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 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 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 * <p> 213 * <dt><i>Identifiers:</i> 214 * <dd> <i>Identifier</i> 215 * <dd> <i>Identifier</i> {@code .} <i>Identifiers</i> 216 * <p> 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 * <p> 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 }