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