1 /*
2 * Copyright (c) 2008, 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.invoke;
27
28 import java.lang.constant.ClassDesc;
29 import java.lang.constant.MethodTypeDesc;
30 import java.lang.invoke.MethodHandles.Lookup;
31 import java.lang.module.ModuleDescriptor;
32 import java.lang.ref.WeakReference;
33 import java.lang.reflect.Method;
34 import java.lang.reflect.Modifier;
35 import java.lang.reflect.UndeclaredThrowableException;
36 import java.security.AccessController;
37 import java.security.PrivilegedAction;
38 import java.util.ArrayList;
39 import java.util.Arrays;
40 import java.util.Collections;
41 import java.util.HashSet;
42 import java.util.List;
43 import java.util.Objects;
44 import java.util.Set;
45 import java.util.WeakHashMap;
46 import java.util.concurrent.atomic.AtomicInteger;
47 import java.util.stream.Stream;
48
49 import jdk.internal.access.JavaLangReflectAccess;
50 import jdk.internal.access.SharedSecrets;
51 import java.lang.classfile.ClassHierarchyResolver;
52 import java.lang.classfile.ClassFile;
53 import java.lang.classfile.CodeBuilder;
54 import java.lang.classfile.TypeKind;
55 import jdk.internal.misc.PreviewFeatures;
56 import jdk.internal.module.Modules;
57 import jdk.internal.reflect.CallerSensitive;
58 import jdk.internal.reflect.Reflection;
59 import jdk.internal.util.ClassFileDumper;
60 import sun.reflect.misc.ReflectUtil;
61
62 import static java.lang.constant.ConstantDescs.*;
63 import static java.lang.invoke.MethodHandleStatics.*;
64 import static java.lang.invoke.MethodType.methodType;
65 import static java.lang.module.ModuleDescriptor.Modifier.SYNTHETIC;
66 import static java.lang.classfile.ClassFile.*;
67
68 /**
69 * This class consists exclusively of static methods that help adapt
70 * method handles to other JVM types, such as interfaces.
71 *
72 * @since 1.7
73 */
74 public class MethodHandleProxies {
75
76 private MethodHandleProxies() { } // do not instantiate
77
78 /**
79 * Produces an instance of the given single-method interface which redirects
80 * its calls to the given method handle.
81 * <p>
82 * A single-method interface is an interface which declares a uniquely named method.
83 * When determining the uniquely named method of a single-method interface,
84 * the public {@code Object} methods ({@code toString}, {@code equals}, {@code hashCode})
85 * are disregarded as are any default (non-abstract) methods.
86 * For example, {@link java.util.Comparator} is a single-method interface,
87 * even though it re-declares the {@code Object.equals} method and also
88 * declares default methods, such as {@code Comparator.reverse}.
89 * <p>
90 * The interface must be public, not {@linkplain Class#isHidden() hidden},
91 * and not {@linkplain Class#isSealed() sealed}.
92 * No additional access checks are performed.
93 * <p>
94 * The resulting instance of the required type will respond to
95 * invocation of the type's uniquely named method by calling
96 * the given target on the incoming arguments,
97 * and returning or throwing whatever the target
98 * returns or throws. The invocation will be as if by
99 * {@code target.invoke}.
100 * The target's type will be checked before the
101 * instance is created, as if by a call to {@code asType},
102 * which may result in a {@code WrongMethodTypeException}.
103 * <p>
104 * The uniquely named method is allowed to be multiply declared,
105 * with distinct type descriptors. (E.g., it can be overloaded,
106 * or can possess bridge methods.) All such declarations are
107 * connected directly to the target method handle.
108 * Argument and return types are adjusted by {@code asType}
109 * for each individual declaration.
110 * <p>
111 * The wrapper instance will implement the requested interface
112 * and its super-types, but no other single-method interfaces.
113 * This means that the instance will not unexpectedly
114 * pass an {@code instanceof} test for any unrequested type.
115 * <p style="font-size:smaller;">
116 * <em>Implementation Note:</em>
117 * Therefore, each instance must implement a unique single-method interface.
118 * Implementations may not bundle together
119 * multiple single-method interfaces onto single implementation classes
120 * in the style of {@link java.desktop/java.awt.AWTEventMulticaster}.
121 * <p>
122 * The method handle may throw an <em>undeclared exception</em>,
123 * which means any checked exception (or other checked throwable)
124 * not declared by the requested type's single abstract method.
125 * If this happens, the throwable will be wrapped in an instance of
126 * {@link java.lang.reflect.UndeclaredThrowableException UndeclaredThrowableException}
127 * and thrown in that wrapped form.
128 * <p>
129 * Like {@link java.lang.Integer#valueOf Integer.valueOf},
130 * {@code asInterfaceInstance} is a factory method whose results are defined
131 * by their behavior.
132 * It is not guaranteed to return a new instance for every call.
133 * <p>
134 * Because of the possibility of {@linkplain java.lang.reflect.Method#isBridge bridge methods}
135 * and other corner cases, the interface may also have several abstract methods
136 * with the same name but having distinct descriptors (types of returns and parameters).
137 * In this case, all the methods are bound in common to the one given target.
138 * The type check and effective {@code asType} conversion is applied to each
139 * method type descriptor, and all abstract methods are bound to the target in common.
140 * Beyond this type check, no further checks are made to determine that the
141 * abstract methods are related in any way.
142 * <p>
143 * Future versions of this API may accept additional types,
144 * such as abstract classes with single abstract methods.
145 * Future versions of this API may also equip wrapper instances
146 * with one or more additional public "marker" interfaces.
147 * <p>
148 * If a security manager is installed, this method is caller sensitive.
149 * During any invocation of the target method handle via the returned wrapper,
150 * the original creator of the wrapper (the caller) will be visible
151 * to context checks requested by the security manager.
152 *
153 * @param <T> the desired type of the wrapper, a single-method interface
154 * @param intfc a class object representing {@code T}
155 * @param target the method handle to invoke from the wrapper
156 * @return a correctly-typed wrapper for the given target
157 * @throws NullPointerException if either argument is null
158 * @throws IllegalArgumentException if the {@code intfc} is not a
159 * valid argument to this method
160 * @throws WrongMethodTypeException if the target cannot
161 * be converted to the type required by the requested interface
162 */
163 @SuppressWarnings("doclint:reference") // cross-module links
164 @CallerSensitive
165 public static <T> T asInterfaceInstance(final Class<T> intfc, final MethodHandle target) {
166 if (!intfc.isInterface() || !Modifier.isPublic(intfc.getModifiers()))
167 throw newIllegalArgumentException("not a public interface", intfc.getName());
168 if (intfc.isSealed())
169 throw newIllegalArgumentException("a sealed interface", intfc.getName());
170 if (intfc.isHidden())
171 throw newIllegalArgumentException("a hidden interface", intfc.getName());
172 Objects.requireNonNull(target);
173 final MethodHandle mh;
174 @SuppressWarnings("removal")
175 var sm = System.getSecurityManager();
176 if (sm != null) {
177 final Class<?> caller = Reflection.getCallerClass();
178 final ClassLoader ccl = caller != null ? caller.getClassLoader() : null;
179 ReflectUtil.checkProxyPackageAccess(ccl, intfc);
180 mh = ccl != null ? bindCaller(target, caller) : target;
181 } else {
182 mh = target;
183 }
184
185 // Define one hidden class for each interface. Create an instance of
186 // the hidden class for a given target method handle which will be
187 // accessed via getfield. Multiple instances may be created for a
188 // hidden class. This approach allows the generated hidden classes
189 // more shareable.
190 //
191 // The implementation class is weakly referenced; a new class is
192 // defined if the last one has been garbage collected.
193 //
194 // An alternative approach is to define one hidden class with the
195 // target method handle as class data and the target method handle
196 // is loaded via ldc/condy. If more than one target method handles
197 // are used, the extra classes will pollute the same type profiles.
198 // In addition, hidden classes without class data is more friendly
199 // for pre-generation (shifting the dynamic class generation from
200 // runtime to an earlier phrase).
201 Class<?> proxyClass = getProxyClass(intfc); // throws IllegalArgumentException
202 Lookup lookup = new Lookup(proxyClass);
203 Object proxy;
204 try {
205 MethodHandle constructor = lookup.findConstructor(proxyClass,
206 MT_void_Lookup_MethodHandle_MethodHandle)
207 .asType(MT_Object_Lookup_MethodHandle_MethodHandle);
208 proxy = constructor.invokeExact(lookup, target, mh);
209 } catch (Throwable ex) {
210 throw uncaughtException(ex);
211 }
212 assert proxy.getClass().getModule().isNamed() : proxy.getClass() + " " + proxy.getClass().getModule();
213 return intfc.cast(proxy);
214 }
215
216 private record MethodInfo(MethodTypeDesc desc, List<ClassDesc> thrown, String fieldName) {}
217
218 private static final ClassFileDumper DUMPER = ClassFileDumper.getInstance(
219 "jdk.invoke.MethodHandleProxies.dumpClassFiles", "DUMP_MH_PROXY_CLASSFILES");
220
221 private static final Set<Class<?>> WRAPPER_TYPES = Collections.newSetFromMap(new WeakHashMap<>());
222 private static final ClassValue<WeakReferenceHolder<Class<?>>> PROXIES = new ClassValue<>() {
223 @Override
224 protected WeakReferenceHolder<Class<?>> computeValue(Class<?> intfc) {
225 return new WeakReferenceHolder<>(newProxyClass(intfc));
226 }
227 };
228
229 private static Class<?> newProxyClass(Class<?> intfc) {
230 List<MethodInfo> methods = new ArrayList<>();
231 Set<Class<?>> referencedTypes = new HashSet<>();
232 referencedTypes.add(intfc);
233 String uniqueName = null;
234 int count = 0;
235 for (Method m : intfc.getMethods()) {
236 if (!Modifier.isAbstract(m.getModifiers()))
237 continue;
238
239 if (isObjectMethod(m))
240 continue;
241
242 // ensure it's SAM interface
243 String methodName = m.getName();
244 if (uniqueName == null) {
245 uniqueName = methodName;
246 } else if (!uniqueName.equals(methodName)) {
247 // too many abstract methods
248 throw newIllegalArgumentException("not a single-method interface", intfc.getName());
249 }
250
251 // the field name holding the method handle for this method
252 String fieldName = "m" + count++;
253 var mt = methodType(m.getReturnType(), JLRA.getExecutableSharedParameterTypes(m), true);
254 var thrown = JLRA.getExecutableSharedExceptionTypes(m);
255 var exceptionTypeDescs =
256 thrown.length == 0 ? DEFAULT_RETHROWS
257 : Stream.concat(DEFAULT_RETHROWS.stream(),
258 Arrays.stream(thrown).map(MethodHandleProxies::desc))
259 .distinct().toList();
260 methods.add(new MethodInfo(desc(mt), exceptionTypeDescs, fieldName));
261
262 // find the types referenced by this method
263 addElementType(referencedTypes, m.getReturnType());
264 addElementTypes(referencedTypes, JLRA.getExecutableSharedParameterTypes(m));
265 addElementTypes(referencedTypes, JLRA.getExecutableSharedExceptionTypes(m));
266 }
267
268 if (uniqueName == null)
269 throw newIllegalArgumentException("no method in ", intfc.getName());
270
271 // create a dynamic module for each proxy class, which needs access
272 // to the types referenced by the members of the interface including
273 // the parameter types, return type and exception types
274 var loader = intfc.getClassLoader();
275 Module targetModule = newDynamicModule(loader, referencedTypes);
276
277 // generate a class file in the package of the dynamic module
278 String packageName = targetModule.getName();
279 String intfcName = intfc.getName();
280 int i = intfcName.lastIndexOf('.');
281 // jdk.MHProxy#.Interface
282 String className = packageName + "." + (i > 0 ? intfcName.substring(i + 1) : intfcName);
283 byte[] template = createTemplate(loader, ClassDesc.of(className), desc(intfc), uniqueName, methods);
284 // define the dynamic module to the class loader of the interface
285 var definer = new Lookup(intfc).makeHiddenClassDefiner(className, template, Set.of(), DUMPER);
286
287 @SuppressWarnings("removal")
288 var sm = System.getSecurityManager();
289 Lookup lookup;
290 if (sm != null) {
291 @SuppressWarnings("removal")
292 var l = AccessController.doPrivileged((PrivilegedAction<Lookup>) () ->
293 definer.defineClassAsLookup(true));
294 lookup = l;
295 } else {
296 lookup = definer.defineClassAsLookup(true);
297 }
298 // cache the wrapper type
299 var ret = lookup.lookupClass();
300 WRAPPER_TYPES.add(ret);
301 return ret;
302 }
303
304 private static final class WeakReferenceHolder<T> {
305 private volatile WeakReference<T> ref;
306
307 WeakReferenceHolder(T value) {
308 set(value);
309 }
310
311 void set(T value) {
312 ref = new WeakReference<>(value);
313 }
314
315 T get() {
316 return ref.get();
317 }
318 }
319
320 private static Class<?> getProxyClass(Class<?> intfc) {
321 WeakReferenceHolder<Class<?>> r = PROXIES.get(intfc);
322 Class<?> cl = r.get();
323 if (cl != null)
324 return cl;
325
326 // avoid spinning multiple classes in a race
327 synchronized (r) {
328 cl = r.get();
329 if (cl != null)
330 return cl;
331
332 // If the referent is cleared, create a new value and update cached weak reference.
333 cl = newProxyClass(intfc);
334 r.set(cl);
335 return cl;
336 }
337 }
338
339 private static final List<ClassDesc> DEFAULT_RETHROWS = List.of(desc(RuntimeException.class), desc(Error.class));
340 private static final ClassDesc CD_UndeclaredThrowableException = desc(UndeclaredThrowableException.class);
341 private static final ClassDesc CD_IllegalAccessException = desc(IllegalAccessException.class);
342 private static final MethodTypeDesc MTD_void_Throwable = MethodTypeDesc.of(CD_void, CD_Throwable);
343 private static final MethodType MT_void_Lookup_MethodHandle_MethodHandle =
344 methodType(void.class, Lookup.class, MethodHandle.class, MethodHandle.class);
345 private static final MethodType MT_Object_Lookup_MethodHandle_MethodHandle =
346 MT_void_Lookup_MethodHandle_MethodHandle.changeReturnType(Object.class);
347 private static final MethodType MT_MethodHandle_Object = methodType(MethodHandle.class, Object.class);
348 private static final MethodTypeDesc MTD_void_Lookup_MethodHandle_MethodHandle =
349 desc(MT_void_Lookup_MethodHandle_MethodHandle);
350 private static final MethodTypeDesc MTD_void_Lookup = MethodTypeDesc.of(CD_void, CD_MethodHandles_Lookup);
351 private static final MethodTypeDesc MTD_MethodHandle_MethodType = MethodTypeDesc.of(CD_MethodHandle, CD_MethodType);
352 private static final MethodTypeDesc MTD_Class = MethodTypeDesc.of(CD_Class);
353 private static final MethodTypeDesc MTD_int = MethodTypeDesc.of(CD_int);
354 private static final MethodTypeDesc MTD_String = MethodTypeDesc.of(CD_String);
355 private static final MethodTypeDesc MTD_void_String = MethodTypeDesc.of(CD_void, CD_String);
356 private static final String TARGET_NAME = "target";
357 private static final String TYPE_NAME = "interfaceType";
358 private static final String ENSURE_ORIGINAL_LOOKUP = "ensureOriginalLookup";
359
360 /**
361 * Creates an implementation class file for a given interface. One implementation class is
362 * defined for each interface.
363 *
364 * @param ifaceDesc the given interface
365 * @param methodName the name of the single abstract method
366 * @param methods the information for implementation methods
367 * @return the bytes of the implementation classes
368 */
369 private static byte[] createTemplate(ClassLoader loader, ClassDesc proxyDesc, ClassDesc ifaceDesc,
370 String methodName, List<MethodInfo> methods) {
371 return ClassFile.of(ClassHierarchyResolverOption.of(ClassHierarchyResolver.ofClassLoading(loader)))
372 .build(proxyDesc, clb -> {
373 clb.withSuperclass(CD_Object);
374 clb.withFlags((PreviewFeatures.isEnabled() ? ACC_IDENTITY : 0) | ACC_FINAL | ACC_SYNTHETIC);
375 clb.withInterfaceSymbols(ifaceDesc);
376
377 // static and instance fields
378 clb.withField(TYPE_NAME, CD_Class, ACC_PRIVATE | ACC_STATIC | ACC_FINAL);
379 clb.withField(TARGET_NAME, CD_MethodHandle, ACC_PRIVATE | ACC_FINAL);
380 for (var mi : methods) {
381 clb.withField(mi.fieldName, CD_MethodHandle, ACC_PRIVATE | ACC_FINAL);
382 }
383
384 // <clinit>
385 clb.withMethodBody(CLASS_INIT_NAME, MTD_void, ACC_STATIC, cob -> {
386 cob.constantInstruction(ifaceDesc);
387 cob.putstatic(proxyDesc, TYPE_NAME, CD_Class);
388 cob.return_();
389 });
390
391 // <init>(Lookup, MethodHandle target, MethodHandle callerBoundTarget)
392 clb.withMethodBody(INIT_NAME, MTD_void_Lookup_MethodHandle_MethodHandle, 0, cob -> {
393 cob.aload(0);
394 cob.invokespecial(CD_Object, INIT_NAME, MTD_void);
395
396 // call ensureOriginalLookup to verify the given Lookup has access
397 cob.aload(1);
398 cob.invokestatic(proxyDesc, "ensureOriginalLookup", MTD_void_Lookup);
399
400 // this.target = target;
401 cob.aload(0);
402 cob.aload(2);
403 cob.putfield(proxyDesc, TARGET_NAME, CD_MethodHandle);
404
405 // method handles adjusted to the method type of each method
406 for (var mi : methods) {
407 // this.m<i> = callerBoundTarget.asType(xxType);
408 cob.aload(0);
409 cob.aload(3);
410 cob.constantInstruction(mi.desc);
411 cob.invokevirtual(CD_MethodHandle, "asType", MTD_MethodHandle_MethodType);
412 cob.putfield(proxyDesc, mi.fieldName, CD_MethodHandle);
413 }
414
415 // complete
416 cob.return_();
417 });
418
419 // private static void ensureOriginalLookup(Lookup) checks if the given Lookup
420 // has ORIGINAL access to this class, i.e. the lookup class is this class;
421 // otherwise, IllegalAccessException is thrown
422 clb.withMethodBody(ENSURE_ORIGINAL_LOOKUP, MTD_void_Lookup, ACC_PRIVATE | ACC_STATIC, cob -> {
423 var failLabel = cob.newLabel();
424 // check lookupClass
425 cob.aload(0);
426 cob.invokevirtual(CD_MethodHandles_Lookup, "lookupClass", MTD_Class);
427 cob.constantInstruction(proxyDesc);
428 cob.if_acmpne(failLabel);
429 // check original access
430 cob.aload(0);
431 cob.invokevirtual(CD_MethodHandles_Lookup, "lookupModes", MTD_int);
432 cob.constantInstruction(Lookup.ORIGINAL);
433 cob.iand();
434 cob.ifeq(failLabel);
435 // success
436 cob.return_();
437 // throw exception
438 cob.labelBinding(failLabel);
439 cob.new_(CD_IllegalAccessException);
440 cob.dup();
441 cob.aload(0); // lookup
442 cob.invokevirtual(CD_Object, "toString", MTD_String);
443 cob.invokespecial(CD_IllegalAccessException, INIT_NAME, MTD_void_String);
444 cob.athrow();
445 });
446
447 // implementation methods
448 for (MethodInfo mi : methods) {
449 // no need to generate thrown exception attribute
450 clb.withMethodBody(methodName, mi.desc, ACC_PUBLIC, cob -> cob
451 .trying(bcb -> {
452 // return this.handleField.invokeExact(arguments...);
453 bcb.aload(0);
454 bcb.getfield(proxyDesc, mi.fieldName, CD_MethodHandle);
455 for (int j = 0; j < mi.desc.parameterCount(); j++) {
456 bcb.loadInstruction(TypeKind.from(mi.desc.parameterType(j)),
457 bcb.parameterSlot(j));
458 }
459 bcb.invokevirtual(CD_MethodHandle, "invokeExact", mi.desc);
460 bcb.returnInstruction(TypeKind.from(mi.desc.returnType()));
461 }, ctb -> ctb
462 // catch (Error | RuntimeException | Declared ex) { throw ex; }
463 .catchingMulti(mi.thrown, CodeBuilder::athrow)
464 // catch (Throwable ex) { throw new UndeclaredThrowableException(ex); }
465 .catchingAll(cb -> cb
466 .new_(CD_UndeclaredThrowableException)
467 .dup_x1()
468 .swap()
469 .invokespecial(CD_UndeclaredThrowableException,
470 INIT_NAME, MTD_void_Throwable)
471 .athrow()
472 )
473 ));
474 }
475 });
476 }
477
478 private static MethodHandle bindCaller(MethodHandle target, Class<?> hostClass) {
479 return MethodHandleImpl.bindCaller(target, hostClass).withVarargs(target.isVarargsCollector());
480 }
481
482 /**
483 * Determines if the given object was produced by a call to {@link #asInterfaceInstance asInterfaceInstance}.
484 * @param x any reference
485 * @return true if the reference is not null and points to an object produced by {@code asInterfaceInstance}
486 */
487 public static boolean isWrapperInstance(Object x) {
488 return x != null && WRAPPER_TYPES.contains(x.getClass());
489 }
490
491 /**
492 * Produces or recovers a target method handle which is behaviorally
493 * equivalent to the unique method of this wrapper instance.
494 * The object {@code x} must have been produced by a call to {@link #asInterfaceInstance asInterfaceInstance}.
495 * This requirement may be tested via {@link #isWrapperInstance isWrapperInstance}.
496 * @param x any reference
497 * @return a method handle implementing the unique method
498 * @throws IllegalArgumentException if the reference x is not to a wrapper instance
499 */
500 public static MethodHandle wrapperInstanceTarget(Object x) {
501 if (!isWrapperInstance(x))
502 throw new IllegalArgumentException("not a wrapper instance: " + x);
503
504 try {
505 Class<?> type = x.getClass();
506 MethodHandle getter = new Lookup(type).findGetter(type, TARGET_NAME, MethodHandle.class)
507 .asType(MT_MethodHandle_Object);
508 return (MethodHandle) getter.invokeExact(x);
509 } catch (Throwable ex) {
510 throw uncaughtException(ex);
511 }
512 }
513
514 /**
515 * Recovers the unique single-method interface type for which this wrapper instance was created.
516 * The object {@code x} must have been produced by a call to {@link #asInterfaceInstance asInterfaceInstance}.
517 * This requirement may be tested via {@link #isWrapperInstance isWrapperInstance}.
518 * @param x any reference
519 * @return the single-method interface type for which the wrapper was created
520 * @throws IllegalArgumentException if the reference x is not to a wrapper instance
521 */
522 public static Class<?> wrapperInstanceType(Object x) {
523 if (!isWrapperInstance(x))
524 throw new IllegalArgumentException("not a wrapper instance: " + x);
525
526 try {
527 Class<?> type = x.getClass();
528 MethodHandle originalTypeField = new Lookup(type).findStaticGetter(type, TYPE_NAME, Class.class);
529 return (Class<?>) originalTypeField.invokeExact();
530 } catch (Throwable e) {
531 throw uncaughtException(e);
532 }
533 }
534
535 private static ClassDesc desc(Class<?> cl) {
536 return cl.describeConstable().orElseThrow(() -> newInternalError("Cannot convert class "
537 + cl.getName() + " to a constant"));
538 }
539
540 private static MethodTypeDesc desc(MethodType mt) {
541 return mt.describeConstable().orElseThrow(() -> newInternalError("Cannot convert method type "
542 + mt + " to a constant"));
543 }
544
545 private static final JavaLangReflectAccess JLRA = SharedSecrets.getJavaLangReflectAccess();
546 private static final AtomicInteger counter = new AtomicInteger();
547
548 private static String nextModuleName() {
549 return "jdk.MHProxy" + counter.incrementAndGet();
550 }
551
552 /**
553 * Create a dynamic module defined to the given class loader and has
554 * access to the given types.
555 * <p>
556 * The dynamic module contains only one single package named the same as
557 * the name of the dynamic module. It's not exported or open.
558 */
559 private static Module newDynamicModule(ClassLoader ld, Set<Class<?>> types) {
560 Objects.requireNonNull(types);
561
562 // create a dynamic module and setup module access
563 String mn = nextModuleName();
564 ModuleDescriptor descriptor = ModuleDescriptor.newModule(mn, Set.of(SYNTHETIC))
565 .packages(Set.of(mn))
566 .build();
567
568 Module dynModule = Modules.defineModule(ld, descriptor, null);
569 Module javaBase = Object.class.getModule();
570
571 Modules.addReads(dynModule, javaBase);
572 Modules.addOpens(dynModule, mn, javaBase);
573
574 for (Class<?> c : types) {
575 ensureAccess(dynModule, c);
576 }
577 return dynModule;
578 }
579
580 private static boolean isObjectMethod(Method m) {
581 return switch (m.getName()) {
582 case "toString" -> m.getReturnType() == String.class
583 && m.getParameterCount() == 0;
584 case "hashCode" -> m.getReturnType() == int.class
585 && m.getParameterCount() == 0;
586 case "equals" -> m.getReturnType() == boolean.class
587 && m.getParameterCount() == 1
588 && JLRA.getExecutableSharedParameterTypes(m)[0] == Object.class;
589 default -> false;
590 };
591 }
592
593 /*
594 * Ensure the given module can access the given class.
595 */
596 private static void ensureAccess(Module target, Class<?> c) {
597 Module m = c.getModule();
598 // add read edge and qualified export for the target module to access
599 if (!target.canRead(m)) {
600 Modules.addReads(target, m);
601 }
602 String pn = c.getPackageName();
603 if (!m.isExported(pn, target)) {
604 Modules.addExports(m, pn, target);
605 }
606 }
607
608 private static void addElementTypes(Set<Class<?>> types, Class<?>... classes) {
609 for (var cls : classes) {
610 addElementType(types, cls);
611 }
612 }
613
614 private static void addElementType(Set<Class<?>> types, Class<?> cls) {
615 Class<?> e = cls;
616 while (e.isArray()) {
617 e = e.getComponentType();
618 }
619
620 if (!e.isPrimitive()) {
621 types.add(e);
622 }
623 }
624 }