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