then the proxy class is
193 * <em>public</em> in a <em>non-exported</em>, <em>non-open</em> package of
194 * <a href="#dynamicmodule"><em>dynamic module</em>.</a>
195 * The names of the package and the module are unspecified.</li>
196 *
197 * <li>if at least one of all the proxy interfaces is <em>non-public</em>, then
198 * the proxy class is <em>non-public</em> in the package and module of the
199 * non-public interfaces. All the non-public interfaces must be in the same
200 * package and module; otherwise, proxying them is
201 * <a href="#restrictions">not possible</a>.</li>
202 * </ol>
203 * </li>
204 * </ol>
205 *
206 * <p>
207 * Note that if proxy interfaces with a mix of accessibilities -- for example,
208 * an exported public interface and a non-exported non-public interface -- are
209 * proxied by the same instance, then the proxy class's accessibility is
210 * governed by the least accessible proxy interface.
211 * <p>
212 * Note that it is possible for arbitrary code to obtain access to a proxy class
213 * in an open package with {@link AccessibleObject#setAccessible setAccessible},
214 * whereas a proxy class in a non-open package is never accessible to
215 * code outside the module of the proxy class.
216 *
217 * <p>
218 * Throughout this specification, a "non-exported package" refers to a package
219 * that is not exported to all modules, and a "non-open package" refers to
220 * a package that is not open to all modules. Specifically, these terms refer to
221 * a package that either is not exported/open by its containing module or is
222 * exported/open in a qualified fashion by its containing module.
223 *
224 * <h3><a id="dynamicmodule">Dynamic Modules</a></h3>
225 * <p>
226 * A dynamic module is a named module generated at runtime. A proxy class
227 * defined in a dynamic module is encapsulated and not accessible to any module.
228 * Calling {@link Constructor#newInstance(Object...)} on a proxy class in
229 * a dynamic module will throw {@code IllegalAccessException};
230 * {@code Proxy.newProxyInstance} method should be used instead.
231 *
232 * <p>
233 * A dynamic module can read the modules of all of the superinterfaces of a proxy
234 * class and the modules of the classes and interfaces referenced by
235 * all public method signatures of a proxy class. If a superinterface or
236 * a referenced class or interface, say {@code T}, is in a non-exported package,
237 * the {@linkplain Module module} of {@code T} is updated to export the
238 * package of {@code T} to the dynamic module.
239 *
240 * <h3>Methods Duplicated in Multiple Proxy Interfaces</h3>
241 *
242 * <p>When two or more proxy interfaces contain a method with
243 * the same name and parameter signature, the order of the proxy class's
244 * interfaces becomes significant. When such a <i>duplicate method</i>
245 * is invoked on a proxy instance, the {@code Method} object passed
246 * to the invocation handler will not necessarily be the one whose
247 * declaring class is assignable from the reference type of the interface
248 * that the proxy's method was invoked through. This limitation exists
249 * because the corresponding method implementation in the generated proxy
250 * class cannot determine which interface it was invoked through.
251 * Therefore, when a duplicate method is invoked on a proxy instance,
252 * the {@code Method} object for the method in the foremost interface
253 * that contains the method (either directly or inherited through a
254 * superinterface) in the proxy class's list of interfaces is passed to
255 * the invocation handler's {@code invoke} method, regardless of the
256 * reference type through which the method invocation occurred.
257 *
258 * <p>If a proxy interface contains a method with the same name and
259 * parameter signature as the {@code hashCode}, {@code equals},
260 * or {@code toString} methods of {@code java.lang.Object},
261 * when such a method is invoked on a proxy instance, the
262 * {@code Method} object passed to the invocation handler will have
263 * {@code java.lang.Object} as its declaring class. In other words,
264 * the public, non-final methods of {@code java.lang.Object}
265 * logically precede all of the proxy interfaces for the determination of
266 * which {@code Method} object to pass to the invocation handler.
267 *
268 * <p>Note also that when a duplicate method is dispatched to an
269 * invocation handler, the {@code invoke} method may only throw
270 * checked exception types that are assignable to one of the exception
271 * types in the {@code throws} clause of the method in <i>all</i> of
272 * the proxy interfaces that it can be invoked through. If the
273 * {@code invoke} method throws a checked exception that is not
274 * assignable to any of the exception types declared by the method in one
275 * of the proxy interfaces that it can be invoked through, then an
276 * unchecked {@code UndeclaredThrowableException} will be thrown by
277 * the invocation on the proxy instance. This restriction means that not
278 * all of the exception types returned by invoking
279 * {@code getExceptionTypes} on the {@code Method} object
280 * passed to the {@code invoke} method can necessarily be thrown
281 * successfully by the {@code invoke} method.
282 *
283 * @author Peter Jones
284 * @see InvocationHandler
285 * @since 1.3
286 */
287 public class Proxy implements java.io.Serializable {
288 @java.io.Serial
289 private static final long serialVersionUID = -2222568056686623797L;
290
291 /** parameter types of a proxy class constructor */
292 private static final Class<?>[] constructorParams =
293 { InvocationHandler.class };
294
295 /**
296 * a cache of proxy constructors with
297 * {@link Constructor#setAccessible(boolean) accessible} flag already set
298 */
299 private static final ClassLoaderValue<Constructor<?>> proxyCache =
300 new ClassLoaderValue<>();
301
302 /**
303 * the invocation handler for this proxy instance.
304 * @serial
305 */
306 @SuppressWarnings("serial") // Not statically typed as Serializable
307 protected InvocationHandler h;
308
309 /**
310 * Prohibits instantiation.
311 */
312 private Proxy() {
313 }
314
315 /**
316 * Constructs a new {@code Proxy} instance from a subclass
317 * (typically, a dynamic proxy class) with the specified value
318 * for its invocation handler.
319 *
320 * @param h the invocation handler for this proxy instance
321 *
322 * @throws NullPointerException if the given invocation handler, {@code h},
323 * is {@code null}.
324 */
325 protected Proxy(InvocationHandler h) {
326 Objects.requireNonNull(h);
327 this.h = h;
328 }
329
330 /**
331 * Returns the {@code java.lang.Class} object for a proxy class
332 * given a class loader and an array of interfaces. The proxy class
333 * will be defined by the specified class loader and will implement
334 * all of the supplied interfaces. If any of the given interfaces
335 * is non-public, the proxy class will be non-public. If a proxy class
336 * for the same permutation of interfaces has already been defined by the
337 * class loader, then the existing proxy class will be returned; otherwise,
338 * a proxy class for those interfaces will be generated dynamically
339 * and defined by the class loader.
340 *
341 * @param loader the class loader to define the proxy class
342 * @param interfaces the list of interfaces for the proxy class
343 * to implement
344 * @return a proxy class that is defined in the specified class loader
345 * and that implements the specified interfaces
346 * @throws IllegalArgumentException if any of the <a href="#restrictions">
347 * restrictions</a> on the parameters are violated
348 * @throws NullPointerException if the {@code interfaces} array
349 * argument or any of its elements are {@code null}
350 *
351 * @deprecated Proxy classes generated in a named module are encapsulated
352 * and not accessible to code outside its module.
353 * {@link Constructor#newInstance(Object...) Constructor.newInstance}
354 * will throw {@code IllegalAccessException} when it is called on
355 * an inaccessible proxy class.
356 * Use {@link #newProxyInstance(ClassLoader, Class[], InvocationHandler)}
357 * to create a proxy instance instead.
358 *
359 * @see <a href="#membership">Package and Module Membership of Proxy Class</a>
360 */
361 @Deprecated
362 public static Class<?> getProxyClass(ClassLoader loader,
363 Class<?>... interfaces)
364 throws IllegalArgumentException
365 {
366 return getProxyConstructor(loader, interfaces)
367 .getDeclaringClass();
368 }
369
370 /**
371 * Returns the {@code Constructor} object of a proxy class that takes a
372 * single argument of type {@link InvocationHandler}, given a class loader
373 * and an array of interfaces. The returned constructor will have the
374 * {@link Constructor#setAccessible(boolean) accessible} flag already set.
375 *
376 * @param loader the class loader to define the proxy class
377 * @param interfaces the list of interfaces for the proxy class
378 * to implement
379 * @return a Constructor of the proxy class taking single
380 * {@code InvocationHandler} parameter
381 */
382 private static Constructor<?> getProxyConstructor(ClassLoader loader,
383 Class<?>... interfaces)
384 {
385 // optimization for single interface
386 if (interfaces.length == 1) {
387 Class<?> intf = interfaces[0];
388 return proxyCache.sub(intf).computeIfAbsent(
389 loader,
390 (ld, clv) -> new ProxyBuilder(ld, clv.key()).build()
391 );
392 } else {
393 // interfaces cloned
394 final Class<?>[] intfsArray = interfaces.clone();
395 final List<Class<?>> intfs = Arrays.asList(intfsArray);
396 return proxyCache.sub(intfs).computeIfAbsent(
397 loader,
398 (ld, clv) -> new ProxyBuilder(ld, clv.key()).build()
399 );
400 }
401 }
402
403 /**
404 * Builder for a proxy class.
405 *
406 * If the module is not specified in this ProxyBuilder constructor,
407 * it will map from the given loader and interfaces to the module
408 * in which the proxy class will be defined.
409 */
410 private static final class ProxyBuilder {
411 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
412
413 // prefix for all proxy class names
414 private static final String proxyClassNamePrefix = "$Proxy";
415
416 // next number to use for generation of unique proxy class names
417 private static final AtomicLong nextUniqueNumber = new AtomicLong();
418
419 // a reverse cache of defined proxy classes
420 private static final ClassLoaderValue<Boolean> reverseProxyCache =
421 new ClassLoaderValue<>();
422
423 private record ProxyClassContext(Module module, String packageName, int accessFlags) {
424 private ProxyClassContext {
425 if (module.isNamed()) {
426 if (packageName.isEmpty()) {
427 // Per JLS 7.4.2, unnamed package can only exist in unnamed modules.
428 // This means a package-private superinterface exist in the unnamed
429 // package of a named module.
430 throw new InternalError("Unnamed package cannot be added to " + module);
431 }
432
433 if (!module.getDescriptor().packages().contains(packageName)) {
434 throw new InternalError(packageName + " not exist in " + module.getName());
435 }
436
437 if (!module.isOpen(packageName, Proxy.class.getModule())) {
438 // Required for default method invocation
439 throw new InternalError(packageName + " not open to " + Proxy.class.getModule());
440 }
441 } else {
442 if (Modifier.isPublic(accessFlags)) {
443 // All proxy superinterfaces are public, must be in named dynamic module
444 throw new InternalError("public proxy in unnamed module: " + module);
445 }
446 }
447
448 if ((accessFlags & ~Modifier.PUBLIC) != 0) {
449 throw new InternalError("proxy access flags must be Modifier.PUBLIC or 0");
450 }
451 }
452 }
453
454 private static Class<?> defineProxyClass(ProxyClassContext context, List<Class<?>> interfaces) {
455 /*
456 * Choose a name for the proxy class to generate.
457 */
458 long num = nextUniqueNumber.getAndIncrement();
459 String proxyName = context.packageName().isEmpty()
460 ? proxyClassNamePrefix + num
461 : context.packageName() + "." + proxyClassNamePrefix + num;
462
463 ClassLoader loader = context.module().getClassLoader();
464 trace(proxyName, context.module(), loader, interfaces);
465
466 /*
467 * Generate the specified proxy class.
468 */
469 byte[] proxyClassFile = ProxyGenerator.generateProxyClass(loader, proxyName, interfaces,
470 context.accessFlags() | Modifier.FINAL);
471 try {
472 Class<?> pc = JLA.defineClass(loader, proxyName, proxyClassFile,
473 null, "__dynamic_proxy__");
474 reverseProxyCache.sub(pc).putIfAbsent(loader, Boolean.TRUE);
475 return pc;
476 } catch (ClassFormatError e) {
477 /*
478 * A ClassFormatError here means that (barring bugs in the
479 * proxy class generation code) there was some other
480 * invalid aspect of the arguments supplied to the proxy
481 * class creation (such as virtual machine limitations
482 * exceeded).
483 */
484 throw new IllegalArgumentException(e.toString());
485 }
486 }
487
488 /**
489 * Test if given class is a class defined by
490 * {@link #defineProxyClass(ProxyClassContext, List)}
491 */
492 static boolean isProxyClass(Class<?> c) {
493 return Objects.equals(reverseProxyCache.sub(c).get(c.getClassLoader()),
494 Boolean.TRUE);
495 }
496
497 private static boolean isExportedType(Class<?> c) {
498 String pn = c.getPackageName();
499 return Modifier.isPublic(c.getModifiers()) && c.getModule().isExported(pn);
500 }
501
502 private static boolean isPackagePrivateType(Class<?> c) {
503 return !Modifier.isPublic(c.getModifiers());
504 }
505
506 private static String toDetails(Class<?> c) {
507 String access = "unknown";
508 if (isExportedType(c)) {
509 access = "exported";
510 } else if (isPackagePrivateType(c)) {
511 access = "package-private";
512 } else {
513 access = "module-private";
514 }
515 ClassLoader ld = c.getClassLoader();
516 return String.format(" %s/%s %s loader %s",
517 c.getModule().getName(), c.getName(), access, ld);
518 }
519
520 static void trace(String cn,
521 Module module,
522 ClassLoader loader,
523 List<Class<?>> interfaces) {
524 if (isDebug()) {
525 System.err.format("PROXY: %s/%s defined by %s%n",
526 module.getName(), cn, loader);
527 }
528 if (isDebug("debug")) {
529 interfaces.forEach(c -> System.out.println(toDetails(c)));
530 }
531 }
532
533 private static final String DEBUG = System.getProperty("jdk.proxy.debug", "");
534
535 private static boolean isDebug() {
536 return !DEBUG.isEmpty();
537 }
538 private static boolean isDebug(String flag) {
539 return DEBUG.equals(flag);
540 }
541
542 // ProxyBuilder instance members start here....
543
544 private final List<Class<?>> interfaces;
545 private final ProxyClassContext context;
546 ProxyBuilder(ClassLoader loader, List<Class<?>> interfaces) {
547 Objects.requireNonNull(interfaces);
548 if (!VM.isModuleSystemInited()) {
549 throw new InternalError("Proxy is not supported until "
550 + "module system is fully initialized");
551 }
552 if (interfaces.size() > 65535) {
553 throw new IllegalArgumentException("interface limit exceeded: "
554 + interfaces.size());
555 }
556
557 Set<Class<?>> refTypes = referencedTypes(loader, interfaces);
558
559 // IAE if violates any restrictions specified in newProxyInstance
560 validateProxyInterfaces(loader, interfaces, refTypes);
561
562 this.interfaces = interfaces;
563 this.context = proxyClassContext(loader, interfaces, refTypes);
564 assert context.module().getClassLoader() == loader;
565 }
566
567 ProxyBuilder(ClassLoader loader, Class<?> intf) {
568 this(loader, Collections.singletonList(intf));
569 }
570
571 /**
572 * Generate a proxy class and return its proxy Constructor with
573 * accessible flag already set. If the target module does not have access
574 * to any interface types, IllegalAccessError will be thrown by the VM
575 * at defineClass time.
576 */
577 Constructor<?> build() {
578 Class<?> proxyClass = defineProxyClass(context, interfaces);
579
580 final Constructor<?> cons;
581 try {
582 cons = proxyClass.getConstructor(constructorParams);
583 } catch (NoSuchMethodException e) {
584 throw new InternalError(e.toString(), e);
585 }
586 cons.setAccessible(true);
587 return cons;
588 }
589
590 /**
591 * Validate the given proxy interfaces and the given referenced types
592 * are visible to the defining loader.
593 *
594 * @throws IllegalArgumentException if it violates the restrictions
595 * specified in {@link Proxy#newProxyInstance}
596 */
597 private static void validateProxyInterfaces(ClassLoader loader,
598 List<Class<?>> interfaces,
599 Set<Class<?>> refTypes)
600 {
601 Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.size());
602 for (Class<?> intf : interfaces) {
603 /*
604 * Verify that the Class object actually represents an
605 * interface.
606 */
607 if (!intf.isInterface()) {
608 throw new IllegalArgumentException(intf.getName() + " is not an interface");
609 }
610
611 if (intf.isHidden()) {
612 throw new IllegalArgumentException(intf.getName() + " is a hidden interface");
613 }
614
615 if (intf.isSealed()) {
616 throw new IllegalArgumentException(intf.getName() + " is a sealed interface");
617 }
618
619 /*
620 * Verify that the class loader resolves the name of this
621 * interface to the same Class object.
622 */
623 ensureVisible(loader, intf);
624
625 /*
626 * Verify that this interface is not a duplicate.
627 */
628 if (interfaceSet.put(intf, Boolean.TRUE) != null) {
629 throw new IllegalArgumentException("repeated interface: " + intf.getName());
630 }
631 }
632
633 for (Class<?> type : refTypes) {
634 ensureVisible(loader, type);
635 }
636 }
637
638 /*
639 * Returns all types referenced by all public non-static method signatures of
640 * the proxy interfaces
641 */
642 private static Set<Class<?>> referencedTypes(ClassLoader loader,
643 List<Class<?>> interfaces) {
644 var types = new HashSet<Class<?>>();
645 for (var intf : interfaces) {
646 for (Method m : intf.getMethods()) {
647 if (!Modifier.isStatic(m.getModifiers())) {
648 addElementType(types, m.getReturnType());
649 addElementTypes(types, m.getSharedParameterTypes());
650 addElementTypes(types, m.getSharedExceptionTypes());
651 }
652 }
653 }
654 return types;
655 }
656
657 private static void addElementTypes(HashSet<Class<?>> types,
658 Class<?> ... classes) {
659 for (var cls : classes) {
660 addElementType(types, cls);
661 }
662 }
663
664 private static void addElementType(HashSet<Class<?>> types,
665 Class<?> cls) {
666 var type = getElementType(cls);
667 if (!type.isPrimitive()) {
668 types.add(type);
669 }
670 }
671
672 /**
673 * Returns the context for the generated proxy class, including the
674 * module and the package it belongs to and whether it is package-private.
675 *
676 * If any of proxy interface is package-private, then the proxy class
677 * is in the same package and module as the package-private interface.
678 *
679 * If all proxy interfaces are public and in exported packages,
680 * then the proxy class is in a dynamic module in an unconditionally
681 * exported package.
682 *
683 * If all proxy interfaces are public and at least one in a non-exported
684 * package, then the proxy class is in a dynamic module in a
685 * non-exported package.
686 *
687 * The package of proxy class is open to java.base for deep reflective access.
688 *
689 * Reads edge and qualified exports are added for dynamic module to access.
690 */
691 private static ProxyClassContext proxyClassContext(ClassLoader loader,
692 List<Class<?>> interfaces,
693 Set<Class<?>> refTypes) {
694 Map<Class<?>, Module> packagePrivateTypes = new HashMap<>();
695 boolean nonExported = false;
696
697 for (Class<?> intf : interfaces) {
698 Module m = intf.getModule();
699 if (!Modifier.isPublic(intf.getModifiers())) {
700 packagePrivateTypes.put(intf, m);
701 } else {
702 if (!intf.getModule().isExported(intf.getPackageName())) {
703 // module-private types
704 nonExported = true;
705 }
706 }
707 }
708
709 if (packagePrivateTypes.size() > 0) {
710 // all package-private types must be in the same runtime package
711 // i.e. same package name and same module (named or unnamed)
712 //
713 // Configuration will fail if M1 and in M2 defined by the same loader
714 // and both have the same package p (so no need to check class loader)
715 Module targetModule = null;
716 String targetPackageName = null;
717 for (Map.Entry<Class<?>, Module> e : packagePrivateTypes.entrySet()) {
718 Class<?> intf = e.getKey();
719 Module m = e.getValue();
720 if ((targetModule != null && targetModule != m) ||
721 (targetPackageName != null && targetPackageName != intf.getPackageName())) {
722 throw new IllegalArgumentException(
723 "cannot have non-public interfaces in different packages");
724 }
725 if (m.getClassLoader() != loader) {
726 // the specified loader is not the same class loader
727 // of the non-public interface
728 throw new IllegalArgumentException(
729 "non-public interface is not defined by the given loader");
730 }
731
732 targetModule = m;
733 targetPackageName = e.getKey().getPackageName();
734 }
735
736 // validate if the target module can access all other interfaces
737 for (Class<?> intf : interfaces) {
738 Module m = intf.getModule();
739 if (m == targetModule) continue;
740
741 if (!targetModule.canRead(m) || !m.isExported(intf.getPackageName(), targetModule)) {
742 throw new IllegalArgumentException(targetModule + " can't access " + intf.getName());
743 }
744 }
745
746 // opens the package of the non-public proxy class for java.base to access
747 if (targetModule.isNamed()) {
748 Modules.addOpens(targetModule, targetPackageName, Proxy.class.getModule());
749 }
750 // return the module of the package-private interface
751 return new ProxyClassContext(targetModule, targetPackageName, 0);
752 }
753
754 // All proxy interfaces are public. So maps to a dynamic proxy module
755 // and add reads edge and qualified exports, if necessary
756 Module targetModule = getDynamicModule(loader);
757
758 // set up proxy class access to proxy interfaces and types
759 // referenced in the method signature
760 Set<Class<?>> types = new HashSet<>(interfaces);
761 types.addAll(refTypes);
762 for (Class<?> c : types) {
763 ensureAccess(targetModule, c);
764 }
765
766 var pkgName = nonExported ? PROXY_PACKAGE_PREFIX + '.' + targetModule.getName()
767 : targetModule.getName();
768 return new ProxyClassContext(targetModule, pkgName, Modifier.PUBLIC);
769 }
770
771 /*
772 * Ensure the given module can access the given class.
773 */
774 private static void ensureAccess(Module target, Class<?> c) {
775 Module m = c.getModule();
776 if (target == m) return;
777
778 // add read edge and qualified export for the target module to access
779 if (!target.canRead(m)) {
780 Modules.addReads(target, m);
781 }
782 String pn = c.getPackageName();
783 if (!m.isExported(pn, target)) {
784 Modules.addExports(m, pn, target);
785 }
786 }
787
788 /*
789 * Ensure the given class is visible to the class loader.
790 */
791 private static void ensureVisible(ClassLoader ld, Class<?> c) {
792 Class<?> type = null;
793 try {
794 type = Class.forName(c.getName(), false, ld);
795 } catch (ClassNotFoundException e) {
796 }
797 if (type != c) {
798 throw new IllegalArgumentException(c.getName() +
799 " referenced from a method is not visible from class loader: " + JLA.getLoaderNameID(ld));
800 }
801 }
802
803 private static Class<?> getElementType(Class<?> type) {
804 Class<?> e = type;
805 while (e.isArray()) {
806 e = e.getComponentType();
807 }
808 return e;
809 }
810
811 private static final ClassLoaderValue<Module> dynProxyModules =
812 new ClassLoaderValue<>();
813 private static final AtomicInteger counter = new AtomicInteger();
814
815 /*
816 * Define a dynamic module with a package named $MODULE which
817 * is unconditionally exported and another package named
818 * com.sun.proxy.$MODULE which is encapsulated.
819 *
820 * Each class loader will have one dynamic module.
821 */
822 private static Module getDynamicModule(ClassLoader loader) {
823 return dynProxyModules.computeIfAbsent(loader, (ld, clv) -> {
824 // create a dynamic module and setup module access
825 String mn = "jdk.proxy" + counter.incrementAndGet();
826 String pn = PROXY_PACKAGE_PREFIX + "." + mn;
827 ModuleDescriptor descriptor =
828 ModuleDescriptor.newModule(mn, Set.of(SYNTHETIC))
829 .packages(Set.of(pn, mn))
830 .exports(mn)
831 .build();
832 Module m = Modules.defineModule(ld, descriptor, null);
833 Modules.addReads(m, Proxy.class.getModule());
834 Modules.addExports(m, mn);
835 // java.base to create proxy instance and access its Lookup instance
836 Modules.addOpens(m, pn, Proxy.class.getModule());
837 Modules.addOpens(m, mn, Proxy.class.getModule());
838 return m;
839 });
840 }
841 }
842
843 /**
844 * Returns a proxy instance for the specified interfaces
845 * that dispatches method invocations to the specified invocation
846 * handler.
847 * <p>
848 * <a id="restrictions">{@code IllegalArgumentException} will be thrown
849 * if any of the following restrictions is violated:</a>
850 * <ul>
851 * <li>All of {@code Class} objects in the given {@code interfaces} array
852 * must represent {@linkplain Class#isHidden() non-hidden} and
853 * {@linkplain Class#isSealed() non-sealed} interfaces,
854 * not classes or primitive types.
855 *
856 * <li>No two elements in the {@code interfaces} array may
857 * refer to identical {@code Class} objects.
858 *
859 * <li>All of the interface types must be visible by name through the
860 * specified class loader. In other words, for class loader
861 * {@code cl} and every interface {@code i}, the following
862 * expression must be true:<p>
863 * {@code Class.forName(i.getName(), false, cl) == i}
864 *
865 * <li>All of the types referenced by all
866 * public method signatures of the specified interfaces
867 * and those inherited by their superinterfaces
868 * must be visible by name through the specified class loader.
869 *
870 * <li>All non-public interfaces must be in the same package
871 * and module, defined by the specified class loader and
872 * the module of the non-public interfaces can access all of
873 * the interface types; otherwise, it would not be possible for
874 * the proxy class to implement all of the interfaces,
875 * regardless of what package it is defined in.
876 *
877 * <li>For any set of member methods of the specified interfaces
878 * that have the same signature:
879 * <ul>
880 * <li>If the return type of any of the methods is a primitive
881 * type or void, then all of the methods must have that same
882 * return type.
883 * <li>Otherwise, one of the methods must have a return type that
884 * is assignable to all of the return types of the rest of the
885 * methods.
886 * </ul>
887 *
888 * <li>The resulting proxy class must not exceed any limits imposed
889 * on classes by the virtual machine. For example, the VM may limit
890 * the number of interfaces that a class may implement to 65535; in
891 * that case, the size of the {@code interfaces} array must not
892 * exceed 65535.
893 * </ul>
894 *
895 * <p>Note that the order of the specified proxy interfaces is
896 * significant: two requests for a proxy class with the same combination
897 * of interfaces but in a different order will result in two distinct
898 * proxy classes.
899 *
900 * @param loader the class loader to define the proxy class
901 * @param interfaces the list of interfaces for the proxy class
902 * to implement
903 * @param h the invocation handler to dispatch method invocations to
904 * @return a proxy instance with the specified invocation handler of a
905 * proxy class that is defined by the specified class loader
906 * and that implements the specified interfaces
907 * @throws IllegalArgumentException if any of the <a href="#restrictions">
908 * restrictions</a> on the parameters are violated
909 * @throws NullPointerException if the {@code interfaces} array
910 * argument or any of its elements are {@code null}, or
911 * if the invocation handler, {@code h}, is
912 * {@code null}
913 *
914 * @see <a href="#membership">Package and Module Membership of Proxy Class</a>
915 */
916 public static Object newProxyInstance(ClassLoader loader,
917 Class<?>[] interfaces,
918 InvocationHandler h) {
919 Objects.requireNonNull(h);
920
921 /*
922 * Look up or generate the designated proxy class and its constructor.
923 */
924 Constructor<?> cons = getProxyConstructor(loader, interfaces);
925
926 return newProxyInstance(cons, h);
927 }
928
929 private static Object newProxyInstance(Constructor<?> cons, InvocationHandler h) {
930 /*
931 * Invoke its constructor with the designated invocation handler.
932 */
933 try {
934 return cons.newInstance(new Object[]{h});
935 } catch (IllegalAccessException | InstantiationException e) {
936 throw new InternalError(e.toString(), e);
937 } catch (InvocationTargetException e) {
938 Throwable t = e.getCause();
939 if (t instanceof RuntimeException re) {
940 throw re;
941 } else {
942 throw new InternalError(t.toString(), t);
943 }
944 }
945 }
946
947 /**
948 * Returns true if the given class is a proxy class.
949 *
950 * @implNote The reliability of this method is important for the ability
951 * to use it to make security decisions, so its implementation should
952 * not just test if the class in question extends {@code Proxy}.
953 *
954 * @param cl the class to test
955 * @return {@code true} if the class is a proxy class and
956 * {@code false} otherwise
957 * @throws NullPointerException if {@code cl} is {@code null}
958 */
959 public static boolean isProxyClass(Class<?> cl) {
960 return Proxy.class.isAssignableFrom(cl) && ProxyBuilder.isProxyClass(cl);
961 }
962
963 /**
964 * Returns the invocation handler for the specified proxy instance.
965 *
966 * @param proxy the proxy instance to return the invocation handler for
967 * @return the invocation handler for the proxy instance
968 * @throws IllegalArgumentException if the argument is not a
969 * proxy instance
970 */
971 public static InvocationHandler getInvocationHandler(Object proxy)
972 throws IllegalArgumentException
973 {
974 /*
975 * Verify that the object is actually a proxy instance.
976 */
977 if (!isProxyClass(proxy.getClass())) {
978 throw new IllegalArgumentException("not a proxy instance");
979 }
980
981 final Proxy p = (Proxy) proxy;
982 final InvocationHandler ih = p.h;
983 return ih;
984 }
985
986 private static final String PROXY_PACKAGE_PREFIX = "com.sun.proxy";
987
988 /**
989 * A cache of Method -> MethodHandle for default methods.
990 */
991 private static final ClassValue<ConcurrentHashMap<Method, MethodHandle>>
992 DEFAULT_METHODS_MAP = new ClassValue<>() {
993 @Override
994 protected ConcurrentHashMap<Method, MethodHandle> computeValue(Class<?> type) {
995 return new ConcurrentHashMap<>(4);
996 }
997 };
998
999 private static ConcurrentHashMap<Method, MethodHandle> defaultMethodMap(Class<?> proxyClass) {
1000 assert isProxyClass(proxyClass);
1001 return DEFAULT_METHODS_MAP.get(proxyClass);
1002 }
1003
1004 static final Object[] EMPTY_ARGS = new Object[0];
1005
1006 static MethodHandle defaultMethodHandle(Class<? extends Proxy> proxyClass, Method method) {
1007 // lookup the cached method handle
1008 ConcurrentHashMap<Method, MethodHandle> methods = defaultMethodMap(proxyClass);
1009 MethodHandle superMH = methods.get(method);
1010 if (superMH == null) {
1011 MethodType type = methodType(method.getReturnType(), method.getParameterTypes());
1012 MethodHandles.Lookup lookup = MethodHandles.lookup();
1013 Class<?> proxyInterface = findProxyInterfaceOrElseThrow(proxyClass, method);
1014 MethodHandle dmh;
1015 try {
1016 dmh = proxyClassLookup(lookup, proxyClass)
1017 .findSpecial(proxyInterface, method.getName(), type, proxyClass)
1018 .withVarargs(false);
1019 } catch (IllegalAccessException | NoSuchMethodException e) {
1020 // should not reach here
1021 throw new InternalError(e);
1022 }
1023 // this check can be turned into assertion as it is guaranteed to succeed by the virtue of
1024 // looking up a default (instance) method declared or inherited by proxyInterface
1025 // while proxyClass implements (is a subtype of) proxyInterface ...
1026 assert ((BooleanSupplier) () -> {
1027 try {
1028 // make sure that the method type matches
1029 dmh.asType(type.insertParameterTypes(0, proxyClass));
1030 return true;
1031 } catch (WrongMethodTypeException e) {
1032 return false;
1033 }
1034 }).getAsBoolean() : "Wrong method type";
1035 // change return type to Object
1036 MethodHandle mh = dmh.asType(dmh.type().changeReturnType(Object.class));
1037 // wrap any exception thrown with InvocationTargetException
1038 mh = MethodHandles.catchException(mh, Throwable.class, InvocationException.wrapMH());
1039 // spread array of arguments among parameters (skipping 1st parameter - target)
1040 mh = mh.asSpreader(1, Object[].class, type.parameterCount());
1041 // change target type to Object
1042 mh = mh.asType(MethodType.methodType(Object.class, Object.class, Object[].class));
1043
1044 // push MH into cache
1045 MethodHandle cached = methods.putIfAbsent(method, mh);
1046 if (cached != null) {
1047 superMH = cached;
1048 } else {
1049 superMH = mh;
1050 }
1051 }
1052 return superMH;
1053 }
1054
1055 /**
1056 * Finds the first proxy interface that declares the given method
1057 * directly or indirectly.
1058 *
1059 * @throws IllegalArgumentException if not found
1060 */
1061 private static Class<?> findProxyInterfaceOrElseThrow(Class<?> proxyClass, Method method) {
1062 Class<?> declaringClass = method.getDeclaringClass();
1063 if (!declaringClass.isInterface()) {
1064 throw new IllegalArgumentException("\"" + method +
1065 "\" is not a method declared in the proxy class");
1066 }
1067
1068 List<Class<?>> proxyInterfaces = Arrays.asList(proxyClass.getInterfaces());
1069 // the method's declaring class is a proxy interface
1070 if (proxyInterfaces.contains(declaringClass))
1071 return declaringClass;
1072
1073 // find the first proxy interface that inherits the default method
1074 // i.e. the declaring class of the default method is a superinterface
1075 // of the proxy interface
1076 Deque<Class<?>> deque = new ArrayDeque<>();
1077 Set<Class<?>> visited = new HashSet<>();
1078 boolean indirectMethodRef = false;
1079 for (Class<?> proxyIntf : proxyInterfaces) {
1080 assert proxyIntf != declaringClass;
1081 visited.add(proxyIntf);
1082 deque.add(proxyIntf);
1083
1084 // for each proxy interface, traverse its subinterfaces with
1085 // breadth-first search to find a subinterface declaring the
1086 // default method
1087 Class<?> c;
1088 while ((c = deque.poll()) != null) {
1089 if (c == declaringClass) {
1090 try {
1091 // check if this method is the resolved method if referenced from
1092 // this proxy interface (i.e. this method is not implemented
1093 // by any other superinterface)
1094 Method m = proxyIntf.getMethod(method.getName(), method.getSharedParameterTypes());
1095 if (m.getDeclaringClass() == declaringClass) {
1096 return proxyIntf;
1097 }
1098 indirectMethodRef = true;
1099 } catch (NoSuchMethodException e) {}
1100
1101 // skip traversing its superinterfaces
1102 // another proxy interface may extend it and so
1103 // the method's declaring class is left unvisited.
1104 continue;
1105 }
1106 // visit all superinterfaces of one proxy interface to find if
1107 // this proxy interface inherits the method directly or indirectly
1108 visited.add(c);
1109 for (Class<?> superIntf : c.getInterfaces()) {
1110 if (!visited.contains(superIntf) && !deque.contains(superIntf)) {
1111 if (superIntf == declaringClass) {
1112 // fast-path as the matching subinterface is found
1113 deque.addFirst(superIntf);
1114 } else {
1115 deque.add(superIntf);
1116 }
1117 }
1118 }
1119 }
1120 }
1121
1122 throw new IllegalArgumentException("\"" + method + (indirectMethodRef
1123 ? "\" is overridden directly or indirectly by the proxy interfaces"
1124 : "\" is not a method declared in the proxy class"));
1125 }
1126
1127 /**
1128 * This method invokes the proxy's proxyClassLookup method to get a
1129 * Lookup on the proxy class.
1130 *
1131 * @return a lookup for proxy class of this proxy instance
1132 */
1133 private static MethodHandles.Lookup proxyClassLookup(MethodHandles.Lookup caller, Class<?> proxyClass) {
1134 try {
1135 Method m = proxyClass.getDeclaredMethod("proxyClassLookup", MethodHandles.Lookup.class);
1136 m.setAccessible(true);
1137 return (MethodHandles.Lookup) m.invoke(null, caller);
1138 } catch (ReflectiveOperationException e) {
1139 throw new InternalError(e);
1140 }
1141 }
1142
1143 /*
1144 * Invoke the default method of the given proxy with an explicit caller class.
1145 *
1146 * @throws IllegalAccessException if the proxy interface is inaccessible to the caller
1147 * if caller is non-null
1148 */
1149 static Object invokeDefault(Object proxy, Method method, Object[] args, Class<?> caller)
1150 throws Throwable {
1151 // verify that the object is actually a proxy instance
1152 if (!Proxy.isProxyClass(proxy.getClass())) {
1153 throw new IllegalArgumentException("'proxy' is not a proxy instance");
1154 }
1155 if (!method.isDefault()) {
1156 throw new IllegalArgumentException("\"" + method + "\" is not a default method");
1157 }
1158 @SuppressWarnings("unchecked")
1159 Class<? extends Proxy> proxyClass = (Class<? extends Proxy>)proxy.getClass();
1160
1161 // skip access check if caller is null
1162 if (caller != null) {
1163 Class<?> intf = method.getDeclaringClass();
1164 // access check on the default method
1165 method.checkAccess(caller, intf, proxyClass, method.getModifiers());
1166 }
1167
1168 MethodHandle mh = Proxy.defaultMethodHandle(proxyClass, method);
1169 // invoke the super method
1170 try {
1171 // the args array can be null if the number of formal parameters required by
1172 // the method is zero (consistent with Method::invoke)
1173 Object[] params = args != null ? args : Proxy.EMPTY_ARGS;
1174 return mh.invokeExact(proxy, params);
1175 } catch (ClassCastException | NullPointerException e) {
1176 throw new IllegalArgumentException(e.getMessage(), e);
1177 } catch (Proxy.InvocationException e) {
1178 // unwrap and throw the exception thrown by the default method
1179 throw e.getCause();
1180 }
1181 }
1182
1183 /**
1184 * Internal exception type to wrap the exception thrown by the default method
1185 * so that it can distinguish CCE and NPE thrown due to the arguments
1186 * incompatible with the method signature.
1187 */
1188 static class InvocationException extends ReflectiveOperationException {
1189 @java.io.Serial
1190 private static final long serialVersionUID = 0L;
1191
1192 InvocationException(Throwable cause) {
1193 super(cause);
1194 }
1195
1196 /**
1197 * Wraps given cause with InvocationException and throws it.
1198 */
1199 static Object wrap(Throwable cause) throws InvocationException {
1200 throw new InvocationException(cause);
1201 }
1202
1203 @Stable
1204 static MethodHandle wrapMethodHandle;
1205
1206 static MethodHandle wrapMH() {
1207 MethodHandle mh = wrapMethodHandle;
1208 if (mh == null) {
1209 try {
1210 wrapMethodHandle = mh = MethodHandles.lookup().findStatic(
1211 InvocationException.class,
1212 "wrap",
1213 MethodType.methodType(Object.class, Throwable.class)
1214 );
1215 } catch (NoSuchMethodException | IllegalAccessException e) {
1216 throw new InternalError(e);
1217 }
1218 }
1219 return mh;
1220 }
1221 }
1222
1223 }