1 /*
2 * Copyright (c) 2012, 2025, 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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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
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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 import jdk.internal.access.JavaLangInvokeAccess.ReflectableLambdaInfo;
34 import jdk.internal.vm.annotation.AOTSafeClassInitializer;
35
36 /**
37 * <p>Methods to facilitate the creation of simple "function objects" that
38 * implement one or more interfaces by delegation to a provided {@link MethodHandle},
39 * possibly after type adaptation and partial evaluation of arguments. These
40 * methods are typically used as <em>bootstrap methods</em> for {@code invokedynamic}
41 * call sites, to support the <em>lambda expression</em> and <em>method
42 * reference expression</em> features of the Java Programming Language.
43 *
44 * <p>Indirect access to the behavior specified by the provided {@code MethodHandle}
45 * proceeds in order through three phases:
46 * <ul>
47 * <li><p><em>Linkage</em> occurs when the methods in this class are invoked.
48 * They take as arguments an interface to be implemented (typically a
49 * <em>functional interface</em>, one with a single abstract method), a
50 * name and signature of a method from that interface to be implemented, a
51 * {@linkplain MethodHandleInfo direct method handle} describing the desired
52 * implementation behavior for that method, and possibly other additional
53 * metadata, and produce a {@link CallSite} whose target can be used to
54 * create suitable function objects.
55 *
56 * <p>Linkage may involve dynamically loading a new class that implements
57 * the target interface, or re-using a suitable existing class.
58 *
59 * <p>The {@code CallSite} can be considered a "factory" for function
60 * objects and so these linkage methods are referred to as
61 * "metafactories".</li>
62 *
63 * <li><p><em>Capture</em> occurs when the {@code CallSite}'s target is
64 * invoked, typically through an {@code invokedynamic} call site,
65 * producing a function object. This may occur many times for
66 * a single factory {@code CallSite}.
67 *
68 * <p>If the behavior {@code MethodHandle} has additional parameters beyond
69 * those of the specified interface method, these are referred to as
70 * <em>captured parameters</em>, which must be provided as arguments to the
71 * {@code CallSite} target. The expected number and types of captured
72 * parameters are determined during linkage.
73 *
74 * <p>Capture may involve allocation of a new function object, or may return
75 * a suitable existing function object. The identity of a function object
76 * produced by capture is unpredictable, and therefore identity-sensitive
77 * operations (such as reference equality, object locking, and {@code
78 * System.identityHashCode()}) may produce different results in different
79 * implementations, or even upon different invocations in the same
80 * implementation.</li>
81 *
82 * <li><p><em>Invocation</em> occurs when an implemented interface method is
83 * invoked on a function object. This may occur many times for a single
84 * function object. The method referenced by the implementation
85 * {@code MethodHandle} is invoked, passing to it the captured arguments and
86 * the invocation arguments. The result of the method is returned.
87 * </li>
88 * </ul>
89 *
90 * <p>It is sometimes useful to restrict the set of inputs or results permitted
91 * at invocation. For example, when the generic interface {@code Predicate<T>}
92 * is parameterized as {@code Predicate<String>}, the input must be a
93 * {@code String}, even though the method to implement allows any {@code Object}.
94 * At linkage time, an additional {@link MethodType} parameter describes the
95 * "dynamic" method type; on invocation, the arguments and eventual result
96 * are checked against this {@code MethodType}.
97 *
98 * <p>This class provides two forms of linkage methods: a standard version
99 * ({@link #metafactory(MethodHandles.Lookup, String, MethodType, MethodType, MethodHandle, MethodType)})
100 * using an optimized protocol, and an alternate version
101 * {@link #altMetafactory(MethodHandles.Lookup, String, MethodType, Object...)}).
102 * The alternate version is a generalization of the standard version, providing
103 * additional control over the behavior of the generated function objects via
104 * flags and additional arguments. The alternate version adds the ability to
105 * manage the following attributes of function objects:
106 *
107 * <ul>
108 * <li><em>Multiple methods.</em> It is sometimes useful to implement multiple
109 * variations of the method signature, involving argument or return type
110 * adaptation. This occurs when multiple distinct VM signatures for a method
111 * are logically considered to be the same method by the language. The
112 * flag {@code FLAG_BRIDGES} indicates that a list of additional
113 * {@code MethodType}s will be provided, each of which will be implemented
114 * by the resulting function object. These methods will share the same
115 * name and instantiated type.</li>
116 *
117 * <li><em>Multiple interfaces.</em> If needed, more than one interface
118 * can be implemented by the function object. (These additional interfaces
119 * are typically marker interfaces with no methods.) The flag {@code FLAG_MARKERS}
120 * indicates that a list of additional interfaces will be provided, each of
121 * which should be implemented by the resulting function object.</li>
122 *
123 * <li><em>Serializability.</em> The generated function objects do not
124 * generally support serialization. If desired, {@code FLAG_SERIALIZABLE}
125 * can be used to indicate that the function objects should be serializable.
126 * Serializable function objects will use, as their serialized form,
127 * instances of the class {@code SerializedLambda}, which requires additional
128 * assistance from the capturing class (the class described by the
129 * {@link MethodHandles.Lookup} parameter {@code caller}); see
130 * {@link SerializedLambda} for details.</li>
131 * </ul>
132 *
133 * <p>Assume the linkage arguments are as follows:
134 * <ul>
135 * <li>{@code factoryType} (describing the {@code CallSite} signature) has
136 * K parameters of types (D1..Dk) and return type Rd;</li>
137 * <li>{@code interfaceMethodType} (describing the implemented method type) has N
138 * parameters, of types (U1..Un) and return type Ru;</li>
139 * <li>{@code implementation} (the {@code MethodHandle} providing the
140 * implementation) has M parameters, of types (A1..Am) and return type Ra
141 * (if the method describes an instance method, the method type of this
142 * method handle already includes an extra first argument corresponding to
143 * the receiver);</li>
144 * <li>{@code dynamicMethodType} (allowing restrictions on invocation)
145 * has N parameters, of types (T1..Tn) and return type Rt.</li>
146 * </ul>
147 *
148 * <p>Then the following linkage invariants must hold:
149 * <ul>
150 * <li>{@code interfaceMethodType} and {@code dynamicMethodType} have the same
151 * arity N, and for i=1..N, Ti and Ui are the same type, or Ti and Ui are
152 * both reference types and Ti is a subtype of Ui</li>
153 * <li>Either Rt and Ru are the same type, or both are reference types and
154 * Rt is a subtype of Ru</li>
155 * <li>K + N = M</li>
156 * <li>For i=1..K, Di = Ai</li>
157 * <li>For i=1..N, Ti is adaptable to Aj, where j=i+k</li>
158 * <li>The return type Rt is void, or the return type Ra is not void and is
159 * adaptable to Rt</li>
160 * </ul>
161 *
162 * <p>Further, at capture time, if {@code implementation} corresponds to an instance
163 * method, and there are any capture arguments ({@code K > 0}), then the first
164 * capture argument (corresponding to the receiver) must be non-null.
165 *
166 * <p>A type Q is considered adaptable to S as follows:
167 * <table class="striped">
168 * <caption style="display:none">adaptable types</caption>
169 * <thead>
170 * <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>
171 * </thead>
172 * <tbody>
173 * <tr>
174 * <th scope="row">Primitive</th><th scope="row">Primitive</th>
175 * <td>Q can be converted to S via a primitive widening conversion</td>
176 * <td>None</td>
177 * </tr>
178 * <tr>
179 * <th scope="row">Primitive</th><th scope="row">Reference</th>
180 * <td>S is a supertype of the Wrapper(Q)</td>
181 * <td>Cast from Wrapper(Q) to S</td>
182 * </tr>
183 * <tr>
184 * <th scope="row">Reference</th><th scope="row">Primitive</th>
185 * <td>for parameter types: Q is a primitive wrapper and Primitive(Q)
186 * can be widened to S
187 * <br>for return types: If Q is a primitive wrapper, check that
188 * Primitive(Q) can be widened to S</td>
189 * <td>If Q is not a primitive wrapper, cast Q to the base Wrapper(S);
190 * for example Number for numeric types</td>
191 * </tr>
192 * <tr>
193 * <th scope="row">Reference</th><th scope="row">Reference</th>
194 * <td>for parameter types: S is a supertype of Q
195 * <br>for return types: none</td>
196 * <td>Cast from Q to S</td>
197 * </tr>
198 * </tbody>
199 * </table>
200 *
201 * @apiNote These linkage methods are designed to support the evaluation
202 * of <em>lambda expressions</em> and <em>method references</em> in the Java
203 * Language. For every lambda expressions or method reference in the source code,
204 * there is a target type which is a functional interface. Evaluating a lambda
205 * expression produces an object of its target type. The recommended mechanism
206 * for evaluating lambda expressions is to desugar the lambda body to a method,
207 * invoke an invokedynamic call site whose static argument list describes the
208 * sole method of the functional interface and the desugared implementation
209 * method, and returns an object (the lambda object) that implements the target
210 * type. (For method references, the implementation method is simply the
211 * referenced method; no desugaring is needed.)
212 *
213 * <p>The argument list of the implementation method and the argument list of
214 * the interface method(s) may differ in several ways. The implementation
215 * methods may have additional arguments to accommodate arguments captured by
216 * the lambda expression; there may also be differences resulting from permitted
217 * adaptations of arguments, such as casting, boxing, unboxing, and primitive
218 * widening. (Varargs adaptations are not handled by the metafactories; these are
219 * expected to be handled by the caller.)
220 *
221 * <p>Invokedynamic call sites have two argument lists: a static argument list
222 * and a dynamic argument list. The static argument list is stored in the
223 * constant pool; the dynamic argument is pushed on the operand stack at capture
224 * time. The bootstrap method has access to the entire static argument list
225 * (which in this case, includes information describing the implementation method,
226 * the target interface, and the target interface method(s)), as well as a
227 * method signature describing the number and static types (but not the values)
228 * of the dynamic arguments and the static return type of the invokedynamic site.
229 *
230 * <p>The implementation method is described with a direct method handle
231 * referencing a method or constructor. In theory, any method handle could be
232 * used, but this is not compatible with some implementation techniques and
233 * would complicate the work implementations must do.
234 *
235 * <p>Uses besides evaluation of lambda expressions and method references are
236 * unintended. These linkage methods may change their unspecified behaviors at
237 * any time to better suit the Java language features they were designed to
238 * support, and such changes may impact unintended uses. Unintended uses of
239 * these linkage methods may lead to resource leaks, or other unspecified
240 * negative effects.
241 *
242 * @implNote In the reference implementation, the classes implementing the created
243 * function objects are strongly reachable from the defining class loader of the
244 * caller, like classes and interfaces in Java source code. This technique
245 * reduces heap memory use, but as a consequence, the implementation classes can
246 * be unloaded only if the caller class can be unloaded. In particular, if the
247 * caller is a {@linkplain MethodHandles.Lookup.ClassOption#STRONG weak hidden
248 * class}, the implementation class, a strong hidden class, may not be unloaded
249 * even if the caller may be unloaded.
250 *
251 * @since 1.8
252 */
253 @AOTSafeClassInitializer
254 public final class LambdaMetafactory {
255
256 private LambdaMetafactory() {}
257
258 /** Flag for {@link #altMetafactory} indicating the lambda object
259 * must be serializable */
260 public static final int FLAG_SERIALIZABLE = 1 << 0;
261
262 /**
263 * Flag for {@link #altMetafactory} indicating the lambda object implements
264 * other interfaces besides {@code Serializable}
265 */
266 public static final int FLAG_MARKERS = 1 << 1;
267
268 /**
269 * Flag for alternate metafactories indicating the lambda object requires
270 * additional methods that invoke the {@code implementation}
271 */
272 public static final int FLAG_BRIDGES = 1 << 2;
273
274 private static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
275 private static final MethodType[] EMPTY_MT_ARRAY = new MethodType[0];
276
277 // LambdaMetafactory bootstrap methods are startup sensitive, and may be
278 // special cased in java.lang.invoke.BootstrapMethodInvoker to ensure
279 // methods are invoked with exact type information to avoid generating
280 // code for runtime checks. Take care any changes or additions here are
281 // reflected there as appropriate.
282
283 /**
284 * Facilitates the creation of simple "function objects" that implement one
285 * or more interfaces by delegation to a provided {@link MethodHandle},
286 * after appropriate type adaptation and partial evaluation of arguments.
287 * Typically used as a <em>bootstrap method</em> for {@code invokedynamic}
288 * call sites, to support the <em>lambda expression</em> and <em>method
289 * reference expression</em> features of the Java Programming Language.
290 *
291 * <p>This is the standard, streamlined metafactory; additional flexibility
292 * is provided by {@link #altMetafactory(MethodHandles.Lookup, String, MethodType, Object...)}.
293 * A general description of the behavior of this method is provided
294 * {@link LambdaMetafactory above}.
295 *
296 * <p>When the target of the {@code CallSite} returned from this method is
297 * invoked, the resulting function objects are instances of a class which
298 * implements the interface named by the return type of {@code factoryType},
299 * declares a method with the name given by {@code interfaceMethodName} and the
300 * signature given by {@code interfaceMethodType}. It may also override additional
301 * methods from {@code Object}.
302 *
303 * @param caller Represents a lookup context with the accessibility
304 * privileges of the caller. Specifically, the lookup context
305 * must have {@linkplain MethodHandles.Lookup#hasFullPrivilegeAccess()
306 * full privilege access}.
307 * When used with {@code invokedynamic}, this is stacked
308 * automatically by the VM.
309 * @param interfaceMethodName The name of the method to implement. When used with
310 * {@code invokedynamic}, this is provided by the
311 * {@code NameAndType} of the {@code InvokeDynamic}
312 * structure and is stacked automatically by the VM.
313 * @param factoryType The expected signature of the {@code CallSite}. The
314 * parameter types represent the types of capture variables;
315 * the return type is the interface to implement. When
316 * used with {@code invokedynamic}, this is provided by
317 * the {@code NameAndType} of the {@code InvokeDynamic}
318 * structure and is stacked automatically by the VM.
319 * @param interfaceMethodType Signature and return type of method to be
320 * implemented by the function object.
321 * @param implementation A direct method handle describing the implementation
322 * method which should be called (with suitable adaptation
323 * of argument types and return types, and with captured
324 * arguments prepended to the invocation arguments) at
325 * invocation time.
326 * @param dynamicMethodType The signature and return type that should
327 * be enforced dynamically at invocation time.
328 * In simple use cases this is the same as
329 * {@code interfaceMethodType}.
330 * @return a CallSite whose target can be used to perform capture, generating
331 * instances of the interface named by {@code factoryType}
332 * @throws LambdaConversionException If {@code caller} does not have full privilege
333 * access, or if {@code interfaceMethodName} is not a valid JVM
334 * method name, or if the return type of {@code factoryType} is not
335 * an interface, or if {@code implementation} is not a direct method
336 * handle referencing a method or constructor, or if the linkage
337 * invariants are violated, as defined {@link LambdaMetafactory above}.
338 * @throws NullPointerException If any argument is {@code null}.
339 */
340 public static CallSite metafactory(MethodHandles.Lookup caller,
341 String interfaceMethodName,
342 MethodType factoryType,
343 MethodType interfaceMethodType,
344 MethodHandle implementation,
345 MethodType dynamicMethodType)
346 throws LambdaConversionException {
347 return metafactoryInternal(caller, interfaceMethodName, factoryType, interfaceMethodType,
348 implementation, dynamicMethodType, null);
349 }
350
351 static CallSite metafactoryInternal(MethodHandles.Lookup caller,
352 String interfaceMethodName,
353 MethodType factoryType,
354 MethodType interfaceMethodType,
355 MethodHandle implementation,
356 MethodType dynamicMethodType,
357 ReflectableLambdaInfo reflectableLambdaInfo)
358 throws LambdaConversionException {
359 AbstractValidatingLambdaMetafactory mf = new InnerClassLambdaMetafactory(Objects.requireNonNull(caller),
360 Objects.requireNonNull(factoryType),
361 Objects.requireNonNull(interfaceMethodName),
362 Objects.requireNonNull(interfaceMethodType),
363 Objects.requireNonNull(implementation),
364 Objects.requireNonNull(dynamicMethodType),
365 false,
366 EMPTY_CLASS_ARRAY,
367 EMPTY_MT_ARRAY,
368 reflectableLambdaInfo);
369 mf.validateMetafactoryArgs();
370 return mf.buildCallSite();
371 }
372
373 /**
374 * Facilitates the creation of simple "function objects" that implement one
375 * or more interfaces by delegation to a provided {@link MethodHandle},
376 * after appropriate type adaptation and partial evaluation of arguments.
377 * Typically used as a <em>bootstrap method</em> for {@code invokedynamic}
378 * call sites, to support the <em>lambda expression</em> and <em>method
379 * reference expression</em> features of the Java Programming Language.
380 *
381 * <p>This is the general, more flexible metafactory; a streamlined version
382 * is provided by {@link #metafactory(java.lang.invoke.MethodHandles.Lookup,
383 * String, MethodType, MethodType, MethodHandle, MethodType)}.
384 * A general description of the behavior of this method is provided
385 * {@link LambdaMetafactory above}.
386 *
387 * <p>The argument list for this method includes three fixed parameters,
388 * corresponding to the parameters automatically stacked by the VM for the
389 * bootstrap method in an {@code invokedynamic} invocation, and an {@code Object[]}
390 * parameter that contains additional parameters. The declared argument
391 * list for this method is:
392 *
393 * <pre>{@code
394 * CallSite altMetafactory(MethodHandles.Lookup caller,
395 * String interfaceMethodName,
396 * MethodType factoryType,
397 * Object... args)
398 * }</pre>
399 *
400 * <p>but it behaves as if the argument list is as follows:
401 *
402 * <pre>{@code
403 * CallSite altMetafactory(MethodHandles.Lookup caller,
404 * String interfaceMethodName,
405 * MethodType factoryType,
406 * MethodType interfaceMethodType,
407 * MethodHandle implementation,
408 * MethodType dynamicMethodType,
409 * int flags,
410 * int altInterfaceCount, // IF flags has MARKERS set
411 * Class... altInterfaces, // IF flags has MARKERS set
412 * int altMethodCount, // IF flags has BRIDGES set
413 * MethodType... altMethods // IF flags has BRIDGES set
414 * )
415 * }</pre>
416 *
417 * <p>Arguments that appear in the argument list for
418 * {@link #metafactory(MethodHandles.Lookup, String, MethodType, MethodType, MethodHandle, MethodType)}
419 * have the same specification as in that method. The additional arguments
420 * are interpreted as follows:
421 * <ul>
422 * <li>{@code flags} indicates additional options; this is a bitwise
423 * OR of desired flags. Defined flags are {@link #FLAG_BRIDGES},
424 * {@link #FLAG_MARKERS}, and {@link #FLAG_SERIALIZABLE}.</li>
425 * <li>{@code altInterfaceCount} is the number of additional interfaces
426 * the function object should implement, and is present if and only if the
427 * {@code FLAG_MARKERS} flag is set.</li>
428 * <li>{@code altInterfaces} is a variable-length list of additional
429 * interfaces to implement, whose length equals {@code altInterfaceCount},
430 * and is present if and only if the {@code FLAG_MARKERS} flag is set.</li>
431 * <li>{@code altMethodCount} is the number of additional method signatures
432 * the function object should implement, and is present if and only if
433 * the {@code FLAG_BRIDGES} flag is set.</li>
434 * <li>{@code altMethods} is a variable-length list of additional
435 * methods signatures to implement, whose length equals {@code altMethodCount},
436 * and is present if and only if the {@code FLAG_BRIDGES} flag is set.</li>
437 * </ul>
438 *
439 * <p>Each class named by {@code altInterfaces} is subject to the same
440 * restrictions as {@code Rd}, the return type of {@code factoryType},
441 * as described {@link LambdaMetafactory above}. Each {@code MethodType}
442 * named by {@code altMethods} is subject to the same restrictions as
443 * {@code interfaceMethodType}, as described {@link LambdaMetafactory above}.
444 *
445 * <p>When FLAG_SERIALIZABLE is set in {@code flags}, the function objects
446 * will implement {@code Serializable}, and will have a {@code writeReplace}
447 * method that returns an appropriate {@link SerializedLambda}. The
448 * {@code caller} class must have an appropriate {@code $deserializeLambda$}
449 * method, as described in {@link SerializedLambda}.
450 *
451 * <p>When the target of the {@code CallSite} returned from this method is
452 * invoked, the resulting function objects are instances of a class with
453 * the following properties:
454 * <ul>
455 * <li>The class implements the interface named by the return type
456 * of {@code factoryType} and any interfaces named by {@code altInterfaces}</li>
457 * <li>The class declares methods with the name given by {@code interfaceMethodName},
458 * and the signature given by {@code interfaceMethodType} and additional signatures
459 * given by {@code altMethods}</li>
460 * <li>The class may override methods from {@code Object}, and may
461 * implement methods related to serialization.</li>
462 * </ul>
463 *
464 * @param caller Represents a lookup context with the accessibility
465 * privileges of the caller. Specifically, the lookup context
466 * must have {@linkplain MethodHandles.Lookup#hasFullPrivilegeAccess()
467 * full privilege access}.
468 * When used with {@code invokedynamic}, this is stacked
469 * automatically by the VM.
470 * @param interfaceMethodName The name of the method to implement. When used with
471 * {@code invokedynamic}, this is provided by the
472 * {@code NameAndType} of the {@code InvokeDynamic}
473 * structure and is stacked automatically by the VM.
474 * @param factoryType The expected signature of the {@code CallSite}. The
475 * parameter types represent the types of capture variables;
476 * the return type is the interface to implement. When
477 * used with {@code invokedynamic}, this is provided by
478 * the {@code NameAndType} of the {@code InvokeDynamic}
479 * structure and is stacked automatically by the VM.
480 * @param args An array of {@code Object} containing the required
481 * arguments {@code interfaceMethodType}, {@code implementation},
482 * {@code dynamicMethodType}, {@code flags}, and any
483 * optional arguments, as described above
484 * @return a CallSite whose target can be used to perform capture, generating
485 * instances of the interface named by {@code factoryType}
486 * @throws LambdaConversionException If {@code caller} does not have full privilege
487 * access, or if {@code interfaceMethodName} is not a valid JVM
488 * method name, or if the return type of {@code factoryType} is not
489 * an interface, or if any of {@code altInterfaces} is not an
490 * interface, or if {@code implementation} is not a direct method
491 * handle referencing a method or constructor, or if the linkage
492 * invariants are violated, as defined {@link LambdaMetafactory above}.
493 * @throws NullPointerException If any argument, or any component of {@code args},
494 * is {@code null}.
495 * @throws IllegalArgumentException If the number or types of the components
496 * of {@code args} do not follow the above rules, or if
497 * {@code altInterfaceCount} or {@code altMethodCount} are negative
498 * integers.
499 */
500 public static CallSite altMetafactory(MethodHandles.Lookup caller,
501 String interfaceMethodName,
502 MethodType factoryType,
503 Object... args)
504 throws LambdaConversionException {
505 return altMetafactoryInternal(caller, interfaceMethodName, factoryType, null, args);
506 }
507
508 static CallSite altMetafactoryInternal(MethodHandles.Lookup caller,
509 String interfaceMethodName,
510 MethodType factoryType,
511 ReflectableLambdaInfo reflectableLambdaInfo,
512 Object... args)
513 throws LambdaConversionException {
514 Objects.requireNonNull(caller);
515 Objects.requireNonNull(interfaceMethodName);
516 Objects.requireNonNull(factoryType);
517 Objects.requireNonNull(args);
518 int argIndex = 0;
519 MethodType interfaceMethodType = extractArg(args, argIndex++, MethodType.class);
520 MethodHandle implementation = extractArg(args, argIndex++, MethodHandle.class);
521 MethodType dynamicMethodType = extractArg(args, argIndex++, MethodType.class);
522 int flags = extractArg(args, argIndex++, Integer.class);
523 Class<?>[] altInterfaces = EMPTY_CLASS_ARRAY;
524 MethodType[] altMethods = EMPTY_MT_ARRAY;
525 if ((flags & FLAG_MARKERS) != 0) {
526 int altInterfaceCount = extractArg(args, argIndex++, Integer.class);
527 if (altInterfaceCount < 0) {
528 throw new IllegalArgumentException("negative argument count");
529 }
530 if (altInterfaceCount > 0) {
531 altInterfaces = extractArgs(args, argIndex, Class.class, altInterfaceCount);
532 argIndex += altInterfaceCount;
533 }
534 }
535
536 if ((flags & FLAG_BRIDGES) != 0) {
537 int altMethodCount = extractArg(args, argIndex++, Integer.class);
538 if (altMethodCount < 0) {
539 throw new IllegalArgumentException("negative argument count");
540 }
541 if (altMethodCount > 0) {
542 altMethods = extractArgs(args, argIndex, MethodType.class, altMethodCount);
543 argIndex += altMethodCount;
544 }
545 }
546 if (argIndex < args.length) {
547 throw new IllegalArgumentException("too many arguments");
548 }
549
550 boolean isSerializable = ((flags & FLAG_SERIALIZABLE) != 0);
551 if (isSerializable) {
552 boolean foundSerializableSupertype = Serializable.class.isAssignableFrom(factoryType.returnType());
553 for (Class<?> c : altInterfaces)
554 foundSerializableSupertype |= Serializable.class.isAssignableFrom(c);
555 if (!foundSerializableSupertype) {
556 altInterfaces = Arrays.copyOf(altInterfaces, altInterfaces.length + 1);
557 altInterfaces[altInterfaces.length-1] = Serializable.class;
558 }
559 }
560
561 AbstractValidatingLambdaMetafactory mf
562 = new InnerClassLambdaMetafactory(caller,
563 factoryType,
564 interfaceMethodName,
565 interfaceMethodType,
566 implementation,
567 dynamicMethodType,
568 isSerializable,
569 altInterfaces,
570 altMethods,
571 reflectableLambdaInfo);
572 mf.validateMetafactoryArgs();
573 return mf.buildCallSite();
574 }
575
576 private static <T> T extractArg(Object[] args, int index, Class<T> type) {
577 if (index >= args.length) {
578 throw new IllegalArgumentException("missing argument");
579 }
580 Object result = Objects.requireNonNull(args[index]);
581 if (!type.isInstance(result)) {
582 throw new IllegalArgumentException("argument has wrong type");
583 }
584 return type.cast(result);
585 }
586
587 private static <T> T[] extractArgs(Object[] args, int index, Class<T> type, int count) {
588 @SuppressWarnings("unchecked")
589 T[] result = (T[]) Array.newInstance(type, count);
590 for (int i = 0; i < count; i++) {
591 result[i] = extractArg(args, index + i, type);
592 }
593 return result;
594 }
595
596 }