1 /*
2 * Copyright (c) 2012, 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
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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 *
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24 */
25
26 package java.lang.invoke;
27
28 import java.io.Serializable;
29 import java.util.Arrays;
30 import java.lang.reflect.Array;
31 import java.util.Objects;
32
33 /**
34 * <p>Methods to facilitate the creation of simple "function objects" that
35 * implement one or more interfaces by delegation to a provided {@link MethodHandle},
36 * possibly after type adaptation and partial evaluation of arguments. These
37 * methods are typically used as <em>bootstrap methods</em> for {@code invokedynamic}
38 * call sites, to support the <em>lambda expression</em> and <em>method
39 * reference expression</em> features of the Java Programming Language.
40 *
41 * <p>Indirect access to the behavior specified by the provided {@code MethodHandle}
42 * proceeds in order through three phases:
43 * <ul>
44 * <li><p><em>Linkage</em> occurs when the methods in this class are invoked.
45 * They take as arguments an interface to be implemented (typically a
46 * <em>functional interface</em>, one with a single abstract method), a
47 * name and signature of a method from that interface to be implemented, a
48 * {@linkplain MethodHandleInfo direct method handle} describing the desired
49 * implementation behavior for that method, and possibly other additional
50 * metadata, and produce a {@link CallSite} whose target can be used to
51 * create suitable function objects.
52 *
53 * <p>Linkage may involve dynamically loading a new class that implements
54 * the target interface, or re-using a suitable existing class.
55 *
56 * <p>The {@code CallSite} can be considered a "factory" for function
57 * objects and so these linkage methods are referred to as
58 * "metafactories".</li>
59 *
60 * <li><p><em>Capture</em> occurs when the {@code CallSite}'s target is
61 * invoked, typically through an {@code invokedynamic} call site,
62 * producing a function object. This may occur many times for
63 * a single factory {@code CallSite}.
64 *
65 * <p>If the behavior {@code MethodHandle} has additional parameters beyond
66 * those of the specified interface method, these are referred to as
67 * <em>captured parameters</em>, which must be provided as arguments to the
68 * {@code CallSite} target. The expected number and types of captured
69 * parameters are determined during linkage.
70 *
71 * <p>Capture may involve allocation of a new function object, or may return
72 * a suitable existing function object. The identity of a function object
73 * produced by capture is unpredictable, and therefore identity-sensitive
74 * operations (such as reference equality, object locking, and {@code
75 * System.identityHashCode()}) may produce different results in different
76 * implementations, or even upon different invocations in the same
77 * implementation.</li>
78 *
79 * <li><p><em>Invocation</em> occurs when an implemented interface method is
80 * invoked on a function object. This may occur many times for a single
81 * function object. The method referenced by the implementation
82 * {@code MethodHandle} is invoked, passing to it the captured arguments and
83 * the invocation arguments. The result of the method is returned.
84 * </li>
85 * </ul>
86 *
87 * <p>It is sometimes useful to restrict the set of inputs or results permitted
88 * at invocation. For example, when the generic interface {@code Predicate<T>}
89 * is parameterized as {@code Predicate<String>}, the input must be a
90 * {@code String}, even though the method to implement allows any {@code Object}.
91 * At linkage time, an additional {@link MethodType} parameter describes the
92 * "dynamic" method type; on invocation, the arguments and eventual result
93 * are checked against this {@code MethodType}.
94 *
95 * <p>This class provides two forms of linkage methods: a standard version
96 * ({@link #metafactory(MethodHandles.Lookup, String, MethodType, MethodType, MethodHandle, MethodType)})
97 * using an optimized protocol, and an alternate version
98 * {@link #altMetafactory(MethodHandles.Lookup, String, MethodType, Object...)}).
99 * The alternate version is a generalization of the standard version, providing
100 * additional control over the behavior of the generated function objects via
101 * flags and additional arguments. The alternate version adds the ability to
102 * manage the following attributes of function objects:
103 *
104 * <ul>
105 * <li><em>Multiple methods.</em> It is sometimes useful to implement multiple
106 * variations of the method signature, involving argument or return type
107 * adaptation. This occurs when multiple distinct VM signatures for a method
108 * are logically considered to be the same method by the language. The
109 * flag {@code FLAG_BRIDGES} indicates that a list of additional
110 * {@code MethodType}s will be provided, each of which will be implemented
111 * by the resulting function object. These methods will share the same
112 * name and instantiated type.</li>
113 *
114 * <li><em>Multiple interfaces.</em> If needed, more than one interface
115 * can be implemented by the function object. (These additional interfaces
116 * are typically marker interfaces with no methods.) The flag {@code FLAG_MARKERS}
117 * indicates that a list of additional interfaces will be provided, each of
118 * which should be implemented by the resulting function object.</li>
119 *
120 * <li><em>Serializability.</em> The generated function objects do not
121 * generally support serialization. If desired, {@code FLAG_SERIALIZABLE}
122 * can be used to indicate that the function objects should be serializable.
123 * Serializable function objects will use, as their serialized form,
124 * instances of the class {@code SerializedLambda}, which requires additional
125 * assistance from the capturing class (the class described by the
126 * {@link MethodHandles.Lookup} parameter {@code caller}); see
127 * {@link SerializedLambda} for details.</li>
128 * </ul>
129 *
130 * <p>Assume the linkage arguments are as follows:
131 * <ul>
132 * <li>{@code factoryType} (describing the {@code CallSite} signature) has
133 * K parameters of types (D1..Dk) and return type Rd;</li>
134 * <li>{@code interfaceMethodType} (describing the implemented method type) has N
135 * parameters, of types (U1..Un) and return type Ru;</li>
136 * <li>{@code implementation} (the {@code MethodHandle} providing the
137 * implementation) has M parameters, of types (A1..Am) and return type Ra
138 * (if the method describes an instance method, the method type of this
139 * method handle already includes an extra first argument corresponding to
140 * the receiver);</li>
141 * <li>{@code dynamicMethodType} (allowing restrictions on invocation)
142 * has N parameters, of types (T1..Tn) and return type Rt.</li>
143 * </ul>
144 *
145 * <p>Then the following linkage invariants must hold:
146 * <ul>
147 * <li>{@code interfaceMethodType} and {@code dynamicMethodType} have the same
148 * arity N, and for i=1..N, Ti and Ui are the same type, or Ti and Ui are
149 * both reference types and Ti is a subtype of Ui</li>
150 * <li>Either Rt and Ru are the same type, or both are reference types and
151 * Rt is a subtype of Ru</li>
152 * <li>K + N = M</li>
153 * <li>For i=1..K, Di = Ai</li>
154 * <li>For i=1..N, Ti is adaptable to Aj, where j=i+k</li>
155 * <li>The return type Rt is void, or the return type Ra is not void and is
156 * adaptable to Rt</li>
157 * </ul>
158 *
159 * <p>Further, at capture time, if {@code implementation} corresponds to an instance
160 * method, and there are any capture arguments ({@code K > 0}), then the first
161 * capture argument (corresponding to the receiver) must be non-null.
162 *
163 * <p>A type Q is considered adaptable to S as follows:
164 * <table class="striped">
165 * <caption style="display:none">adaptable types</caption>
166 * <thead>
167 * <tr><th scope="col">Q</th><th scope="col">S</th><th scope="col">Link-time checks</th><th scope="col">Invocation-time checks</th></tr>
168 * </thead>
169 * <tbody>
170 * <tr>
171 * <th scope="row">Primitive</th><th scope="row">Primitive</th>
172 * <td>Q can be converted to S via a primitive widening conversion</td>
173 * <td>None</td>
174 * </tr>
175 * <tr>
176 * <th scope="row">Primitive</th><th scope="row">Reference</th>
177 * <td>S is a supertype of the Wrapper(Q)</td>
178 * <td>Cast from Wrapper(Q) to S</td>
179 * </tr>
180 * <tr>
181 * <th scope="row">Reference</th><th scope="row">Primitive</th>
182 * <td>for parameter types: Q is a primitive wrapper and Primitive(Q)
183 * can be widened to S
184 * <br>for return types: If Q is a primitive wrapper, check that
185 * Primitive(Q) can be widened to S</td>
186 * <td>If Q is not a primitive wrapper, cast Q to the base Wrapper(S);
187 * for example Number for numeric types</td>
188 * </tr>
189 * <tr>
190 * <th scope="row">Reference</th><th scope="row">Reference</th>
191 * <td>for parameter types: S is a supertype of Q
192 * <br>for return types: none</td>
193 * <td>Cast from Q to S</td>
194 * </tr>
195 * </tbody>
196 * </table>
197 *
198 * @apiNote These linkage methods are designed to support the evaluation
199 * of <em>lambda expressions</em> and <em>method references</em> in the Java
200 * Language. For every lambda expressions or method reference in the source code,
201 * there is a target type which is a functional interface. Evaluating a lambda
202 * expression produces an object of its target type. The recommended mechanism
203 * for evaluating lambda expressions is to desugar the lambda body to a method,
204 * invoke an invokedynamic call site whose static argument list describes the
205 * sole method of the functional interface and the desugared implementation
206 * method, and returns an object (the lambda object) that implements the target
207 * type. (For method references, the implementation method is simply the
208 * referenced method; no desugaring is needed.)
209 *
210 * <p>The argument list of the implementation method and the argument list of
211 * the interface method(s) may differ in several ways. The implementation
212 * methods may have additional arguments to accommodate arguments captured by
213 * the lambda expression; there may also be differences resulting from permitted
214 * adaptations of arguments, such as casting, boxing, unboxing, and primitive
215 * widening. (Varargs adaptations are not handled by the metafactories; these are
216 * expected to be handled by the caller.)
217 *
218 * <p>Invokedynamic call sites have two argument lists: a static argument list
219 * and a dynamic argument list. The static argument list is stored in the
220 * constant pool; the dynamic argument is pushed on the operand stack at capture
221 * time. The bootstrap method has access to the entire static argument list
222 * (which in this case, includes information describing the implementation method,
223 * the target interface, and the target interface method(s)), as well as a
224 * method signature describing the number and static types (but not the values)
225 * of the dynamic arguments and the static return type of the invokedynamic site.
226 *
227 * <p>The implementation method is described with a direct method handle
228 * referencing a method or constructor. In theory, any method handle could be
229 * used, but this is not compatible with some implementation techniques and
230 * would complicate the work implementations must do.
231 *
232 * <p>Uses besides evaluation of lambda expressions and method references are
233 * unintended. These linkage methods may change their unspecified behaviors at
234 * any time to better suit the Java language features they were designed to
235 * support, and such changes may impact unintended uses. Unintended uses of
236 * these linkage methods may lead to resource leaks, or other unspecified
237 * negative effects.
238 *
239 * @implNote In the reference implementation, the classes implementing the created
240 * function objects are strongly reachable from the defining class loader of the
241 * caller, like classes and interfaces in Java source code. This technique
242 * reduces heap memory use, but as a consequence, the implementation classes can
243 * be unloaded only if the caller class can be unloaded. In particular, if the
244 * caller is a {@linkplain MethodHandles.Lookup.ClassOption#STRONG weak hidden
245 * class}, the implementation class, a strong hidden class, may not be unloaded
246 * even if the caller may be unloaded.
247 *
248 * @since 1.8
249 */
250 public final class LambdaMetafactory {
251
252 private LambdaMetafactory() {}
253
254 /** Flag for {@link #altMetafactory} indicating the lambda object
255 * must be serializable */
256 public static final int FLAG_SERIALIZABLE = 1 << 0;
257
258 /**
259 * Flag for {@link #altMetafactory} indicating the lambda object implements
260 * other interfaces besides {@code Serializable}
261 */
262 public static final int FLAG_MARKERS = 1 << 1;
263
264 /**
265 * Flag for alternate metafactories indicating the lambda object requires
266 * additional methods that invoke the {@code implementation}
267 */
268 public static final int FLAG_BRIDGES = 1 << 2;
269
270 private static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
271 private static final MethodType[] EMPTY_MT_ARRAY = new MethodType[0];
272
273 // LambdaMetafactory bootstrap methods are startup sensitive, and may be
274 // special cased in java.lang.invoke.BootstrapMethodInvoker to ensure
275 // methods are invoked with exact type information to avoid generating
276 // code for runtime checks. Take care any changes or additions here are
277 // reflected there as appropriate.
278
279 /**
280 * Facilitates the creation of simple "function objects" that implement one
281 * or more interfaces by delegation to a provided {@link MethodHandle},
282 * after appropriate type adaptation and partial evaluation of arguments.
283 * Typically used as a <em>bootstrap method</em> for {@code invokedynamic}
284 * call sites, to support the <em>lambda expression</em> and <em>method
285 * reference expression</em> features of the Java Programming Language.
286 *
287 * <p>This is the standard, streamlined metafactory; additional flexibility
288 * is provided by {@link #altMetafactory(MethodHandles.Lookup, String, MethodType, Object...)}.
289 * A general description of the behavior of this method is provided
290 * {@link LambdaMetafactory above}.
291 *
292 * <p>When the target of the {@code CallSite} returned from this method is
293 * invoked, the resulting function objects are instances of a class which
294 * implements the interface named by the return type of {@code factoryType},
295 * declares a method with the name given by {@code interfaceMethodName} and the
296 * signature given by {@code interfaceMethodType}. It may also override additional
297 * methods from {@code Object}.
298 *
299 * @param caller Represents a lookup context with the accessibility
300 * privileges of the caller. Specifically, the lookup context
301 * must have {@linkplain MethodHandles.Lookup#hasFullPrivilegeAccess()
302 * full privilege access}.
303 * When used with {@code invokedynamic}, this is stacked
304 * automatically by the VM.
305 * @param interfaceMethodName The name of the method to implement. When used with
306 * {@code invokedynamic}, this is provided by the
307 * {@code NameAndType} of the {@code InvokeDynamic}
308 * structure and is stacked automatically by the VM.
309 * @param factoryType The expected signature of the {@code CallSite}. The
310 * parameter types represent the types of capture variables;
311 * the return type is the interface to implement. When
312 * used with {@code invokedynamic}, this is provided by
313 * the {@code NameAndType} of the {@code InvokeDynamic}
314 * structure and is stacked automatically by the VM.
315 * @param interfaceMethodType Signature and return type of method to be
316 * implemented by the function object.
317 * @param implementation A direct method handle describing the implementation
318 * method which should be called (with suitable adaptation
319 * of argument types and return types, and with captured
320 * arguments prepended to the invocation arguments) at
321 * invocation time.
322 * @param dynamicMethodType The signature and return type that should
323 * be enforced dynamically at invocation time.
324 * In simple use cases this is the same as
325 * {@code interfaceMethodType}.
326 * @return a CallSite whose target can be used to perform capture, generating
327 * instances of the interface named by {@code factoryType}
328 * @throws LambdaConversionException If {@code caller} does not have full privilege
329 * access, or if {@code interfaceMethodName} is not a valid JVM
330 * method name, or if the return type of {@code factoryType} is not
331 * an interface, or if {@code implementation} is not a direct method
332 * handle referencing a method or constructor, or if the linkage
333 * invariants are violated, as defined {@link LambdaMetafactory above}.
334 * @throws NullPointerException If any argument is {@code null}.
335 */
336 public static CallSite metafactory(MethodHandles.Lookup caller,
337 String interfaceMethodName,
338 MethodType factoryType,
339 MethodType interfaceMethodType,
340 MethodHandle implementation,
341 MethodType dynamicMethodType)
342 throws LambdaConversionException {
343 AbstractValidatingLambdaMetafactory mf;
344 mf = new InnerClassLambdaMetafactory(Objects.requireNonNull(caller),
345 Objects.requireNonNull(factoryType),
346 Objects.requireNonNull(interfaceMethodName),
347 Objects.requireNonNull(interfaceMethodType),
348 Objects.requireNonNull(implementation),
349 Objects.requireNonNull(dynamicMethodType),
350 false,
351 EMPTY_CLASS_ARRAY,
352 EMPTY_MT_ARRAY);
353 mf.validateMetafactoryArgs();
354 return mf.buildCallSite();
355 }
356
357 /**
358 * Facilitates the creation of simple "function objects" that implement one
359 * or more interfaces by delegation to a provided {@link MethodHandle},
360 * after appropriate type adaptation and partial evaluation of arguments.
361 * Typically used as a <em>bootstrap method</em> for {@code invokedynamic}
362 * call sites, to support the <em>lambda expression</em> and <em>method
363 * reference expression</em> features of the Java Programming Language.
364 *
365 * <p>This is the general, more flexible metafactory; a streamlined version
366 * is provided by {@link #metafactory(java.lang.invoke.MethodHandles.Lookup,
367 * String, MethodType, MethodType, MethodHandle, MethodType)}.
368 * A general description of the behavior of this method is provided
369 * {@link LambdaMetafactory above}.
370 *
371 * <p>The argument list for this method includes three fixed parameters,
372 * corresponding to the parameters automatically stacked by the VM for the
373 * bootstrap method in an {@code invokedynamic} invocation, and an {@code Object[]}
374 * parameter that contains additional parameters. The declared argument
375 * list for this method is:
376 *
377 * <pre>{@code
378 * CallSite altMetafactory(MethodHandles.Lookup caller,
379 * String interfaceMethodName,
380 * MethodType factoryType,
381 * Object... args)
382 * }</pre>
383 *
384 * <p>but it behaves as if the argument list is as follows:
385 *
386 * <pre>{@code
387 * CallSite altMetafactory(MethodHandles.Lookup caller,
388 * String interfaceMethodName,
389 * MethodType factoryType,
390 * MethodType interfaceMethodType,
391 * MethodHandle implementation,
392 * MethodType dynamicMethodType,
393 * int flags,
394 * int altInterfaceCount, // IF flags has MARKERS set
395 * Class... altInterfaces, // IF flags has MARKERS set
396 * int altMethodCount, // IF flags has BRIDGES set
397 * MethodType... altMethods // IF flags has BRIDGES set
398 * )
399 * }</pre>
400 *
401 * <p>Arguments that appear in the argument list for
402 * {@link #metafactory(MethodHandles.Lookup, String, MethodType, MethodType, MethodHandle, MethodType)}
403 * have the same specification as in that method. The additional arguments
404 * are interpreted as follows:
405 * <ul>
406 * <li>{@code flags} indicates additional options; this is a bitwise
407 * OR of desired flags. Defined flags are {@link #FLAG_BRIDGES},
408 * {@link #FLAG_MARKERS}, and {@link #FLAG_SERIALIZABLE}.</li>
409 * <li>{@code altInterfaceCount} is the number of additional interfaces
410 * the function object should implement, and is present if and only if the
411 * {@code FLAG_MARKERS} flag is set.</li>
412 * <li>{@code altInterfaces} is a variable-length list of additional
413 * interfaces to implement, whose length equals {@code altInterfaceCount},
414 * and is present if and only if the {@code FLAG_MARKERS} flag is set.</li>
415 * <li>{@code altMethodCount} is the number of additional method signatures
416 * the function object should implement, and is present if and only if
417 * the {@code FLAG_BRIDGES} flag is set.</li>
418 * <li>{@code altMethods} is a variable-length list of additional
419 * methods signatures to implement, whose length equals {@code altMethodCount},
420 * and is present if and only if the {@code FLAG_BRIDGES} flag is set.</li>
421 * </ul>
422 *
423 * <p>Each class named by {@code altInterfaces} is subject to the same
424 * restrictions as {@code Rd}, the return type of {@code factoryType},
425 * as described {@link LambdaMetafactory above}. Each {@code MethodType}
426 * named by {@code altMethods} is subject to the same restrictions as
427 * {@code interfaceMethodType}, as described {@link LambdaMetafactory above}.
428 *
429 * <p>When FLAG_SERIALIZABLE is set in {@code flags}, the function objects
430 * will implement {@code Serializable}, and will have a {@code writeReplace}
431 * method that returns an appropriate {@link SerializedLambda}. The
432 * {@code caller} class must have an appropriate {@code $deserializeLambda$}
433 * method, as described in {@link SerializedLambda}.
434 *
435 * <p>When the target of the {@code CallSite} returned from this method is
436 * invoked, the resulting function objects are instances of a class with
437 * the following properties:
438 * <ul>
439 * <li>The class implements the interface named by the return type
440 * of {@code factoryType} and any interfaces named by {@code altInterfaces}</li>
441 * <li>The class declares methods with the name given by {@code interfaceMethodName},
442 * and the signature given by {@code interfaceMethodType} and additional signatures
443 * given by {@code altMethods}</li>
444 * <li>The class may override methods from {@code Object}, and may
445 * implement methods related to serialization.</li>
446 * </ul>
447 *
448 * @param caller Represents a lookup context with the accessibility
449 * privileges of the caller. Specifically, the lookup context
450 * must have {@linkplain MethodHandles.Lookup#hasFullPrivilegeAccess()
451 * full privilege access}.
452 * When used with {@code invokedynamic}, this is stacked
453 * automatically by the VM.
454 * @param interfaceMethodName The name of the method to implement. When used with
455 * {@code invokedynamic}, this is provided by the
456 * {@code NameAndType} of the {@code InvokeDynamic}
457 * structure and is stacked automatically by the VM.
458 * @param factoryType The expected signature of the {@code CallSite}. The
459 * parameter types represent the types of capture variables;
460 * the return type is the interface to implement. When
461 * used with {@code invokedynamic}, this is provided by
462 * the {@code NameAndType} of the {@code InvokeDynamic}
463 * structure and is stacked automatically by the VM.
464 * @param args An array of {@code Object} containing the required
465 * arguments {@code interfaceMethodType}, {@code implementation},
466 * {@code dynamicMethodType}, {@code flags}, and any
467 * optional arguments, as described above
468 * @return a CallSite whose target can be used to perform capture, generating
469 * instances of the interface named by {@code factoryType}
470 * @throws LambdaConversionException If {@code caller} does not have full privilege
471 * access, or if {@code interfaceMethodName} is not a valid JVM
472 * method name, or if the return type of {@code factoryType} is not
473 * an interface, or if any of {@code altInterfaces} is not an
474 * interface, or if {@code implementation} is not a direct method
475 * handle referencing a method or constructor, or if the linkage
476 * invariants are violated, as defined {@link LambdaMetafactory above}.
477 * @throws NullPointerException If any argument, or any component of {@code args},
478 * is {@code null}.
479 * @throws IllegalArgumentException If the number or types of the components
480 * of {@code args} do not follow the above rules, or if
481 * {@code altInterfaceCount} or {@code altMethodCount} are negative
482 * integers.
483 */
484 public static CallSite altMetafactory(MethodHandles.Lookup caller,
485 String interfaceMethodName,
486 MethodType factoryType,
487 Object... args)
488 throws LambdaConversionException {
489 Objects.requireNonNull(caller);
490 Objects.requireNonNull(interfaceMethodName);
491 Objects.requireNonNull(factoryType);
492 Objects.requireNonNull(args);
493 int argIndex = 0;
494 MethodType interfaceMethodType = extractArg(args, argIndex++, MethodType.class);
495 MethodHandle implementation = extractArg(args, argIndex++, MethodHandle.class);
496 MethodType dynamicMethodType = extractArg(args, argIndex++, MethodType.class);
497 int flags = extractArg(args, argIndex++, Integer.class);
498 Class<?>[] altInterfaces = EMPTY_CLASS_ARRAY;
499 MethodType[] altMethods = EMPTY_MT_ARRAY;
500 if ((flags & FLAG_MARKERS) != 0) {
501 int altInterfaceCount = extractArg(args, argIndex++, Integer.class);
502 if (altInterfaceCount < 0) {
503 throw new IllegalArgumentException("negative argument count");
504 }
505 if (altInterfaceCount > 0) {
506 altInterfaces = extractArgs(args, argIndex, Class.class, altInterfaceCount);
507 argIndex += altInterfaceCount;
508 }
509 }
510 if ((flags & FLAG_BRIDGES) != 0) {
511 int altMethodCount = extractArg(args, argIndex++, Integer.class);
512 if (altMethodCount < 0) {
513 throw new IllegalArgumentException("negative argument count");
514 }
515 if (altMethodCount > 0) {
516 altMethods = extractArgs(args, argIndex, MethodType.class, altMethodCount);
517 argIndex += altMethodCount;
518 }
519 }
520 if (argIndex < args.length) {
521 throw new IllegalArgumentException("too many arguments");
522 }
523
524 boolean isSerializable = ((flags & FLAG_SERIALIZABLE) != 0);
525 if (isSerializable) {
526 boolean foundSerializableSupertype = Serializable.class.isAssignableFrom(factoryType.returnType());
527 for (Class<?> c : altInterfaces)
528 foundSerializableSupertype |= Serializable.class.isAssignableFrom(c);
529 if (!foundSerializableSupertype) {
530 altInterfaces = Arrays.copyOf(altInterfaces, altInterfaces.length + 1);
531 altInterfaces[altInterfaces.length-1] = Serializable.class;
532 }
533 }
534
535 AbstractValidatingLambdaMetafactory mf
536 = new InnerClassLambdaMetafactory(caller,
537 factoryType,
538 interfaceMethodName,
539 interfaceMethodType,
540 implementation,
541 dynamicMethodType,
542 isSerializable,
543 altInterfaces,
544 altMethods);
545 mf.validateMetafactoryArgs();
546 return mf.buildCallSite();
547 }
548
549 private static <T> T extractArg(Object[] args, int index, Class<T> type) {
550 if (index >= args.length) {
551 throw new IllegalArgumentException("missing argument");
552 }
553 Object result = Objects.requireNonNull(args[index]);
554 if (!type.isInstance(result)) {
555 throw new IllegalArgumentException("argument has wrong type");
556 }
557 return type.cast(result);
558 }
559
560 private static <T> T[] extractArgs(Object[] args, int index, Class<T> type, int count) {
561 @SuppressWarnings("unchecked")
562 T[] result = (T[]) Array.newInstance(type, count);
563 for (int i = 0; i < count; i++) {
564 result[i] = extractArg(args, index + i, type);
565 }
566 return result;
567 }
568
569 }