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>If an annotation returned by a method in this interface contains
140 * (directly or indirectly) a {@link Class}-valued member referring to
141 * a class that is not accessible in this VM, attempting to read the class
142 * by calling the relevant Class-returning method on the returned annotation
143 * will result in a {@link TypeNotPresentException}.
144 *
145 * <p>Similarly, attempting to read an enum-valued member will result in
146 * a {@link EnumConstantNotPresentException} if the enum constant in the
147 * annotation is no longer present in the enum type.
148 *
149 * <p>If an annotation type <i>T</i> is (meta-)annotated with an
150 * {@code @Repeatable} annotation whose value element indicates a type
151 * <i>TC</i>, but <i>TC</i> does not declare a {@code value()} method
152 * with a return type of <i>T</i>{@code []}, then an exception of type
153 * {@link java.lang.annotation.AnnotationFormatError} is thrown.
154 *
155 * <p>Finally, attempting to read a member whose definition has evolved
156 * incompatibly will result in a {@link
157 * java.lang.annotation.AnnotationTypeMismatchException} or an
158 * {@link java.lang.annotation.IncompleteAnnotationException}.
159 *
160 * @see java.lang.EnumConstantNotPresentException
161 * @see java.lang.TypeNotPresentException
162 * @see AnnotationFormatError
163 * @see java.lang.annotation.AnnotationTypeMismatchException
164 * @see java.lang.annotation.IncompleteAnnotationException
165 * @since 1.5
166 * @author Josh Bloch
167 */
168 public interface AnnotatedElement {
169 /**
170 * Returns true if an annotation for the specified type
171 * is <em>present</em> on this element, else false. This method
172 * is designed primarily for convenient access to marker annotations.
173 *
174 * <p>The truth value returned by this method is equivalent to:
175 * {@code getAnnotation(annotationClass) != null}
176 *
177 * <p>The body of the default method is specified to be the code
178 * above.
179 *
180 * @param annotationClass the Class object corresponding to the
181 * annotation type
182 * @return true if an annotation for the specified annotation
183 * type is present on this element, else false
184 * @throws NullPointerException if the given annotation class is null
185 * @since 1.5
186 */
187 default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
188 return getAnnotation(annotationClass) != null;
189 }
190
191 /**
192 * Returns this element's annotation for the specified type if
193 * such an annotation is <em>present</em>, else null.
194 *
195 * @param <T> the type of the annotation to query for and return if present
196 * @param annotationClass the Class object corresponding to the
197 * annotation type
198 * @return this element's annotation for the specified annotation type if
199 * present on this element, else null
200 * @throws NullPointerException if the given annotation class is null
201 * @since 1.5
202 */
203 <T extends Annotation> T getAnnotation(Class<T> annotationClass);
204
205 /**
206 * Returns annotations that are <em>present</em> on this element.
207 *
208 * If there are no annotations <em>present</em> on this element, the return
209 * value is an array of length 0.
210 *
211 * The caller of this method is free to modify the returned array; it will
212 * have no effect on the arrays returned to other callers.
213 *
214 * @return annotations present on this element
215 * @since 1.5
216 */
217 Annotation[] getAnnotations();
218
219 /**
220 * Returns annotations that are <em>associated</em> with this element.
221 *
222 * If there are no annotations <em>associated</em> with this element, the return
223 * value is an array of length 0.
224 *
225 * The difference between this method and {@link #getAnnotation(Class)}
226 * is that this method detects if its argument is a <em>repeatable
227 * annotation type</em> (JLS 9.6), and if so, attempts to find one or
228 * more annotations of that type by "looking through" a container
229 * annotation.
230 *
231 * The caller of this method is free to modify the returned array; it will
232 * have no effect on the arrays returned to other callers.
233 *
234 * @implSpec The default implementation first calls {@link
235 * #getDeclaredAnnotationsByType(Class)} passing {@code
236 * annotationClass} as the argument. If the returned array has
237 * size greater than zero, the array is returned. If the returned
238 * array has size zero and this {@code AnnotatedElement} is a
239 * class and the argument type is an inheritable annotation type,
240 * and the superclass of this {@code AnnoatedElement} is non-null,
241 * then the returned result is the result of calling {@code
242 * getAnnotationsByType} on the superclass with {@code
243 * annotationClass} as the argument. Otherwise, a zero-length
244 * array is returned.
245 *
246 * @param <T> the type of the annotation to query for and return if present
247 * @param annotationClass the Class object corresponding to the
248 * annotation type
249 * @return all this element's annotations for the specified annotation type if
250 * associated with this element, else an array of length zero
251 * @throws NullPointerException if the given annotation class is null
252 * @since 1.8
253 */
254 default <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
255 /*
256 * Definition of associated: directly or indirectly present OR
257 * neither directly nor indirectly present AND the element is
258 * a Class, the annotation type is inheritable, and the
259 * annotation type is associated with the superclass of the
260 * element.
261 */
262 T[] result = getDeclaredAnnotationsByType(annotationClass);
263
264 if (result.length == 0 && // Neither directly nor indirectly present
265 this instanceof Class && // the element is a class
266 AnnotationType.getInstance(annotationClass).isInherited()) { // Inheritable
267 Class<?> superClass = ((Class<?>) this).getSuperclass();
268 if (superClass != null) {
269 // Determine if the annotation is associated with the
270 // superclass
271 result = superClass.getAnnotationsByType(annotationClass);
272 }
273 }
274
275 return result;
276 }
277
278 /**
279 * Returns this element's annotation for the specified type if
280 * such an annotation is <em>directly present</em>, else null.
281 *
282 * This method ignores inherited annotations. (Returns null if no
283 * annotations are directly present on this element.)
284 *
285 * @implSpec The default implementation first performs a null check
286 * and then loops over the results of {@link
287 * #getDeclaredAnnotations} returning the first annotation whose
288 * annotation type matches the argument type.
289 *
290 * @param <T> the type of the annotation to query for and return if directly present
291 * @param annotationClass the Class object corresponding to the
292 * annotation type
293 * @return this element's annotation for the specified annotation type if
294 * directly present on this element, else null
295 * @throws NullPointerException if the given annotation class is null
296 * @since 1.8
297 */
298 default <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
299 Objects.requireNonNull(annotationClass);
300 // Loop over all directly-present annotations looking for a matching one
301 for (Annotation annotation : getDeclaredAnnotations()) {
302 if (annotationClass.equals(annotation.annotationType())) {
303 // More robust to do a dynamic cast at runtime instead
304 // of compile-time only.
305 return annotationClass.cast(annotation);
306 }
307 }
308 return null;
309 }
310
311 /**
312 * Returns this element's annotation(s) for the specified type if
313 * such annotations are either <em>directly present</em> or
314 * <em>indirectly present</em>. This method ignores inherited
315 * annotations.
316 *
317 * If there are no specified annotations directly or indirectly
318 * present on this element, the return value is an array of length
319 * 0.
320 *
321 * The difference between this method and {@link
322 * #getDeclaredAnnotation(Class)} is that this method detects if its
323 * argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so,
324 * attempts to find one or more annotations of that type by "looking
325 * through" a container annotation if one is present.
326 *
327 * The caller of this method is free to modify the returned array; it will
328 * have no effect on the arrays returned to other callers.
329 *
330 * @implSpec The default implementation may call {@link
331 * #getDeclaredAnnotation(Class)} one or more times to find a
332 * directly present annotation and, if the annotation type is
333 * repeatable, to find a container annotation. If annotations of
334 * the annotation type {@code annotationClass} are found to be both
335 * directly and indirectly present, then {@link
336 * #getDeclaredAnnotations()} will get called to determine the
337 * order of the elements in the returned array.
338 *
339 * <p>Alternatively, the default implementation may call {@link
340 * #getDeclaredAnnotations()} a single time and the returned array
341 * examined for both directly and indirectly present
342 * annotations. The results of calling {@link
343 * #getDeclaredAnnotations()} are assumed to be consistent with the
344 * results of calling {@link #getDeclaredAnnotation(Class)}.
345 *
346 * @param <T> the type of the annotation to query for and return
347 * if directly or indirectly present
348 * @param annotationClass the Class object corresponding to the
349 * annotation type
350 * @return all this element's annotations for the specified annotation type if
351 * directly or indirectly present on this element, else an array of length zero
352 * @throws NullPointerException if the given annotation class is null
353 * @since 1.8
354 */
355 default <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
356 Objects.requireNonNull(annotationClass);
357 return AnnotationSupport.
358 getDirectlyAndIndirectlyPresent(Arrays.stream(getDeclaredAnnotations()).
359 collect(Collectors.toMap(Annotation::annotationType,
360 Function.identity(),
361 ((first,second) -> first),
362 LinkedHashMap::new)),
363 annotationClass);
364 }
365
366
367 /**
368 * Returns annotations that are <em>directly present</em> on this element.
369 * This method ignores inherited annotations.
370 *
371 * If there are no annotations <em>directly present</em> on this element,
372 * the return value is an array of length 0.
373 *
374 * The caller of this method is free to modify the returned array; it will
375 * have no effect on the arrays returned to other callers.
376 *
377 * @return annotations directly present on this element
378 * @since 1.5
379 */
380 Annotation[] getDeclaredAnnotations();
381 }