Mon, 14 Jan 2013 19:52:36 +0100
7193719: Support repeating annotations in javax.lang.model
Reviewed-by: jjg
1 /*
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26 package javax.lang.model.element;
29 import java.lang.annotation.Annotation;
30 import java.lang.annotation.AnnotationTypeMismatchException;
31 import java.lang.annotation.IncompleteAnnotationException;
32 import java.util.List;
33 import java.util.Set;
35 import javax.lang.model.type.*;
36 import javax.lang.model.util.*;
39 /**
40 * Represents a program element such as a package, class, or method.
41 * Each element represents a static, language-level construct
42 * (and not, for example, a runtime construct of the virtual machine).
43 *
44 * <p> Elements should be compared using the {@link #equals(Object)}
45 * method. There is no guarantee that any particular element will
46 * always be represented by the same object.
47 *
48 * <p> To implement operations based on the class of an {@code
49 * Element} object, either use a {@linkplain ElementVisitor visitor} or
50 * use the result of the {@link #getKind} method. Using {@code
51 * instanceof} is <em>not</em> necessarily a reliable idiom for
52 * determining the effective class of an object in this modeling
53 * hierarchy since an implementation may choose to have a single object
54 * implement multiple {@code Element} subinterfaces.
55 *
56 * @author Joseph D. Darcy
57 * @author Scott Seligman
58 * @author Peter von der Ahé
59 * @see Elements
60 * @see TypeMirror
61 * @since 1.6
62 */
63 public interface Element {
65 /**
66 * Returns the type defined by this element.
67 *
68 * <p> A generic element defines a family of types, not just one.
69 * If this is a generic element, a <i>prototypical</i> type is
70 * returned. This is the element's invocation on the
71 * type variables corresponding to its own formal type parameters.
72 * For example,
73 * for the generic class element {@code C<N extends Number>},
74 * the parameterized type {@code C<N>} is returned.
75 * The {@link Types} utility interface has more general methods
76 * for obtaining the full range of types defined by an element.
77 *
78 * @see Types
79 *
80 * @return the type defined by this element
81 */
82 TypeMirror asType();
84 /**
85 * Returns the {@code kind} of this element.
86 *
87 * @return the kind of this element
88 */
89 ElementKind getKind();
91 /**
92 * Returns the annotations that are directly present on this element.
93 *
94 * <p> To get inherited annotations as well, use
95 * {@link Elements#getAllAnnotationMirrors(Element) getAllAnnotationMirrors}.
96 *
97 * @see ElementFilter
98 *
99 * @return the annotations directly present on this element;
100 * an empty list if there are none
101 */
102 List<? extends AnnotationMirror> getAnnotationMirrors();
104 /**
105 * Returns this element's annotation for the specified type if
106 * such an annotation is present, else {@code null}. The
107 * annotation may be either inherited or directly present on this
108 * element.
109 *
110 * <p> The annotation returned by this method could contain an element
111 * whose value is of type {@code Class}.
112 * This value cannot be returned directly: information necessary to
113 * locate and load a class (such as the class loader to use) is
114 * not available, and the class might not be loadable at all.
115 * Attempting to read a {@code Class} object by invoking the relevant
116 * method on the returned annotation
117 * will result in a {@link MirroredTypeException},
118 * from which the corresponding {@link TypeMirror} may be extracted.
119 * Similarly, attempting to read a {@code Class[]}-valued element
120 * will result in a {@link MirroredTypesException}.
121 *
122 * <blockquote>
123 * <i>Note:</i> This method is unlike others in this and related
124 * interfaces. It operates on runtime reflective information —
125 * representations of annotation types currently loaded into the
126 * VM — rather than on the representations defined by and used
127 * throughout these interfaces. Consequently, calling methods on
128 * the returned annotation object can throw many of the exceptions
129 * that can be thrown when calling methods on an annotation object
130 * returned by core reflection. This method is intended for
131 * callers that are written to operate on a known, fixed set of
132 * annotation types.
133 * </blockquote>
134 *
135 * @param <A> the annotation type
136 * @param annotationType the {@code Class} object corresponding to
137 * the annotation type
138 * @return this element's annotation for the specified annotation
139 * type if present on this element, else {@code null}
140 *
141 * @see #getAnnotationMirrors()
142 * @see java.lang.reflect.AnnotatedElement#getAnnotation
143 * @see EnumConstantNotPresentException
144 * @see AnnotationTypeMismatchException
145 * @see IncompleteAnnotationException
146 * @see MirroredTypeException
147 * @see MirroredTypesException
148 */
149 <A extends Annotation> A getAnnotation(Class<A> annotationType);
151 /**
152 * Returns an array of all of this element's annotation for the
153 * specified type if such annotations are present, else an empty
154 * array. The annotation may be either inherited or directly
155 * present on this element. This method will look through a container
156 * annotation (if present) if the supplied annotation type is
157 * repeatable.
158 *
159 * <p> The annotations returned by this method could contain an element
160 * whose value is of type {@code Class}.
161 * This value cannot be returned directly: information necessary to
162 * locate and load a class (such as the class loader to use) is
163 * not available, and the class might not be loadable at all.
164 * Attempting to read a {@code Class} object by invoking the relevant
165 * method on the returned annotation
166 * will result in a {@link MirroredTypeException},
167 * from which the corresponding {@link TypeMirror} may be extracted.
168 * Similarly, attempting to read a {@code Class[]}-valued element
169 * will result in a {@link MirroredTypesException}.
170 *
171 * <blockquote>
172 * <i>Note:</i> This method is unlike others in this and related
173 * interfaces. It operates on runtime reflective information —
174 * representations of annotation types currently loaded into the
175 * VM — rather than on the representations defined by and used
176 * throughout these interfaces. Consequently, calling methods on
177 * the returned annotation object can throw many of the exceptions
178 * that can be thrown when calling methods on an annotation object
179 * returned by core reflection. This method is intended for
180 * callers that are written to operate on a known, fixed set of
181 * annotation types.
182 * </blockquote>
183 *
184 * @param <A> the annotation type
185 * @param annotationType the {@code Class} object corresponding to
186 * the annotation type
187 * @return this element's annotations for the specified annotation
188 * type if present on this element, else an empty array
189 *
190 * @see #getAnnotationMirrors()
191 * @see #getAnnotation()
192 * @see java.lang.reflect.AnnotatedElement#getAnnotations
193 * @see EnumConstantNotPresentException
194 * @see AnnotationTypeMismatchException
195 * @see IncompleteAnnotationException
196 * @see MirroredTypeException
197 * @see MirroredTypesException
198 */
199 <A extends Annotation> A[] getAnnotations(Class<A> annotationType);
201 /**
202 * Returns the modifiers of this element, excluding annotations.
203 * Implicit modifiers, such as the {@code public} and {@code static}
204 * modifiers of interface members, are included.
205 *
206 * @return the modifiers of this element, or an empty set if there are none
207 */
208 Set<Modifier> getModifiers();
210 /**
211 * Returns the simple (unqualified) name of this element. The
212 * name of a generic type does not include any reference to its
213 * formal type parameters.
214 *
215 * For example, the simple name of the type element {@code
216 * java.util.Set<E>} is {@code "Set"}.
217 *
218 * If this element represents an unnamed {@linkplain
219 * PackageElement#getSimpleName package}, an empty name is
220 * returned.
221 *
222 * If it represents a {@linkplain ExecutableElement#getSimpleName
223 * constructor}, the name "{@code <init>}" is returned. If it
224 * represents a {@linkplain ExecutableElement#getSimpleName static
225 * initializer}, the name "{@code <clinit>}" is returned.
226 *
227 * If it represents an {@linkplain TypeElement#getSimpleName
228 * anonymous class} or {@linkplain ExecutableElement#getSimpleName
229 * instance initializer}, an empty name is returned.
230 *
231 * @return the simple name of this element
232 * @see PackageElement#getSimpleName
233 * @see ExecutableElement#getSimpleName
234 * @see TypeElement#getSimpleName
235 * @see VariableElement#getSimpleName
236 */
237 Name getSimpleName();
239 /**
240 * Returns the innermost element
241 * within which this element is, loosely speaking, enclosed.
242 * <ul>
243 * <li> If this element is one whose declaration is lexically enclosed
244 * immediately within the declaration of another element, that other
245 * element is returned.
246 *
247 * <li> If this is a {@linkplain TypeElement#getEnclosingElement
248 * top-level type}, its package is returned.
249 *
250 * <li> If this is a {@linkplain
251 * PackageElement#getEnclosingElement package}, {@code null} is
252 * returned.
253 *
254 * <li> If this is a {@linkplain
255 * TypeParameterElement#getEnclosingElement type parameter},
256 * {@linkplain TypeParameterElement#getGenericElement the
257 * generic element} of the type parameter is returned.
258 *
259 * <li> If this is a {@linkplain
260 * VariableElement#getEnclosingElement method or constructor
261 * parameter}, {@linkplain ExecutableElement the executable
262 * element} which declares the parameter is returned.
263 *
264 * </ul>
265 *
266 * @return the enclosing element, or {@code null} if there is none
267 * @see Elements#getPackageOf
268 */
269 Element getEnclosingElement();
271 /**
272 * Returns the elements that are, loosely speaking, directly
273 * enclosed by this element.
274 *
275 * A {@linkplain TypeElement#getEnclosedElements class or
276 * interface} is considered to enclose the fields, methods,
277 * constructors, and member types that it directly declares.
278 *
279 * A {@linkplain PackageElement#getEnclosedElements package}
280 * encloses the top-level classes and interfaces within it, but is
281 * not considered to enclose subpackages.
282 *
283 * Other kinds of elements are not currently considered to enclose
284 * any elements; however, that may change as this API or the
285 * programming language evolves.
286 *
287 * <p>Note that elements of certain kinds can be isolated using
288 * methods in {@link ElementFilter}.
289 *
290 * @return the enclosed elements, or an empty list if none
291 * @see PackageElement#getEnclosedElements
292 * @see TypeElement#getEnclosedElements
293 * @see Elements#getAllMembers
294 * @jls 8.8.9 Default Constructor
295 * @jls 8.9 Enums
296 */
297 List<? extends Element> getEnclosedElements();
299 /**
300 * Returns {@code true} if the argument represents the same
301 * element as {@code this}, or {@code false} otherwise.
302 *
303 * <p>Note that the identity of an element involves implicit state
304 * not directly accessible from the element's methods, including
305 * state about the presence of unrelated types. Element objects
306 * created by different implementations of these interfaces should
307 * <i>not</i> be expected to be equal even if "the same"
308 * element is being modeled; this is analogous to the inequality
309 * of {@code Class} objects for the same class file loaded through
310 * different class loaders.
311 *
312 * @param obj the object to be compared with this element
313 * @return {@code true} if the specified object represents the same
314 * element as this
315 */
316 boolean equals(Object obj);
318 /**
319 * Obeys the general contract of {@link Object#hashCode Object.hashCode}.
320 *
321 * @see #equals
322 */
323 int hashCode();
325 /**
326 * Applies a visitor to this element.
327 *
328 * @param <R> the return type of the visitor's methods
329 * @param <P> the type of the additional parameter to the visitor's methods
330 * @param v the visitor operating on this element
331 * @param p additional parameter to the visitor
332 * @return a visitor-specified result
333 */
334 <R, P> R accept(ElementVisitor<R, P> v, P p);
335 }