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