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

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package java.lang.reflect;

import java.lang.annotation.Annotation;
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. 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 <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 <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><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>
 *
 * <li>An annotation <i>A</i> is <em>associated</em> with an element <i>E</i>
 * if either:
 *
 * <ul>
 *
 * <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
 * 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 <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
 * 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</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:
     * {@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</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
     *        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<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 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
     * 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.
     *
     * @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
     */
    <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass);

    /**
     * Returns this element's annotation for the specified type if
     * 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 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
     */
    <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass);

    /**
     * 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 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 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 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
     */
    <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass);

    /**
     * Returns annotations that are <em>directly present</em> on this element.
     * 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.
     *
     * 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();
}