1 /*
2 * Copyright (c) 2005, 2013, 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
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9 * by Oracle in the LICENSE file that accompanied this code.
10 *
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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).
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24 */
25
26 package javax.annotation.processing;
27
28 import java.util.Set;
29 import javax.lang.model.util.Elements;
30 import javax.lang.model.AnnotatedConstruct;
31 import javax.lang.model.element.*;
32 import javax.lang.model.SourceVersion;
33
34 /**
35 * The interface for an annotation processor.
36 *
37 * <p>Annotation processing happens in a sequence of {@linkplain
38 * javax.annotation.processing.RoundEnvironment rounds}. On each
39 * round, a processor may be asked to {@linkplain #process process} a
40 * subset of the annotations found on the source and class files
41 * produced by a prior round. The inputs to the first round of
42 * processing are the initial inputs to a run of the tool; these
43 * initial inputs can be regarded as the output of a virtual zeroth
44 * round of processing. If a processor was asked to process on a
45 * given round, it will be asked to process on subsequent rounds,
46 * including the last round, even if there are no annotations for it
47 * to process. The tool infrastructure may also ask a processor to
48 * process files generated implicitly by the tool's operation.
49 *
50 * <p> Each implementation of a {@code Processor} must provide a
51 * public no-argument constructor to be used by tools to instantiate
52 * the processor. The tool infrastructure will interact with classes
53 * implementing this interface as follows:
54 *
55 * <ol>
56 *
57 * <li>If an existing {@code Processor} object is not being used, to
58 * create an instance of a processor the tool calls the no-arg
59 * constructor of the processor class.
60 *
61 * <li>Next, the tool calls the {@link #init init} method with
62 * an appropriate {@code ProcessingEnvironment}.
63 *
64 * <li>Afterwards, the tool calls {@link #getSupportedAnnotationTypes
65 * getSupportedAnnotationTypes}, {@link #getSupportedOptions
66 * getSupportedOptions}, and {@link #getSupportedSourceVersion
67 * getSupportedSourceVersion}. These methods are only called once per
68 * run, not on each round.
69 *
70 * <li>As appropriate, the tool calls the {@link #process process}
71 * method on the {@code Processor} object; a new {@code Processor}
72 * object is <em>not</em> created for each round.
73 *
74 * </ol>
75 *
76 * If a processor object is created and used without the above
77 * protocol being followed, then the processor's behavior is not
78 * defined by this interface specification.
79 *
80 * <p> The tool uses a <i>discovery process</i> to find annotation
81 * processors and decide whether or not they should be run. By
82 * configuring the tool, the set of potential processors can be
83 * controlled. For example, for a {@link javax.tools.JavaCompiler
84 * JavaCompiler} the list of candidate processors to run can be
85 * {@linkplain javax.tools.JavaCompiler.CompilationTask#setProcessors
86 * set directly} or controlled by a {@linkplain
87 * javax.tools.StandardLocation#ANNOTATION_PROCESSOR_PATH search path}
88 * used for a {@linkplain java.util.ServiceLoader service-style}
89 * lookup. Other tool implementations may have different
90 * configuration mechanisms, such as command line options; for
91 * details, refer to the particular tool's documentation. Which
92 * processors the tool asks to {@linkplain #process run} is a function
93 * of the types of the annotations <em>{@linkplain AnnotatedConstruct present}</em>
94 * on the {@linkplain
95 * RoundEnvironment#getRootElements root elements}, what {@linkplain
96 * #getSupportedAnnotationTypes annotation types a processor
97 * supports}, and whether or not a processor {@linkplain #process
98 * claims the annotation types it processes}. A processor will be asked to
99 * process a subset of the annotation types it supports, possibly an
100 * empty set.
101 *
102 * For a given round, the tool computes the set of annotation types
103 * that are present on the elements enclosed within the root elements.
104 * If there is at least one annotation type present, then as
105 * processors claim annotation types, they are removed from the set of
106 * unmatched annotation types. When the set is empty or no more
107 * processors are available, the round has run to completion. If
108 * there are no annotation types present, annotation processing still
109 * occurs but only <i>universal processors</i> which support
110 * processing all annotation types, {@code "*"}, can claim the (empty)
111 * set of annotation types.
112 *
113 * <p>An annotation type is considered present if there is at least
114 * one annotation of that type present on an element enclosed within
115 * the root elements of a round. For this purpose, a type parameter is
116 * considered to be enclosed by its {@linkplain
117 * TypeParameterElement#getGenericElement generic
118 * element}. Annotations on {@linkplain
119 * java.lang.annotation.ElementType#TYPE_USE type uses}, as opposed to
120 * annotations on elements, are ignored when computing whether or not
121 * an annotation type is present.
122 *
123 * <p>An annotation is present if it meets the definition of being
124 * present given in {@link AnnotatedConstruct}. In brief, an
125 * annotation is considered present for the purposes of discovery if
126 * it is directly present or present via inheritance. An annotation is
127 * <em>not</em> considered present by virtue of being wrapped by a
128 * container annotation. Operationally, this is equivalent to an
129 * annotation being present on an element if and only if it would be
130 * included in the results of {@link
131 * Elements#getAllAnnotationMirrors(Element)} called on that element. Since
132 * annotations inside container annotations are not considered
133 * present, to properly process {@linkplain
134 * java.lang.annotation.Repeatable repeatable annotation types},
135 * processors are advised to include both the repeatable annotation
136 * type and its containing annotation type in the set of {@linkplain
137 * #getSupportedAnnotationTypes() supported annotation types} of a
138 * processor.
139 *
140 * <p>Note that if a processor supports {@code "*"} and returns {@code
141 * true}, all annotations are claimed. Therefore, a universal
142 * processor being used to, for example, implement additional validity
143 * checks should return {@code false} so as to not prevent other such
144 * checkers from being able to run.
145 *
146 * <p>If a processor throws an uncaught exception, the tool may cease
147 * other active annotation processors. If a processor raises an
148 * error, the current round will run to completion and the subsequent
149 * round will indicate an {@linkplain RoundEnvironment#errorRaised
150 * error was raised}. Since annotation processors are run in a
151 * cooperative environment, a processor should throw an uncaught
152 * exception only in situations where no error recovery or reporting
153 * is feasible.
154 *
155 * <p>The tool environment is not required to support annotation
156 * processors that access environmental resources, either {@linkplain
157 * RoundEnvironment per round} or {@linkplain ProcessingEnvironment
158 * cross-round}, in a multi-threaded fashion.
159 *
160 * <p>If the methods that return configuration information about the
161 * annotation processor return {@code null}, return other invalid
162 * input, or throw an exception, the tool infrastructure must treat
163 * this as an error condition.
164 *
165 * <p>To be robust when running in different tool implementations, an
166 * annotation processor should have the following properties:
167 *
168 * <ol>
169 *
170 * <li>The result of processing a given input is not a function of the presence or absence
171 * of other inputs (orthogonality).
172 *
173 * <li>Processing the same input produces the same output (consistency).
174 *
175 * <li>Processing input <i>A</i> followed by processing input <i>B</i>
176 * is equivalent to processing <i>B</i> then <i>A</i>
177 * (commutativity)
178 *
179 * <li>Processing an input does not rely on the presence of the output
180 * of other annotation processors (independence)
181 *
182 * </ol>
183 *
184 * <p>The {@link Filer} interface discusses restrictions on how
185 * processors can operate on files.
186 *
187 * <p>Note that implementors of this interface may find it convenient
188 * to extend {@link AbstractProcessor} rather than implementing this
189 * interface directly.
190 *
191 * @author Joseph D. Darcy
192 * @author Scott Seligman
193 * @author Peter von der Ahé
194 * @since 1.6
195 */
196 public interface Processor {
197 /**
198 * Returns the options recognized by this processor. An
199 * implementation of the processing tool must provide a way to
200 * pass processor-specific options distinctly from options passed
201 * to the tool itself, see {@link ProcessingEnvironment#getOptions
202 * getOptions}.
203 *
204 * <p>Each string returned in the set must be a period separated
205 * sequence of {@linkplain
206 * javax.lang.model.SourceVersion#isIdentifier identifiers}:
207 *
208 * <blockquote>
209 * <dl>
210 * <dt><i>SupportedOptionString:</i>
211 * <dd><i>Identifiers</i>
212 *
213 * <dt><i>Identifiers:</i>
214 * <dd> <i>Identifier</i>
215 * <dd> <i>Identifier</i> {@code .} <i>Identifiers</i>
216 *
217 * <dt><i>Identifier:</i>
218 * <dd>Syntactic identifier, including keywords and literals
219 * </dl>
220 * </blockquote>
221 *
222 * <p> A tool might use this information to determine if any
223 * options provided by a user are unrecognized by any processor,
224 * in which case it may wish to report a warning.
225 *
226 * @return the options recognized by this processor or an
227 * empty collection if none
228 * @see javax.annotation.processing.SupportedOptions
229 */
230 Set<String> getSupportedOptions();
231
232 /**
233 * Returns the names of the annotation types supported by this
234 * processor. An element of the result may be the canonical
235 * (fully qualified) name of a supported annotation type.
236 * Alternately it may be of the form "<tt><i>name</i>.*</tt>"
237 * representing the set of all annotation types with canonical
238 * names beginning with "<tt><i>name.</i></tt>". Finally, {@code
239 * "*"} by itself represents the set of all annotation types,
240 * including the empty set. Note that a processor should not
241 * claim {@code "*"} unless it is actually processing all files;
242 * claiming unnecessary annotations may cause a performance
243 * slowdown in some environments.
244 *
245 * <p>Each string returned in the set must be accepted by the
246 * following grammar:
247 *
248 * <blockquote>
249 * <dl>
250 * <dt><i>SupportedAnnotationTypeString:</i>
251 * <dd><i>TypeName</i> <i>DotStar</i><sub><i>opt</i></sub>
252 * <dd><tt>*</tt>
253 *
254 * <dt><i>DotStar:</i>
255 * <dd><tt>.</tt> <tt>*</tt>
256 * </dl>
257 * </blockquote>
258 *
259 * where <i>TypeName</i> is as defined in
260 * <cite>The Java™ Language Specification</cite>.
261 *
262 * @return the names of the annotation types supported by this processor
263 * @see javax.annotation.processing.SupportedAnnotationTypes
264 * @jls 3.8 Identifiers
265 * @jls 6.5.5 Meaning of Type Names
266 */
267 Set<String> getSupportedAnnotationTypes();
268
269 /**
270 * Returns the latest source version supported by this annotation
271 * processor.
272 *
273 * @return the latest source version supported by this annotation
274 * processor.
275 * @see javax.annotation.processing.SupportedSourceVersion
276 * @see ProcessingEnvironment#getSourceVersion
277 */
278 SourceVersion getSupportedSourceVersion();
279
280 /**
281 * Initializes the processor with the processing environment.
282 *
283 * @param processingEnv environment for facilities the tool framework
284 * provides to the processor
285 */
286 void init(ProcessingEnvironment processingEnv);
287
288 /**
289 * Processes a set of annotation types on type elements
290 * originating from the prior round and returns whether or not
291 * these annotation types are claimed by this processor. If {@code
292 * true} is returned, the annotation types are claimed and subsequent
293 * processors will not be asked to process them; if {@code false}
294 * is returned, the annotation types are unclaimed and subsequent
295 * processors may be asked to process them. A processor may
296 * always return the same boolean value or may vary the result
297 * based on chosen criteria.
298 *
299 * <p>The input set will be empty if the processor supports {@code
300 * "*"} and the root elements have no annotations. A {@code
301 * Processor} must gracefully handle an empty set of annotations.
302 *
303 * @param annotations the annotation types requested to be processed
304 * @param roundEnv environment for information about the current and prior round
305 * @return whether or not the set of annotation types are claimed by this processor
306 */
307 boolean process(Set<? extends TypeElement> annotations,
308 RoundEnvironment roundEnv);
309
310 /**
311 * Returns to the tool infrastructure an iterable of suggested
312 * completions to an annotation. Since completions are being asked
313 * for, the information provided about the annotation may be
314 * incomplete, as if for a source code fragment. A processor may
315 * return an empty iterable. Annotation processors should focus
316 * their efforts on providing completions for annotation members
317 * with additional validity constraints known to the processor, for
318 * example an {@code int} member whose value should lie between 1
319 * and 10 or a string member that should be recognized by a known
320 * grammar, such as a regular expression or a URL.
321 *
322 * <p>Since incomplete programs are being modeled, some of the
323 * parameters may only have partial information or may be {@code
324 * null}. At least one of {@code element} and {@code userText}
325 * must be non-{@code null}. If {@code element} is non-{@code
326 * null}, {@code annotation} and {@code member} may be {@code
327 * null}. Processors may not throw a {@code NullPointerException}
328 * if some parameters are {@code null}; if a processor has no
329 * completions to offer based on the provided information, an
330 * empty iterable can be returned. The processor may also return
331 * a single completion with an empty value string and a message
332 * describing why there are no completions.
333 *
334 * <p>Completions are informative and may reflect additional
335 * validity checks performed by annotation processors. For
336 * example, consider the simple annotation:
337 *
338 * <blockquote>
339 * <pre>
340 * @MersennePrime {
341 * int value();
342 * }
343 * </pre>
344 * </blockquote>
345 *
346 * (A Mersenne prime is prime number of the form
347 * 2<sup><i>n</i></sup> - 1.) Given an {@code AnnotationMirror}
348 * for this annotation type, a list of all such primes in the
349 * {@code int} range could be returned without examining any other
350 * arguments to {@code getCompletions}:
351 *
352 * <blockquote>
353 * <pre>
354 * import static javax.annotation.processing.Completions.*;
355 * ...
356 * return Arrays.asList({@link Completions#of(String) of}("3"),
357 * of("7"),
358 * of("31"),
359 * of("127"),
360 * of("8191"),
361 * of("131071"),
362 * of("524287"),
363 * of("2147483647"));
364 * </pre>
365 * </blockquote>
366 *
367 * A more informative set of completions would include the number
368 * of each prime:
369 *
370 * <blockquote>
371 * <pre>
372 * return Arrays.asList({@link Completions#of(String, String) of}("3", "M2"),
373 * of("7", "M3"),
374 * of("31", "M5"),
375 * of("127", "M7"),
376 * of("8191", "M13"),
377 * of("131071", "M17"),
378 * of("524287", "M19"),
379 * of("2147483647", "M31"));
380 * </pre>
381 * </blockquote>
382 *
383 * However, if the {@code userText} is available, it can be checked
384 * to see if only a subset of the Mersenne primes are valid. For
385 * example, if the user has typed
386 *
387 * <blockquote>
388 * <code>
389 * @MersennePrime(1
390 * </code>
391 * </blockquote>
392 *
393 * the value of {@code userText} will be {@code "1"}; and only
394 * two of the primes are possible completions:
395 *
396 * <blockquote>
397 * <pre>
398 * return Arrays.asList(of("127", "M7"),
399 * of("131071", "M17"));
400 * </pre>
401 * </blockquote>
402 *
403 * Sometimes no valid completion is possible. For example, there
404 * is no in-range Mersenne prime starting with 9:
405 *
406 * <blockquote>
407 * <code>
408 * @MersennePrime(9
409 * </code>
410 * </blockquote>
411 *
412 * An appropriate response in this case is to either return an
413 * empty list of completions,
414 *
415 * <blockquote>
416 * <pre>
417 * return Collections.emptyList();
418 * </pre>
419 * </blockquote>
420 *
421 * or a single empty completion with a helpful message
422 *
423 * <blockquote>
424 * <pre>
425 * return Arrays.asList(of("", "No in-range Mersenne primes start with 9"));
426 * </pre>
427 * </blockquote>
428 *
429 * @param element the element being annotated
430 * @param annotation the (perhaps partial) annotation being
431 * applied to the element
432 * @param member the annotation member to return possible completions for
433 * @param userText source code text to be completed
434 *
435 * @return suggested completions to the annotation
436 */
437 Iterable<? extends Completion> getCompletions(Element element,
438 AnnotationMirror annotation,
439 ExecutableElement member,
440 String userText);
441 }