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