1 /*
2 * Copyright (c) 2012, 2021, 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
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20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 * questions.
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 * @since 1.8
233 */
234 public final class LambdaMetafactory {
235
236 private LambdaMetafactory() {}
237
238 /** Flag for {@link #altMetafactory} indicating the lambda object
239 * must be serializable */
240 public static final int FLAG_SERIALIZABLE = 1 << 0;
241
242 /**
243 * Flag for {@link #altMetafactory} indicating the lambda object implements
244 * other interfaces besides {@code Serializable}
245 */
246 public static final int FLAG_MARKERS = 1 << 1;
247
248 /**
249 * Flag for alternate metafactories indicating the lambda object requires
250 * additional methods that invoke the {@code implementation}
251 */
252 public static final int FLAG_BRIDGES = 1 << 2;
253
254 private static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
255 private static final MethodType[] EMPTY_MT_ARRAY = new MethodType[0];
256
257 // LambdaMetafactory bootstrap methods are startup sensitive, and may be
258 // special cased in java.lang.invoke.BootstrapMethodInvoker to ensure
259 // methods are invoked with exact type information to avoid generating
260 // code for runtime checks. Take care any changes or additions here are
261 // reflected there as appropriate.
262
263 /**
264 * Facilitates the creation of simple "function objects" that implement one
265 * or more interfaces by delegation to a provided {@link MethodHandle},
266 * after appropriate type adaptation and partial evaluation of arguments.
267 * Typically used as a <em>bootstrap method</em> for {@code invokedynamic}
268 * call sites, to support the <em>lambda expression</em> and <em>method
269 * reference expression</em> features of the Java Programming Language.
270 *
271 * <p>This is the standard, streamlined metafactory; additional flexibility
272 * is provided by {@link #altMetafactory(MethodHandles.Lookup, String, MethodType, Object...)}.
273 * A general description of the behavior of this method is provided
274 * {@link LambdaMetafactory above}.
275 *
276 * <p>When the target of the {@code CallSite} returned from this method is
277 * invoked, the resulting function objects are instances of a class which
278 * implements the interface named by the return type of {@code factoryType},
279 * declares a method with the name given by {@code interfaceMethodName} and the
280 * signature given by {@code interfaceMethodType}. It may also override additional
281 * methods from {@code Object}.
282 *
283 * @param caller Represents a lookup context with the accessibility
284 * privileges of the caller. Specifically, the lookup context
285 * must have {@linkplain MethodHandles.Lookup#hasFullPrivilegeAccess()
286 * full privilege access}.
287 * When used with {@code invokedynamic}, this is stacked
288 * automatically by the VM.
289 * @param interfaceMethodName The name of the method to implement. When used with
290 * {@code invokedynamic}, this is provided by the
291 * {@code NameAndType} of the {@code InvokeDynamic}
292 * structure and is stacked automatically by the VM.
293 * @param factoryType The expected signature of the {@code CallSite}. The
294 * parameter types represent the types of capture variables;
295 * the return type is the interface to implement. When
296 * used with {@code invokedynamic}, this is provided by
297 * the {@code NameAndType} of the {@code InvokeDynamic}
298 * structure and is stacked automatically by the VM.
299 * @param interfaceMethodType Signature and return type of method to be
300 * implemented by the function object.
301 * @param implementation A direct method handle describing the implementation
302 * method which should be called (with suitable adaptation
303 * of argument types and return types, and with captured
304 * arguments prepended to the invocation arguments) at
305 * invocation time.
306 * @param dynamicMethodType The signature and return type that should
307 * be enforced dynamically at invocation time.
308 * In simple use cases this is the same as
309 * {@code interfaceMethodType}.
310 * @return a CallSite whose target can be used to perform capture, generating
311 * instances of the interface named by {@code factoryType}
312 * @throws LambdaConversionException If {@code caller} does not have full privilege
313 * access, or if {@code interfaceMethodName} is not a valid JVM
314 * method name, or if the return type of {@code factoryType} is not
315 * an interface, or if the return type of {@code factoryType} is a value
316 * interface, or if {@code implementation} is not a direct method
317 * handle referencing a method or constructor, or if the linkage
318 * invariants are violated, as defined {@link LambdaMetafactory above}.
319 * @throws NullPointerException If any argument is {@code null}.
320 * @throws SecurityException If a security manager is present, and it
321 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
322 * from {@code caller} to the package of {@code implementation}.
323 */
324 public static CallSite metafactory(MethodHandles.Lookup caller,
325 String interfaceMethodName,
326 MethodType factoryType,
327 MethodType interfaceMethodType,
328 MethodHandle implementation,
329 MethodType dynamicMethodType)
330 throws LambdaConversionException {
331 AbstractValidatingLambdaMetafactory mf;
332 mf = new InnerClassLambdaMetafactory(Objects.requireNonNull(caller),
333 Objects.requireNonNull(factoryType),
334 Objects.requireNonNull(interfaceMethodName),
335 Objects.requireNonNull(interfaceMethodType),
336 Objects.requireNonNull(implementation),
337 Objects.requireNonNull(dynamicMethodType),
338 false,
339 EMPTY_CLASS_ARRAY,
340 EMPTY_MT_ARRAY);
341 mf.validateMetafactoryArgs();
342 return mf.buildCallSite();
343 }
344
345 /**
346 * Facilitates the creation of simple "function objects" that implement one
347 * or more interfaces by delegation to a provided {@link MethodHandle},
348 * after appropriate type adaptation and partial evaluation of arguments.
349 * Typically used as a <em>bootstrap method</em> for {@code invokedynamic}
350 * call sites, to support the <em>lambda expression</em> and <em>method
351 * reference expression</em> features of the Java Programming Language.
352 *
353 * <p>This is the general, more flexible metafactory; a streamlined version
354 * is provided by {@link #metafactory(java.lang.invoke.MethodHandles.Lookup,
355 * String, MethodType, MethodType, MethodHandle, MethodType)}.
356 * A general description of the behavior of this method is provided
357 * {@link LambdaMetafactory above}.
358 *
359 * <p>The argument list for this method includes three fixed parameters,
360 * corresponding to the parameters automatically stacked by the VM for the
361 * bootstrap method in an {@code invokedynamic} invocation, and an {@code Object[]}
362 * parameter that contains additional parameters. The declared argument
363 * list for this method is:
364 *
365 * <pre>{@code
366 * CallSite altMetafactory(MethodHandles.Lookup caller,
367 * String interfaceMethodName,
368 * MethodType factoryType,
369 * Object... args)
370 * }</pre>
371 *
372 * <p>but it behaves as if the argument list is as follows:
373 *
374 * <pre>{@code
375 * CallSite altMetafactory(MethodHandles.Lookup caller,
376 * String interfaceMethodName,
377 * MethodType factoryType,
378 * MethodType interfaceMethodType,
379 * MethodHandle implementation,
380 * MethodType dynamicMethodType,
381 * int flags,
382 * int altInterfaceCount, // IF flags has MARKERS set
383 * Class... altInterfaces, // IF flags has MARKERS set
384 * int altMethodCount, // IF flags has BRIDGES set
385 * MethodType... altMethods // IF flags has BRIDGES set
386 * )
387 * }</pre>
388 *
389 * <p>Arguments that appear in the argument list for
390 * {@link #metafactory(MethodHandles.Lookup, String, MethodType, MethodType, MethodHandle, MethodType)}
391 * have the same specification as in that method. The additional arguments
392 * are interpreted as follows:
393 * <ul>
394 * <li>{@code flags} indicates additional options; this is a bitwise
395 * OR of desired flags. Defined flags are {@link #FLAG_BRIDGES},
396 * {@link #FLAG_MARKERS}, and {@link #FLAG_SERIALIZABLE}.</li>
397 * <li>{@code altInterfaceCount} is the number of additional interfaces
398 * the function object should implement, and is present if and only if the
399 * {@code FLAG_MARKERS} flag is set.</li>
400 * <li>{@code altInterfaces} is a variable-length list of additional
401 * interfaces to implement, whose length equals {@code altInterfaceCount},
402 * and is present if and only if the {@code FLAG_MARKERS} flag is set.</li>
403 * <li>{@code altMethodCount} is the number of additional method signatures
404 * the function object should implement, and is present if and only if
405 * the {@code FLAG_BRIDGES} flag is set.</li>
406 * <li>{@code altMethods} is a variable-length list of additional
407 * methods signatures to implement, whose length equals {@code altMethodCount},
408 * and is present if and only if the {@code FLAG_BRIDGES} flag is set.</li>
409 * </ul>
410 *
411 * <p>Each class named by {@code altInterfaces} is subject to the same
412 * restrictions as {@code Rd}, the return type of {@code factoryType},
413 * as described {@link LambdaMetafactory above}. Each {@code MethodType}
414 * named by {@code altMethods} is subject to the same restrictions as
415 * {@code interfaceMethodType}, as described {@link LambdaMetafactory above}.
416 *
417 * <p>When FLAG_SERIALIZABLE is set in {@code flags}, the function objects
418 * will implement {@code Serializable}, and will have a {@code writeReplace}
419 * method that returns an appropriate {@link SerializedLambda}. The
420 * {@code caller} class must have an appropriate {@code $deserializeLambda$}
421 * method, as described in {@link SerializedLambda}.
422 *
423 * <p>When the target of the {@code CallSite} returned from this method is
424 * invoked, the resulting function objects are instances of a class with
425 * the following properties:
426 * <ul>
427 * <li>The class implements the interface named by the return type
428 * of {@code factoryType} and any interfaces named by {@code altInterfaces}</li>
429 * <li>The class declares methods with the name given by {@code interfaceMethodName},
430 * and the signature given by {@code interfaceMethodType} and additional signatures
431 * given by {@code altMethods}</li>
432 * <li>The class may override methods from {@code Object}, and may
433 * implement methods related to serialization.</li>
434 * </ul>
435 *
436 * @param caller Represents a lookup context with the accessibility
437 * privileges of the caller. Specifically, the lookup context
438 * must have {@linkplain MethodHandles.Lookup#hasFullPrivilegeAccess()
439 * full privilege access}.
440 * When used with {@code invokedynamic}, this is stacked
441 * automatically by the VM.
442 * @param interfaceMethodName The name of the method to implement. When used with
443 * {@code invokedynamic}, this is provided by the
444 * {@code NameAndType} of the {@code InvokeDynamic}
445 * structure and is stacked automatically by the VM.
446 * @param factoryType The expected signature of the {@code CallSite}. The
447 * parameter types represent the types of capture variables;
448 * the return type is the interface to implement. When
449 * used with {@code invokedynamic}, this is provided by
450 * the {@code NameAndType} of the {@code InvokeDynamic}
451 * structure and is stacked automatically by the VM.
452 * @param args An array of {@code Object} containing the required
453 * arguments {@code interfaceMethodType}, {@code implementation},
454 * {@code dynamicMethodType}, {@code flags}, and any
455 * optional arguments, as described above
456 * @return a CallSite whose target can be used to perform capture, generating
457 * instances of the interface named by {@code factoryType}
458 * @throws LambdaConversionException If {@code caller} does not have full privilege
459 * access, or if {@code interfaceMethodName} is not a valid JVM
460 * method name, or if the return type of {@code factoryType} is not
461 * an interface, or if any of {@code altInterfaces} is not an
462 * interface, or if {@code implementation} is not a direct method
463 * handle referencing a method or constructor, or if the linkage
464 * invariants are violated, as defined {@link LambdaMetafactory above}.
465 * @throws NullPointerException If any argument, or any component of {@code args},
466 * is {@code null}.
467 * @throws IllegalArgumentException If the number or types of the components
468 * of {@code args} do not follow the above rules, or if
469 * {@code altInterfaceCount} or {@code altMethodCount} are negative
470 * integers.
471 * @throws SecurityException If a security manager is present, and it
472 * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
473 * from {@code caller} to the package of {@code implementation}.
474 */
475 public static CallSite altMetafactory(MethodHandles.Lookup caller,
476 String interfaceMethodName,
477 MethodType factoryType,
478 Object... args)
479 throws LambdaConversionException {
480 Objects.requireNonNull(caller);
481 Objects.requireNonNull(interfaceMethodName);
482 Objects.requireNonNull(factoryType);
483 Objects.requireNonNull(args);
484 int argIndex = 0;
485 MethodType interfaceMethodType = extractArg(args, argIndex++, MethodType.class);
486 MethodHandle implementation = extractArg(args, argIndex++, MethodHandle.class);
487 MethodType dynamicMethodType = extractArg(args, argIndex++, MethodType.class);
488 int flags = extractArg(args, argIndex++, Integer.class);
489 Class<?>[] altInterfaces = EMPTY_CLASS_ARRAY;
490 MethodType[] altMethods = EMPTY_MT_ARRAY;
491 if ((flags & FLAG_MARKERS) != 0) {
492 int altInterfaceCount = extractArg(args, argIndex++, Integer.class);
493 if (altInterfaceCount < 0) {
494 throw new IllegalArgumentException("negative argument count");
495 }
496 if (altInterfaceCount > 0) {
497 altInterfaces = extractArgs(args, argIndex, Class.class, altInterfaceCount);
498 argIndex += altInterfaceCount;
499 }
500 }
501 if ((flags & FLAG_BRIDGES) != 0) {
502 int altMethodCount = extractArg(args, argIndex++, Integer.class);
503 if (altMethodCount < 0) {
504 throw new IllegalArgumentException("negative argument count");
505 }
506 if (altMethodCount > 0) {
507 altMethods = extractArgs(args, argIndex, MethodType.class, altMethodCount);
508 argIndex += altMethodCount;
509 }
510 }
511 if (argIndex < args.length) {
512 throw new IllegalArgumentException("too many arguments");
513 }
514
515 boolean isSerializable = ((flags & FLAG_SERIALIZABLE) != 0);
516 if (isSerializable) {
517 boolean foundSerializableSupertype = Serializable.class.isAssignableFrom(factoryType.returnType());
518 for (Class<?> c : altInterfaces)
519 foundSerializableSupertype |= Serializable.class.isAssignableFrom(c);
520 if (!foundSerializableSupertype) {
521 altInterfaces = Arrays.copyOf(altInterfaces, altInterfaces.length + 1);
522 altInterfaces[altInterfaces.length-1] = Serializable.class;
523 }
524 }
525
526 AbstractValidatingLambdaMetafactory mf
527 = new InnerClassLambdaMetafactory(caller,
528 factoryType,
529 interfaceMethodName,
530 interfaceMethodType,
531 implementation,
532 dynamicMethodType,
533 isSerializable,
534 altInterfaces,
535 altMethods);
536 mf.validateMetafactoryArgs();
537 return mf.buildCallSite();
538 }
539
540 private static <T> T extractArg(Object[] args, int index, Class<T> type) {
541 if (index >= args.length) {
542 throw new IllegalArgumentException("missing argument");
543 }
544 Object result = Objects.requireNonNull(args[index]);
545 if (!type.isInstance(result)) {
546 throw new IllegalArgumentException("argument has wrong type");
547 }
548 return type.cast(result);
549 }
550
551 private static <T> T[] extractArgs(Object[] args, int index, Class<T> type, int count) {
552 @SuppressWarnings("unchecked")
553 T[] result = (T[]) Array.newInstance(type, count);
554 for (int i = 0; i < count; i++) {
555 result[i] = extractArg(args, index + i, type);
556 }
557 return result;
558 }
559
560 }