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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* published by the Free Software Foundation. Oracle designates this
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*
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
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*
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package java.lang.reflect;
import java.lang.annotation.Annotation;
import java.lang.annotation.AnnotationFormatError;
import java.lang.annotation.Repeatable;
import java.util.Objects;
import sun.reflect.annotation.AnnotationSupport;
import sun.reflect.annotation.AnnotationType;
/**
* 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.
*
* 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.
*
*
The terms directly present, indirectly present,
* present, and associated are used throughout this
* interface to describe precisely which annotations are returned by
* methods:
*
*
*
* - An annotation A is directly present on an
* element E if E has a {@code
* RuntimeVisibleAnnotations} or {@code
* RuntimeVisibleParameterAnnotations} or {@code
* RuntimeVisibleTypeAnnotations} attribute, and the attribute
* contains A.
*
*
- An annotation A is indirectly present on an
* element E if E has a {@code RuntimeVisibleAnnotations} or
* {@code RuntimeVisibleParameterAnnotations} or {@code RuntimeVisibleTypeAnnotations}
* attribute, and A 's type is repeatable, and the attribute contains
* exactly one annotation whose value element contains A and whose
* type is the containing annotation type of A 's type.
*
*
- An annotation A is present on an element E if either:
*
*
*
* - A is directly present on E; or
*
*
- No annotation of A 's type is directly present on
* E, and E is a class, and A 's type is
* inheritable, and A is present on the superclass of E.
*
*
*
* - An annotation A is associated with an element E
* if either:
*
*
*
* - A is directly or indirectly present on E; or
*
*
- No annotation of A 's type is directly or indirectly
* present on E, and E is a class, and A's type
* is inheritable, and A is associated with the superclass of
* E.
*
*
*
*
*
* The table below summarizes which kind of annotation presence
* different methods in this interface examine.
*
*
* Overview of kind of presence detected by different AnnotatedElement methods
* | Kind of Presence |
*
|---|
| Method | Directly Present | Indirectly Present | Present | Associated |
*
|---|
| {@code T} | {@link #getAnnotation(Class) getAnnotation(Class<T>)}
* | | | X | |
*
* | {@code Annotation[]} | {@link #getAnnotations getAnnotations()}
* | | | X | |
*
* | {@code T[]} | {@link #getAnnotationsByType(Class) getAnnotationsByType(Class<T>)}
* | | | | X |
*
* | {@code T} | {@link #getDeclaredAnnotation(Class) getDeclaredAnnotation(Class<T>)}
* | X | | | |
*
* | {@code Annotation[]} | {@link #getDeclaredAnnotations getDeclaredAnnotations()}
* | X | | | |
*
* | {@code T[]} | {@link #getDeclaredAnnotationsByType(Class) getDeclaredAnnotationsByType(Class<T>)}
* | X | X | | |
*
*
*
* For an invocation of {@code get[Declared]AnnotationsByType( Class <
* T >)}, the order of annotations which are directly or indirectly
* present on an element E is computed as if indirectly present
* annotations on E are directly present on E in place
* of their container annotation, in the order in which they appear in
* the value element of the container annotation.
*
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}.
*
*
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.
*
*
If an annotation type T is (meta-)annotated with an
* {@code @Repeatable} annotation whose value element indicates a type
* TC, but TC does not declare a {@code value()} method
* with a return type of T{@code []}, then an exception of type
* {@link java.lang.annotation.AnnotationFormatError} is thrown.
*
*
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.
*
*
The truth value returned by this method is equivalent to:
* {@code getAnnotation(annotationClass) != null}
*
*
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 annotationClass) {
return getAnnotation(annotationClass) != null;
}
/**
* Returns this element's annotation for the specified type if
* such an annotation is present, else null.
*
* @param 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 getAnnotation(Class annotationClass);
/**
* Returns annotations that are present on this element.
*
* If there are no annotations present 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 associated with this element.
*
* If there are no annotations associated 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 repeatable
* annotation type (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.
*
* @implSpec The default implementation first calls {@link
* #getDeclaredAnnotationsByType(Class)} passing {@code
* annotationClass} as the argument. If the returned array has
* size greater than zero, the array is returned. If the returned
* array has size zero and this {@code AnnotatedElement} is a
* class and the argument type is an inheritable annotation type,
* and the superclass of this {@code AnnoatedElement} is non-null,
* then the returned result is the result of calling {@code
* getAnnotationsByType} on the superclass with {@code
* annotationClass} as the argument. Otherwise, a zero-length
* array is returned.
*
* @param 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
*/
default T[] getAnnotationsByType(Class annotationClass) {
/*
* Definition of associated: directly or indirectly present OR
* neither directly nor indirectly present AND the element is
* a Class, the annotation type is inheritable, and the
* annotation type is associated with the superclass of the
* element.
*/
T[] result = getDeclaredAnnotationsByType(annotationClass);
if (result.length == 0 && // Neither directly nor indirectly present
this instanceof Class && // the element is a class
AnnotationType.getInstance(annotationClass).isInherited()) { // Inheritable
Class superClass = ((Class) this).getSuperclass();
if (superClass != null) {
// Determine if the annotation is associated with the
// superclass
result = superClass.getAnnotationsByType(annotationClass);
}
}
return result;
}
/**
* Returns this element's annotation for the specified type if
* such an annotation is directly present, else null.
*
* This method ignores inherited annotations. (Returns null if no
* annotations are directly present on this element.)
*
* @implSpec The default implementation first performs a null check
* and then loops over the results of {@link
* #getDeclaredAnnotations} returning the first annotation whose
* annotation type matches the argument type.
*
* @param 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
*/
default T getDeclaredAnnotation(Class annotationClass) {
Objects.requireNonNull(annotationClass);
// Loop over all directly-present annotations looking for a matching one
for (Annotation annotation : getDeclaredAnnotations()) {
if (annotationClass.equals(annotation.annotationType())) {
// More robust to do a dynamic cast at runtime instead
// of compile-time only.
return annotationClass.cast(annotation);
}
}
return null;
}
/**
* Returns this element's annotation(s) for the specified type if
* such annotations are either directly present or
* indirectly present. 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 repeatable annotation type (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.
*
* @implSpec The default implementation may call {@link
* #getDeclaredAnnotation(Class)} one or more times to find a
* directly present annotation and, if the annotation type is
* repeatable, to find a container annotation. If annotations of
* the annotation type {@code annotationClass} are found to be both
* directly and indirectly present, then {@link
* #getDeclaredAnnotations()} will get called to determine the
* order of the elements in the returned array.
*
* Alternatively, the default implementation may call {@link
* #getDeclaredAnnotations()} a single time and the returned array
* examined for both directly and indirectly present
* annotations. The results of calling {@link
* #getDeclaredAnnotations()} are assumed to be consistent with the
* results of calling {@link #getDeclaredAnnotation(Class)}.
*
* @param 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
*/
default T[] getDeclaredAnnotationsByType(Class annotationClass) {
Objects.requireNonNull(annotationClass);
int resultSize = 0;
T directlyPresent = getDeclaredAnnotation(annotationClass);
if (directlyPresent != null) {
resultSize++;
}
Repeatable repeatable = annotationClass.getAnnotation(Repeatable.class);
if (repeatable == null) {
@SuppressWarnings("unchecked")
T[] returnValue = (T[]) Array.newInstance(annotationClass, resultSize);
if (directlyPresent != null)
returnValue[0] = directlyPresent;
return returnValue;
} else {
// directlyPresent may or may not be null
// Look through a container to see if an annotation is
// indirectly present
Class containerType = repeatable.value();
Annotation container = getDeclaredAnnotation(containerType);
T[] indirectlyPresent = null;
if (container != null) {
indirectlyPresent = AnnotationSupport.getValueArray(container);
resultSize += indirectlyPresent.length;
}
// Final result size is known
// todo: review comment for accuracy...
/*
* If resultSize is 0, indirectlyPresent is either
* assigned to the result of the initial Array.newInstance
* call or indirectlyPresent is assigned to a zero-length
* value array from an empty container annotation. In
* either case, a zero-length array is immutable and does
* not need to reallocated before being returned.
*
* If resultSize is nonzero, then indirectlyPresent points
* to the result calling a method on an annotation and
* annotations are required to implement a no sharing
* policy. Therefore, it is not required to copy the
* elements of indirectlyPresent into a new array of the
* same size.
*/
if (indirectlyPresent == null || indirectlyPresent.length == 0) {
@SuppressWarnings("unchecked")
T[] returnValue = (T[]) Array.newInstance(annotationClass, resultSize);
if (resultSize == 1)
returnValue[0] = directlyPresent;
return returnValue;
} else {
// assert indirectlyPresent != null && indirectlyPresent.length > 0;
if (resultSize == indirectlyPresent.length){
// assert directlyPresent == null;
return indirectlyPresent;
} else {
// assert directlyPresent != null && indirectlyPresent.length > 0;
@SuppressWarnings("unchecked")
T[] returnValue = (T[]) Array.newInstance(annotationClass, resultSize);
// Determine whether the directly present annotation
// comes before or after the indirectly present ones.
int indirectOffset = 0;
for (Annotation a : getDeclaredAnnotations()) {
Class annotationType = a.annotationType();
if (annotationType.equals(annotationClass)) {
indirectOffset = 1;
break;
} else if (annotationType.equals(containerType)) {
break;
}
}
for (int i = 0; i < indirectlyPresent.length; i++) {
returnValue[i + indirectOffset] = indirectlyPresent[i];
}
returnValue[(indirectOffset == 1) ? 0 : resultSize - 1] = directlyPresent;
return returnValue;
}
}
}
}
/**
* Returns annotations that are directly present on this element.
* This method ignores inherited annotations.
*
* If there are no annotations directly present 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();
}