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 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 align=right>{@code Annotation[]}</td><td>{@link #getAnnotations getAnnotations()}
116 * <td></td><td></td><td>X</td><td></td>
117 * </tr>
118 * <tr><td 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 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 align=right>{@code Annotation[]}</td><td>{@link #getDeclaredAnnotations getDeclaredAnnotations()}
125 * <td>X</td><td></td><td></td><td></td>
126 * </tr>
127 * <tr><td 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> is <em>not</em> behaviorally compatible
177 * with respect to the {@code
178 * get[Declared]AnnotationsByType(Class<T>)} methods, because those
179 * methods will now recognize an annotation of type <i>TC</i> as a
180 * container annotation and will "look through" it to expose
181 * annotations of type <i>T</i>.
182 *
183 * </ul>
184 *
185 * <li>If an annotation of type <i>T</i> is present on an
186 * element and <i>T</i> is made repeatable and more annotations of
187 * type <i>T</i> are added to the element:
188 *
189 * <ul>
190 *
191 * <li> The addition of the additional annotations is both source
192 * compatible and binary compatible.
193 *
194 * <li>The addition of the additional annotations changes the results
195 * of the {@code get[Declared]Annotation(Class<T>)} methods and {@code
196 * get[Declared]Annotations()} methods, because those methods will now
197 * only see a container annotation on the element and not see an
198 * annotation of type <i>T</i>.
199 *
200 * <li>The addition of the additional annotations changes the results
201 * of the {@code get[Declared]AnnotationsByType(Class<T>)} methods,
202 * because their results will expose the additional annotations of
203 * type <i>T</i> whereas previously they exposed only a single
204 * annotation of type <i>T</i>.
205 *
206 * </ul>
207 *
208 * </ul>
209 *
210 * <p>If an annotation returned by a method in this interface contains
211 * (directly or indirectly) a {@link Class}-valued member referring to
212 * a class that is not accessible in this VM, attempting to read the class
213 * by calling the relevant Class-returning method on the returned annotation
214 * will result in a {@link TypeNotPresentException}.
215 *
216 * <p>Similarly, attempting to read an enum-valued member will result in
217 * a {@link EnumConstantNotPresentException} if the enum constant in the
218 * annotation is no longer present in the enum type.
219 *
220 * <p>If an annotation type <i>T</i> is (meta-)annotated with an
221 * {@code @Repeatable} annotation whose value element indicates a type
222 * <i>TC</i>, but <i>TC</i> does not declare a {@code value()} method
223 * with a return type of <i>T</i>{@code []}, then an exception of type
224 * {@link java.lang.annotation.AnnotationFormatError} is thrown.
225 *
226 * <p>Finally, attempting to read a member whose definition has evolved
227 * incompatibly will result in a {@link
228 * java.lang.annotation.AnnotationTypeMismatchException} or an
229 * {@link java.lang.annotation.IncompleteAnnotationException}.
230 *
231 * @see java.lang.EnumConstantNotPresentException
232 * @see java.lang.TypeNotPresentException
233 * @see AnnotationFormatError
234 * @see java.lang.annotation.AnnotationTypeMismatchException
235 * @see java.lang.annotation.IncompleteAnnotationException
236 * @since 1.5
237 * @author Josh Bloch
238 */
239 public interface AnnotatedElement {
240 /**
241 * Returns true if an annotation for the specified type
242 * is <em>present</em> on this element, else false. This method
243 * is designed primarily for convenient access to marker annotations.
244 *
245 * <p>The truth value returned by this method is equivalent to:
246 * {@code getAnnotation(annotationClass) != null}
247 *
248 * <p>The body of the default method is specified to be the code
249 * above.
250 *
251 * @param annotationClass the Class object corresponding to the
252 * annotation type
253 * @return true if an annotation for the specified annotation
254 * type is present on this element, else false
255 * @throws NullPointerException if the given annotation class is null
256 * @since 1.5
257 */
258 default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
259 return getAnnotation(annotationClass) != null;
260 }
261
262 /**
263 * Returns this element's annotation for the specified type if
264 * such an annotation is <em>present</em>, else null.
265 *
266 * @param <T> the type of the annotation to query for and return if present
267 * @param annotationClass the Class object corresponding to the
268 * annotation type
269 * @return this element's annotation for the specified annotation type if
270 * present on this element, else null
271 * @throws NullPointerException if the given annotation class is null
272 * @since 1.5
273 */
274 <T extends Annotation> T getAnnotation(Class<T> annotationClass);
275
276 /**
277 * Returns annotations that are <em>present</em> on this element.
278 *
279 * If there are no annotations <em>present</em> on this element, the return
280 * value is an array of length 0.
281 *
282 * The caller of this method is free to modify the returned array; it will
283 * have no effect on the arrays returned to other callers.
284 *
285 * @return annotations present on this element
286 * @since 1.5
287 */
288 Annotation[] getAnnotations();
289
290 /**
291 * Returns annotations that are <em>associated</em> with this element.
292 *
293 * If there are no annotations <em>associated</em> with this element, the return
294 * value is an array of length 0.
295 *
296 * The difference between this method and {@link #getAnnotation(Class)}
297 * is that this method detects if its argument is a <em>repeatable
298 * annotation type</em> (JLS 9.6), and if so, attempts to find one or
299 * more annotations of that type by "looking through" a container
300 * annotation.
301 *
302 * The caller of this method is free to modify the returned array; it will
303 * have no effect on the arrays returned to other callers.
304 *
305 * @implSpec The default implementation first calls {@link
306 * #getDeclaredAnnotationsByType(Class)} passing {@code
307 * annotationClass} as the argument. If the returned array has
308 * length greater than zero, the array is returned. If the returned
309 * array is zero-length and this {@code AnnotatedElement} is a
310 * class and the argument type is an inheritable annotation type,
311 * and the superclass of this {@code AnnotatedElement} is non-null,
312 * then the returned result is the result of calling {@link
313 * #getAnnotationsByType(Class)} on the superclass with {@code
314 * annotationClass} as the argument. Otherwise, a zero-length
315 * array is returned.
316 *
317 * @param <T> the type of the annotation to query for and return if present
318 * @param annotationClass the Class object corresponding to the
319 * annotation type
320 * @return all this element's annotations for the specified annotation type if
321 * associated with this element, else an array of length zero
322 * @throws NullPointerException if the given annotation class is null
323 * @since 1.8
324 */
325 default <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
326 /*
327 * Definition of associated: directly or indirectly present OR
328 * neither directly nor indirectly present AND the element is
329 * a Class, the annotation type is inheritable, and the
330 * annotation type is associated with the superclass of the
331 * element.
332 */
333 T[] result = getDeclaredAnnotationsByType(annotationClass);
334
335 if (result.length == 0 && // Neither directly nor indirectly present
336 this instanceof Class && // the element is a class
337 AnnotationType.getInstance(annotationClass).isInherited()) { // Inheritable
338 Class<?> superClass = ((Class<?>) this).getSuperclass();
339 if (superClass != null) {
340 // Determine if the annotation is associated with the
341 // superclass
342 result = superClass.getAnnotationsByType(annotationClass);
343 }
344 }
345
346 return result;
347 }
348
349 /**
350 * Returns this element's annotation for the specified type if
351 * such an annotation is <em>directly present</em>, else null.
352 *
353 * This method ignores inherited annotations. (Returns null if no
354 * annotations are directly present on this element.)
355 *
356 * @implSpec The default implementation first performs a null check
357 * and then loops over the results of {@link
358 * #getDeclaredAnnotations} returning the first annotation whose
359 * annotation type matches the argument type.
360 *
361 * @param <T> the type of the annotation to query for and return if directly present
362 * @param annotationClass the Class object corresponding to the
363 * annotation type
364 * @return this element's annotation for the specified annotation type if
365 * directly present on this element, else null
366 * @throws NullPointerException if the given annotation class is null
367 * @since 1.8
368 */
369 default <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
370 Objects.requireNonNull(annotationClass);
371 // Loop over all directly-present annotations looking for a matching one
372 for (Annotation annotation : getDeclaredAnnotations()) {
373 if (annotationClass.equals(annotation.annotationType())) {
374 // More robust to do a dynamic cast at runtime instead
375 // of compile-time only.
376 return annotationClass.cast(annotation);
377 }
378 }
379 return null;
380 }
381
382 /**
383 * Returns this element's annotation(s) for the specified type if
384 * such annotations are either <em>directly present</em> or
385 * <em>indirectly present</em>. This method ignores inherited
386 * annotations.
387 *
388 * If there are no specified annotations directly or indirectly
389 * present on this element, the return value is an array of length
390 * 0.
391 *
392 * The difference between this method and {@link
393 * #getDeclaredAnnotation(Class)} is that this method detects if its
394 * argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so,
395 * attempts to find one or more annotations of that type by "looking
396 * through" a container annotation if one is present.
397 *
398 * The caller of this method is free to modify the returned array; it will
399 * have no effect on the arrays returned to other callers.
400 *
401 * @implSpec The default implementation may call {@link
402 * #getDeclaredAnnotation(Class)} one or more times to find a
403 * directly present annotation and, if the annotation type is
404 * repeatable, to find a container annotation. If annotations of
405 * the annotation type {@code annotationClass} are found to be both
406 * directly and indirectly present, then {@link
407 * #getDeclaredAnnotations()} will get called to determine the
408 * order of the elements in the returned array.
409 *
410 * <p>Alternatively, the default implementation may call {@link
411 * #getDeclaredAnnotations()} a single time and the returned array
412 * examined for both directly and indirectly present
413 * annotations. The results of calling {@link
414 * #getDeclaredAnnotations()} are assumed to be consistent with the
415 * results of calling {@link #getDeclaredAnnotation(Class)}.
416 *
417 * @param <T> the type of the annotation to query for and return
418 * if directly or indirectly present
419 * @param annotationClass the Class object corresponding to the
420 * annotation type
421 * @return all this element's annotations for the specified annotation type if
422 * directly or indirectly present on this element, else an array of length zero
423 * @throws NullPointerException if the given annotation class is null
424 * @since 1.8
425 */
426 default <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
427 Objects.requireNonNull(annotationClass);
428 return AnnotationSupport.
429 getDirectlyAndIndirectlyPresent(Arrays.stream(getDeclaredAnnotations()).
430 collect(Collectors.toMap(Annotation::annotationType,
431 Function.identity(),
432 ((first,second) -> first),
433 LinkedHashMap::new)),
434 annotationClass);
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 }