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