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
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. It is permissible for the caller to modify the
36 * arrays returned by accessors for array-valued enum members; it will
37 * have no affect on the arrays returned to other callers.
38 *
39 * <p>The {@link #getAnnotationsByType(Class)} and {@link
40 * #getDeclaredAnnotationsByType(Class)} methods support multiple
41 * annotations of the same type on an element. If the argument to either method
42 * is a repeatable annotation type (JLS 9.6), then the method will "look
43 * through" a container annotation (JLS 9.7) which was generated at
44 * compile-time to wrap multiple annotations of the argument type.
45 *
46 * <p>The terms <em>directly present</em> and <em>present</em> are used
47 * throughout this interface to describe precisely which annotations are
48 * returned by methods:
49 *
50 * <ul>
51 * <li>An annotation A is <em>directly present</em> on an element E if E is
52 * associated with a RuntimeVisibleAnnotations or
53 * RuntimeVisibleParameterAnnotations attribute, and:
54 *
55 * <ul>
56 * <li>for an invocation of {@code get[Declared]Annotation(Class<T>)} or
57 * {@code get[Declared]Annotations()}, the attribute contains A.
58 *
59 * <li>for an invocation of {@code get[Declared]AnnotationsByType(Class<T>)}, the
60 * attribute either contains A or, if the type of A is repeatable, contains
61 * exactly one annotation whose value element contains A and whose type is the
62 * containing annotation type of A's type (JLS 9.6).
63 * </ul>
64 *
65 * <p>
66 * <li>An annotation A is <em>present</em> on an element E if either:
67 *
68 * <ul>
69 * <li>A is <em>directly present</em> on E; or
70 *
71 * <li>A is not <em>directly present</em> on E, and E is a class, and A's type
72 * is inheritable (JLS 9.6.3.3), and A is <em>present</em> on the superclass of
73 * E.
74 * </ul>
75 *
76 * </ul>
77 *
78 * <p>If an annotation returned by a method in this interface contains
79 * (directly or indirectly) a {@link Class}-valued member referring to
80 * a class that is not accessible in this VM, attempting to read the class
81 * by calling the relevant Class-returning method on the returned annotation
82 * will result in a {@link TypeNotPresentException}.
83 *
84 * <p>Similarly, attempting to read an enum-valued member will result in
85 * a {@link EnumConstantNotPresentException} if the enum constant in the
86 * annotation is no longer present in the enum type.
87 *
88 * <p>Attempting to read annotations of a repeatable annotation type T
89 * that are contained in an annotation whose type is not, in fact, the
90 * containing annotation type of T, will result in an {@link
91 * AnnotationFormatError}.
92 *
93 * <p>Finally, attempting to read a member whose definition has evolved
94 * incompatibly will result in a {@link
95 * java.lang.annotation.AnnotationTypeMismatchException} or an
96 * {@link java.lang.annotation.IncompleteAnnotationException}.
97 *
98 * @see java.lang.EnumConstantNotPresentException
99 * @see java.lang.TypeNotPresentException
100 * @see AnnotationFormatError
101 * @see java.lang.annotation.AnnotationTypeMismatchException
102 * @see java.lang.annotation.IncompleteAnnotationException
103 * @since 1.5
104 * @author Josh Bloch
105 */
106 public interface AnnotatedElement {
107 /**
108 * Returns true if an annotation for the specified type
109 * is present on this element, else false. This method
110 * is designed primarily for convenient access to marker annotations.
111 *
112 * <p>The truth value returned by this method is equivalent to:
113 * {@code getAnnotation(annotationClass) != null}
114 *
115 * <p>The body of the default method is specified to be the code
116 * above.
117 *
118 * @param annotationClass the Class object corresponding to the
119 * annotation type
120 * @return true if an annotation for the specified annotation
121 * type is present on this element, else false
122 * @throws NullPointerException if the given annotation class is null
123 * @since 1.5
124 */
125 default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
126 return getAnnotation(annotationClass) != null;
127 }
128
129 /**
130 * Returns this element's annotation for the specified type if
131 * such an annotation is present, else null.
132 *
133 * @param <T> the type of the annotation to query for and return if present
134 * @param annotationClass the Class object corresponding to the
135 * annotation type
136 * @return this element's annotation for the specified annotation type if
137 * present on this element, else null
138 * @throws NullPointerException if the given annotation class is null
139 * @since 1.5
140 */
141 <T extends Annotation> T getAnnotation(Class<T> annotationClass);
142
143 /**
144 * Returns annotations that are <em>present</em> on this element.
145 *
146 * If there are no annotations <em>present</em> on this element, the return
147 * value is an array of length 0.
148 *
149 * The difference between this method and {@link #getAnnotation(Class)}
150 * is that this method detects if its argument is a <em>repeatable
151 * annotation type</em> (JLS 9.6), and if so, attempts to find one or
152 * more annotations of that type by "looking through" a container
153 * annotation.
154 *
155 * The caller of this method is free to modify the returned array; it will
156 * have no effect on the arrays returned to other callers.
157 *
158 * @param <T> the type of the annotation to query for and return if present
159 * @param annotationClass the Class object corresponding to the
160 * annotation type
161 * @return all this element's annotations for the specified annotation type if
162 * present on this element, else an array of length zero
163 * @throws NullPointerException if the given annotation class is null
164 * @since 1.8
165 */
166 <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass);
167
168 /**
169 * Returns annotations that are <em>present</em> on this element.
170 *
171 * If there are no annotations <em>present</em> on this element, the return
172 * value is an array of length 0.
173 *
174 * The caller of this method is free to modify the returned array; it will
175 * have no effect on the arrays returned to other callers.
176 *
177 * @return annotations present on this element
178 * @since 1.5
179 */
180 Annotation[] getAnnotations();
181
182 /**
183 * Returns this element's annotation for the specified type if
184 * such an annotation is present, else null.
185 *
186 * This method ignores inherited annotations. (Returns null if no
187 * annotations are directly present on this element.)
188 *
189 * @param <T> the type of the annotation to query for and return if present
190 * @param annotationClass the Class object corresponding to the
191 * annotation type
192 * @return this element's annotation for the specified annotation type if
193 * present on this element, else null
194 * @throws NullPointerException if the given annotation class is null
195 * @since 1.8
196 */
197 <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass);
198
199 /**
200 * Returns annotations that are <em>directly present</em> on this element.
201 * This method ignores inherited annotations.
202 *
203 * If there are no annotations <em>directly present</em> on this element,
204 * the return value is an array of length 0.
205 *
206 * The difference between this method and {@link
207 * #getDeclaredAnnotation(Class)} is that this method detects if its
208 * argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so,
209 * attempts to find one or more annotations of that type by "looking
210 * through" a container annotation.
211 *
212 * The caller of this method is free to modify the returned array; it will
213 * have no effect on the arrays returned to other callers.
214 *
215 * @param <T> the type of the annotation to query for and return
216 * if directly present
217 * @param annotationClass the Class object corresponding to the
218 * annotation type
219 * @return all this element's annotations for the specified annotation type if
220 * present on this element, else an array of length zero
221 * @throws NullPointerException if the given annotation class is null
222 * @since 1.8
223 */
224 <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass);
225
226 /**
227 * Returns annotations that are <em>directly present</em> on this element.
228 * This method ignores inherited annotations.
229 *
230 * If there are no annotations <em>directly present</em> on this element,
231 * the return value is an array of length 0.
232 *
233 * The caller of this method is free to modify the returned array; it will
234 * have no effect on the arrays returned to other callers.
235 *
236 * @return annotations directly present on this element
237 * @since 1.5
238 */
239 Annotation[] getDeclaredAnnotations();
240 }