451 lines
19 KiB
451 lines
19 KiB
/*
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* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.lang.reflect;
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import java.lang.annotation.Annotation;
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import java.lang.annotation.AnnotationFormatError;
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import java.lang.annotation.Repeatable;
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import java.util.Arrays;
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import java.util.LinkedHashMap;
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import java.util.Map;
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import java.util.Objects;
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import java.util.function.Function;
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import java.util.stream.Collectors;
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import sun.reflect.annotation.AnnotationSupport;
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import sun.reflect.annotation.AnnotationType;
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/**
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* Represents an annotated element of the program currently running in this
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* VM. This interface allows annotations to be read reflectively. All
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* annotations returned by methods in this interface are immutable and
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* serializable. The arrays returned by methods of this interface may be modified
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* by callers without affecting the arrays returned to other callers.
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*
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* <p>The {@link #getAnnotationsByType(Class)} and {@link
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* #getDeclaredAnnotationsByType(Class)} methods support multiple
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* annotations of the same type on an element. If the argument to
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* either method is a repeatable annotation type (JLS 9.6), then the
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* method will "look through" a container annotation (JLS 9.7), if
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* present, and return any annotations inside the container. Container
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* annotations may be generated at compile-time to wrap multiple
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* annotations of the argument type.
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*
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* <p>The terms <em>directly present</em>, <em>indirectly present</em>,
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* <em>present</em>, and <em>associated</em> are used throughout this
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* interface to describe precisely which annotations are returned by
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* methods:
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*
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* <ul>
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*
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* <li> An annotation <i>A</i> is <em>directly present</em> on an
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* element <i>E</i> if <i>E</i> has a {@code
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* RuntimeVisibleAnnotations} or {@code
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* RuntimeVisibleParameterAnnotations} or {@code
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* RuntimeVisibleTypeAnnotations} attribute, and the attribute
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* contains <i>A</i>.
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*
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* <li>An annotation <i>A</i> is <em>indirectly present</em> on an
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* element <i>E</i> if <i>E</i> has a {@code RuntimeVisibleAnnotations} or
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* {@code RuntimeVisibleParameterAnnotations} or {@code RuntimeVisibleTypeAnnotations}
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* attribute, and <i>A</i> 's type is repeatable, and the attribute contains
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* exactly one annotation whose value element contains <i>A</i> and whose
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* type is the containing annotation type of <i>A</i> 's type.
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*
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* <li>An annotation <i>A</i> is present on an element <i>E</i> if either:
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*
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* <ul>
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*
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* <li><i>A</i> is directly present on <i>E</i>; or
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*
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* <li>No annotation of <i>A</i> 's type is directly present on
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* <i>E</i>, and <i>E</i> is a class, and <i>A</i> 's type is
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* inheritable, and <i>A</i> is present on the superclass of <i>E</i>.
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*
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* </ul>
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*
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* <li>An annotation <i>A</i> is <em>associated</em> with an element <i>E</i>
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* if either:
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*
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* <ul>
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*
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* <li><i>A</i> is directly or indirectly present on <i>E</i>; or
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*
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* <li>No annotation of <i>A</i> 's type is directly or indirectly
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* present on <i>E</i>, and <i>E</i> is a class, and <i>A</i>'s type
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* is inheritable, and <i>A</i> is associated with the superclass of
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* <i>E</i>.
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*
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* </ul>
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*
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* </ul>
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*
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* <p>The table below summarizes which kind of annotation presence
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* different methods in this interface examine.
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*
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* <table border>
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* <caption>Overview of kind of presence detected by different AnnotatedElement methods</caption>
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* <tr><th colspan=2></th><th colspan=4>Kind of Presence</th>
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* <tr><th colspan=2>Method</th><th>Directly Present</th><th>Indirectly Present</th><th>Present</th><th>Associated</th>
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* <tr><td align=right>{@code T}</td><td>{@link #getAnnotation(Class) getAnnotation(Class<T>)}
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* <td></td><td></td><td>X</td><td></td>
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* </tr>
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* <tr><td align=right>{@code Annotation[]}</td><td>{@link #getAnnotations getAnnotations()}
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* <td></td><td></td><td>X</td><td></td>
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* </tr>
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* <tr><td align=right>{@code T[]}</td><td>{@link #getAnnotationsByType(Class) getAnnotationsByType(Class<T>)}
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* <td></td><td></td><td></td><td>X</td>
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* </tr>
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* <tr><td align=right>{@code T}</td><td>{@link #getDeclaredAnnotation(Class) getDeclaredAnnotation(Class<T>)}
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* <td>X</td><td></td><td></td><td></td>
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* </tr>
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* <tr><td align=right>{@code Annotation[]}</td><td>{@link #getDeclaredAnnotations getDeclaredAnnotations()}
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* <td>X</td><td></td><td></td><td></td>
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* </tr>
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* <tr><td align=right>{@code T[]}</td><td>{@link #getDeclaredAnnotationsByType(Class) getDeclaredAnnotationsByType(Class<T>)}
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* <td>X</td><td>X</td><td></td><td></td>
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* </tr>
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* </table>
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*
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* <p>For an invocation of {@code get[Declared]AnnotationsByType( Class <
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* T >)}, the order of annotations which are directly or indirectly
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* present on an element <i>E</i> is computed as if indirectly present
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* annotations on <i>E</i> are directly present on <i>E</i> in place
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* of their container annotation, in the order in which they appear in
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* the value element of the container annotation.
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*
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* <p>There are several compatibility concerns to keep in mind if an
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* annotation type <i>T</i> is originally <em>not</em> repeatable and
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* later modified to be repeatable.
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*
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* The containing annotation type for <i>T</i> is <i>TC</i>.
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*
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* <ul>
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*
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* <li>Modifying <i>T</i> to be repeatable is source and binary
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* compatible with existing uses of <i>T</i> and with existing uses
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* of <i>TC</i>.
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*
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* That is, for source compatibility, source code with annotations of
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* type <i>T</i> or of type <i>TC</i> will still compile. For binary
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* compatibility, class files with annotations of type <i>T</i> or of
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* type <i>TC</i> (or with other kinds of uses of type <i>T</i> or of
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* type <i>TC</i>) will link against the modified version of <i>T</i>
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* if they linked against the earlier version.
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*
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* (An annotation type <i>TC</i> may informally serve as an acting
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* containing annotation type before <i>T</i> is modified to be
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* formally repeatable. Alternatively, when <i>T</i> is made
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* repeatable, <i>TC</i> can be introduced as a new type.)
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*
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* <li>If an annotation type <i>TC</i> is present on an element, and
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* <i>T</i> is modified to be repeatable with <i>TC</i> as its
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* containing annotation type then:
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*
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* <ul>
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*
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* <li>The change to <i>T</i> is behaviorally compatible with respect
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* to the {@code get[Declared]Annotation(Class<T>)} (called with an
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* argument of <i>T</i> or <i>TC</i>) and {@code
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* get[Declared]Annotations()} methods because the results of the
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* methods will not change due to <i>TC</i> becoming the containing
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* annotation type for <i>T</i>.
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*
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* <li>The change to <i>T</i> changes the results of the {@code
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* get[Declared]AnnotationsByType(Class<T>)} methods called with an
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* argument of <i>T</i>, because those methods will now recognize an
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* annotation of type <i>TC</i> as a container annotation for <i>T</i>
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* and will "look through" it to expose annotations of type <i>T</i>.
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*
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* </ul>
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*
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* <li>If an annotation of type <i>T</i> is present on an
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* element and <i>T</i> is made repeatable and more annotations of
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* type <i>T</i> are added to the element:
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*
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* <ul>
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*
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* <li> The addition of the annotations of type <i>T</i> is both
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* source compatible and binary compatible.
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*
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* <li>The addition of the annotations of type <i>T</i> changes the results
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* of the {@code get[Declared]Annotation(Class<T>)} methods and {@code
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* get[Declared]Annotations()} methods, because those methods will now
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* only see a container annotation on the element and not see an
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* annotation of type <i>T</i>.
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*
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* <li>The addition of the annotations of type <i>T</i> changes the
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* results of the {@code get[Declared]AnnotationsByType(Class<T>)}
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* methods, because their results will expose the additional
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* annotations of type <i>T</i> whereas previously they exposed only a
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* single annotation of type <i>T</i>.
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*
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* </ul>
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*
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* </ul>
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*
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* <p>If an annotation returned by a method in this interface contains
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* (directly or indirectly) a {@link Class}-valued member referring to
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* a class that is not accessible in this VM, attempting to read the class
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* by calling the relevant Class-returning method on the returned annotation
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* will result in a {@link TypeNotPresentException}.
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*
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* <p>Similarly, attempting to read an enum-valued member will result in
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* a {@link EnumConstantNotPresentException} if the enum constant in the
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* annotation is no longer present in the enum type.
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*
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* <p>If an annotation type <i>T</i> is (meta-)annotated with an
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* {@code @Repeatable} annotation whose value element indicates a type
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* <i>TC</i>, but <i>TC</i> does not declare a {@code value()} method
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* with a return type of <i>T</i>{@code []}, then an exception of type
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* {@link java.lang.annotation.AnnotationFormatError} is thrown.
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*
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* <p>Finally, attempting to read a member whose definition has evolved
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* incompatibly will result in a {@link
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* java.lang.annotation.AnnotationTypeMismatchException} or an
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* {@link java.lang.annotation.IncompleteAnnotationException}.
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*
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* @see java.lang.EnumConstantNotPresentException
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* @see java.lang.TypeNotPresentException
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* @see AnnotationFormatError
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* @see java.lang.annotation.AnnotationTypeMismatchException
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* @see java.lang.annotation.IncompleteAnnotationException
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* @since 1.5
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* @author Josh Bloch
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*/
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public interface AnnotatedElement {
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/**
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* Returns true if an annotation for the specified type
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* is <em>present</em> on this element, else false. This method
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* is designed primarily for convenient access to marker annotations.
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*
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* <p>The truth value returned by this method is equivalent to:
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* {@code getAnnotation(annotationClass) != null}
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*
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* <p>The body of the default method is specified to be the code
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* above.
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*
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* @param annotationClass the Class object corresponding to the
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* annotation type
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* @return true if an annotation for the specified annotation
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* type is present on this element, else false
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* @throws NullPointerException if the given annotation class is null
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* @since 1.5
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*/
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default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
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return getAnnotation(annotationClass) != null;
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}
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/**
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* Returns this element's annotation for the specified type if
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* such an annotation is <em>present</em>, else null.
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*
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* @param <T> the type of the annotation to query for and return if present
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* @param annotationClass the Class object corresponding to the
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* annotation type
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* @return this element's annotation for the specified annotation type if
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* present on this element, else null
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* @throws NullPointerException if the given annotation class is null
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* @since 1.5
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*/
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<T extends Annotation> T getAnnotation(Class<T> annotationClass);
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/**
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* Returns annotations that are <em>present</em> on this element.
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*
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* If there are no annotations <em>present</em> on this element, the return
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* value is an array of length 0.
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*
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* The caller of this method is free to modify the returned array; it will
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* have no effect on the arrays returned to other callers.
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*
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* @return annotations present on this element
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* @since 1.5
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*/
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Annotation[] getAnnotations();
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/**
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* Returns annotations that are <em>associated</em> with this element.
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*
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* If there are no annotations <em>associated</em> with this element, the return
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* value is an array of length 0.
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*
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* The difference between this method and {@link #getAnnotation(Class)}
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* is that this method detects if its argument is a <em>repeatable
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* annotation type</em> (JLS 9.6), and if so, attempts to find one or
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* more annotations of that type by "looking through" a container
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* annotation.
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*
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* The caller of this method is free to modify the returned array; it will
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* have no effect on the arrays returned to other callers.
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*
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* @implSpec The default implementation first calls {@link
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* #getDeclaredAnnotationsByType(Class)} passing {@code
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* annotationClass} as the argument. If the returned array has
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* length greater than zero, the array is returned. If the returned
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* array is zero-length and this {@code AnnotatedElement} is a
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* class and the argument type is an inheritable annotation type,
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* and the superclass of this {@code AnnotatedElement} is non-null,
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* then the returned result is the result of calling {@link
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* #getAnnotationsByType(Class)} on the superclass with {@code
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* annotationClass} as the argument. Otherwise, a zero-length
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* array is returned.
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*
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* @param <T> the type of the annotation to query for and return if present
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* @param annotationClass the Class object corresponding to the
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* annotation type
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* @return all this element's annotations for the specified annotation type if
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* associated with this element, else an array of length zero
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* @throws NullPointerException if the given annotation class is null
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* @since 1.8
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*/
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default <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
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/*
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* Definition of associated: directly or indirectly present OR
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* neither directly nor indirectly present AND the element is
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* a Class, the annotation type is inheritable, and the
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* annotation type is associated with the superclass of the
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* element.
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*/
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T[] result = getDeclaredAnnotationsByType(annotationClass);
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if (result.length == 0 && // Neither directly nor indirectly present
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this instanceof Class && // the element is a class
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AnnotationType.getInstance(annotationClass).isInherited()) { // Inheritable
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Class<?> superClass = ((Class<?>) this).getSuperclass();
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if (superClass != null) {
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// Determine if the annotation is associated with the
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// superclass
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result = superClass.getAnnotationsByType(annotationClass);
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}
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}
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return result;
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}
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/**
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* Returns this element's annotation for the specified type if
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* such an annotation is <em>directly present</em>, else null.
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*
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* This method ignores inherited annotations. (Returns null if no
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* annotations are directly present on this element.)
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*
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* @implSpec The default implementation first performs a null check
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* and then loops over the results of {@link
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* #getDeclaredAnnotations} returning the first annotation whose
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* annotation type matches the argument type.
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*
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* @param <T> the type of the annotation to query for and return if directly present
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* @param annotationClass the Class object corresponding to the
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* annotation type
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* @return this element's annotation for the specified annotation type if
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* directly present on this element, else null
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* @throws NullPointerException if the given annotation class is null
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* @since 1.8
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*/
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default <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
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Objects.requireNonNull(annotationClass);
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// Loop over all directly-present annotations looking for a matching one
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for (Annotation annotation : getDeclaredAnnotations()) {
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if (annotationClass.equals(annotation.annotationType())) {
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// More robust to do a dynamic cast at runtime instead
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// of compile-time only.
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return annotationClass.cast(annotation);
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}
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}
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return null;
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}
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/**
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* Returns this element's annotation(s) for the specified type if
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* such annotations are either <em>directly present</em> or
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* <em>indirectly present</em>. This method ignores inherited
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* annotations.
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*
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* If there are no specified annotations directly or indirectly
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* present on this element, the return value is an array of length
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* 0.
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*
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* The difference between this method and {@link
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* #getDeclaredAnnotation(Class)} is that this method detects if its
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* argument is a <em>repeatable annotation type</em> (JLS 9.6), and if so,
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* attempts to find one or more annotations of that type by "looking
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* through" a container annotation if one is present.
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*
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* The caller of this method is free to modify the returned array; it will
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* have no effect on the arrays returned to other callers.
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*
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* @implSpec The default implementation may call {@link
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* #getDeclaredAnnotation(Class)} one or more times to find a
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* directly present annotation and, if the annotation type is
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* repeatable, to find a container annotation. If annotations of
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* the annotation type {@code annotationClass} are found to be both
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* directly and indirectly present, then {@link
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* #getDeclaredAnnotations()} will get called to determine the
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* order of the elements in the returned array.
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*
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* <p>Alternatively, the default implementation may call {@link
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* #getDeclaredAnnotations()} a single time and the returned array
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* examined for both directly and indirectly present
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* annotations. The results of calling {@link
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* #getDeclaredAnnotations()} are assumed to be consistent with the
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* results of calling {@link #getDeclaredAnnotation(Class)}.
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*
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* @param <T> the type of the annotation to query for and return
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* if directly or indirectly present
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* @param annotationClass the Class object corresponding to the
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* annotation type
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* @return all this element's annotations for the specified annotation type if
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* directly or indirectly present on this element, else an array of length zero
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* @throws NullPointerException if the given annotation class is null
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* @since 1.8
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*/
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default <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
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Objects.requireNonNull(annotationClass);
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return AnnotationSupport.
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getDirectlyAndIndirectlyPresent(Arrays.stream(getDeclaredAnnotations()).
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collect(Collectors.toMap(Annotation::annotationType,
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Function.identity(),
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((first,second) -> first),
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LinkedHashMap::new)),
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annotationClass);
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}
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/**
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* Returns annotations that are <em>directly present</em> on this element.
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* This method ignores inherited annotations.
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*
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* If there are no annotations <em>directly present</em> on this element,
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* the return value is an array of length 0.
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*
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* The caller of this method is free to modify the returned array; it will
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* have no effect on the arrays returned to other callers.
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*
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* @return annotations directly present on this element
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* @since 1.5
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*/
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Annotation[] getDeclaredAnnotations();
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}
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