* <tr>
* <tr>
* </tr>
* <tr>
* </tr>
* <tr>
* </tr>
* <tr>
* </tr>
* <tr>
* </tr>
* <tr>
* </tr>
* </table>
*
* <p>For an invocation of {@code get[Declared]AnnotationsByType( Class <
* T >)}, the order of annotations which are directly or indirectly
* present on an element <i>E is computed as if indirectly present
* annotations on <i>E are directly present on
E in place
* of their container annotation, in the order in which they appear in
* the value element of the container annotation.
*
* <p>There are several compatibility concerns to keep in mind if an
* annotation type <i>T is originally
not repeatable and
* later modified to be repeatable.
*
* The containing annotation type for <i>T is
TC.
*
* <ul>
*
* <li>Modifying
T to be repeatable is source and binary
* compatible with existing uses of <i>T and with existing uses
* of <i>TC.
*
* That is, for source compatibility, source code with annotations of
* type <i>T or of type
TC will still compile. For binary
* compatibility, class files with annotations of type <i>T or of
* type <i>TC (or with other kinds of uses of type
T or of
* type <i>TC) will link against the modified version of
T
* if they linked against the earlier version.
*
* (An annotation type <i>TC may informally serve as an acting
* containing annotation type before <i>T is modified to be
* formally repeatable. Alternatively, when <i>T is made
* repeatable, <i>TC can be introduced as a new type.)
*
* <li>If an annotation type
TC is present on an element, and
* <i>T is modified to be repeatable with
TC as its
* containing annotation type then:
*
* <ul>
*
* <li>The change to
T is behaviorally compatible with respect
* to the {@code get[Declared]Annotation(Class<T>)} (called with an
* argument of <i>T or
TC) and {@code
* get[Declared]Annotations()} methods because the results of the
* methods will not change due to <i>TC becoming the containing
* annotation type for <i>T.
*
* <li>The change to
T changes the results of the {@code
* get[Declared]AnnotationsByType(Class<T>)} methods called with an
* argument of <i>T, because those methods will now recognize an
* annotation of type <i>TC as a container annotation for
T
* and will "look through" it to expose annotations of type <i>T.
*
* </ul>
*
* <li>If an annotation of type
T is present on an
* element and <i>T is made repeatable and more annotations of
* type <i>T are added to the element:
*
* <ul>
*
* <li> The addition of the annotations of type
T is both
* source compatible and binary compatible.
*
* <li>The addition of the annotations of type
T changes the results
* of the {@code get[Declared]Annotation(Class<T>)} methods and {@code
* get[Declared]Annotations()} methods, because those methods will now
* only see a container annotation on the element and not see an
* annotation of type <i>T.
*
* <li>The addition of the annotations of type
T changes the
* results of the {@code get[Declared]AnnotationsByType(Class<T>)}
* methods, because their results will expose the additional
* annotations of type <i>T whereas previously they exposed only a
* single annotation of type <i>T.
*
* </ul>
*
* </ul>
*
* <p>If an annotation returned by a method in this interface contains
* (directly or indirectly) a {@link Class}-valued member referring to
* a class that is not accessible in this VM, attempting to read the class
* by calling the relevant Class-returning method on the returned annotation
* will result in a {@link TypeNotPresentException}.
*
* <p>Similarly, attempting to read an enum-valued member will result in
* a {@link EnumConstantNotPresentException} if the enum constant in the
* annotation is no longer present in the enum type.
*
* <p>If an annotation type
T is (meta-)annotated with an
* {@code @Repeatable} annotation whose value element indicates a type
* <i>TC, but
TC does not declare a {@code value()} method
* with a return type of <i>T{@code []}, then an exception of type
* {@link java.lang.annotation.AnnotationFormatError} is thrown.
*
* <p>Finally, attempting to read a member whose definition has evolved
* incompatibly will result in a {@link
* java.lang.annotation.AnnotationTypeMismatchException} or an
* {@link java.lang.annotation.IncompleteAnnotationException}.
*
* @see java.lang.EnumConstantNotPresentException
* @see java.lang.TypeNotPresentException
* @see AnnotationFormatError
* @see java.lang.annotation.AnnotationTypeMismatchException
* @see java.lang.annotation.IncompleteAnnotationException
* @since 1.5
* @author Josh Bloch
*/
public interface AnnotatedElement {
/**
* Returns true if an annotation for the specified type
* is <em>present on this element, else false. This method
* is designed primarily for convenient access to marker annotations.
*
* <p>The truth value returned by this method is equivalent to:
* {@code getAnnotation(annotationClass) != null}
*
* <p>The body of the default method is specified to be the code
* above.
*
* @param annotationClass the Class object corresponding to the
* annotation type
* @return true if an annotation for the specified annotation
* type is present on this element, else false
* @throws NullPointerException if the given annotation class is null
* @since 1.5
*/
default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
return getAnnotation(annotationClass) != null;
}
/**
* Returns this element's annotation for the specified type if
* such an annotation is <em>present, else null.
*
* @param <T> the type of the annotation to query for and return if present
* @param annotationClass the Class object corresponding to the
* annotation type
* @return this element's annotation for the specified annotation type if
* present on this element, else null
* @throws NullPointerException if the given annotation class is null
* @since 1.5
*/
<T extends Annotation> T getAnnotation(Class
annotationClass);
/**
* Returns annotations that are <em>present on this element.
*
* If there are no annotations <em>present on this element, the return
* value is an array of length 0.
*
* The caller of this method is free to modify the returned array; it will
* have no effect on the arrays returned to other callers.
*
* @return annotations present on this element
* @since 1.5
*/
Annotation[] getAnnotations();
/**
* Returns annotations that are <em>associated with this element.
*
* If there are no annotations <em>associated with this element, the return
* value is an array of length 0.
*
* The difference between this method and {@link #getAnnotation(Class)}
* is that this method detects if its argument is a <em>repeatable
* annotation type</em> (JLS 9.6), and if so, attempts to find one or
* more annotations of that type by "looking through" a container
* annotation.
*
* The caller of this method is free to modify the returned array; it will
* have no effect on the arrays returned to other callers.
*
* @implSpec The default implementation first calls {@link
* #getDeclaredAnnotationsByType(Class)} passing {@code
* annotationClass} as the argument. If the returned array has
* length greater than zero, the array is returned. If the returned
* array is zero-length and this {@code AnnotatedElement} is a
* class and the argument type is an inheritable annotation type,
* and the superclass of this {@code AnnotatedElement} is non-null,
* then the returned result is the result of calling {@link
* #getAnnotationsByType(Class)} on the superclass with {@code
* annotationClass} as the argument. Otherwise, a zero-length
* array is returned.
*
* @param <T> the type of the annotation to query for and return if present
* @param annotationClass the Class object corresponding to the
* annotation type
* @return all this element's annotations for the specified annotation type if
* associated with this element, else an array of length zero
* @throws NullPointerException if the given annotation class is null
* @since 1.8
*/
default <T extends Annotation> T[] getAnnotationsByType(Class annotationClass) {
/*
* Definition of associated: directly or indirectly present OR
* neither directly nor indirectly present AND the element is
* a Class, the annotation type is inheritable, and the
* annotation type is associated with the superclass of the
* element.
*/
T[] result = getDeclaredAnnotationsByType(annotationClass);
if (result.length == 0 && // Neither directly nor indirectly present
this instanceof Class && // the element is a class
AnnotationType.getInstance(annotationClass).isInherited()) { // Inheritable
Class<?> superClass = ((Class) this).getSuperclass();
if (superClass != null) {
// Determine if the annotation is associated with the
// superclass
result = superClass.getAnnotationsByType(annotationClass);
}
}
return result;
}
/**
* Returns this element's annotation for the specified type if
* such an annotation is <em>directly present, else null.
*
* This method ignores inherited annotations. (Returns null if no
* annotations are directly present on this element.)
*
* @implSpec The default implementation first performs a null check
* and then loops over the results of {@link
* #getDeclaredAnnotations} returning the first annotation whose
* annotation type matches the argument type.
*
* @param <T> the type of the annotation to query for and return if directly present
* @param annotationClass the Class object corresponding to the
* annotation type
* @return this element's annotation for the specified annotation type if
* directly present on this element, else null
* @throws NullPointerException if the given annotation class is null
* @since 1.8
*/
default <T extends Annotation> T getDeclaredAnnotation(Class annotationClass) {
Objects.requireNonNull(annotationClass);
// Loop over all directly-present annotations looking for a matching one
for (Annotation annotation : getDeclaredAnnotations()) {
if (annotationClass.equals(annotation.annotationType())) {
// More robust to do a dynamic cast at runtime instead
// of compile-time only.
return annotationClass.cast(annotation);
}
}
return null;
}
/**
* Returns this element's annotation(s) for the specified type if
* such annotations are either <em>directly present or
* <em>indirectly present. This method ignores inherited
* annotations.
*
* If there are no specified annotations directly or indirectly
* present on this element, the return value is an array of length
* 0.
*
* The difference between this method and {@link
* #getDeclaredAnnotation(Class)} is that this method detects if its
* argument is a <em>repeatable annotation type (JLS 9.6), and if so,
* attempts to find one or more annotations of that type by "looking
* through" a container annotation if one is present.
*
* The caller of this method is free to modify the returned array; it will
* have no effect on the arrays returned to other callers.
*
* @implSpec The default implementation may call {@link
* #getDeclaredAnnotation(Class)} one or more times to find a
* directly present annotation and, if the annotation type is
* repeatable, to find a container annotation. If annotations of
* the annotation type {@code annotationClass} are found to be both
* directly and indirectly present, then {@link
* #getDeclaredAnnotations()} will get called to determine the
* order of the elements in the returned array.
*
* <p>Alternatively, the default implementation may call {@link
* #getDeclaredAnnotations()} a single time and the returned array
* examined for both directly and indirectly present
* annotations. The results of calling {@link
* #getDeclaredAnnotations()} are assumed to be consistent with the
* results of calling {@link #getDeclaredAnnotation(Class)}.
*
* @param <T> the type of the annotation to query for and return
* if directly or indirectly present
* @param annotationClass the Class object corresponding to the
* annotation type
* @return all this element's annotations for the specified annotation type if
* directly or indirectly present on this element, else an array of length zero
* @throws NullPointerException if the given annotation class is null
* @since 1.8
*/
default <T extends Annotation> T[] getDeclaredAnnotationsByType(Class annotationClass) {
Objects.requireNonNull(annotationClass);
return AnnotationSupport.
getDirectlyAndIndirectlyPresent(Arrays.stream(getDeclaredAnnotations()).
collect(Collectors.toMap(Annotation::annotationType,
Function.identity(),
((first,second) -> first),
LinkedHashMap::new)),
annotationClass);
}
/**
* Returns annotations that are <em>directly present on this element.
* This method ignores inherited annotations.
*
* If there are no annotations <em>directly present on this element,
* the return value is an array of length 0.
*
* The caller of this method is free to modify the returned array; it will
* have no effect on the arrays returned to other callers.
*
* @return annotations directly present on this element
* @since 1.5
*/
Annotation[] getDeclaredAnnotations();
}
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The AnnotatedElement.java Java example source code
/*
* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.lang.reflect;
import java.lang.annotation.Annotation;
import java.lang.annotation.AnnotationFormatError;
import java.lang.annotation.Repeatable;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Objects;
import java.util.function.Function;
import java.util.stream.Collectors;
import sun.reflect.annotation.AnnotationSupport;
import sun.reflect.annotation.AnnotationType;
/**
* Represents an annotated element of the program currently running in this
* VM. This interface allows annotations to be read reflectively. All
* annotations returned by methods in this interface are immutable and
* serializable. The arrays returned by methods of this interface may be modified
* by callers without affecting the arrays returned to other callers.
*
* <p>The {@link #getAnnotationsByType(Class)} and {@link
* #getDeclaredAnnotationsByType(Class)} methods support multiple
* annotations of the same type on an element. If the argument to
* either method is a repeatable annotation type (JLS 9.6), then the
* method will "look through" a container annotation (JLS 9.7), if
* present, and return any annotations inside the container. Container
* annotations may be generated at compile-time to wrap multiple
* annotations of the argument type.
*
* <p>The terms directly present, indirectly present,
* <em>present, and associated are used throughout this
* interface to describe precisely which annotations are returned by
* methods:
*
* <ul>
*
* <li> An annotation A is directly present on an
* element <i>E if E has a {@code
* RuntimeVisibleAnnotations} or {@code
* RuntimeVisibleParameterAnnotations} or {@code
* RuntimeVisibleTypeAnnotations} attribute, and the attribute
* contains <i>A.
*
* <li>An annotation A is indirectly present on an
* element <i>E if E has a {@code RuntimeVisibleAnnotations} or
* {@code RuntimeVisibleParameterAnnotations} or {@code RuntimeVisibleTypeAnnotations}
* attribute, and <i>A 's type is repeatable, and the attribute contains
* exactly one annotation whose value element contains <i>A and whose
* type is the containing annotation type of <i>A 's type.
*
* <li>An annotation A is present on an element E if either:
*
* <ul>
*
* <li>A is directly present on E; or
*
* <li>No annotation of A 's type is directly present on
* <i>E, and E is a class, and A 's type is
* inheritable, and <i>A is present on the superclass of E.
*
* </ul>
*
* <li>An annotation A is associated with an element E
* if either:
*
* <ul>
*
* <li>A is directly or indirectly present on E; or
*
* <li>No annotation of A 's type is directly or indirectly
* present on <i>E, and E is a class, and A's type
* is inheritable, and <i>A is associated with the superclass of
* <i>E.
*
* </ul>
*
* </ul>
*
* <p>The table below summarizes which kind of annotation presence
* different methods in this interface examine.
*
* <table border>
* <caption>Overview of kind of presence detected by different AnnotatedElement methods
* <tr> | | Kind of Presence | Method | Directly Present | Indirectly Present | Present | Associated | {@code T} | {@link #getAnnotation(Class) getAnnotation(Class<T>)}
* <td> | | X | | {@code Annotation[]} | {@link #getAnnotations getAnnotations()}
* <td> | | X | | {@code T[]} | {@link #getAnnotationsByType(Class) getAnnotationsByType(Class<T>)}
* <td> | | | X | {@code T} | {@link #getDeclaredAnnotation(Class) getDeclaredAnnotation(Class<T>)}
* <td>X | | | | {@code Annotation[]} | {@link #getDeclaredAnnotations getDeclaredAnnotations()}
* <td>X | | | | {@code T[]} | {@link #getDeclaredAnnotationsByType(Class) getDeclaredAnnotationsByType(Class<T>)}
* <td>X | X | | |
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