8010679: Clarify "present" and annotation ordering in Core Reflection for Annotations
Reviewed-by: abuckley, jfranck
This commit is contained in:
Joe Darcy
parent
593f3c74ba
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25154dcc20
@ -32,49 +32,101 @@ import java.lang.annotation.AnnotationFormatError;
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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. It is permissible for the caller to modify the
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* arrays returned by accessors for array-valued enum members; it will
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* have no affect on the arrays returned to other callers.
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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 either method
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* is a repeatable annotation type (JLS 9.6), then the method will "look
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* through" a container annotation (JLS 9.7) which was generated at
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* compile-time to wrap multiple annotations of the argument type.
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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> and <em>present</em> are used
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* throughout this interface to describe precisely which annotations are
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* returned by methods:
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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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* <li>An annotation A is <em>directly present</em> on an element E if E is
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* associated with a RuntimeVisibleAnnotations or
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* RuntimeVisibleParameterAnnotations attribute, and:
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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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* <li>for an invocation of {@code get[Declared]Annotation(Class<T>)} or
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* {@code get[Declared]Annotations()}, the attribute contains A.
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*
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* <li>for an invocation of {@code get[Declared]AnnotationsByType(Class<T>)}, the
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* attribute either contains A or, if the type of A is repeatable, contains
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* exactly one annotation whose value element contains A and whose type is the
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* containing annotation type of A's type (JLS 9.6).
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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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* <p>
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* <li>An annotation A is <em>present</em> on an element E if either:
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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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* <li>A is <em>directly present</em> on E; or
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*
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* <li>A is not <em>directly present</em> on E, and E is a class, and A's type
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* is inheritable (JLS 9.6.3.3), and A is <em>present</em> on the superclass of
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* E.
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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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* <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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@ -85,10 +137,11 @@ import java.lang.annotation.AnnotationFormatError;
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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>Attempting to read annotations of a repeatable annotation type T
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* that are contained in an annotation whose type is not, in fact, the
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* containing annotation type of T, will result in an {@link
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* AnnotationFormatError}.
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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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@ -106,7 +159,7 @@ import java.lang.annotation.AnnotationFormatError;
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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 present on this element, else false. This method
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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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@ -128,7 +181,7 @@ public interface AnnotatedElement {
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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 present, else null.
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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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@ -146,6 +199,20 @@ public interface AnnotatedElement {
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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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@ -159,65 +226,54 @@ public interface AnnotatedElement {
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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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* present on this element, else an array of length zero
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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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<T extends Annotation> T[] getAnnotationsByType(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 this element's annotation for the specified type if
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* such an annotation is present, else null.
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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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* @param <T> the type of the annotation to query for and return if present
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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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* present on this element, else null
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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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<T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass);
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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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* 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 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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* 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.
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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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* @param <T> the type of the annotation to query for and return
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* if directly present
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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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* present on this element, else an array of length zero
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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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