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.  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.
 *
 * <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.
 *
 * <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:
 *
 * <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:
 *
 * <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).
 * </ul>
 *
 * <p>
 * <li>An annotation A is <em>present</em> on an element E 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.
 * </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>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>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 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 present, else null.
     *
     * @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 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 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
     * @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.
     *
     * This method ignores inherited annotations. (Returns null if no
     * annotations are directly present on this element.)
     *
     * @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 1.8
     */
    <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass);

    /**
     * Returns annotations that are <em>directly present</em> on this element.
     * This method ignores inherited annotations.
     *
     * If there are no annotations <em>directly present</em> 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.
     *
     * 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 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
     * @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();
}