8010679: Clarify "present" and annotation ordering in Core Reflection for Annotations

Reviewed-by: abuckley, jfranck

src/share/classes/java/lang/reflect/AnnotatedElement.java

@@ -32,49 +32,101 @@ import java.lang.annotation.AnnotationFormatError;
  * 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.  It is permissible for the caller to modify the
- * arrays returned by accessors for array-valued enum members; it will
- * have no affect on the arrays returned to other callers.
+ * 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) which was generated at
- * compile-time to wrap multiple annotations of the argument type.
+ * 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 <em>directly present</em> and <em>present</em> are used
- * throughout this interface to describe precisely which annotations are
- * returned by methods:
+ * <p>The terms <em>directly present</em>, <em>indirectly present</em>,
+ * <em>present</em>, and <em>associated</em> are used throughout this
+ * interface to describe precisely which annotations are returned by
+ * methods:
  *
  * <ul>
- * <li>An annotation A is <em>directly present</em> on an element E if E is
- * associated with a RuntimeVisibleAnnotations or
- * RuntimeVisibleParameterAnnotations attribute, and:
+ *
+ * <li> An annotation <i>A</i> is <em>directly present</em> on an
+ * element <i>E</i> if <i>E</i> has a {@code
+ * RuntimeVisibleAnnotations} or {@code
+ * RuntimeVisibleParameterAnnotations} or {@code
+ * RuntimeVisibleTypeAnnotations} attribute, and the attribute
+ * contains <i>A</i>.
+ *
+ * <li>An annotation <i>A</i> is <em>indirectly present</em> on an
+ * element <i>E</i> if <i>E</i> has a {@code RuntimeVisibleAnnotations} or
+ * {@code RuntimeVisibleParameterAnnotations} or {@code RuntimeVisibleTypeAnnotations}
+ * attribute, and <i>A</i> 's type is repeatable, and the attribute contains
+ * exactly one annotation whose value element contains <i>A</i> and whose
+ * type is the containing annotation type of <i>A</i> 's type.
+ *
+ * <li>An annotation <i>A</i> is present on an element <i>E</i> if either:
  *
  * <ul>
- * <li>for an invocation of {@code get[Declared]Annotation(Class<T>)} or
- * {@code get[Declared]Annotations()}, the attribute contains A.
  *
- * <li>for an invocation of {@code get[Declared]AnnotationsByType(Class<T>)}, the
- * attribute either contains A or, if the type of A is repeatable, contains
- * exactly one annotation whose value element contains A and whose type is the
- * containing annotation type of A's type (JLS 9.6).
+ * <li><i>A</i> is directly present on <i>E</i>; or
+ *
+ * <li>No annotation of <i>A</i> 's type is directly present on
+ * <i>E</i>, and <i>E</i> is a class, and <i>A</i> 's type is
+ * inheritable, and <i>A</i> is present on the superclass of <i>E</i>.
+ *
  * </ul>
  *
- * <p>
- * <li>An annotation A is <em>present</em> on an element E if either:
+ * <li>An annotation <i>A</i> is <em>associated</em> with an element <i>E</i>
+ * if either:
  *
  * <ul>
- * <li>A is <em>directly present</em> on E; or
  *
- * <li>A is not <em>directly present</em> on E, and E is a class, and A's type
- * is inheritable (JLS 9.6.3.3), and A is <em>present</em> on the superclass of
- * E.
+ * <li><i>A</i> is directly or indirectly present on <i>E</i>; or
+ *
+ * <li>No annotation of <i>A</i> 's type is directly or indirectly
+ * present on <i>E</i>, and <i>E</i> is a class, and <i>A</i>'s type
+ * is inheritable, and <i>A</i> is associated with the superclass of
+ * <i>E</i>.
+ *
  * </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</caption>
+ * <tr><th colspan=2></th><th colspan=4>Kind of Presence</th>
+ * <tr><th colspan=2>Method</th><th>Directly Present</th><th>Indirectly Present</th><th>Present</th><th>Associated</th>
+ * <tr><td align=right>{@code T}</td><td>{@link #getAnnotation(Class) getAnnotation(Class&lt;T&gt;)}
+ * <td></td><td></td><td>X</td><td></td>
+ * </tr>
+ * <tr><td align=right>{@code Annotation[]}</td><td>{@link #getAnnotations getAnnotations()}
+ * <td></td><td></td><td>X</td><td></td>
+ * </tr>
+ * <tr><td align=right>{@code T[]}</td><td>{@link #getAnnotationsByType(Class) getAnnotationsByType(Class&lt;T&gt;)}
+ * <td></td><td></td><td></td><td>X</td>
+ * </tr>
+ * <tr><td align=right>{@code T}</td><td>{@link #getDeclaredAnnotation(Class) getDeclaredAnnotation(Class&lt;T&gt;)}
+ * <td>X</td><td></td><td></td><td></td>
+ * </tr>
+ * <tr><td align=right>{@code Annotation[]}</td><td>{@link #getDeclaredAnnotations getDeclaredAnnotations()}
+ * <td>X</td><td></td><td></td><td></td>
+ * </tr>
+ * <tr><td align=right>{@code T[]}</td><td>{@link #getDeclaredAnnotationsByType(Class) getDeclaredAnnotationsByType(Class&lt;T&gt;)}
+ * <td>X</td><td>X</td><td></td><td></td>
+ * </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</i> is computed as if indirectly present
+ * annotations on <i>E</i> are directly present on <i>E</i> in place
+ * of their container annotation, in the order in which they appear in
+ * the value element of the container annotation.
+
  * <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
@@ -85,10 +137,11 @@ import java.lang.annotation.AnnotationFormatError;
  * a {@link EnumConstantNotPresentException} if the enum constant in the
  * annotation is no longer present in the enum type.
  *
- * <p>Attempting to read annotations of a repeatable annotation type T
- * that are contained in an annotation whose type is not, in fact, the
- * containing annotation type of T, will result in an {@link
- * AnnotationFormatError}.
+ * <p>If an annotation type <i>T</i> is (meta-)annotated with an
+ * {@code @Repeatable} annotation whose value element indicates a type
+ * <i>TC</i>, but <i>TC</i> does not declare a {@code value()} method
+ * with a return type of <i>T</i>{@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
@@ -106,7 +159,7 @@ import java.lang.annotation.AnnotationFormatError;
 public interface AnnotatedElement {
     /**
      * Returns true if an annotation for the specified type
-     * is present on this element, else false.  This method
+     * is <em>present</em> 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:
@@ -128,7 +181,7 @@ public interface AnnotatedElement {
 
    /**
      * Returns this element's annotation for the specified type if
-     * such an annotation is present, else null.
+     * such an annotation is <em>present</em>, else null.
      *
      * @param <T> the type of the annotation to query for and return if present
      * @param annotationClass the Class object corresponding to the
@@ -146,6 +199,20 @@ public interface AnnotatedElement {
      * If there are no annotations <em>present</em> 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</em> with this element.
+     *
+     * If there are no annotations <em>associated</em> 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
@@ -159,65 +226,54 @@ public interface AnnotatedElement {
      * @param annotationClass the Class object corresponding to the
      *        annotation type
      * @return all this element's annotations for the specified annotation type if
-     *     present on this element, else an array of length zero
+     *     associated with this element, else an array of length zero
      * @throws NullPointerException if the given annotation class is null
      * @since 1.8
      */
     <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass);
 
-    /**
-     * Returns annotations that are <em>present</em> on this element.
-     *
-     * If there are no annotations <em>present</em> 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 this element's annotation for the specified type if
-     * such an annotation is present, else null.
+     * such an annotation is <em>directly present</em>, else null.
      *
      * This method ignores inherited annotations. (Returns null if no
      * annotations are directly present on this element.)
      *
-     * @param <T> the type of the annotation to query for and return if present
+     * @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
-     *     present on this element, else null
+     *     directly present on this element, else null
      * @throws NullPointerException if the given annotation class is null
      * @since 1.8
      */
     <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass);
 
     /**
-     * Returns annotations that are <em>directly present</em> on this element.
-     * This method ignores inherited annotations.
+     * Returns this element's annotation(s) for the specified type if
+     * such annotations are either <em>directly present</em> or
+     * <em>indirectly present</em>. This method ignores inherited
+     * annotations.
      *
-     * If there are no annotations <em>directly present</em> on this element,
-     * the return value is an array of length 0.
+     * 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</em> (JLS 9.6), and if so,
      * attempts to find one or more annotations of that type by "looking
-     * through" a container annotation.
+     * 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.
      *
      * @param <T> the type of the annotation to query for and return
-     * if directly present
+     * 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
-     *     present on this element, else an array of length zero
+     *     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
      */