1 /* 2 * Copyright (c) 2003, 2018, 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 java.lang.reflect; 27 28 import java.lang.annotation.Annotation; 29 import java.lang.annotation.AnnotationFormatError; 30 import java.lang.annotation.Repeatable; 31 import java.util.Arrays; 32 import java.util.LinkedHashMap; 33 import java.util.Map; 34 import java.util.Objects; 35 import java.util.function.Function; 36 import java.util.stream.Collectors; 37 import sun.reflect.annotation.AnnotationSupport; 38 import sun.reflect.annotation.AnnotationType; 39 40 /** 41 * Represents an annotated element of the program currently running in this 42 * VM. This interface allows annotations to be read reflectively. All 43 * annotations returned by methods in this interface are immutable and 44 * serializable. The arrays returned by methods of this interface may be modified 45 * by callers without affecting the arrays returned to other callers. 46 * 47 * <p>The {@link #getAnnotationsByType(Class)} and {@link 48 * #getDeclaredAnnotationsByType(Class)} methods support multiple 49 * annotations of the same type on an element. If the argument to 50 * either method is a repeatable annotation type (JLS 9.6), then the 51 * method will "look through" a container annotation (JLS 9.7), if 52 * present, and return any annotations inside the container. Container 53 * annotations may be generated at compile-time to wrap multiple 54 * annotations of the argument type. 55 * 56 * <p>The terms <em>directly present</em>, <em>indirectly present</em>, 57 * <em>present</em>, and <em>associated</em> are used throughout this 58 * interface to describe precisely which annotations are returned by 59 * methods: 60 * 61 * <ul> 62 * 63 * <li> An annotation <i>A</i> is <em>directly present</em> on an 64 * element <i>E</i> if <i>E</i> has a {@code 65 * RuntimeVisibleAnnotations} or {@code 66 * RuntimeVisibleParameterAnnotations} or {@code 67 * RuntimeVisibleTypeAnnotations} attribute, and the attribute 68 * contains <i>A</i>. 69 * 70 * <li>An annotation <i>A</i> is <em>indirectly present</em> on an 71 * element <i>E</i> if <i>E</i> has a {@code RuntimeVisibleAnnotations} or 72 * {@code RuntimeVisibleParameterAnnotations} or {@code RuntimeVisibleTypeAnnotations} 73 * attribute, and <i>A</i> 's type is repeatable, and the attribute contains 74 * exactly one annotation whose value element contains <i>A</i> and whose 75 * type is the containing annotation type of <i>A</i> 's type. 76 * 77 * <li>An annotation <i>A</i> is <em>present</em> on an element <i>E</i> if either: 78 * 79 * <ul> 80 * 81 * <li><i>A</i> is directly present on <i>E</i>; or 82 * 83 * <li>No annotation of <i>A</i> 's type is directly present on 84 * <i>E</i>, and <i>E</i> is a class, and <i>A</i> 's type is 85 * inheritable, and <i>A</i> is present on the superclass of <i>E</i>. 86 * 87 * </ul> 88 * 89 * <li>An annotation <i>A</i> is <em>associated</em> with an element <i>E</i> 90 * if either: 91 * 92 * <ul> 93 * 94 * <li><i>A</i> is directly or indirectly present on <i>E</i>; or 95 * 96 * <li>No annotation of <i>A</i> 's type is directly or indirectly 97 * present on <i>E</i>, and <i>E</i> is a class, and <i>A</i>'s type 98 * is inheritable, and <i>A</i> is associated with the superclass of 99 * <i>E</i>. 100 * 101 * </ul> 102 * 103 * </ul> 104 * 105 * <p>The table below summarizes which kind of annotation presence 106 * different methods in this interface examine. 107 * 108 * <table class="plain"> 109 * <caption>Overview of kind of presence detected by different AnnotatedElement methods</caption> 110 * <thead> 111 * <tr><th colspan=2 scope="col">Method</th> 112 * <th colspan=4 scope="col">Kind of Presence</th> 113 * <tr><th scope="col">Return Type</th> 114 * <th scope="col">Signature</th> 115 * <th scope="col">Directly Present</th> 116 * <th scope="col">Indirectly Present</th> 117 * <th scope="col">Present</th> 118 * <th scope="col">Associated</th> 119 * </thead> 120 * <tbody> 121 * <tr><td style="text-align:right">{@code T}</td> 122 * <th scope="row" style="font-weight:normal; text-align:left">{@link #getAnnotation(Class) getAnnotation(Class<T>)} 123 * <td></td><td></td><td style="text-align:center">X</td><td></td> 124 * </tr> 125 * <tr><td style="text-align:right">{@code Annotation[]}</td> 126 * <th scope="row" style="font-weight:normal; text-align:left">{@link #getAnnotations getAnnotations()} 127 * <td></td><td></td><td style="text-align:center">X</td><td></td> 128 * </tr> 129 * <tr><td style="text-align:right">{@code T[]}</td> 130 * <th scope="row" style="font-weight:normal; text-align:left">{@link #getAnnotationsByType(Class) getAnnotationsByType(Class<T>)} 131 * <td></td><td></td><td></td><td style="text-align:center">X</td> 132 * </tr> 133 * <tr><td style="text-align:right">{@code T}</td> 134 * <th scope="row" style="font-weight:normal; text-align:left">{@link #getDeclaredAnnotation(Class) getDeclaredAnnotation(Class<T>)} 135 * <td style="text-align:center">X</td><td></td><td></td><td></td> 136 * </tr> 137 * <tr><td style="text-align:right">{@code Annotation[]}</td> 138 * <th scope="row" style="font-weight:normal; text-align:left">{@link #getDeclaredAnnotations getDeclaredAnnotations()} 139 * <td style="text-align:center">X</td><td></td><td></td><td></td> 140 * </tr> 141 * <tr><td style="text-align:right">{@code T[]}</td> 142 * <th scope="row" style="font-weight:normal; text-align:left">{@link #getDeclaredAnnotationsByType(Class) getDeclaredAnnotationsByType(Class<T>)} 143 * <td style="text-align:center">X</td><td style="text-align:center">X</td><td></td><td></td> 144 * </tr> 145 * </tbody> 146 * </table> 147 * 148 * <p>For an invocation of {@code get[Declared]AnnotationsByType(Class <T>)}, 149 * the order of annotations which are directly or indirectly 150 * present on an element <i>E</i> is computed as if indirectly present 151 * annotations on <i>E</i> are directly present on <i>E</i> in place 152 * of their container annotation, in the order in which they appear in 153 * the value element of the container annotation. 154 * 155 * <p>There are several compatibility concerns to keep in mind if an 156 * annotation type <i>T</i> is originally <em>not</em> repeatable and 157 * later modified to be repeatable. 158 * 159 * The containing annotation type for <i>T</i> is <i>TC</i>. 160 * 161 * <ul> 162 * 163 * <li>Modifying <i>T</i> to be repeatable is source and binary 164 * compatible with existing uses of <i>T</i> and with existing uses 165 * of <i>TC</i>. 166 * 167 * That is, for source compatibility, source code with annotations of 168 * type <i>T</i> or of type <i>TC</i> will still compile. For binary 169 * compatibility, class files with annotations of type <i>T</i> or of 170 * type <i>TC</i> (or with other kinds of uses of type <i>T</i> or of 171 * type <i>TC</i>) will link against the modified version of <i>T</i> 172 * if they linked against the earlier version. 173 * 174 * (An annotation type <i>TC</i> may informally serve as an acting 175 * containing annotation type before <i>T</i> is modified to be 176 * formally repeatable. Alternatively, when <i>T</i> is made 177 * repeatable, <i>TC</i> can be introduced as a new type.) 178 * 179 * <li>If an annotation type <i>TC</i> is present on an element, and 180 * <i>T</i> is modified to be repeatable with <i>TC</i> as its 181 * containing annotation type then: 182 * 183 * <ul> 184 * 185 * <li>The change to <i>T</i> is behaviorally compatible with respect 186 * to the {@code get[Declared]Annotation(Class<T>)} (called with an 187 * argument of <i>T</i> or <i>TC</i>) and {@code 188 * get[Declared]Annotations()} methods because the results of the 189 * methods will not change due to <i>TC</i> becoming the containing 190 * annotation type for <i>T</i>. 191 * 192 * <li>The change to <i>T</i> changes the results of the {@code 193 * get[Declared]AnnotationsByType(Class<T>)} methods called with an 194 * argument of <i>T</i>, because those methods will now recognize an 195 * annotation of type <i>TC</i> as a container annotation for <i>T</i> 196 * and will "look through" it to expose annotations of type <i>T</i>. 197 * 198 * </ul> 199 * 200 * <li>If an annotation of type <i>T</i> is present on an 201 * element and <i>T</i> is made repeatable and more annotations of 202 * type <i>T</i> are added to the element: 203 * 204 * <ul> 205 * 206 * <li> The addition of the annotations of type <i>T</i> is both 207 * source compatible and binary compatible. 208 * 209 * <li>The addition of the annotations of type <i>T</i> changes the results 210 * of the {@code get[Declared]Annotation(Class<T>)} methods and {@code 211 * get[Declared]Annotations()} methods, because those methods will now 212 * only see a container annotation on the element and not see an 213 * annotation of type <i>T</i>. 214 * 215 * <li>The addition of the annotations of type <i>T</i> changes the 216 * results of the {@code get[Declared]AnnotationsByType(Class<T>)} 217 * methods, because their results will expose the additional 218 * annotations of type <i>T</i> whereas previously they exposed only a 219 * single annotation of type <i>T</i>. 220 * 221 * </ul> 222 * 223 * </ul> 224 * 225 * <p>If an annotation returned by a method in this interface contains 226 * (directly or indirectly) a {@link Class}-valued member referring to 227 * a class that is not accessible in this VM, attempting to read the class 228 * by calling the relevant Class-returning method on the returned annotation 229 * will result in a {@link TypeNotPresentException}. 230 * 231 * <p>Similarly, attempting to read an enum-valued member will result in 232 * a {@link EnumConstantNotPresentException} if the enum constant in the 233 * annotation is no longer present in the enum type. 234 * 235 * <p>If an annotation type <i>T</i> is (meta-)annotated with an 236 * {@code @Repeatable} annotation whose value element indicates a type 237 * <i>TC</i>, but <i>TC</i> does not declare a {@code value()} method 238 * with a return type of <i>T</i>{@code []}, then an exception of type 239 * {@link java.lang.annotation.AnnotationFormatError} is thrown. 240 * 241 * <p>Finally, attempting to read a member whose definition has evolved 242 * incompatibly will result in a {@link 243 * java.lang.annotation.AnnotationTypeMismatchException} or an 244 * {@link java.lang.annotation.IncompleteAnnotationException}. 245 * 246 * @see java.lang.EnumConstantNotPresentException 247 * @see java.lang.TypeNotPresentException 248 * @see AnnotationFormatError 249 * @see java.lang.annotation.AnnotationTypeMismatchException 250 * @see java.lang.annotation.IncompleteAnnotationException 251 * @since 1.5 252 * @author Josh Bloch 253 */ 254 public interface AnnotatedElement { 255 /** 256 * Returns true if an annotation for the specified type 257 * is <em>present</em> on this element, else false. This method 258 * is designed primarily for convenient access to marker annotations. 259 * 260 * <p>The truth value returned by this method is equivalent to: 261 * {@code getAnnotation(annotationClass) != null} 262 * 263 * <p>The body of the default method is specified to be the code 264 * above. 265 * 266 * @param annotationClass the Class object corresponding to the 267 * annotation type 268 * @return true if an annotation for the specified annotation 269 * type is present on this element, else false 270 * @throws NullPointerException if the given annotation class is null 271 * @since 1.5 272 */ isAnnotationPresent(Class<? extends Annotation> annotationClass)273 default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) { 274 return getAnnotation(annotationClass) != null; 275 } 276 277 /** 278 * Returns this element's annotation for the specified type if 279 * such an annotation is <em>present</em>, else null. 280 * 281 * @param <T> the type of the annotation to query for and return if present 282 * @param annotationClass the Class object corresponding to the 283 * annotation type 284 * @return this element's annotation for the specified annotation type if 285 * present on this element, else null 286 * @throws NullPointerException if the given annotation class is null 287 * @since 1.5 288 */ getAnnotation(Class<T> annotationClass)289 <T extends Annotation> T getAnnotation(Class<T> annotationClass); 290 291 /** 292 * Returns annotations that are <em>present</em> on this element. 293 * 294 * If there are no annotations <em>present</em> on this element, the return 295 * value is an array of length 0. 296 * 297 * The caller of this method is free to modify the returned array; it will 298 * have no effect on the arrays returned to other callers. 299 * 300 * @return annotations present on this element 301 * @since 1.5 302 */ getAnnotations()303 Annotation[] getAnnotations(); 304 305 /** 306 * Returns annotations that are <em>associated</em> with this element. 307 * 308 * If there are no annotations <em>associated</em> with this element, the return 309 * value is an array of length 0. 310 * 311 * The difference between this method and {@link #getAnnotation(Class)} 312 * is that this method detects if its argument is a <em>repeatable 313 * annotation type</em> (JLS 9.6), and if so, attempts to find one or 314 * more annotations of that type by "looking through" a container 315 * annotation. 316 * 317 * The caller of this method is free to modify the returned array; it will 318 * have no effect on the arrays returned to other callers. 319 * 320 * @implSpec The default implementation first calls {@link 321 * #getDeclaredAnnotationsByType(Class)} passing {@code 322 * annotationClass} as the argument. If the returned array has 323 * length greater than zero, the array is returned. If the returned 324 * array is zero-length and this {@code AnnotatedElement} is a 325 * class and the argument type is an inheritable annotation type, 326 * and the superclass of this {@code AnnotatedElement} is non-null, 327 * then the returned result is the result of calling {@link 328 * #getAnnotationsByType(Class)} on the superclass with {@code 329 * annotationClass} as the argument. Otherwise, a zero-length 330 * array is returned. 331 * 332 * @param <T> the type of the annotation to query for and return if present 333 * @param annotationClass the Class object corresponding to the 334 * annotation type 335 * @return all this element's annotations for the specified annotation type if 336 * associated with this element, else an array of length zero 337 * @throws NullPointerException if the given annotation class is null 338 * @since 1.8 339 */ getAnnotationsByType(Class<T> annotationClass)340 default <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) { 341 /* 342 * Definition of associated: directly or indirectly present OR 343 * neither directly nor indirectly present AND the element is 344 * a Class, the annotation type is inheritable, and the 345 * annotation type is associated with the superclass of the 346 * element. 347 */ 348 T[] result = getDeclaredAnnotationsByType(annotationClass); 349 350 if (result.length == 0 && // Neither directly nor indirectly present 351 this instanceof Class && // the element is a class 352 AnnotationType.getInstance(annotationClass).isInherited()) { // Inheritable 353 Class<?> superClass = ((Class<?>) this).getSuperclass(); 354 if (superClass != null) { 355 // Determine if the annotation is associated with the 356 // superclass 357 result = superClass.getAnnotationsByType(annotationClass); 358 } 359 } 360 361 return result; 362 } 363 364 /** 365 * Returns this element's annotation for the specified type if 366 * such an annotation is <em>directly present</em>, else null. 367 * 368 * This method ignores inherited annotations. (Returns null if no 369 * annotations are directly present on this element.) 370 * 371 * @implSpec The default implementation first performs a null check 372 * and then loops over the results of {@link 373 * #getDeclaredAnnotations} returning the first annotation whose 374 * annotation type matches the argument type. 375 * 376 * @param <T> the type of the annotation to query for and return if directly present 377 * @param annotationClass the Class object corresponding to the 378 * annotation type 379 * @return this element's annotation for the specified annotation type if 380 * directly present on this element, else null 381 * @throws NullPointerException if the given annotation class is null 382 * @since 1.8 383 */ getDeclaredAnnotation(Class<T> annotationClass)384 default <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) { 385 Objects.requireNonNull(annotationClass); 386 // Loop over all directly-present annotations looking for a matching one 387 for (Annotation annotation : getDeclaredAnnotations()) { 388 if (annotationClass.equals(annotation.annotationType())) { 389 // More robust to do a dynamic cast at runtime instead 390 // of compile-time only. 391 return annotationClass.cast(annotation); 392 } 393 } 394 return null; 395 } 396 397 /** 398 * Returns this element's annotation(s) for the specified type if 399 * such annotations are either <em>directly present</em> or 400 * <em>indirectly present</em>. This method ignores inherited 401 * annotations. 402 * 403 * If there are no specified annotations directly or indirectly 404 * present on this element, the return value is an array of length 405 * 0. 406 * 407 * The difference between this method and {@link 408 * #getDeclaredAnnotation(Class)} is that this method detects if its 409 * argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so, 410 * attempts to find one or more annotations of that type by "looking 411 * through" a container annotation if one is present. 412 * 413 * The caller of this method is free to modify the returned array; it will 414 * have no effect on the arrays returned to other callers. 415 * 416 * @implSpec The default implementation may call {@link 417 * #getDeclaredAnnotation(Class)} one or more times to find a 418 * directly present annotation and, if the annotation type is 419 * repeatable, to find a container annotation. If annotations of 420 * the annotation type {@code annotationClass} are found to be both 421 * directly and indirectly present, then {@link 422 * #getDeclaredAnnotations()} will get called to determine the 423 * order of the elements in the returned array. 424 * 425 * <p>Alternatively, the default implementation may call {@link 426 * #getDeclaredAnnotations()} a single time and the returned array 427 * examined for both directly and indirectly present 428 * annotations. The results of calling {@link 429 * #getDeclaredAnnotations()} are assumed to be consistent with the 430 * results of calling {@link #getDeclaredAnnotation(Class)}. 431 * 432 * @param <T> the type of the annotation to query for and return 433 * if directly or indirectly present 434 * @param annotationClass the Class object corresponding to the 435 * annotation type 436 * @return all this element's annotations for the specified annotation type if 437 * directly or indirectly present on this element, else an array of length zero 438 * @throws NullPointerException if the given annotation class is null 439 * @since 1.8 440 */ getDeclaredAnnotationsByType(Class<T> annotationClass)441 default <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) { 442 Objects.requireNonNull(annotationClass); 443 return AnnotationSupport. 444 getDirectlyAndIndirectlyPresent(Arrays.stream(getDeclaredAnnotations()). 445 collect(Collectors.toMap(Annotation::annotationType, 446 Function.identity(), 447 ((first,second) -> first), 448 LinkedHashMap::new)), 449 annotationClass); 450 } 451 452 /** 453 * Returns annotations that are <em>directly present</em> on this element. 454 * This method ignores inherited annotations. 455 * 456 * If there are no annotations <em>directly present</em> on this element, 457 * the return value is an array of length 0. 458 * 459 * The caller of this method is free to modify the returned array; it will 460 * have no effect on the arrays returned to other callers. 461 * 462 * @return annotations directly present on this element 463 * @since 1.5 464 */ getDeclaredAnnotations()465 Annotation[] getDeclaredAnnotations(); 466 } 467