1 /* 2 * Copyright (C) 2016 The Android Open Source Project 3 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27 package java.lang.reflect; 28 29 import java.lang.annotation.Annotation; 30 import java.util.Objects; 31 import libcore.reflect.AnnotatedElements; 32 33 // Android-changed: Removed some references to bytecode spec below that do not 34 // apply and added a note about annotation ordering. 35 /** 36 * Represents an annotated element of the program currently running in this 37 * VM. This interface allows annotations to be read reflectively. All 38 * annotations returned by methods in this interface are immutable and 39 * serializable. The arrays returned by methods of this interface may be modified 40 * by callers without affecting the arrays returned to other callers. 41 * 42 * <p>Android note: methods that return multiple annotations of different types such as 43 * {@link #getAnnotations()} and {@link #getDeclaredAnnotations()} can be affected 44 * by the explicit character-code ordering of annotations types specified by the DEX format. 45 * Annotations of different types on a single element are not guaranteed to be returned in the order 46 * they are declared in source. 47 * 48 * <p>The {@link #getAnnotationsByType(Class)} and {@link 49 * #getDeclaredAnnotationsByType(Class)} methods support multiple 50 * annotations of the same type on an element. If the argument to 51 * either method is a repeatable annotation type (JLS 9.6), then the 52 * method will "look through" a container annotation (JLS 9.7), if 53 * present, and return any annotations inside the container. Container 54 * annotations may be generated at compile-time to wrap multiple 55 * annotations of the argument type. 56 * 57 * <p>The terms <em>directly present</em>, <em>indirectly present</em>, 58 * <em>present</em>, and <em>associated</em> are used throughout this 59 * interface to describe precisely which annotations are returned by 60 * methods: 61 * 62 * <ul> 63 * 64 * <li> An annotation <i>A</i> is <em>directly present</em> on an 65 * element <i>E</i> if <i>E</i> is annotated by <i>A</i> in the original source. 66 * 67 * <li>An annotation <i>A</i> is <em>indirectly present</em> on an 68 * element <i>E</i> if <i>E</i> is annotated by a container annotation 69 * of <i>A</i>. 70 * 71 * <li>An annotation <i>A</i> is present on an element <i>E</i> if either: 72 * 73 * <ul> 74 * 75 * <li><i>A</i> is directly present on <i>E</i>; or 76 * 77 * <li>No annotation of <i>A</i> 's type is directly present on 78 * <i>E</i>, and <i>E</i> is a class, and <i>A</i> 's type is 79 * inheritable, and <i>A</i> is present on the superclass of <i>E</i>. 80 * 81 * </ul> 82 * 83 * <li>An annotation <i>A</i> is <em>associated</em> with an element <i>E</i> 84 * if either: 85 * 86 * <ul> 87 * 88 * <li><i>A</i> is directly or indirectly present on <i>E</i>; or 89 * 90 * <li>No annotation of <i>A</i> 's type is directly or indirectly 91 * present on <i>E</i>, and <i>E</i> is a class, and <i>A</i>'s type 92 * is inheritable, and <i>A</i> is associated with the superclass of 93 * <i>E</i>. 94 * 95 * </ul> 96 * 97 * </ul> 98 * 99 * <p>The table below summarizes which kind of annotation presence 100 * different methods in this interface examine. 101 * 102 * <table border> 103 * <caption>Overview of kind of presence detected by different AnnotatedElement methods</caption> 104 * <tr><th colspan=2></th><th colspan=4>Kind of Presence</th> 105 * <tr><th colspan=2>Method</th><th>Directly Present</th><th>Indirectly Present</th><th>Present</th><th>Associated</th> 106 * <tr><td align=right>{@code T}</td><td>{@link #getAnnotation(Class) getAnnotation(Class<T>)} 107 * <td></td><td></td><td>X</td><td></td> 108 * </tr> 109 * <tr><td align=right>{@code Annotation[]}</td><td>{@link #getAnnotations getAnnotations()} 110 * <td></td><td></td><td>X</td><td></td> 111 * </tr> 112 * <tr><td align=right>{@code T[]}</td><td>{@link #getAnnotationsByType(Class) getAnnotationsByType(Class<T>)} 113 * <td></td><td></td><td></td><td>X</td> 114 * </tr> 115 * <tr><td align=right>{@code T}</td><td>{@link #getDeclaredAnnotation(Class) getDeclaredAnnotation(Class<T>)} 116 * <td>X</td><td></td><td></td><td></td> 117 * </tr> 118 * <tr><td align=right>{@code Annotation[]}</td><td>{@link #getDeclaredAnnotations getDeclaredAnnotations()} 119 * <td>X</td><td></td><td></td><td></td> 120 * </tr> 121 * <tr><td align=right>{@code T[]}</td><td>{@link #getDeclaredAnnotationsByType(Class) getDeclaredAnnotationsByType(Class<T>)} 122 * <td>X</td><td>X</td><td></td><td></td> 123 * </tr> 124 * </table> 125 * 126 * <p>For an invocation of {@code get[Declared]AnnotationsByType( Class < 127 * T >)}, the order of annotations which are directly or indirectly 128 * present on an element <i>E</i> is computed as if indirectly present 129 * annotations on <i>E</i> are directly present on <i>E</i> in place 130 * of their container annotation, in the order in which they appear in 131 * the value element of the container annotation. 132 * 133 * <p>There are several compatibility concerns to keep in mind if an 134 * annotation type <i>T</i> is originally <em>not</em> repeatable and 135 * later modified to be repeatable. 136 * 137 * The containing annotation type for <i>T</i> is <i>TC</i>. 138 * 139 * <ul> 140 * 141 * <li>Modifying <i>T</i> to be repeatable is source and binary 142 * compatible with existing uses of <i>T</i> and with existing uses 143 * of <i>TC</i>. 144 * 145 * That is, for source compatibility, source code with annotations of 146 * type <i>T</i> or of type <i>TC</i> will still compile. For binary 147 * compatibility, class files with annotations of type <i>T</i> or of 148 * type <i>TC</i> (or with other kinds of uses of type <i>T</i> or of 149 * type <i>TC</i>) will link against the modified version of <i>T</i> 150 * if they linked against the earlier version. 151 * 152 * (An annotation type <i>TC</i> may informally serve as an acting 153 * containing annotation type before <i>T</i> is modified to be 154 * formally repeatable. Alternatively, when <i>T</i> is made 155 * repeatable, <i>TC</i> can be introduced as a new type.) 156 * 157 * <li>If an annotation type <i>TC</i> is present on an element, and 158 * <i>T</i> is modified to be repeatable with <i>TC</i> as its 159 * containing annotation type then: 160 * 161 * <ul> 162 * 163 * <li>The change to <i>T</i> is behaviorally compatible with respect 164 * to the {@code get[Declared]Annotation(Class<T>)} (called with an 165 * argument of <i>T</i> or <i>TC</i>) and {@code 166 * get[Declared]Annotations()} methods because the results of the 167 * methods will not change due to <i>TC</i> becoming the containing 168 * annotation type for <i>T</i>. 169 * 170 * <li>The change to <i>T</i> changes the results of the {@code 171 * get[Declared]AnnotationsByType(Class<T>)} methods called with an 172 * argument of <i>T</i>, because those methods will now recognize an 173 * annotation of type <i>TC</i> as a container annotation for <i>T</i> 174 * and will "look through" it to expose annotations of type <i>T</i>. 175 * 176 * </ul> 177 * 178 * <li>If an annotation of type <i>T</i> is present on an 179 * element and <i>T</i> is made repeatable and more annotations of 180 * type <i>T</i> are added to the element: 181 * 182 * <ul> 183 * 184 * <li> The addition of the annotations of type <i>T</i> is both 185 * source compatible and binary compatible. 186 * 187 * <li>The addition of the annotations of type <i>T</i> changes the results 188 * of the {@code get[Declared]Annotation(Class<T>)} methods and {@code 189 * get[Declared]Annotations()} methods, because those methods will now 190 * only see a container annotation on the element and not see an 191 * annotation of type <i>T</i>. 192 * 193 * <li>The addition of the annotations of type <i>T</i> changes the 194 * results of the {@code get[Declared]AnnotationsByType(Class<T>)} 195 * methods, because their results will expose the additional 196 * annotations of type <i>T</i> whereas previously they exposed only a 197 * single annotation of type <i>T</i>. 198 * 199 * </ul> 200 * 201 * </ul> 202 * 203 * <p>If an annotation returned by a method in this interface contains 204 * (directly or indirectly) a {@link Class}-valued member referring to 205 * a class that is not accessible in this VM, attempting to read the class 206 * by calling the relevant Class-returning method on the returned annotation 207 * will result in a {@link TypeNotPresentException}. 208 * 209 * <p>Similarly, attempting to read an enum-valued member will result in 210 * a {@link EnumConstantNotPresentException} if the enum constant in the 211 * annotation is no longer present in the enum type. 212 * 213 * <p>If an annotation type <i>T</i> is (meta-)annotated with an 214 * {@code @Repeatable} annotation whose value element indicates a type 215 * <i>TC</i>, but <i>TC</i> does not declare a {@code value()} method 216 * with a return type of <i>T</i>{@code []}, then an exception of type 217 * {@link java.lang.annotation.AnnotationFormatError} is thrown. 218 * 219 * <p>Finally, attempting to read a member whose definition has evolved 220 * incompatibly will result in a {@link 221 * java.lang.annotation.AnnotationTypeMismatchException} or an 222 * {@link java.lang.annotation.IncompleteAnnotationException}. 223 * 224 * @see java.lang.EnumConstantNotPresentException 225 * @see java.lang.TypeNotPresentException 226 * @see AnnotationFormatError 227 * @see java.lang.annotation.AnnotationTypeMismatchException 228 * @see java.lang.annotation.IncompleteAnnotationException 229 * @since 1.5 230 * @author Josh Bloch 231 */ 232 public interface AnnotatedElement { 233 /** 234 * Returns true if an annotation for the specified type 235 * is <em>present</em> on this element, else false. This method 236 * is designed primarily for convenient access to marker annotations. 237 * 238 * <p>The truth value returned by this method is equivalent to: 239 * {@code getAnnotation(annotationClass) != null} 240 * 241 * <p>The body of the default method is specified to be the code 242 * above. 243 * 244 * @param annotationClass the Class object corresponding to the 245 * annotation type 246 * @return true if an annotation for the specified annotation 247 * type is present on this element, else false 248 * @throws NullPointerException if the given annotation class is null 249 * @since 1.5 250 */ isAnnotationPresent(Class<? extends Annotation> annotationClass)251 default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) { 252 return getAnnotation(annotationClass) != null; 253 } 254 255 /** 256 * Returns this element's annotation for the specified type if 257 * such an annotation is <em>present</em>, else null. 258 * 259 * @param <T> the type of the annotation to query for and return if present 260 * @param annotationClass the Class object corresponding to the 261 * annotation type 262 * @return this element's annotation for the specified annotation type if 263 * present on this element, else null 264 * @throws NullPointerException if the given annotation class is null 265 * @since 1.5 266 */ getAnnotation(Class<T> annotationClass)267 <T extends Annotation> T getAnnotation(Class<T> annotationClass); 268 269 /** 270 * Returns annotations that are <em>present</em> on this element. 271 * 272 * If there are no annotations <em>present</em> on this element, the return 273 * value is an array of length 0. 274 * 275 * The caller of this method is free to modify the returned array; it will 276 * have no effect on the arrays returned to other callers. 277 * 278 * @return annotations present on this element 279 * @since 1.5 280 */ getAnnotations()281 Annotation[] getAnnotations(); 282 283 /** 284 * Returns annotations that are <em>associated</em> with this element. 285 * 286 * If there are no annotations <em>associated</em> with this element, the return 287 * value is an array of length 0. 288 * 289 * The difference between this method and {@link #getAnnotation(Class)} 290 * is that this method detects if its argument is a <em>repeatable 291 * annotation type</em> (JLS 9.6), and if so, attempts to find one or 292 * more annotations of that type by "looking through" a container 293 * annotation. 294 * 295 * The caller of this method is free to modify the returned array; it will 296 * have no effect on the arrays returned to other callers. 297 * 298 * @implSpec The default implementation first calls {@link 299 * #getDeclaredAnnotationsByType(Class)} passing {@code 300 * annotationClass} as the argument. If the returned array has 301 * length greater than zero, the array is returned. If the returned 302 * array is zero-length and this {@code AnnotatedElement} is a 303 * class and the argument type is an inheritable annotation type, 304 * and the superclass of this {@code AnnotatedElement} is non-null, 305 * then the returned result is the result of calling {@link 306 * #getAnnotationsByType(Class)} on the superclass with {@code 307 * annotationClass} as the argument. Otherwise, a zero-length 308 * array is returned. 309 * 310 * @param <T> the type of the annotation to query for and return if present 311 * @param annotationClass the Class object corresponding to the 312 * annotation type 313 * @return all this element's annotations for the specified annotation type if 314 * associated with this element, else an array of length zero 315 * @throws NullPointerException if the given annotation class is null 316 * @since 1.8 317 */ getAnnotationsByType(Class<T> annotationClass)318 default <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) { 319 // This method does not handle inherited annotations and is intended for use for 320 // {@code Method}, {@code Field}, {@code Package}. The {@link Class#getAnnotationsByType} 321 // is implemented explicitly. Therefore this implementation does not fulfill the documented 322 // default implementation for {@link AnnotatedElement#getAnnotationsByType(Class)} but in an 323 // undetectable way because Class is final. 324 return AnnotatedElements.getDirectOrIndirectAnnotationsByType(this, annotationClass); 325 } 326 327 /** 328 * Returns this element's annotation for the specified type if 329 * such an annotation is <em>directly present</em>, else null. 330 * 331 * This method ignores inherited annotations. (Returns null if no 332 * annotations are directly present on this element.) 333 * 334 * @implSpec The default implementation first performs a null check 335 * and then loops over the results of {@link 336 * #getDeclaredAnnotations} returning the first annotation whose 337 * annotation type matches the argument type. 338 * 339 * @param <T> the type of the annotation to query for and return if directly present 340 * @param annotationClass the Class object corresponding to the 341 * annotation type 342 * @return this element's annotation for the specified annotation type if 343 * directly present on this element, else null 344 * @throws NullPointerException if the given annotation class is null 345 * @since 1.8 346 */ getDeclaredAnnotation(Class<T> annotationClass)347 default <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) { 348 Objects.requireNonNull(annotationClass); 349 // Loop over all directly-present annotations looking for a matching one 350 for (Annotation annotation : getDeclaredAnnotations()) { 351 if (annotationClass.equals(annotation.annotationType())) { 352 // More robust to do a dynamic cast at runtime instead 353 // of compile-time only. 354 return annotationClass.cast(annotation); 355 } 356 } 357 return null; 358 } 359 360 /** 361 * Returns this element's annotation(s) for the specified type if 362 * such annotations are either <em>directly present</em> or 363 * <em>indirectly present</em>. This method ignores inherited 364 * annotations. 365 * 366 * If there are no specified annotations directly or indirectly 367 * present on this element, the return value is an array of length 368 * 0. 369 * 370 * The difference between this method and {@link 371 * #getDeclaredAnnotation(Class)} is that this method detects if its 372 * argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so, 373 * attempts to find one or more annotations of that type by "looking 374 * through" a container annotation if one is present. 375 * 376 * The caller of this method is free to modify the returned array; it will 377 * have no effect on the arrays returned to other callers. 378 * 379 * @implSpec The default implementation may call {@link 380 * #getDeclaredAnnotation(Class)} one or more times to find a 381 * directly present annotation and, if the annotation type is 382 * repeatable, to find a container annotation. If annotations of 383 * the annotation type {@code annotationClass} are found to be both 384 * directly and indirectly present, then {@link 385 * #getDeclaredAnnotations()} will get called to determine the 386 * order of the elements in the returned array. 387 * 388 * <p>Alternatively, the default implementation may call {@link 389 * #getDeclaredAnnotations()} a single time and the returned array 390 * examined for both directly and indirectly present 391 * annotations. The results of calling {@link 392 * #getDeclaredAnnotations()} are assumed to be consistent with the 393 * results of calling {@link #getDeclaredAnnotation(Class)}. 394 * 395 * @param <T> the type of the annotation to query for and return 396 * if directly or indirectly present 397 * @param annotationClass the Class object corresponding to the 398 * annotation type 399 * @return all this element's annotations for the specified annotation type if 400 * directly or indirectly present on this element, else an array of length zero 401 * @throws NullPointerException if the given annotation class is null 402 * @since 1.8 403 */ getDeclaredAnnotationsByType(Class<T> annotationClass)404 default <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) { 405 return AnnotatedElements.getDirectOrIndirectAnnotationsByType(this, annotationClass); 406 } 407 408 /** 409 * Returns annotations that are <em>directly present</em> on this element. 410 * This method ignores inherited annotations. 411 * 412 * If there are no annotations <em>directly present</em> on this element, 413 * the return value is an array of length 0. 414 * 415 * The caller of this method is free to modify the returned array; it will 416 * have no effect on the arrays returned to other callers. 417 * 418 * @return annotations directly present on this element 419 * @since 1.5 420 */ getDeclaredAnnotations()421 Annotation[] getDeclaredAnnotations(); 422 } 423