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
22 * or visit www.oracle.com if you need additional information or have any
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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)} on the argument type. If
231 * the returned array has size greater than zero, the array is
232 * returned. If the returned array has size zero and this {@code
233 * AnnotatedElement} is a class and the argument type is an
234 * inheritable annotation, and the superclass of this {@code
235 * AnnoatedElement} is non-null, then the result of {@code
236 * getAnnotationsByType(annotationClass)} on the superclass is
237 * returned. Otherwise, a zero-length array is returned.
238 *
239 * @param <T> the type of the annotation to query for and return if present
240 * @param annotationClass the Class object corresponding to the
241 * annotation type
242 * @return all this element's annotations for the specified annotation type if
243 * associated with this element, else an array of length zero
244 * @throws NullPointerException if the given annotation class is null
245 * @since 1.8
246 */
247 default <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
248 /*
249 * Definition of associated: directly or indirectly present OR
250 * neither directly nor indirectly present AND the element is
251 * a Class, the annotation type is inheritable, and the
252 * annotation type is associated with the superclass of the
253 * element.
254 */
255 T[] result = getDeclaredAnnotationsByType(annotationClass);
256
257 if (result.length == 0 && // Neither directly nor indirectly present
258 this instanceof Class && // the element is a class
259 AnnotationType.getInstance(annotationClass).isInherited()) { // Inheritable
260 Class<?> superClass = ((Class<?>) this).getSuperclass();
261 if (superClass != null) {
262 // Determine if the annotation is associated with the
263 // superclass
264 result = superClass.getAnnotationsByType(annotationClass);
265 }
266 }
267
268 return result;
269 }
270
271 /**
272 * Returns this element's annotation for the specified type if
273 * such an annotation is <em>directly present</em>, else null.
274 *
275 * This method ignores inherited annotations. (Returns null if no
276 * annotations are directly present on this element.)
277 *
278 * @implSpec The default implementation first performs a null check
279 * and then loops over the results of {@link
280 * getDeclaredAnnotations} returning the first annotation whose
281 * annotation type matches the argument type.
282 *
283 * @param <T> the type of the annotation to query for and return if directly present
284 * @param annotationClass the Class object corresponding to the
285 * annotation type
286 * @return this element's annotation for the specified annotation type if
287 * directly present on this element, else null
288 * @throws NullPointerException if the given annotation class is null
289 * @since 1.8
290 */
291 default <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
292 Objects.requireNonNull(annotationClass);
293 // Loop over all directly-present annotations looking for a matching one
294 for (Annotation annotation : getDeclaredAnnotations()) {
295 if (annotationClass.equals(annotation.annotationType())) {
296 // More robust to do a dynamic cast at runtime instead
297 // of compile-time only.
298 return annotationClass.cast(annotation);
299 }
300 }
301 return null;
302 }
303
304 /**
305 * Returns this element's annotation(s) for the specified type if
306 * such annotations are either <em>directly present</em> or
307 * <em>indirectly present</em>. This method ignores inherited
308 * annotations.
309 *
310 * If there are no specified annotations directly or indirectly
311 * present on this element, the return value is an array of length
312 * 0.
313 *
314 * The difference between this method and {@link
315 * #getDeclaredAnnotation(Class)} is that this method detects if its
316 * argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so,
317 * attempts to find one or more annotations of that type by "looking
318 * through" a container annotation if one is present.
319 *
320 * The caller of this method is free to modify the returned array; it will
321 * have no effect on the arrays returned to other callers.
322 *
323 * @implSpec The default implementation may call {@link
324 * #getDeclaredAnnotation(Class)} one or more times to find a
325 * directly present annotation and, if the annotation type is
326 * repeatable, to find a container annotation. If the annotation
327 * type is both directly and indirectly present, {@link
328 * getDeclaredAnnotations()} will get called to determine the
329 * order of the elements in the returned array. Alternatively,
330 * {@link getDeclaredAnnotations()} may be called a single time
331 * and the returned array examined for both directly and
332 * indirectly present annotations. The results of calling {@link
333 * getDeclaredAnnotations()} are assumed to be consistent with the
334 * results of calling {@code #getDeclaredAnnotation}
335 *
336 * @param <T> the type of the annotation to query for and return
337 * if directly or indirectly present
338 * @param annotationClass the Class object corresponding to the
339 * annotation type
340 * @return all this element's annotations for the specified annotation type if
341 * directly or indirectly present on this element, else an array of length zero
342 * @throws NullPointerException if the given annotation class is null
343 * @since 1.8
344 */
345 default <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass)
346 {
347 Objects.requireNonNull(annotationClass);
348 int resultSize = 0;
349 T directlyPresent = getDeclaredAnnotation(annotationClass);
350
351 if (directlyPresent != null) {
352 resultSize++;
353 }
354
355 Repeatable repeatable = annotationClass.getAnnotation(Repeatable.class);
356 if (repeatable == null) {
357 @SuppressWarnings("unchecked")
358 T[] returnValue = (T[]) Array.newInstance(annotationClass, resultSize);
359 if (directlyPresent != null)
360 returnValue[0] = directlyPresent;
361 return returnValue;
362 } else {
363 // directlyPresent may or may not be null
364
365 // Look through a container to see if an annotation is
366 // indirectly present
367 Class<? extends Annotation> containerType = repeatable.value();
368 Annotation container = getDeclaredAnnotation(containerType);
369 T[] indirectlyPresent = null;
370
371 if (container != null) {
372 indirectlyPresent = AnnotationSupport.getValueArray(container);
373 resultSize += indirectlyPresent.length;
374 }
375
376 // Final result size is known
377
378 // todo: review comment for accuracy...
379 /*
380 * If resultSize is 0, indirectlyPresent is either
381 * assigned to the result of the initial Array.newInstance
382 * call or indirectlyPresent is assigned to a zero-length
383 * value array from an empty container annotation. In
384 * either case, a zero-length array is immutable and does
385 * not need to reallocated before being returned.
386 *
387 * If resultSize is nonzero, then indirectlyPresent points
388 * to the result calling a method on an annotation and
389 * annotations are required to implement a no sharing
390 * policy. Therefore, it is not required to copy the
391 * elements of indirectlyPresent into a new array of the
392 * same size.
393 */
394 if (indirectlyPresent == null || indirectlyPresent.length == 0) {
395 @SuppressWarnings("unchecked")
396 T[] returnValue = (T[]) Array.newInstance(annotationClass, resultSize);
397 if (resultSize == 1)
398 returnValue[0] = directlyPresent;
399 return returnValue;
400 } else {
401 // assert indirectlyPresent != null && indirectlyPresent.length > 0;
402
403 if (resultSize == indirectlyPresent.length){
404 // assert resultSize == 0 || directlyPresent == null;
405 return indirectlyPresent;
406 } else {
407 // assert directlyPresent != null && indirectlyPresent.length > 0;
408 @SuppressWarnings("unchecked")
409 T[] returnValue = (T[]) Array.newInstance(annotationClass, resultSize);
410
411 // Determine whether the directly present annotation
412 // comes before or after the indirectly present ones.
413
414 int indirectOffset = 0;
415
416 for (Annotation a : getDeclaredAnnotations()) {
417 if (a.annotationType().equals(annotationClass)) {
418 indirectOffset = 1;
419 break;
420 } else if (a.annotationType().equals(containerType)) {
421 break;
422 }
423 }
424
425 for (int i = 0; i < indirectlyPresent.length; i++) {
426 returnValue[i + indirectOffset] = indirectlyPresent[i];
427 }
428
429 returnValue[(indirectOffset == 1) ? 0 : resultSize - 1] = directlyPresent;
430 return returnValue;
431 }
432 }
433 }
434 }
435
436
437 /**
438 * Returns annotations that are <em>directly present</em> on this element.
439 * This method ignores inherited annotations.
440 *
441 * If there are no annotations <em>directly present</em> on this element,
442 * the return value is an array of length 0.
443 *
444 * The caller of this method is free to modify the returned array; it will
445 * have no effect on the arrays returned to other callers.
446 *
447 * @return annotations directly present on this element
448 * @since 1.5
449 */
450 Annotation[] getDeclaredAnnotations();
451 }