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
30 /**
31 * Represents an annotated element of the program currently running in this
32 * VM. This interface allows annotations to be read reflectively. All
33 * annotations returned by methods in this interface are immutable and
34 * serializable. It is permissible for the caller to modify the
35 * arrays returned by accessors for array-valued enum members; it will
36 * have no affect on 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 either method
41 * is a repeatable annotation type (JLS 9.6), then the method will "look
42 * through" a container annotation (JLS 9.7) which was generated at
43 * compile-time to wrap multiple annotations of the argument type.
44 *
45 * <p>The terms <em>directly present</em> and <em>present</em> are used
46 * throughout this interface to describe precisely which annotations are
47 * returned by methods:
48 *
49 * <ul>
50 * <li>An annotation A is <em>directly present</em> on an element E if E is
51 * associated with a RuntimeVisibleAnnotations or
52 * RuntimeVisibleParameterAnnotations attribute, and:
53 *
54 * <ul>
55 * <li>for an invocation of {@code get[Declared]Annotation(Class<T>)} or
56 * {@code get[Declared]Annotations()}, the attribute contains A.
57 *
58 * <li>for an invocation of {@code get[Declared]AnnotationsByType(Class<T>)}, the
59 * attribute either contains A or, if the type of A is repeatable, contains
60 * exactly one annotation whose value element contains A and whose type is the
61 * containing annotation type of A's type (JLS 9.6).
62 * </ul>
63 *
64 * <p>
65 * <li>An annotation A is <em>present</em> on an element E if either:
66 *
67 * <ul>
68 * <li>A is <em>directly present</em> on E; or
69 *
70 * <li>A is not <em>directly present</em> on E, and E is a class, and A's type
71 * is inheritable (JLS 9.6.3.3), and A is <em>present</em> on the superclass of
72 * E.
73 * </ul>
74 *
75 * </ul>
76 *
77 * <p>If an annotation returned by a method in this interface contains
78 * (directly or indirectly) a {@link Class}-valued member referring to
79 * a class that is not accessible in this VM, attempting to read the class
80 * by calling the relevant Class-returning method on the returned annotation
81 * will result in a {@link TypeNotPresentException}.
82 *
83 * <p>Similarly, attempting to read an enum-valued member will result in
84 * a {@link EnumConstantNotPresentException} if the enum constant in the
85 * annotation is no longer present in the enum type.
86 *
87 * <p>Attempting to read annotations of a repeatable annotation type T
88 * that are contained in an annotation whose type is not, in fact, the
89 * containing annotation type of T will result in an
90 * InvalidContainerAnnotationError.
91 *
92 * <p>Finally, attempting to read a member whose definition has evolved
93 * incompatibly will result in a {@link
94 * java.lang.annotation.AnnotationTypeMismatchException} or an
95 * {@link java.lang.annotation.IncompleteAnnotationException}.
96 *
97 * @see java.lang.EnumConstantNotPresentException
98 * @see java.lang.TypeNotPresentException
99 * @see java.lang.annotation.AnnotationFormatError
100 * @see java.lang.annotation.AnnotationTypeMismatchException
101 * @see java.lang.annotation.IncompleteAnnotationException
102 * @see java.lang.annotation.InvalidContainerAnnotationError
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 annotationClass the Class object corresponding to the
134 * annotation type
135 * @return this element's annotation for the specified annotation type if
136 * present on this element, else null
137 * @throws NullPointerException if the given annotation class is null
138 * @since 1.5
139 */
140 <T extends Annotation> T getAnnotation(Class<T> annotationClass);
141
142 /**
143 * Returns annotations that are <em>present</em> on this element.
144 *
145 * If there are no annotations <em>present</em> on this element, the return
146 * value is an array of length 0.
147 *
148 * The difference between this method and {@link #getAnnotation(Class)}
149 * is that this method detects if its argument is a <em>repeatable
150 * annotation type</em> (JLS 9.6), and if so, attempts to find one or
151 * more annotations of that type by "looking through" a container
152 * annotation.
153 *
154 * The caller of this method is free to modify the returned array; it will
155 * have no effect on the arrays returned to other callers.
156 *
157 * @param annotationClass the Class object corresponding to the
158 * annotation type
159 * @return all this element's annotations for the specified annotation type if
160 * present on this element, else an array of length zero
161 * @throws NullPointerException if the given annotation class is null
162 * @since 1.8
163 */
164 <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass);
165
166 /**
167 * Returns annotations that are <em>present</em> on this element.
168 *
169 * If there are no annotations <em>present</em> on this element, the return
170 * value is an array of length 0.
171 *
172 * The caller of this method is free to modify the returned array; it will
173 * have no effect on the arrays returned to other callers.
174 *
175 * @return annotations present on this element
176 * @since 1.5
177 */
178 Annotation[] getAnnotations();
179
180 /**
181 * Returns this element's annotation for the specified type if
182 * such an annotation is present, else null.
183 *
184 * This method ignores inherited annotations. (Returns null if no
185 * annotations are directly present on this element.)
186 *
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 1.8
193 */
194 <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass);
195
196 /**
197 * Returns annotations that are <em>directly present</em> on this element.
198 * This method ignores inherited annotations.
199 *
200 * If there are no annotations <em>directly present</em> on this element,
201 * the return value is an array of length 0.
202 *
203 * The difference between this method and {@link
204 * #getDeclaredAnnotation(Class)} is that this method detects if its
205 * argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so,
206 * attempts to find one or more annotations of that type by "looking
207 * through" a container annotation.
208 *
209 * The caller of this method is free to modify the returned array; it will
210 * have no effect on the arrays returned to other callers.
211 *
212 * @param annotationClass the Class object corresponding to the
213 * annotation type
214 * @return all this element's annotations for the specified annotation type if
215 * present on this element, else an array of length zero
216 * @throws NullPointerException if the given annotation class is null
217 * @since 1.8
218 */
219 <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass);
220
221 /**
222 * Returns annotations that are <em>directly present</em> on this element.
223 * This method ignores inherited annotations.
224 *
225 * If there are no annotations <em>directly present</em> on this element,
226 * the return value is an array of length 0.
227 *
228 * The caller of this method is free to modify the returned array; it will
229 * have no effect on the arrays returned to other callers.
230 *
231 * @return annotations directly present on this element
232 * @since 1.5
233 */
234 Annotation[] getDeclaredAnnotations();
235 }