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.io.IOException;
 29 import java.lang.classfile.*;
 30 import java.lang.classfile.attribute.ExceptionsAttribute;
 31 import java.lang.classfile.constantpool.*;
 32 import java.lang.constant.ClassDesc;
 33 import java.lang.constant.MethodTypeDesc;
 34 import java.nio.file.Files;
 35 import java.nio.file.Path;
 36 import java.util.ArrayList;
 37 import java.util.LinkedHashMap;
 38 import java.util.List;
 39 import java.util.ListIterator;
 40 import java.util.Map;
 41 import java.util.Objects;
 42 import jdk.internal.constant.ConstantUtils;
 43 import jdk.internal.constant.MethodTypeDescImpl;
 44 import jdk.internal.constant.ReferenceClassDescImpl;
 45 import sun.security.action.GetBooleanAction;
 46 
 47 import static java.lang.classfile.ClassFile.*;
 48 import java.lang.classfile.attribute.StackMapFrameInfo;
 49 import java.lang.classfile.attribute.StackMapTableAttribute;
 50 
 51 import static java.lang.constant.ConstantDescs.*;
 52 import static jdk.internal.constant.ConstantUtils.*;
 53 
 54 /**
 55  * ProxyGenerator contains the code to generate a dynamic proxy class
 56  * for the java.lang.reflect.Proxy API.
 57  * <p>
 58  * The external interface to ProxyGenerator is the static
 59  * "generateProxyClass" method.
 60  */
 61 final class ProxyGenerator {
 62 
 63     private static final ClassFile CF_CONTEXT =
 64             ClassFile.of(ClassFile.StackMapsOption.DROP_STACK_MAPS);
 65 
 66     private static final ClassDesc
 67             CD_ClassLoader = ReferenceClassDescImpl.ofValidated("Ljava/lang/ClassLoader;"),
 68             CD_Class_array = ReferenceClassDescImpl.ofValidated("[Ljava/lang/Class;"),
 69             CD_ClassNotFoundException = ReferenceClassDescImpl.ofValidated("Ljava/lang/ClassNotFoundException;"),
 70             CD_NoClassDefFoundError = ReferenceClassDescImpl.ofValidated("Ljava/lang/NoClassDefFoundError;"),
 71             CD_IllegalAccessException = ReferenceClassDescImpl.ofValidated("Ljava/lang/IllegalAccessException;"),
 72             CD_InvocationHandler = ReferenceClassDescImpl.ofValidated("Ljava/lang/reflect/InvocationHandler;"),
 73             CD_Method = ReferenceClassDescImpl.ofValidated("Ljava/lang/reflect/Method;"),
 74             CD_NoSuchMethodError = ReferenceClassDescImpl.ofValidated("Ljava/lang/NoSuchMethodError;"),
 75             CD_NoSuchMethodException = ReferenceClassDescImpl.ofValidated("Ljava/lang/NoSuchMethodException;"),
 76             CD_Object_array = ReferenceClassDescImpl.ofValidated("[Ljava/lang/Object;"),
 77             CD_Proxy = ReferenceClassDescImpl.ofValidated("Ljava/lang/reflect/Proxy;"),
 78             CD_UndeclaredThrowableException = ReferenceClassDescImpl.ofValidated("Ljava/lang/reflect/UndeclaredThrowableException;");
 79 
 80     private static final MethodTypeDesc
 81             MTD_boolean = MethodTypeDescImpl.ofValidated(CD_boolean),
 82             MTD_void_InvocationHandler = MethodTypeDescImpl.ofValidated(CD_void, CD_InvocationHandler),
 83             MTD_void_String = MethodTypeDescImpl.ofValidated(CD_void, CD_String),
 84             MTD_void_Throwable = MethodTypeDescImpl.ofValidated(CD_void, CD_Throwable),
 85             MTD_Class = MethodTypeDescImpl.ofValidated(CD_Class),
 86             MTD_Class_String_boolean_ClassLoader = MethodTypeDescImpl.ofValidated(CD_Class, CD_String, CD_boolean, CD_ClassLoader),
 87             MTD_ClassLoader = MethodTypeDescImpl.ofValidated(CD_ClassLoader),
 88             MTD_Method_String_Class_array = MethodTypeDescImpl.ofValidated(CD_Method, CD_String, CD_Class_array),
 89             MTD_MethodHandles$Lookup = MethodTypeDescImpl.ofValidated(CD_MethodHandles_Lookup),
 90             MTD_MethodHandles$Lookup_MethodHandles$Lookup = MethodTypeDescImpl.ofValidated(CD_MethodHandles_Lookup, CD_MethodHandles_Lookup),
 91             MTD_Object_Object_Method_ObjectArray = MethodTypeDescImpl.ofValidated(CD_Object, CD_Object, CD_Method, CD_Object_array),
 92             MTD_String = MethodTypeDescImpl.ofValidated(CD_String);
 93 
 94     private static final String NAME_LOOKUP_ACCESSOR = "proxyClassLookup";
 95 
 96     private static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
 97 
 98     /**
 99      * name of field for storing a proxy instance's invocation handler
100      */
101     private static final String NAME_HANDLER_FIELD = "h";
102 
103     /**
104      * debugging flag for saving generated class files
105      */
106     @SuppressWarnings("removal")
107     private static final boolean SAVE_GENERATED_FILES =
108             java.security.AccessController.doPrivileged(
109                     new GetBooleanAction(
110                             "jdk.proxy.ProxyGenerator.saveGeneratedFiles"));
111 
112     /* Preloaded ProxyMethod objects for methods in java.lang.Object */
113     private static final Method OBJECT_HASH_CODE_METHOD;
114     private static final Method OBJECT_EQUALS_METHOD;
115     private static final Method OBJECT_TO_STRING_METHOD;
116 
117     private static final String OBJECT_HASH_CODE_SIG;
118     private static final String OBJECT_EQUALS_SIG;
119     private static final String OBJECT_TO_STRING_SIG;
120 
121     static {
122         try {
123             OBJECT_HASH_CODE_METHOD = Object.class.getMethod("hashCode");
124             OBJECT_HASH_CODE_SIG = OBJECT_HASH_CODE_METHOD.toShortSignature();
125             OBJECT_EQUALS_METHOD = Object.class.getMethod("equals", Object.class);
126             OBJECT_EQUALS_SIG = OBJECT_EQUALS_METHOD.toShortSignature();
127             OBJECT_TO_STRING_METHOD = Object.class.getMethod("toString");
128             OBJECT_TO_STRING_SIG = OBJECT_TO_STRING_METHOD.toShortSignature();
129         } catch (NoSuchMethodException e) {
130             throw new NoSuchMethodError(e.getMessage());
131         }
132     }
133 
134     private final ConstantPoolBuilder cp;
135     private final List<StackMapFrameInfo.VerificationTypeInfo> classLoaderLocal, throwableStack;
136     private final NameAndTypeEntry exInit;
137     private final ClassEntry objectCE, proxyCE, uteCE, classCE;
138     private final FieldRefEntry handlerField;
139     private final InterfaceMethodRefEntry invocationHandlerInvoke;
140     private final MethodRefEntry uteInit, classGetMethod, classForName, throwableGetMessage;
141 
142 
143     /**
144      * ClassEntry for this proxy class
145      */
146     private final ClassEntry thisClassCE;
147 
148     /**
149      * Proxy interfaces
150      */
151     private final List<Class<?>> interfaces;
152 
153     /**
154      * Proxy class access flags
155      */
156     private final int accessFlags;
157 
158     /**
159      * Maps method signature string to list of ProxyMethod objects for
160      * proxy methods with that signature.
161      * Kept in insertion order to make it easier to compare old and new.
162      */
163     private final Map<String, List<ProxyMethod>> proxyMethods = new LinkedHashMap<>();
164 
165     /**
166      * Ordinal of next ProxyMethod object added to proxyMethods.
167      * Indexes are reserved for hashcode(0), equals(1), toString(2).
168      */
169     private int proxyMethodCount = 3;
170 
171     /**
172      * Construct a ProxyGenerator to generate a proxy class with the
173      * specified name and for the given interfaces.
174      * <p>
175      * A ProxyGenerator object contains the state for the ongoing
176      * generation of a particular proxy class.
177      */
178     private ProxyGenerator(String className, List<Class<?>> interfaces,
179                            int accessFlags) {
180         this.cp = ConstantPoolBuilder.of();
181         this.thisClassCE = cp.classEntry(ConstantUtils.binaryNameToDesc(className));
182         this.interfaces = interfaces;
183         this.accessFlags = accessFlags;
184         var throwable = cp.classEntry(CD_Throwable);
185         this.classLoaderLocal = List.of(StackMapFrameInfo.ObjectVerificationTypeInfo.of(cp.classEntry(CD_ClassLoader)));
186         this.throwableStack = List.of(StackMapFrameInfo.ObjectVerificationTypeInfo.of(throwable));
187         this.exInit = cp.nameAndTypeEntry(INIT_NAME, MTD_void_String);
188         this.objectCE = cp.classEntry(CD_Object);
189         this.proxyCE = cp.classEntry(CD_Proxy);
190         this.classCE = cp.classEntry(CD_Class);
191         this.handlerField = cp.fieldRefEntry(proxyCE, cp.nameAndTypeEntry(NAME_HANDLER_FIELD, CD_InvocationHandler));
192         this.invocationHandlerInvoke = cp.interfaceMethodRefEntry(CD_InvocationHandler, "invoke", MTD_Object_Object_Method_ObjectArray);
193         this.uteCE = cp.classEntry(CD_UndeclaredThrowableException);
194         this.uteInit = cp.methodRefEntry(uteCE, cp.nameAndTypeEntry(INIT_NAME, MTD_void_Throwable));
195         this.classGetMethod = cp.methodRefEntry(classCE, cp.nameAndTypeEntry("getMethod", MTD_Method_String_Class_array));
196         this.classForName = cp.methodRefEntry(classCE, cp.nameAndTypeEntry("forName", MTD_Class_String_boolean_ClassLoader));
197         this.throwableGetMessage = cp.methodRefEntry(throwable, cp.nameAndTypeEntry("getMessage", MTD_String));
198     }
199 
200     /**
201      * Generate a proxy class given a name and a list of proxy interfaces.
202      *
203      * @param name        the class name of the proxy class
204      * @param interfaces  proxy interfaces
205      * @param accessFlags access flags of the proxy class
206      */
207     @SuppressWarnings("removal")
208     static byte[] generateProxyClass(ClassLoader loader,
209                                      final String name,
210                                      List<Class<?>> interfaces,
211                                      int accessFlags) {
212         Objects.requireNonNull(interfaces);
213         ProxyGenerator gen = new ProxyGenerator(name, interfaces, accessFlags);
214         final byte[] classFile = gen.generateClassFile();
215 
216         if (SAVE_GENERATED_FILES) {
217             java.security.AccessController.doPrivileged(
218                     new java.security.PrivilegedAction<Void>() {
219                         public Void run() {
220                             try {
221                                 int i = name.lastIndexOf('.');
222                                 Path path;
223                                 if (i > 0) {
224                                     Path dir = Path.of(name.substring(0, i).replace('.', '/'));
225                                     Files.createDirectories(dir);
226                                     path = dir.resolve(name.substring(i + 1) + ".class");
227                                 } else {
228                                     path = Path.of(name + ".class");
229                                 }
230                                 Files.write(path, classFile);
231                                 return null;
232                             } catch (IOException e) {
233                                 throw new InternalError(
234                                         "I/O exception saving generated file: " + e);
235                             }
236                         }
237                     });
238         }
239 
240         return classFile;
241     }
242 
243     /**
244      * {@return the entries of the given type}
245      * @param types the {@code Class} objects, not primitive types nor array types
246      */
247     private static List<ClassEntry> toClassEntries(ConstantPoolBuilder cp, List<Class<?>> types) {
248         var ces = new ArrayList<ClassEntry>(types.size());
249         for (var t : types)
250             ces.add(cp.classEntry(ConstantUtils.binaryNameToDesc(t.getName())));
251         return ces;
252     }
253 
254     /**
255      * For a given set of proxy methods with the same signature, check
256      * that their return types are compatible according to the Proxy
257      * specification.
258      *
259      * Specifically, if there is more than one such method, then all
260      * of the return types must be reference types, and there must be
261      * one return type that is assignable to each of the rest of them.
262      */
263     private static void checkReturnTypes(List<ProxyMethod> methods) {
264         /*
265          * If there is only one method with a given signature, there
266          * cannot be a conflict.  This is the only case in which a
267          * primitive (or void) return type is allowed.
268          */
269         if (methods.size() < 2) {
270             return;
271         }
272 
273         /*
274          * List of return types that are not yet known to be
275          * assignable from ("covered" by) any of the others.
276          */
277         List<Class<?>> uncoveredReturnTypes = new ArrayList<>(1);
278 
279         nextNewReturnType:
280         for (ProxyMethod pm : methods) {
281             Class<?> newReturnType = pm.returnType;
282             if (newReturnType.isPrimitive()) {
283                 throw new IllegalArgumentException(
284                         "methods with same signature " +
285                                 pm.shortSignature +
286                                 " but incompatible return types: " +
287                                 newReturnType.getName() + " and others");
288             }
289             boolean added = false;
290 
291             /*
292              * Compare the new return type to the existing uncovered
293              * return types.
294              */
295             ListIterator<Class<?>> liter = uncoveredReturnTypes.listIterator();
296             while (liter.hasNext()) {
297                 Class<?> uncoveredReturnType = liter.next();
298 
299                 /*
300                  * If an existing uncovered return type is assignable
301                  * to this new one, then we can forget the new one.
302                  */
303                 if (newReturnType.isAssignableFrom(uncoveredReturnType)) {
304                     assert !added;
305                     continue nextNewReturnType;
306                 }
307 
308                 /*
309                  * If the new return type is assignable to an existing
310                  * uncovered one, then should replace the existing one
311                  * with the new one (or just forget the existing one,
312                  * if the new one has already be put in the list).
313                  */
314                 if (uncoveredReturnType.isAssignableFrom(newReturnType)) {
315                     // (we can assume that each return type is unique)
316                     if (!added) {
317                         liter.set(newReturnType);
318                         added = true;
319                     } else {
320                         liter.remove();
321                     }
322                 }
323             }
324 
325             /*
326              * If we got through the list of existing uncovered return
327              * types without an assignability relationship, then add
328              * the new return type to the list of uncovered ones.
329              */
330             if (!added) {
331                 uncoveredReturnTypes.add(newReturnType);
332             }
333         }
334 
335         /*
336          * We shouldn't end up with more than one return type that is
337          * not assignable from any of the others.
338          */
339         if (uncoveredReturnTypes.size() > 1) {
340             ProxyMethod pm = methods.getFirst();
341             throw new IllegalArgumentException(
342                     "methods with same signature " +
343                             pm.shortSignature +
344                             " but incompatible return types: " + uncoveredReturnTypes);
345         }
346     }
347 
348     /**
349      * Given the exceptions declared in the throws clause of a proxy method,
350      * compute the exceptions that need to be caught from the invocation
351      * handler's invoke method and rethrown intact in the method's
352      * implementation before catching other Throwables and wrapping them
353      * in UndeclaredThrowableExceptions.
354      *
355      * The exceptions to be caught are returned in a List object.  Each
356      * exception in the returned list is guaranteed to not be a subclass of
357      * any of the other exceptions in the list, so the catch blocks for
358      * these exceptions may be generated in any order relative to each other.
359      *
360      * Error and RuntimeException are each always contained by the returned
361      * list (if none of their superclasses are contained), since those
362      * unchecked exceptions should always be rethrown intact, and thus their
363      * subclasses will never appear in the returned list.
364      *
365      * The returned List will be empty if java.lang.Throwable is in the
366      * given list of declared exceptions, indicating that no exceptions
367      * need to be caught.
368      */
369     private static List<Class<?>> computeUniqueCatchList(Class<?>[] exceptions) {
370         List<Class<?>> uniqueList = new ArrayList<>();
371         // unique exceptions to catch
372 
373         uniqueList.add(Error.class);            // always catch/rethrow these
374         uniqueList.add(RuntimeException.class);
375 
376         nextException:
377         for (Class<?> ex : exceptions) {
378             if (ex.isAssignableFrom(Throwable.class)) {
379                 /*
380                  * If Throwable is declared to be thrown by the proxy method,
381                  * then no catch blocks are necessary, because the invoke
382                  * can, at most, throw Throwable anyway.
383                  */
384                 uniqueList.clear();
385                 break;
386             } else if (!Throwable.class.isAssignableFrom(ex)) {
387                 /*
388                  * Ignore types that cannot be thrown by the invoke method.
389                  */
390                 continue;
391             }
392             /*
393              * Compare this exception against the current list of
394              * exceptions that need to be caught:
395              */
396             for (int j = 0; j < uniqueList.size(); ) {
397                 Class<?> ex2 = uniqueList.get(j);
398                 if (ex2.isAssignableFrom(ex)) {
399                     /*
400                      * if a superclass of this exception is already on
401                      * the list to catch, then ignore this one and continue;
402                      */
403                     continue nextException;
404                 } else if (ex.isAssignableFrom(ex2)) {
405                     /*
406                      * if a subclass of this exception is on the list
407                      * to catch, then remove it;
408                      */
409                     uniqueList.remove(j);
410                 } else {
411                     j++;        // else continue comparing.
412                 }
413             }
414             // This exception is unique (so far): add it to the list to catch.
415             uniqueList.add(ex);
416         }
417         return uniqueList;
418     }
419 
420     /**
421      * Add to the given list all of the types in the "from" array that
422      * are not already contained in the list and are assignable to at
423      * least one of the types in the "with" array.
424      * <p>
425      * This method is useful for computing the greatest common set of
426      * declared exceptions from duplicate methods inherited from
427      * different interfaces.
428      */
429     private static void collectCompatibleTypes(Class<?>[] from,
430                                                Class<?>[] with,
431                                                List<Class<?>> list) {
432         for (Class<?> fc : from) {
433             if (!list.contains(fc)) {
434                 for (Class<?> wc : with) {
435                     if (wc.isAssignableFrom(fc)) {
436                         list.add(fc);
437                         break;
438                     }
439                 }
440             }
441         }
442     }
443 
444     /**
445      * Generate a class file for the proxy class.  This method drives the
446      * class file generation process.






447      */
448     private byte[] generateClassFile() {
449         /*
450          * Add proxy methods for the hashCode, equals,
451          * and toString methods of java.lang.Object.  This is done before
452          * the methods from the proxy interfaces so that the methods from
453          * java.lang.Object take precedence over duplicate methods in the
454          * proxy interfaces.
455          */
456         addProxyMethod(new ProxyMethod(OBJECT_HASH_CODE_METHOD, OBJECT_HASH_CODE_SIG, "m0"));
457         addProxyMethod(new ProxyMethod(OBJECT_EQUALS_METHOD, OBJECT_EQUALS_SIG, "m1"));
458         addProxyMethod(new ProxyMethod(OBJECT_TO_STRING_METHOD, OBJECT_TO_STRING_SIG, "m2"));
459 
460         /*
461          * Accumulate all of the methods from the proxy interfaces.
462          */
463         for (Class<?> intf : interfaces) {
464             for (Method m : intf.getMethods()) {
465                 if (!Modifier.isStatic(m.getModifiers())) {
466                     addProxyMethod(m, intf);
467                 }
468             }
469         }
470 
471         /*
472          * For each set of proxy methods with the same signature,
473          * verify that the methods' return types are compatible.
474          */
475         for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
476             checkReturnTypes(sigmethods);
477         }
478 
479         return CF_CONTEXT.build(thisClassCE, cp, clb -> {
480             clb.withSuperclass(proxyCE);
481             clb.withFlags(accessFlags);
482             clb.withInterfaces(toClassEntries(cp, interfaces));
483             generateConstructor(clb);
484 
485             for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
486                 for (ProxyMethod pm : sigmethods) {
487                     // add static field for the Method object
488                     clb.withField(pm.methodFieldName, CD_Method, ACC_PRIVATE | ACC_STATIC | ACC_FINAL);
489 
490                     // Generate code for proxy method
491                     pm.generateMethod(clb);
492                 }
493             }
494 
495             generateStaticInitializer(clb);
496             generateLookupAccessor(clb);
497         });
498     }
499 
500     /**
501      * Add another method to be proxied, either by creating a new
502      * ProxyMethod object or augmenting an old one for a duplicate
503      * method.
504      *
505      * "fromClass" indicates the proxy interface that the method was
506      * found through, which may be different from (a subinterface of)
507      * the method's "declaring class".  Note that the first Method
508      * object passed for a given name and descriptor identifies the
509      * Method object (and thus the declaring class) that will be
510      * passed to the invocation handler's "invoke" method for a given
511      * set of duplicate methods.
512      */
513     private void addProxyMethod(Method m, Class<?> fromClass) {
514         Class<?> returnType = m.getReturnType();
515         Class<?>[] exceptionTypes = m.getSharedExceptionTypes();
516 
517         String sig = m.toShortSignature();
518         List<ProxyMethod> sigmethods = proxyMethodsFor(sig);
519         for (ProxyMethod pm : sigmethods) {
520             if (returnType == pm.returnType) {
521                 /*
522                  * Found a match: reduce exception types to the
523                  * greatest set of exceptions that can be thrown
524                  * compatibly with the throws clauses of both
525                  * overridden methods.
526                  */
527                 List<Class<?>> legalExceptions = new ArrayList<>();
528                 collectCompatibleTypes(
529                         exceptionTypes, pm.exceptionTypes, legalExceptions);
530                 collectCompatibleTypes(
531                         pm.exceptionTypes, exceptionTypes, legalExceptions);
532                 pm.exceptionTypes = legalExceptions.toArray(EMPTY_CLASS_ARRAY);
533                 return;
534             }
535         }
536         sigmethods.add(new ProxyMethod(m, sig, returnType,
537                 exceptionTypes, fromClass, "m" + proxyMethodCount++));
538     }
539 
540     private List<ProxyMethod> proxyMethodsFor(String sig) {
541         return proxyMethods.computeIfAbsent(sig, _ -> new ArrayList<>(3));
542     }
543 
544     /**
545      * Add an existing ProxyMethod (hashcode, equals, toString).
546      *
547      * @param pm an existing ProxyMethod
548      */
549     private void addProxyMethod(ProxyMethod pm) {
550         proxyMethodsFor(pm.shortSignature).add(pm);
551     }
552 
553     /**
554      * Generate the constructor method for the proxy class.
555      */
556     private void generateConstructor(ClassBuilder clb) {
557         clb.withMethodBody(INIT_NAME, MTD_void_InvocationHandler, ACC_PUBLIC, cob -> cob
558                .aload(0)
559                .aload(1)
560                .invokespecial(cp.methodRefEntry(proxyCE,
561                    cp.nameAndTypeEntry(INIT_NAME, MTD_void_InvocationHandler)))
562                .return_());
563     }
564 
565     /**
566      * Generate the class initializer.
567      * Discussion: Currently, for Proxy to work with SecurityManager,
568      * we rely on the parameter classes of the methods to be computed
569      * from Proxy instead of via user code paths like bootstrap method
570      * lazy evaluation. That might change if we can pass in the live
571      * Method objects directly..
572      */
573     private void generateStaticInitializer(ClassBuilder clb) {
574         clb.withMethodBody(CLASS_INIT_NAME, MTD_void, ACC_STATIC, cob -> {
575             // Put ClassLoader at local variable index 0, used by
576             // Class.forName(String, boolean, ClassLoader) calls
577             cob.ldc(thisClassCE)
578                .invokevirtual(cp.methodRefEntry(classCE,
579                        cp.nameAndTypeEntry("getClassLoader", MTD_ClassLoader)))
580                .astore(0);
581             var ts = cob.newBoundLabel();
582             for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
583                 for (ProxyMethod pm : sigmethods) {
584                     pm.codeFieldInitialization(cob);
585                 }
586             }
587             cob.return_();
588             var c1 = cob.newBoundLabel();
589             var nsmError = cp.classEntry(CD_NoSuchMethodError);
590             cob.exceptionCatch(ts, c1, c1, CD_NoSuchMethodException)
591                .new_(nsmError)
592                .dup_x1()
593                .swap()
594                .invokevirtual(throwableGetMessage)
595                .invokespecial(cp.methodRefEntry(nsmError, exInit))
596                .athrow();
597             var c2 = cob.newBoundLabel();
598             var ncdfError = cp.classEntry(CD_NoClassDefFoundError);
599             cob.exceptionCatch(ts, c1, c2, CD_ClassNotFoundException)
600                .new_(ncdfError)
601                .dup_x1()
602                .swap()
603                .invokevirtual(throwableGetMessage)
604                .invokespecial(cp.methodRefEntry(ncdfError, exInit))
605                .athrow();
606             cob.with(StackMapTableAttribute.of(List.of(
607                        StackMapFrameInfo.of(c1, classLoaderLocal, throwableStack),
608                        StackMapFrameInfo.of(c2, classLoaderLocal, throwableStack))));
609 
610         });
611     }
612 
613     /**
614      * Generate the static lookup accessor method that returns the Lookup
615      * on this proxy class if the caller's lookup class is java.lang.reflect.Proxy;
616      * otherwise, IllegalAccessException is thrown
617      */
618     private void generateLookupAccessor(ClassBuilder clb) {
619         clb.withMethod(NAME_LOOKUP_ACCESSOR,
620                 MTD_MethodHandles$Lookup_MethodHandles$Lookup,
621                 ACC_PRIVATE | ACC_STATIC,
622                 mb -> mb.with(ExceptionsAttribute.of(List.of(mb.constantPool().classEntry(CD_IllegalAccessException))))
623                         .withCode(cob -> {
624                             Label failLabel = cob.newLabel();
625                             ClassEntry mhl = cp.classEntry(CD_MethodHandles_Lookup);
626                             ClassEntry iae = cp.classEntry(CD_IllegalAccessException);
627                             cob.aload(0)
628                                .invokevirtual(cp.methodRefEntry(mhl, cp.nameAndTypeEntry("lookupClass", MTD_Class)))
629                                .ldc(proxyCE)
630                                .if_acmpne(failLabel)
631                                .aload(0)
632                                .invokevirtual(cp.methodRefEntry(mhl, cp.nameAndTypeEntry("hasFullPrivilegeAccess", MTD_boolean)))
633                                .ifeq(failLabel)
634                                .invokestatic(CD_MethodHandles, "lookup", MTD_MethodHandles$Lookup)
635                                .areturn()
636                                .labelBinding(failLabel)
637                                .new_(iae)
638                                .dup()
639                                .aload(0)
640                                .invokevirtual(cp.methodRefEntry(mhl, cp.nameAndTypeEntry("toString", MTD_String)))
641                                .invokespecial(cp.methodRefEntry(iae, exInit))
642                                .athrow()
643                                .with(StackMapTableAttribute.of(List.of(
644                                        StackMapFrameInfo.of(failLabel,
645                                                List.of(StackMapFrameInfo.ObjectVerificationTypeInfo.of(mhl)),
646                                                List.of()))));
647                         }));
648     }
649 
650     /**
651      * A ProxyMethod object represents a proxy method in the proxy class
652      * being generated: a method whose implementation will encode and
653      * dispatch invocations to the proxy instance's invocation handler.
654      */
655     private class ProxyMethod {
656 
657         private final Method method;
658         private final String shortSignature;
659         private final Class<?> fromClass;
660         private final Class<?> returnType;
661         private final String methodFieldName;
662         private Class<?>[] exceptionTypes;
663         private final FieldRefEntry methodField;
664 
665         private ProxyMethod(Method method, String sig,
666                             Class<?> returnType, Class<?>[] exceptionTypes,
667                             Class<?> fromClass, String methodFieldName) {
668             this.method = method;
669             this.shortSignature = sig;
670             this.returnType = returnType;
671             this.exceptionTypes = exceptionTypes;
672             this.fromClass = fromClass;
673             this.methodFieldName = methodFieldName;
674             this.methodField = cp.fieldRefEntry(thisClassCE,
675                 cp.nameAndTypeEntry(methodFieldName, CD_Method));
676         }
677 
678         private Class<?>[] parameterTypes() {
679             return method.getSharedParameterTypes();
680         }
681 
682         /**
683          * Create a new specific ProxyMethod with a specific field name
684          *
685          * @param method          The method for which to create a proxy
686          */
687         private ProxyMethod(Method method, String sig, String methodFieldName) {
688             this(method, sig, method.getReturnType(),
689                  method.getSharedExceptionTypes(), method.getDeclaringClass(), methodFieldName);
690         }
691 
692         /**
693          * Generate this method, including the code and exception table entry.
694          */
695         private void generateMethod(ClassBuilder clb) {
696             var desc = methodTypeDesc(returnType, parameterTypes());
697             int accessFlags = (method.isVarArgs()) ? ACC_VARARGS | ACC_PUBLIC | ACC_FINAL
698                                                    : ACC_PUBLIC | ACC_FINAL;
699             clb.withMethod(method.getName(), desc, accessFlags, mb ->
700                   mb.with(ExceptionsAttribute.of(toClassEntries(cp, List.of(exceptionTypes))))
701                     .withCode(cob -> {
702                         var catchList = computeUniqueCatchList(exceptionTypes);
703                         cob.aload(cob.receiverSlot())
704                            .getfield(handlerField)
705                            .aload(cob.receiverSlot())
706                            .getstatic(methodField);
707                         Class<?>[] parameterTypes = parameterTypes();
708                         if (parameterTypes.length > 0) {
709                             // Create an array and fill with the parameters converting primitives to wrappers
710                             cob.loadConstant(parameterTypes.length)
711                                .anewarray(objectCE);
712                             for (int i = 0; i < parameterTypes.length; i++) {
713                                 cob.dup()
714                                    .loadConstant(i);
715                                 codeWrapArgument(cob, parameterTypes[i], cob.parameterSlot(i));
716                                 cob.aastore();
717                             }
718                         } else {
719                             cob.aconst_null();
720                         }
721 
722                         cob.invokeinterface(invocationHandlerInvoke);
723 
724                         if (returnType == void.class) {
725                             cob.pop()
726                                .return_();
727                         } else {
728                             codeUnwrapReturnValue(cob, returnType);
729                         }
730                         if (!catchList.isEmpty()) {
731                             var c1 = cob.newBoundLabel();
732                             for (var exc : catchList) {
733                                 cob.exceptionCatch(cob.startLabel(), c1, c1, referenceClassDesc(exc));
734                             }
735                             cob.athrow();   // just rethrow the exception
736                             var c2 = cob.newBoundLabel();
737                             cob.exceptionCatchAll(cob.startLabel(), c1, c2)
738                                .new_(uteCE)
739                                .dup_x1()
740                                .swap()
741                                .invokespecial(uteInit)
742                                .athrow()
743                                .with(StackMapTableAttribute.of(List.of(
744                                     StackMapFrameInfo.of(c1, List.of(), throwableStack),
745                                     StackMapFrameInfo.of(c2, List.of(), throwableStack))));
746                         }
747                     }));
748         }
749 
750         /**
751          * Generate code for wrapping an argument of the given type
752          * whose value can be found at the specified local variable
753          * index, in order for it to be passed (as an Object) to the
754          * invocation handler's "invoke" method.
755          */
756         private void codeWrapArgument(CodeBuilder cob, Class<?> type, int slot) {
757             if (type.isPrimitive()) {
758                 cob.loadLocal(TypeKind.from(type).asLoadable(), slot);
759                 PrimitiveTypeInfo prim = PrimitiveTypeInfo.get(type);
760                 cob.invokestatic(prim.wrapperMethodRef(cp));
761             } else {
762                 cob.aload(slot);
763             }
764         }
765 
766         /**
767          * Generate code for unwrapping a return value of the given
768          * type from the invocation handler's "invoke" method (as type
769          * Object) to its correct type.
770          */
771         private void codeUnwrapReturnValue(CodeBuilder cob, Class<?> type) {
772             if (type.isPrimitive()) {
773                 PrimitiveTypeInfo prim = PrimitiveTypeInfo.get(type);
774 
775                 cob.checkcast(prim.wrapperClass)
776                    .invokevirtual(prim.unwrapMethodRef(cp))
777                    .return_(TypeKind.from(type).asLoadable());
778             } else {
779                 cob.checkcast(referenceClassDesc(type))
780                    .areturn();
781             }
782         }
783 
784         /**
785          * Generate code for initializing the static field that stores
786          * the Method object for this proxy method. A class loader is
787          * anticipated at local variable index 0.
788          * The generated code must be run in an AccessController.doPrivileged
789          * block if a SecurityManager is present, as otherwise the code
790          * cannot pass {@code null} ClassLoader to forName.
791          */
792         private void codeFieldInitialization(CodeBuilder cob) {
793             var cp = cob.constantPool();
794             codeClassForName(cob, fromClass);
795 
796             Class<?>[] parameterTypes = parameterTypes();
797             cob.ldc(method.getName())
798                .loadConstant(parameterTypes.length)
799                .anewarray(classCE);
800 
801             // Construct an array with the parameter types mapping primitives to Wrapper types
802             for (int i = 0; i < parameterTypes.length; i++) {
803                 cob.dup()
804                    .loadConstant(i);
805                 if (parameterTypes[i].isPrimitive()) {
806                     PrimitiveTypeInfo prim = PrimitiveTypeInfo.get(parameterTypes[i]);
807                     cob.getstatic(prim.typeFieldRef(cp));
808                 } else {
809                     codeClassForName(cob, parameterTypes[i]);
810                 }
811                 cob.aastore();
812             }
813             // lookup the method
814             cob.invokevirtual(classGetMethod)
815                .putstatic(methodField);
816         }
817 
818         /*
819          * =============== Code Generation Utility Methods ===============
820          */
821 
822         /**
823          * Generate code to invoke the Class.forName with the name of the given
824          * class to get its Class object at runtime.  The code is written to
825          * the supplied stream.  Note that the code generated by this method
826          * may cause the checked ClassNotFoundException to be thrown. A class
827          * loader is anticipated at local variable index 0.
828          */
829         private void codeClassForName(CodeBuilder cob, Class<?> cl) {
830             if (cl == Object.class) {
831                 cob.ldc(objectCE);
832             } else {
833                 cob.ldc(cl.getName())
834                         .iconst_0() // false
835                         .aload(0)// classLoader
836                         .invokestatic(classForName);
837             }
838         }
839 
840         @Override
841         public String toString() {
842             return method.toShortString();
843         }
844     }
845 
846     /**
847      * A PrimitiveTypeInfo object contains bytecode-related information about
848      * a primitive type in its instance fields. The struct for a particular
849      * primitive type can be obtained using the static "get" method.
850      */
851     private enum PrimitiveTypeInfo {
852         BYTE(byte.class, CD_byte, CD_Byte),
853         CHAR(char.class, CD_char, CD_Character),
854         DOUBLE(double.class, CD_double, CD_Double),
855         FLOAT(float.class, CD_float, CD_Float),
856         INT(int.class, CD_int, CD_Integer),
857         LONG(long.class, CD_long, CD_Long),
858         SHORT(short.class, CD_short, CD_Short),
859         BOOLEAN(boolean.class, CD_boolean, CD_Boolean);
860 
861         /**
862          * wrapper class
863          */
864         private final ClassDesc wrapperClass;
865         /**
866          * wrapper factory method type
867          */
868         private final MethodTypeDesc wrapperMethodType;
869         /**
870          * wrapper class method name for retrieving primitive value
871          */
872         private final String unwrapMethodName;
873         /**
874          * wrapper class method type for retrieving primitive value
875          */
876         private final MethodTypeDesc unwrapMethodType;
877 
878         PrimitiveTypeInfo(Class<?> primitiveClass, ClassDesc baseType, ClassDesc wrapperClass) {
879             assert baseType.isPrimitive();
880             this.wrapperClass = wrapperClass;
881             this.wrapperMethodType = MethodTypeDescImpl.ofValidated(wrapperClass, baseType);
882             this.unwrapMethodName = primitiveClass.getName() + "Value";
883             this.unwrapMethodType = MethodTypeDescImpl.ofValidated(baseType);
884         }
885 
886         public static PrimitiveTypeInfo get(Class<?> cl) {
887             // Uses if chain for speed: 8284880
888             if (cl == int.class)     return INT;
889             if (cl == long.class)    return LONG;
890             if (cl == boolean.class) return BOOLEAN;
891             if (cl == short.class)   return SHORT;
892             if (cl == byte.class)    return BYTE;
893             if (cl == char.class)    return CHAR;
894             if (cl == float.class)   return FLOAT;
895             if (cl == double.class)  return DOUBLE;
896             throw new AssertionError(cl);
897         }
898 
899         public MethodRefEntry wrapperMethodRef(ConstantPoolBuilder cp) {
900             return cp.methodRefEntry(wrapperClass, "valueOf", wrapperMethodType);
901         }
902 
903         public MethodRefEntry unwrapMethodRef(ConstantPoolBuilder cp) {
904             return cp.methodRefEntry(wrapperClass, unwrapMethodName, unwrapMethodType);
905         }
906 
907         public FieldRefEntry typeFieldRef(ConstantPoolBuilder cp) {
908             return cp.fieldRefEntry(wrapperClass, "TYPE", CD_Class);
909         }
910     }
911 }
--- EOF ---