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 style="text-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 style="text-align:right">{@code Annotation[]}</td><td>{@link #getAnnotations getAnnotations()}
116 * <td></td><td></td><td>X</td><td></td>
117 * </tr>
118 * <tr><td style="text-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 style="text-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 style="text-align:right">{@code Annotation[]}</td><td>{@link #getDeclaredAnnotations getDeclaredAnnotations()}
125 * <td>X</td><td></td><td></td><td></td>
126 * </tr>
127 * <tr><td style="text-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 */
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 */
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 */
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 */
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 */
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 */
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 */
449 Annotation[] getDeclaredAnnotations();
450 }