1 /*
2 * Copyright (c) 2022, 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 /**
27 * <h2>Provides classfile parsing, generation, and transformation library.</h2>
28 * The {@code java.lang.classfile} package contains classes for reading, writing, and
29 * modifying Java class files, as specified in Chapter {@jvms 4} of the <cite>Java
30 * Java Virtual Machine Specification</cite>.
31 *
32 * <h2>Reading classfiles</h2>
33 * The main class for reading classfiles is {@link java.lang.classfile.ClassModel}; we
34 * convert bytes into a {@link java.lang.classfile.ClassModel} with {@link
35 * java.lang.classfile.ClassFile#parse(byte[])}:
36 * <p>
37 * {@snippet lang=java :
38 * ClassModel cm = ClassFile.of().parse(bytes);
39 * }
40 * <p>
41 * There are several additional overloads of {@code parse} that let you specify
42 * various processing options.
43 * <p>
44 * A {@link java.lang.classfile.ClassModel} is an immutable description of a class
45 * file. It provides accessor methods to get at class metadata (e.g., {@link
46 * java.lang.classfile.ClassModel#thisClass()}, {@link java.lang.classfile.ClassModel#flags()}),
47 * as well as subordinate classfile entities ({@link java.lang.classfile.ClassModel#fields()},
48 * {@link java.lang.classfile.ClassModel#attributes()}). A {@link
49 * java.lang.classfile.ClassModel} is inflated lazily; most parts of the classfile are
50 * not parsed until they are actually needed.
51 * <p>
52 * We can enumerate the names of the fields and methods in a class by:
53 * {@snippet lang="java" class="PackageSnippets" region="enumerateFieldsMethods1"}
54 * <p>
55 * When we enumerate the methods, we get a {@link java.lang.classfile.MethodModel} for each method; like a
56 * {@code ClassModel}, it gives us access to method metadata and
57 * the ability to descend into subordinate entities such as the bytecodes of the
58 * method body. In this way, a {@code ClassModel} is the root of a
59 * tree, with children for fields, methods, and attributes, and {@code MethodModel} in
60 * turn has its own children (attributes, {@code CodeModel}, etc.)
61 * <p>
62 * Methods like {@link java.lang.classfile.ClassModel#methods} allows us to traverse the class structure
63 * explicitly, going straight to the parts we are interested in. This is useful
64 * for certain kinds of analysis, but if we wanted to process the whole
65 * classfile, we may want something more organized. A {@link
66 * java.lang.classfile.ClassModel} also provides us with a view of the classfile as a
67 * series of class <em>elements</em>, which may include methods, fields, attributes,
68 * and more, and which can be distinguished with pattern matching. We could
69 * rewrite the above example as:
70 * {@snippet lang="java" class="PackageSnippets" region="enumerateFieldsMethods2"}
71 * <p>
72 * The models returned as elements from traversing {@code ClassModel} can in
73 * turn be sources of elements. If we wanted to
74 * traverse a classfile and enumerate all the classes for which we access fields
75 * and methods, we can pick out the class elements that describe methods, then
76 * in turn pick out the method elements that describe the code attribute, and
77 * finally pick out the code elements that describe field access and invocation
78 * instructions:
79 * {@snippet lang="java" class="PackageSnippets" region="gatherDependencies1"}
80 * <p>
81 * This same query could alternately be processed as a stream pipeline over
82 * class elements:
83 * {@snippet lang="java" class="PackageSnippets" region="gatherDependencies2"}
84 *
85 * <h3>Models and elements</h3>
86 * The view of classfiles presented by this API is framed in terms of
87 * <em>models</em> and <em>elements</em>. Models represent complex structures,
88 * such as classes, methods, fields, record elements, or the code body of a
89 * method. Models can be explored either via random-access navigation (such as
90 * the {@link java.lang.classfile.ClassModel#methods()} accessor) or as a linear
91 * sequence of <em>elements</em>. (Elements can in turn also be models; a {@link
92 * java.lang.classfile.FieldModel} is also an element of a class.) For each model type
93 * (e.g., {@link java.lang.classfile.MethodModel}), there is a corresponding element
94 * type ({@link java.lang.classfile.MethodElement}). Models and elements are immutable
95 * and are inflated lazily so creating a model does not necessarily require
96 * processing its entire content.
97 *
98 * <h3>The constant pool</h3>
99 * Much of the interesting content in a classfile lives in the <em>constant
100 * pool</em>. {@link java.lang.classfile.ClassModel} provides a lazily-inflated,
101 * read-only view of the constant pool via {@link java.lang.classfile.ClassModel#constantPool()}.
102 * Descriptions of classfile content is often exposed in the form of various
103 * subtypes of {@link java.lang.classfile.constantpool.PoolEntry}, such as {@link
104 * java.lang.classfile.constantpool.ClassEntry} or {@link java.lang.classfile.constantpool.Utf8Entry}.
105 * <p>
106 * Constant pool entries are also exposed through models and elements; in the
107 * above traversal example, the {@link java.lang.classfile.instruction.InvokeInstruction}
108 * element exposed a method for {@code owner} that corresponds to a {@code
109 * Constant_Class_info} entry in the constant pool.
110 *
111 * <h3>Attributes</h3>
112 * Much of the contents of a classfile is stored in attributes; attributes are
113 * found on classes, methods, fields, record components, and on the {@code Code}
114 * attribute. Most attributes are surfaced as elements; for example, {@link
115 * java.lang.classfile.attribute.SignatureAttribute} is a {@link
116 * java.lang.classfile.ClassElement}, {@link java.lang.classfile.MethodElement}, and {@link
117 * java.lang.classfile.FieldElement} since it can appear in all of those places, and is
118 * included when iterating the elements of the corresponding model.
119 * <p>
120 * Some attributes are not surfaced as elements; these are attributes that are
121 * tightly coupled to -- and logically part of -- other parts of the class file.
122 * These include the {@code BootstrapMethods}, {@code LineNumberTable}, {@code
123 * StackMapTable}, {@code LocalVariableTable}, and {@code
124 * LocalVariableTypeTable} attributes. These are processed by the library and
125 * treated as part of the structure they are coupled to (the entries of the
126 * {@code BootstrapMethods} attribute are treated as part of the constant pool;
127 * line numbers and local variable metadata are modeled as elements of {@link
128 * java.lang.classfile.CodeModel}.)
129 * <p>
130 * The {@code Code} attribute, in addition to being modeled as a {@link
131 * java.lang.classfile.MethodElement}, is also a model in its own right ({@link
132 * java.lang.classfile.CodeModel}) due to its complex structure.
133 * <p>
134 * Each standard attribute has an interface (in {@code java.lang.classfile.attribute})
135 * which exposes the contents of the attribute and provides factories to
136 * construct the attribute. For example, the {@code Signature} attribute is
137 * defined by the {@link java.lang.classfile.attribute.SignatureAttribute} class, and
138 * provides accessors for {@link java.lang.classfile.attribute.SignatureAttribute#signature()}
139 * as well as factories taking {@link java.lang.classfile.constantpool.Utf8Entry} or
140 * {@link java.lang.String}.
141 *
142 * <h3>Custom attributes</h3>
143 * Attributes are converted between their classfile form and their corresponding
144 * object form via an {@link java.lang.classfile.AttributeMapper}. An {@code
145 * AttributeMapper} provides the
146 * {@link java.lang.classfile.AttributeMapper#readAttribute(AttributedElement,
147 * ClassReader, int)} method for mapping from the classfile format
148 * to an attribute instance, and the
149 * {@link java.lang.classfile.AttributeMapper#writeAttribute(java.lang.classfile.BufWriter,
150 * java.lang.Object)} method for mapping back to the classfile format. It also
151 * contains metadata including the attribute name, the set of classfile entities
152 * where the attribute is applicable, and whether multiple attributes of the
153 * same kind are allowed on a single entity.
154 * <p>
155 * There are built-in attribute mappers (in {@link java.lang.classfile.Attributes}) for
156 * each of the attribute types defined in section {@jvms 4.7} of <cite>The Java Virtual
157 * Machine Specification</cite>, as well as several common nonstandard attributes used by the
158 * JDK such as {@code CharacterRangeTable}.
159 * <p>
160 * Unrecognized attributes are delivered as elements of type {@link
161 * java.lang.classfile.attribute.UnknownAttribute}, which provide access only to the
162 * {@code byte[]} contents of the attribute.
163 * <p>
164 * For nonstandard attributes, user-provided attribute mappers can be specified
165 * through the use of the {@link
166 * java.lang.classfile.ClassFile.AttributeMapperOption#of(java.util.function.Function)}}
167 * classfile option. Implementations of custom attributes should extend {@link
168 * java.lang.classfile.CustomAttribute}.
169 *
170 * <h3>Options</h3>
171 * <p>
172 * {@link java.lang.classfile.ClassFile#of(java.lang.classfile.ClassFile.Option[])}
173 * accepts a list of options. {@link java.lang.classfile.ClassFile.Option} is a base interface
174 * for some statically enumerated options, as well as factories for more complex options,
175 * including:
176 * <ul>
177 * <li>{@link java.lang.classfile.ClassFile.StackMapsOption}
178 * -- generate stackmaps (default is {@code STACK_MAPS_WHEN_REQUIRED})</li>
179 * <li>{@link java.lang.classfile.ClassFile.DebugElementsOption}
180 * -- processing of debug information, such as local variable metadata (default is {@code PASS_DEBUG}) </li>
181 * <li>{@link java.lang.classfile.ClassFile.LineNumbersOption}
182 * -- processing of line numbers (default is {@code PASS_LINE_NUMBERS}) </li>
183 * <li>{@link java.lang.classfile.ClassFile.AttributesProcessingOption}
184 * -- unrecognized or problematic original attributes (default is {@code PASS_ALL_ATTRIBUTES})</li>
185 * <li>{@link java.lang.classfile.ClassFile.ConstantPoolSharingOption}}
186 * -- share constant pool when transforming (default is {@code SHARED_POOL})</li>
187 * <li>{@link java.lang.classfile.ClassFile.ClassHierarchyResolverOption#of(java.lang.classfile.ClassHierarchyResolver)}
188 * -- specify a custom class hierarchy resolver used by stack map generation</li>
189 * <li>{@link java.lang.classfile.ClassFile.AttributeMapperOption#of(java.util.function.Function)}
190 * -- specify format of custom attributes</li>
191 * </ul>
192 * <p>
193 * Most options allow you to request that certain parts of the classfile be
194 * skipped during traversal, such as debug information or unrecognized
195 * attributes. Some options allow you to suppress generation of portions of the
196 * classfile, such as stack maps. Many of these options are to access
197 * performance tradeoffs; processing debug information and line numbers has a
198 * cost (both in writing and reading.) If you don't need this information, you
199 * can suppress it with options to gain some performance.
200 *
201 * <h2>Writing classfiles</h2>
202 * ClassFile generation is accomplished through <em>builders</em>. For each
203 * entity type that has a model, there is also a corresponding builder type;
204 * classes are built through {@link java.lang.classfile.ClassBuilder}, methods through
205 * {@link java.lang.classfile.MethodBuilder}, etc.
206 * <p>
207 * Rather than creating builders directly, builders are provided as an argument
208 * to a user-provided lambda. To generate the familiar "hello world" program,
209 * we ask for a class builder, and use that class builder to create method
210 * builders for the constructor and {@code main} method, and in turn use the
211 * method builders to create a {@code Code} attribute and use the code builders
212 * to generate the instructions:
213 * {@snippet lang="java" class="PackageSnippets" region="helloWorld1"}
214 * <p>
215 * The convenience methods {@code ClassBuilder.buildMethodBody} allows us to ask
216 * {@link ClassBuilder} to create code builders to build method bodies directly,
217 * skipping the method builder custom lambda:
218 * {@snippet lang="java" class="PackageSnippets" region="helloWorld2"}
219 * <p>
220 * Builders often support multiple ways of expressing the same entity at
221 * different levels of abstraction. For example, the {@code invokevirtual}
222 * instruction invoking {@code println} could have been generated with {@link
223 * java.lang.classfile.CodeBuilder#invokevirtual(java.lang.constant.ClassDesc,
224 * java.lang.String, java.lang.constant.MethodTypeDesc) CodeBuilder.invokevirtual}, {@link
225 * java.lang.classfile.CodeBuilder#invokeInstruction(java.lang.classfile.Opcode,
226 * java.lang.constant.ClassDesc, java.lang.String, java.lang.constant.MethodTypeDesc,
227 * boolean) CodeBuilder.invokeInstruction}, or {@link
228 * java.lang.classfile.CodeBuilder#with(java.lang.classfile.ClassFileElement)
229 * CodeBuilder.with}.
230 * <p>
231 * The convenience method {@code CodeBuilder.invokevirtual} behaves as if it calls
232 * the convenience method {@code CodeBuilder.invokeInstruction}, which in turn behaves
233 * as if it calls method {@code CodeBuilder.with}. This composing of method calls on the
234 * builder enables the composing of transforms (as described later).
235 *
236 * <h3>Symbolic information</h3>
237 * To describe symbolic information for classes and types, the API uses the
238 * nominal descriptor abstractions from {@code java.lang.constant} such as {@link
239 * java.lang.constant.ClassDesc} and {@link java.lang.constant.MethodTypeDesc},
240 * which is less error-prone than using raw strings.
241 * <p>
242 * If a constant pool entry has a nominal representation then it provides a
243 * method returning the corresponding nominal descriptor type e.g.
244 * method {@link java.lang.classfile.constantpool.ClassEntry#asSymbol} returns
245 * {@code ClassDesc}.
246 * <p>
247 * Where appropriate builders provide two methods for building an element with
248 * symbolic information, one accepting nominal descriptors, and the other
249 * accepting constant pool entries.
250 *
251 * <h3>Consistency checks, syntax checks and verification</h3>
252 * No consistency checks are performed while building or transforming classfiles
253 * (except for null arguments checks). All builders and classfile elements factory
254 * methods accepts the provided information without implicit validation.
255 * However, fatal inconsistencies (like for example invalid code sequence or
256 * unresolved labels) affects internal tools and may cause exceptions later in
257 * the classfile building process.
258 * <p>
259 * Using nominal descriptors assures the right serial form is applied by the
260 * ClassFile API library based on the actual context. Also these nominal
261 * descriptors are validated during their construction, so it is not possible to
262 * create them with invalid content by mistake. Following example pass class
263 * name to the {@link java.lang.constant.ClassDesc#of} method for validation
264 * and the library performs automatic conversion to the right internal form of
265 * the class name when serialized in the constant pool as a class entry.
266 * {@snippet lang=java :
267 * var validClassEntry = constantPoolBuilder.classEntry(ClassDesc.of("mypackage.MyClass"));
268 * }
269 * <p>
270 * On the other hand it is possible to use builders methods and factories accepting
271 * constant pool entries directly. Constant pool entries can be constructed also
272 * directly from raw values, with no additional conversions or validations.
273 * Following example uses intentionally wrong class name form and it is applied
274 * without any validation or conversion.
275 * {@snippet lang=java :
276 * var invalidClassEntry = constantPoolBuilder.classEntry(
277 * constantPoolBuilder.utf8Entry("mypackage.MyClass"));
278 * }
279 * <p>
280 * More complex verification of a classfile can be achieved by invocation of
281 * {@link java.lang.classfile.ClassFile#verify}.
282 *
283 * <h2>Transforming classfiles</h2>
284 * ClassFile Processing APIs are most frequently used to combine reading and
285 * writing into transformation, where a classfile is read, localized changes are
286 * made, but much of the classfile is passed through unchanged. For each kind
287 * of builder, {@code XxxBuilder} has a method {@code with(XxxElement)} so that
288 * elements that we wish to pass through unchanged can be handed directly back
289 * to the builder.
290 * <p>
291 * If we wanted to strip out methods whose names starts with "debug", we could
292 * get an existing {@link java.lang.classfile.ClassModel}, build a new classfile that
293 * provides a {@link java.lang.classfile.ClassBuilder}, iterate the elements of the
294 * original {@link java.lang.classfile.ClassModel}, and pass through all of them to
295 * the builder except the methods we want to drop:
296 * {@snippet lang="java" class="PackageSnippets" region="stripDebugMethods1"}
297 * <p>
298 * This hands every class element, except for those corresponding to methods
299 * whose names start with {@code debug}, back to the builder. Transformations
300 * can of course be more complicated, diving into method bodies and instructions
301 * and transforming those as well, but the same structure is repeated at every
302 * level, since every entity has corresponding model, builder, and element
303 * abstractions.
304 * <p>
305 * Transformation can be viewed as a "flatMap" operation on the sequence of
306 * elements; for every element, we could pass it through unchanged, drop it, or
307 * replace it with one or more elements. Because transformation is such a
308 * common operation on classfiles, each model type has a corresponding {@code
309 * XxxTransform} type (which describes a transform on a sequence of {@code
310 * XxxElement}) and each builder type has {@code transformYyy} methods for transforming
311 * its child models. A transform is simply a functional interface that takes a
312 * builder and an element, and an implementation "flatMap"s elements
313 * into the builder. We could express the above as:
314 * {@snippet lang="java" class="PackageSnippets" region="stripDebugMethods2"}
315 * <p>
316 * {@code ClassTransform.dropping} convenience method allow us to simplify the same
317 * transformation construction and express the above as:
318 * {@snippet lang="java" class="PackageSnippets" region="stripDebugMethods3"}
319 *
320 * <h3>Lifting transforms</h3>
321 * While the example using transformations are only slightly shorter, the
322 * advantage of expressing transformation in this way is that the transform
323 * operations can be more easily combined. Suppose we want to redirect
324 * invocations of static methods on {@code Foo} to the corresponding method on
325 * {@code Bar} instead. We could express this as a transformation on {@link
326 * java.lang.classfile.CodeElement}:
327 * {@snippet lang="java" class="PackageSnippets" region="fooToBarTransform"}
328 * <p>
329 * We can then <em>lift</em> this transformation on code elements into a
330 * transformation on method elements. This intercepts method elements that
331 * correspond to a {@code Code} attribute, dives into its code elements, and
332 * applies the code transform to them, and passes other method elements through
333 * unchanged:
334 * {@snippet lang=java :
335 * MethodTransform mt = MethodTransform.transformingCode(fooToBar);
336 * }
337 * <p>
338 * and further lift the transform on method elements into one on class
339 * elements:
340 * {@snippet lang=java :
341 * ClassTransform ct = ClassTransform.transformingMethods(mt);
342 * }
343 * <p>
344 * or lift the code transform into the class transform directly:
345 * {@snippet lang=java :
346 * ClassTransform ct = ClassTransform.transformingMethodBodiess(fooToBar);
347 * }
348 * <p>
349 * and then transform the classfile:
350 * {@snippet lang=java :
351 * var cc = ClassFile.of();
352 * byte[] newBytes = cc.transform(cc.parse(bytes), ct);
353 * }
354 * <p>
355 * This is much more concise (and less error-prone) than the equivalent
356 * expressed by traversing the classfile structure directly:
357 * {@snippet lang="java" class="PackageSnippets" region="fooToBarUnrolled"}
358 *
359 * <h3>Composing transforms</h3>
360 * Transforms on the same type of element can be composed in sequence, where the
361 * output of the first is fed to the input of the second. Suppose we want to
362 * instrument all method calls, where we print the name of a method before
363 * calling it:
364 * {@snippet lang="java" class="PackageSnippets" region="instrumentCallsTransform"}
365 * <p>
366 * Then we can compose {@code fooToBar} and {@code instrumentCalls} with {@link
367 * java.lang.classfile.CodeTransform#andThen(java.lang.classfile.CodeTransform)}:
368 * <p>
369 * {@snippet lang=java :
370 * var cc = ClassFile.of();
371 * byte[] newBytes = cc.transform(cc.parse(bytes),
372 * ClassTransform.transformingMethods(
373 * MethodTransform.transformingCode(
374 * fooToBar.andThen(instrumentCalls))));
375 * }
376 *
377 * Transform {@code instrumentCalls} will receive all code elements produced by
378 * transform {@code forToBar}, either those code elements from the original classfile
379 * or replacements (replacing static invocations to {@code Foo} with those to {@code Bar}).
380 *
381 * <h3>Constant pool sharing</h3>
382 * Transformation doesn't merely handle the logistics of reading, transforming
383 * elements, and writing. Most of the time when we are transforming a
384 * classfile, we are making relatively minor changes. To optimize such cases,
385 * transformation seeds the new classfile with a copy of the constant pool from
386 * the original classfile; this enables significant optimizations (methods and
387 * attributes that are not transformed can be processed by bulk-copying their
388 * bytes, rather than parsing them and regenerating their contents.) If
389 * constant pool sharing is not desired it can be suppressed
390 * with the {@link java.lang.classfile.ClassFile.ConstantPoolSharingOption} option.
391 * Such suppression may be beneficial when transformation removes many elements,
392 * resulting in many unreferenced constant pool entries.
393 *
394 * <h3>Transformation handling of unknown classfile elements</h3>
395 * Custom classfile transformations might be unaware of classfile elements
396 * introduced by future JDK releases. To achieve deterministic stability,
397 * classfile transforms interested in consuming all classfile elements should be
398 * implemented strictly to throw exceptions if running on a newer JDK, if the
399 * transformed class file is a newer version, or if a new and unknown classfile
400 * element appears. As for example in the following strict compatibility-checking
401 * transformation snippets:
402 * {@snippet lang="java" class="PackageSnippets" region="strictTransform1"}
403 * {@snippet lang="java" class="PackageSnippets" region="strictTransform2"}
404 * {@snippet lang="java" class="PackageSnippets" region="strictTransform3"}
405 * <p>
406 * Conversely, classfile transforms that are only interested in consuming a portion
407 * of classfile elements do not need to concern with new and unknown classfile
408 * elements and may pass them through. Following example shows such future-proof
409 * code transformation:
410 * {@snippet lang="java" class="PackageSnippets" region="benevolentTransform"}
411 *
412 * <h2>API conventions</h2>
413 * <p>
414 * The API is largely derived from a <a href="#data_model"><em>data model</em></a>
415 * for the classfile format, which defines each element kind (which includes models and
416 * attributes) and its properties. For each element kind, there is a
417 * corresponding interface to describe that element, and factory methods to
418 * create that element. Some element kinds also have convenience methods on the
419 * corresponding builder (e.g., {@link
420 * java.lang.classfile.CodeBuilder#invokevirtual(java.lang.constant.ClassDesc,
421 * java.lang.String, java.lang.constant.MethodTypeDesc)}).
422 * <p>
423 * Most symbolic information in elements is represented by constant pool entries
424 * (for example, the owner of a field is represented by a {@link
425 * java.lang.classfile.constantpool.ClassEntry}.) Factories and builders also
426 * accept nominal descriptors from {@code java.lang.constant} (e.g., {@link
427 * java.lang.constant.ClassDesc}.)
428 *
429 * <h2><a id="data_model"></a>Data model</h2>
430 * We define each kind of element by its name, an optional arity indicator (zero
431 * or more, zero or one, exactly one), and a list of components. The elements
432 * of a class are fields, methods, and the attributes that can appear on
433 * classes:
434 * <p>
435 * {@snippet lang="text" :
436 * ClassElement =
437 * FieldModel*(UtfEntry name, Utf8Entry descriptor)
438 * | MethodModel*(UtfEntry name, Utf8Entry descriptor)
439 * | ModuleAttribute?(int flags, ModuleEntry moduleName, UtfEntry moduleVersion,
440 * List<ModuleRequireInfo> requires, List<ModuleOpenInfo> opens,
441 * List<ModuleExportInfo> exports, List<ModuleProvidesInfo> provides,
442 * List<ClassEntry> uses)
443 * | ModulePackagesAttribute?(List<PackageEntry> packages)
444 * | ModuleTargetAttribute?(Utf8Entry targetPlatform)
445 * | ModuleHashesAttribute?(Utf8Entry algorithm, List<HashInfo> hashes)
446 * | ModuleResolutionAttribute?(int resolutionFlags)
447 * | SourceFileAttribute?(Utf8Entry sourceFile)
448 * | SourceDebugExtensionsAttribute?(byte[] contents)
449 * | CompilationIDAttribute?(Utf8Entry compilationId)
450 * | SourceIDAttribute?(Utf8Entry sourceId)
451 * | NestHostAttribute?(ClassEntry nestHost)
452 * | NestMembersAttribute?(List<ClassEntry> nestMembers)
453 * | RecordAttribute?(List<RecordComponent> components)
454 * | EnclosingMethodAttribute?(ClassEntry className, NameAndTypeEntry method)
455 * | InnerClassesAttribute?(List<InnerClassInfo> classes)
456 * | PermittedSubclassesAttribute?(List<ClassEntry> permittedSubclasses)
457 * | DeclarationElement*
458 * }
459 *<p>
460 * where {@code DeclarationElement} are the elements that are common to all declarations
461 * (classes, methods, fields) and so are factored out:
462 *
463 * {@snippet lang="text" :
464 * DeclarationElement =
465 * SignatureAttribute?(Utf8Entry signature)
466 * | SyntheticAttribute?()
467 * | DeprecatedAttribute?()
468 * | RuntimeInvisibleAnnotationsAttribute?(List<Annotation> annotations)
469 * | RuntimeVisibleAnnotationsAttribute?(List<Annotation> annotations)
470 * | CustomAttribute*
471 * | UnknownAttribute*
472 * }
473 *
474 * Fields and methods are models with their own elements. The elements of fields
475 * and methods are fairly simple; most of the complexity of methods lives in the
476 * {@link java.lang.classfile.CodeModel} (which models the {@code Code} attribute
477 * along with the code-related attributes: stack map table, local variable table,
478 * line number table, etc.)
479 *
480 * {@snippet lang="text" :
481 * FieldElement =
482 * DeclarationElement
483 * | ConstantValueAttribute?(ConstantValueEntry constant)
484 *
485 * MethodElement =
486 * DeclarationElement
487 * | CodeModel?()
488 * | AnnotationDefaultAttribute?(ElementValue defaultValue)
489 * | MethodParametersAttribute?(List<MethodParameterInfo> parameters)
490 * | ExceptionsAttribute?(List<ClassEntry> exceptions)
491 * }
492 *
493 * {@link java.lang.classfile.CodeModel} is unique in that its elements are <em>ordered</em>.
494 * Elements of {@code Code} include ordinary bytecodes, as well as a number of pseudo-instructions
495 * representing branch targets, line number metadata, local variable metadata, and
496 * catch blocks.
497 *
498 * {@snippet lang="text" :
499 * CodeElement = Instruction | PseudoInstruction
500 *
501 * Instruction =
502 * LoadInstruction(TypeKind type, int slot)
503 * | StoreInstruction(TypeKind type, int slot)
504 * | IncrementInstruction(int slot, int constant)
505 * | BranchInstruction(Opcode opcode, Label target)
506 * | LookupSwitchInstruction(Label defaultTarget, List<SwitchCase> cases)
507 * | TableSwitchInstruction(Label defaultTarget, int low, int high,
508 * List<SwitchCase> cases)
509 * | ReturnInstruction(TypeKind kind)
510 * | ThrowInstruction()
511 * | FieldInstruction(Opcode opcode, FieldRefEntry field)
512 * | InvokeInstruction(Opcode opcode, MemberRefEntry method, boolean isInterface)
513 * | InvokeDynamicInstruction(InvokeDynamicEntry invokedynamic)
514 * | NewObjectInstruction(ClassEntry className)
515 * | NewReferenceArrayInstruction(ClassEntry componentType)
516 * | NewPrimitiveArrayInstruction(TypeKind typeKind)
517 * | NewMultiArrayInstruction(ClassEntry componentType, int dims)
518 * | ArrayLoadInstruction(Opcode opcode)
519 * | ArrayStoreInstruction(Opcode opcode)
520 * | TypeCheckInstruction(Opcode opcode, ClassEntry className)
521 * | ConvertInstruction(TypeKind from, TypeKind to)
522 * | OperatorInstruction(Opcode opcode)
523 * | ConstantInstruction(ConstantDesc constant)
524 * | StackInstruction(Opcode opcode)
525 * | MonitorInstruction(Opcode opcode)
526 * | NopInstruction()
527 *
528 * PseudoInstruction =
529 * | LabelTarget(Label label)
530 * | LineNumber(int line)
531 * | ExceptionCatch(Label tryStart, Label tryEnd, Label handler, ClassEntry exception)
532 * | LocalVariable(int slot, UtfEntry name, Utf8Entry type, Label startScope, Label endScope)
533 * | LocalVariableType(int slot, Utf8Entry name, Utf8Entry type, Label startScope, Label endScope)
534 * | CharacterRange(int rangeStart, int rangeEnd, int flags, Label startScope, Label endScope)
535 * }
536 *
537 * @since 22
538 */
539 @PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
540 package java.lang.classfile;
541
542 import jdk.internal.javac.PreviewFeature;