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 *
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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
31 /**
32 * Represents an annotated element of the program currently running in this
33 * VM. This interface allows annotations to be read reflectively. All
34 * annotations returned by methods in this interface are immutable and
35 * serializable. The arrays returned by methods of this interface may be modified
36 * by callers without affecting the arrays returned to other callers.
37 *
38 * <p>The {@link #getAnnotationsByType(Class)} and {@link
39 * #getDeclaredAnnotationsByType(Class)} methods support multiple
40 * annotations of the same type on an element. If the argument to
41 * either method is a repeatable annotation type (JLS 9.6), then the
42 * method will "look through" a container annotation (JLS 9.7), if
43 * present, and return any annotations inside the container. Container
44 * annotations may be generated at compile-time to wrap multiple
45 * annotations of the argument type.
46 *
47 * <p>The terms <em>directly present</em>, <em>indirectly present</em>,
48 * <em>present</em>, and <em>associated</em> are used throughout this
49 * interface to describe precisely which annotations are returned by
50 * methods:
51 *
52 * <ul>
53 *
54 * <li> An annotation <i>A</i> is <em>directly present</em> on an
55 * element <i>E</i> if <i>E</i> has a {@code
56 * RuntimeVisibleAnnotations} or {@code
57 * RuntimeVisibleParameterAnnotations} or {@code
58 * RuntimeVisibleTypeAnnotations} attribute, and the attribute
59 * contains <i>A</i>.
60 *
61 * <li>An annotation <i>A</i> is <em>indirectly present</em> on an
62 * element <i>E</i> if <i>E</i> has a {@code RuntimeVisibleAnnotations} or
63 * {@code RuntimeVisibleParameterAnnotations} or {@code RuntimeVisibleTypeAnnotations}
64 * attribute, and <i>A</i> 's type is repeatable, and the attribute contains
65 * exactly one annotation whose value element contains <i>A</i> and whose
66 * type is the containing annotation type of <i>A</i> 's type.
67 *
68 * <li>An annotation <i>A</i> is present on an element <i>E</i> if either:
69 *
70 * <ul>
71 *
72 * <li><i>A</i> is directly present on <i>E</i>; or
73 *
74 * <li>No annotation of <i>A</i> 's type is directly present on
75 * <i>E</i>, and <i>E</i> is a class, and <i>A</i> 's type is
76 * inheritable, and <i>A</i> is present on the superclass of <i>E</i>.
77 *
78 * </ul>
79 *
80 * <li>An annotation <i>A</i> is <em>associated</em> with an element <i>E</i>
81 * if either:
82 *
83 * <ul>
84 *
85 * <li><i>A</i> is directly or indirectly present on <i>E</i>; or
86 *
87 * <li>No annotation of <i>A</i> 's type is directly or indirectly
88 * present on <i>E</i>, and <i>E</i> is a class, and <i>A</i>'s type
89 * is inheritable, and <i>A</i> is associated with the superclass of
90 * <i>E</i>.
91 *
92 * </ul>
93 *
94 * </ul>
95 *
96 * <p>The table below summarizes which kind of annotation presence
97 * different methods in this interface examine.
98 *
99 * <table border>
100 * <caption>Overview of kind of presence detected by different AnnotatedElement methods</caption>
101 * <tr><th colspan=2></th><th colspan=4>Kind of Presence</th>
102 * <tr><th colspan=2>Method</th><th>Directly Present</th><th>Indirectly Present</th><th>Present</th><th>Associated</th>
103 * <tr><td align=right>{@code T}</td><td>{@link #getAnnotation(Class) getAnnotation(Class<T>)}
104 * <td></td><td></td><td>X</td><td></td>
105 * </tr>
106 * <tr><td align=right>{@code Annotation[]}</td><td>{@link #getAnnotations getAnnotations()}
107 * <td></td><td></td><td>X</td><td></td>
108 * </tr>
109 * <tr><td align=right>{@code T[]}</td><td>{@link #getAnnotationsByType(Class) getAnnotationsByType(Class<T>)}
110 * <td></td><td></td><td></td><td>X</td>
111 * </tr>
112 * <tr><td align=right>{@code T}</td><td>{@link #getDeclaredAnnotation(Class) getDeclaredAnnotation(Class<T>)}
113 * <td>X</td><td></td><td></td><td></td>
114 * </tr>
115 * <tr><td align=right>{@code Annotation[]}</td><td>{@link #getDeclaredAnnotations getDeclaredAnnotations()}
116 * <td>X</td><td></td><td></td><td></td>
117 * </tr>
118 * <tr><td align=right>{@code T[]}</td><td>{@link #getDeclaredAnnotationsByType(Class) getDeclaredAnnotationsByType(Class<T>)}
119 * <td>X</td><td>X</td><td></td><td></td>
120 * </tr>
121 * </table>
122 *
123 * <p>For an invocation of {@code get[Declared]AnnotationsByType( Class <
124 * T >)}, the order of annotations which are directly or indirectly
125 * present on an element <i>E</i> is computed as if indirectly present
126 * annotations on <i>E</i> are directly present on <i>E</i> in place
127 * of their container annotation, in the order in which they appear in
128 * the value element of the container annotation.
129
130 * <p>If an annotation returned by a method in this interface contains
131 * (directly or indirectly) a {@link Class}-valued member referring to
132 * a class that is not accessible in this VM, attempting to read the class
133 * by calling the relevant Class-returning method on the returned annotation
134 * will result in a {@link TypeNotPresentException}.
135 *
136 * <p>Similarly, attempting to read an enum-valued member will result in
137 * a {@link EnumConstantNotPresentException} if the enum constant in the
138 * annotation is no longer present in the enum type.
139 *
140 * <p>If an annotation type <i>T</i> is (meta-)annotated with an
141 * {@code @Repeatable} annotation whose value element indicates a type
142 * <i>TC</i>, but <i>TC</i> does not declare a {@code value()} method
143 * with a return type of <i>T</i>{@code []}, then an exception of type
144 * {@link java.lang.annotation.AnnotationFormatError} is thrown.
145 *
146 * <p>Finally, attempting to read a member whose definition has evolved
147 * incompatibly will result in a {@link
148 * java.lang.annotation.AnnotationTypeMismatchException} or an
149 * {@link java.lang.annotation.IncompleteAnnotationException}.
150 *
151 * @see java.lang.EnumConstantNotPresentException
152 * @see java.lang.TypeNotPresentException
153 * @see AnnotationFormatError
154 * @see java.lang.annotation.AnnotationTypeMismatchException
155 * @see java.lang.annotation.IncompleteAnnotationException
156 * @since 1.5
157 * @author Josh Bloch
158 */
159 public interface AnnotatedElement {
160 /**
161 * Returns true if an annotation for the specified type
162 * is <em>present</em> on this element, else false. This method
163 * is designed primarily for convenient access to marker annotations.
164 *
165 * <p>The truth value returned by this method is equivalent to:
166 * {@code getAnnotation(annotationClass) != null}
167 *
168 * <p>The body of the default method is specified to be the code
169 * above.
170 *
171 * @param annotationClass the Class object corresponding to the
172 * annotation type
173 * @return true if an annotation for the specified annotation
174 * type is present on this element, else false
175 * @throws NullPointerException if the given annotation class is null
176 * @since 1.5
177 */
178 default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
179 return getAnnotation(annotationClass) != null;
180 }
181
182 /**
183 * Returns this element's annotation for the specified type if
184 * such an annotation is <em>present</em>, else null.
185 *
186 * @param <T> the type of the annotation to query for and return if present
187 * @param annotationClass the Class object corresponding to the
188 * annotation type
189 * @return this element's annotation for the specified annotation type if
190 * present on this element, else null
191 * @throws NullPointerException if the given annotation class is null
192 * @since 1.5
193 */
194 <T extends Annotation> T getAnnotation(Class<T> annotationClass);
195
196 /**
197 * Returns annotations that are <em>present</em> on this element.
198 *
199 * If there are no annotations <em>present</em> on this element, the return
200 * value is an array of length 0.
201 *
202 * The caller of this method is free to modify the returned array; it will
203 * have no effect on the arrays returned to other callers.
204 *
205 * @return annotations present on this element
206 * @since 1.5
207 */
208 Annotation[] getAnnotations();
209
210 /**
211 * Returns annotations that are <em>associated</em> with this element.
212 *
213 * If there are no annotations <em>associated</em> with this element, the return
214 * value is an array of length 0.
215 *
216 * The difference between this method and {@link #getAnnotation(Class)}
217 * is that this method detects if its argument is a <em>repeatable
218 * annotation type</em> (JLS 9.6), and if so, attempts to find one or
219 * more annotations of that type by "looking through" a container
220 * annotation.
221 *
222 * The caller of this method is free to modify the returned array; it will
223 * have no effect on the arrays returned to other callers.
224 *
225 * @param <T> the type of the annotation to query for and return if present
226 * @param annotationClass the Class object corresponding to the
227 * annotation type
228 * @return all this element's annotations for the specified annotation type if
229 * associated with this element, else an array of length zero
230 * @throws NullPointerException if the given annotation class is null
231 * @since 1.8
232 */
233 <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass);
234
235 /**
236 * Returns this element's annotation for the specified type if
237 * such an annotation is <em>directly present</em>, else null.
238 *
239 * This method ignores inherited annotations. (Returns null if no
240 * annotations are directly present on this element.)
241 *
242 * @param <T> the type of the annotation to query for and return if directly present
243 * @param annotationClass the Class object corresponding to the
244 * annotation type
245 * @return this element's annotation for the specified annotation type if
246 * directly present on this element, else null
247 * @throws NullPointerException if the given annotation class is null
248 * @since 1.8
249 */
250 <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass);
251
252 /**
253 * Returns this element's annotation(s) for the specified type if
254 * such annotations are either <em>directly present</em> or
255 * <em>indirectly present</em>. This method ignores inherited
256 * annotations.
257 *
258 * If there are no specified annotations directly or indirectly
259 * present on this element, the return value is an array of length
260 * 0.
261 *
262 * The difference between this method and {@link
263 * #getDeclaredAnnotation(Class)} is that this method detects if its
264 * argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so,
265 * attempts to find one or more annotations of that type by "looking
266 * through" a container annotation if one is present.
267 *
268 * The caller of this method is free to modify the returned array; it will
269 * have no effect on the arrays returned to other callers.
270 *
271 * @param <T> the type of the annotation to query for and return
272 * if directly or indirectly present
273 * @param annotationClass the Class object corresponding to the
274 * annotation type
275 * @return all this element's annotations for the specified annotation type if
276 * directly or indirectly present on this element, else an array of length zero
277 * @throws NullPointerException if the given annotation class is null
278 * @since 1.8
279 */
280 <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass);
281
282 /**
283 * Returns annotations that are <em>directly present</em> on this element.
284 * This method ignores inherited annotations.
285 *
286 * If there are no annotations <em>directly present</em> on this element,
287 * the return value is an array of length 0.
288 *
289 * The caller of this method is free to modify the returned array; it will
290 * have no effect on the arrays returned to other callers.
291 *
292 * @return annotations directly present on this element
293 * @since 1.5
294 */
295 Annotation[] getDeclaredAnnotations();
296 }